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[ARCHIVED THREAD] - Full Auto CMMG Guard Tuning (Page 1 of 4)
Posted: 11/17/2018 9:16:19 PM EDT
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As several of you know, I've been trying to get my 9mm CMMG Guard to run as smooth as an MP5 for the past several months.
Here is what it is up against: Full size MP5 
MP5K PDW 
In several posts I have mentioned that the smoothest configuration I had with the 9mm CMMG Guard was with: 1. A5 Buffer Tube 2. 556 Tubb Flat wire spring 3. 9mm Blitzkrieg/Kynshot hydraulic buffer Pictured below is that configuration (622 RPM) but I still wanted to smooth it out some more. Basically shoot flatter with less dot bounce. 
I have tried the tuning kit and find that it makes it too bouncy. 525 RPM is nice but too bouncy. (note that I've also tested the 2.0 and 1.0 Guard weights but left that data out for brevity, pictured below is a standard Colt 3.5 Oz weight same as the heaviest one CMMG provides in their tuning kit.) 
I was thinking that I need more delay but STATIC mass in the carrier just gets bouncy. Pictured below is a 1.8 Tungsten weight and I just put the pin in the carrier that is normally used for the static weight and a spring between the between the weight and the pin. When the carrier is thrusting rearward, intertia of this tungsten weight is going forward... further delaying the blowback. This is working very well for me. 
However, I wanted to try different springs that I thought would last longer than the springs I picked up at a surplus store. (You can see I had to cut this one) Picture below shows a 12lb multiwave compression spring on top of a conventional compression spring that I was testing. I've tested 6,12 and 20 lb multiwave comression springs. If you look closely you can see that both springs were getting damaged from getting battered by the pin in the carrier. 
Pictured below is my latest testing with a 2.2 Tungsten weight and Conical compression spring. 572 RPM and shooting flatter than the MP5. Note that I still think the MP5 is 'softer' but this is actually flatter (at least for me) Since it isn't as soft as the MP5, you must have some proper technique in shooting it correctly. Also at 572RPM it has a very nice RoF and single round bursts are way easier than an MP5. Oh..and also note that I am now using a hardened stainless steel washer to go behind the pin in the carrier so the spring doesn't get deformed. 
ETA: I have a lot of data that is not presented here in regards to how I got to this point and the various configurations I tested. I am working on updating my page at the following link with a lot of these details: http://c3junkie.com/?page_id=538 |
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Quoted:
Does the additional tungsten weight damage the kynshot buffer at all? Or do you have it cut so it is flush with the end of the BCG and always has some slight tension from the conical spring? |
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Quoted:
That's a great idea! What's the rate of the conical springs? Also, with the tungsten are they custom made or did you source them from somewhere? Same link Ive posted before..just changed the title and put new stuff on top. I reference the part number for that spring in that link. But there are other details i need to post up there. I will try to add more later today. Kinda hard to explain without more pics. |
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Wonder if you could speed it up to 900 or so if it would smooth out more. |
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Sure that is easy. However, if you look at my link. I have 4 goals I'm trying to obtain. One of them is to bring the RoF down so that pulling a single round burst is easy while still maintaining softness and flatness. That is what is hard to do. |
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Quoted:
Ive started working on all the details on this link:http://c3junkie.com/?page_id=538 Same link Ive posted before..just changed the title and put new stuff on top. I reference the part number for that spring in that link. But there are other details i need to post up there. I will try to add more later today. Kinda hard to explain without more pics. One thing I was wondering about...if you drilled another pin hole in the carrier to move the tungsten further forward and installed a second spring between it and the buffer, would that make things even smoother? Basically allowing the weight to be dynamic on both ends of the stoke? Something like this: Attached File |
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Quoted: Awesome, thanks for the reference! One thing I was wondering about...if you drilled another pin hole in the carrier to move the tungsten further forward and installed a second spring between it and the buffer, would that make things even smoother? Basically allowing the weight to be dynamic on both ends of the stoke? Something like this: https://www.AR15.Com/media/mediaFiles/444683/dynamic_mass_png-743224.JPG I was also thinking it would be easier for most people to acquire steel weights vs tungsten as well and if you had the pin further forward could possibly use the 2.0 oz steel weight that comes in the Guard tuning kit. So many different scenarios and so little time! |
Have you looked into running a wave spring?
 
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Yes look at the picture I posted above with a plastic bag labeled 12 lb. That was a wave spring. I've tried 6,12 and 20 lb wave springs
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Quoted:
Yeah..I was thinking the same thing. I might be able to pull that off using my shorter 1.8 tungsten weight with a spring in front and back and no washer for a few rounds just to see what it feels like. (as I know without a washer, the spring is going to get mangled pretty quick). I was also thinking it would be easier for most people to acquire steel weights vs tungsten as well and if you had the pin further forward could possibly use the 2.0 oz steel weight that comes in the Guard tuning kit. So many different scenarios and so little time! Quoted:
Yeah..I was thinking the same thing. I might be able to pull that off using my shorter 1.8 tungsten weight with a spring in front and back and no washer for a few rounds just to see what it feels like. (as I know without a washer, the spring is going to get mangled pretty quick). I was also thinking it would be easier for most people to acquire steel weights vs tungsten as well and if you had the pin further forward could possibly use the 2.0 oz steel weight that comes in the Guard tuning kit. So many different scenarios and so little time! Quoted:
Is the tungsten and spring strictly for your full auto ROF slowdown? or does it also make it softer/smoother (in semi auto/suppressed)? |
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I'm also curious about this. It sounds like there was a noticeable difference in overall smoothness/softness compared to static weight? Both semi & auto? True statement? Quoted:
Is the tungsten and spring strictly for your full auto ROF slowdown? or does it also make it softer/smoother (in semi auto/suppressed)? For Semi vs Auto, I think it really depends on the person. Many people can't tell the difference. When I did my testing yesterday, I had a co-worker with me that has a few guns but hasn't shot much full auto at all. 2nd time actually, 1st time was some of my other guns. I had him shoot the Mini UZI, MP5K PDW and the Guard. All in full auto. He said the Guard was the best of all 3. I was thinking he would say the MP5. I've been trying to just focus primarily on full auto and paying attention to the dot bounce so haven't really done much thinking about semi...that said, several times I've been thinking I had a few rounds left firing bursts and there would only be one round left in the mag and after firing the last round and looking at the dot and feeling the action, I clearly recall thinking 'damn that shit is smooth'. |
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Great data; love reading it!
What're your initial thoughts regarding tungsten weight differences? 2.2oz with the conical spring is smoother that the 1.8oz with same spring? About the same? ETA: "If" you had more room in the carrier, do you think the 20# wave spring would produce better results that the conical? i.e if it had more room for deflection? |
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Great data; love reading it! What're your initial thoughts regarding tungsten weight differences? 2.2oz with the conical spring is smoother that the 1.8oz with same spring? About the same? ETA: "If" you had more room in the carrier, do you think the 20# wave spring would produce better results that the conical? i.e if it had more room for deflection? As mentioned here: https://www.ar15.com/forums/AR-15/Thoughts-on-the-CMMG-Guard-/15-713060/?page=12 I had participated in a SMG match back in Sept and had 6 or 7 malfunctions out of 8 stages. That was before I had contacted CMMG about their ejector spring details and that they are now standardizing the 9mm to use the 45 Guard ejector springs which are shorter but stronger than a 556 ejector spring. So I'm not sure if 3.5oz is really too heavy for my configuration or it was just the ejector spring the entire time....not to mention 3.5oz of static weight is different from a dynamic weight. So I'm keeping a close eye my reliability with this 2.2 oz and my ejector spring health. On that note, I did swap out my ejector spring when I did my latest testing. I had received the replacement springs from CMMG but never swapped them as I had already swapped my ejector springs with new 556 ones I had on hand and was curious how long they would last. I was starting to have a few failures to eject and sure enough the ejector spring was all shrunk/mangled up like previous ones and shorter than the new CMMG one. I think the new 556 ejector spring lasted less than 2K of full auto 9mm before it died on me. I have about 300 rounds on the new CMMG one in one of my 9mm Guard carriers. I think the 20lb wave spring would be better as I think it is more robust than the conical compression as that is really just one strand of wire....but so is the buffer spring, hammer spring and just about every other spring in the AR :).... After looking at my the pictures of the cheap washer getting bent over as well as the springs getting hammered, you know there is some serious inertia going on in there. I have been thinking about cutting another piece of tungsten that is between the 1.8 and 2.2 in length that would be optimal for the .3" wave spring + thick washer but for now, I'm thinking to just run the 2.2 for a bit since going smaller on the tungsten will most likely increase RoF....and I want to know if the 2.2 is going to be too heavy or not. |
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@amphibian
Absolutely amazing work. Thank you for sharing all your results and lessons with us. Question: In your opinion, do you think the Guard setup is 'gentle' enough for use on a RR? I was leery of a 9mm Colt setup based on everything I've read here, but the RDB system seems soft enough that it shouldn't damage a RR. |
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Question: In your opinion, do you think the Guard setup is 'gentle' enough for use on a RR? I was leery of a 9mm Colt setup based on everything I've read here, but the RDB system seems soft enough that it shouldn't damage a RR. Yes, I would have no hesitation using the Guard on an expensive transferrable lower....even in its default config recommended by CMMG. It runs really fast with their recommended config though. |
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Thanks! Yes, I would have no hesitation using the Guard on an expensive transferrable lower....even in its default config recommended by CMMG. It runs really fast with their recommended config though. |
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Quoted: Amphibian what about the same question but with an RLL and protector with a properly relieved receiver? Thanks for all your input. Much appreciated. However, Ferris Bueller said it best: "It is so choice. If you have the means, I highly recommend picking one up." https://vimeo.com/302204819 |
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I don't have a RLL but would think that the Guard system would be less of an impact than any SBR 556 setup. If you go with just the A5, 556 Tubb Spring and 9mm Kynshot hydraulic buffer (which again works with 556 uppers as well) it will be very soft shooting.
I don't want to get too off track but I'm also working on a new web page going into RoF tuning of other setups using that buffer/buffer tube/spring or variation of this arrangement for other 556 uppers, 5.45, 7.62x39, 300BLk and 9mm Belt Fed. Regarding the Freedom Ordnance 9mm Belt fed, it is straight blowback and really snappy. Using the A5, 556 Tubb Spring and 9mm Kynshot hydraulic buffer has smoothed it out considerably but obviously not where the radially delayed Guard is. I am thinking about doing the spring loaded weight with that setup but the bolt has some more challenges which may work for some of you RLL guys. Pictured below is a top view of the bolt. It does already have a .25" hole in the carrier drilled more forward than the Guard or any Colt pattern bolt but it is drilled top to bottom not side to side. Additionally there is a big horizontal slot that goes through both sides. I think a spring would just fall out one of the side windows. Tried to embed image but didn't work so click here to see a top view of bolt off their site. Pictured below is the bolt weight it comes with. The bolt has a slight concave path for the weight to 'track' in the top and bottom in addition to the counterbored ledge in the back of the carrier. The ID for the weight to slide in is a little under .50" so not like a milspec carrier. I'm thinking about boring out the weight and based on my calculations, I should be able to get a 9/32" diameter piece of Tungsten in there weighing in at 1oz and some room in the front for a compression spring. I was thinking if this works, the same method could be used for other configurations where you are not going to cross pin the weight. For RLL users, you could do something similar....a bolt weight 'sleeve' that would hold the weight and spring. It gets really thin by the buffer detent pin groove at the bottom of the carrier though so was thinking if the sleeve had 'wings' on the right and left or even a cross pin that is perpendicular to the buffer detent pin. If we are not talking about the FM9 bolt, a RLL user should be able to get a bolt sleeve made for a milspec .625" ID carrier to hold more weight. 
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| amphibian. Do you think using the .308 Tubb spring with the A5-Kynshot setup would work, or help with the FO 9mm belt fed upper? I've read some online posts with guys using a .308 spring with "standard" 9mm bolts. I'm looking for the best way to prevent damage to my Colt M16 lower. |
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amphibian. Do you think using the .308 Tubb spring with the A5-Kynshot setup would work, or help with the FO 9mm belt fed upper? I've read some online posts with guys using a .308 spring with "standard" 9mm bolts. I'm looking for the best way to prevent damage to my Colt M16 lower. |
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Best deals I could find on BF to replicate the setup:
Buffer - $108.76 directly at blitzkrieg (promo code THANKFUL) A5 tube- $38 at Optics Planet (promo code BFCYBER) Tubbs Spring - $25 at Midway. If you get 2 this is the cheapest with a free shipping code. $22/each at Tubbs but shipping was expensive for me. CMMG has 10% off and free shipping for a complete upper Optics Planet has the 8" barrel and BCG combo for $300 using the BFCYBER code cant wait to get this put together and pester you with more questions Amphibian 
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Keep an eye on Botach for the buffer. On sale for $90 over there for at least a month but they are out of stock of the 9mm version. I bought one from them as a spare.
https://www.botach.com/search.php?search_query=kynshotion=product The PSA PA10 tube is the same internal length as the A5 (http://c3junkie.com/?page_id=571) for only $20 but out of stock as well. |
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has anyone ever made a rare earth magnet buffer? |
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In response to HDSledge from the other thread about the roller lock system of the MP5 and why I think still think a delayed roller blowback upper for the AR platform would still be good.
It is because even with all the tuning I've done with the Guard, I still think the MP5 is softer. As mentioned in the other thread. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> While the Guard is a step in the right direction, it is not delayed enough for my tastes hence why I kept tweaking mine. As an example, say you push a cleaning rod down the muzzle on a standard 556 AR15 with no round and the bolt forward, it will not move as it needs gas going into the BCG to push the carrier away from the bolt which acts as a 'stationary PISTON' as described in Stoner's patent. (It is annoying to keep hearing the AR15 described as DI like the Ljungman operating system). The bolt in an AR15 is truly locked when in battery. While on the Guard, if you do that the bolt will move immediately. It will rotate from the angled lugs and immediately start pushing the carrier back as well via the cam pin. So it is delayed in a sense of converting the linear energy to a rotational or angular one. That conversion robs energy from the initial recoil impulse that all blowback guns have. I know CMMG posted that in their testing they could easily cut different angles on the 9mm bolt to control this and make it shoot slower but said they are too busy to mess with that at this time. I think they selected what they have now to have the largest window of reliability they can get based on all the variables they test with. Now on the MP5, it would not move immediately, you will feel some resistance from the rollers. As a round is actually detonated, the rollers are pushing out and delaying even more. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> All that said the MP5 while soft shooting is not really tunable...It shoots too fast and the ergonomics and optics selections are limited. I know people are going to say, I can pull singles on the MP5. Well so can I....(well on the full size at 800RPM not the K.) Yes, I can do it but it is clearly easier to do if it were to run slower. On that note, with my current Guard setup running at around 572 RPM, I can have even novice shooters pull singles on it. In fact, everyone that I've let shoot my MP5K PDW side by side the Guard have all said they found the Guard to be more pleasant and controllable to shoot. Not sure if that is due to the high RoF of the MP5K PDW or what. I think if you had a roller delayed blowback upper on the AR, you could get the super soft recoil impulse of the MP5 but with all the buffer and spring options available for the AR platform get it down to a really slow RoF as well. You asked about sweet spot for RoF. For me, this depends on the platform. I find it is easier to pull singles with a mushy trigger like the MP5 and UZI. For example, I can pull singles easier on a mushy MP5 or UZI trigger at 800 RPM vs an M16 running at 800 RPM. With the M16's shorter resetting trigger, it gets harder for me to consistently get singles when it starts going over 700 RPM. You can see in my pictures posted above, that I have been able to get all kinds of RoF with the Guard under 700 RPM but with varying levels of 'bounciness'. I personally would prefer less bouncy and fast vs slow and bouncy. Think about being able to write your name on a wall with a full auto....you need it to be smooth do that and be able to pull singles to dot your I's if you got an I in your name. In my last post that was 572 RPM with the Guard and my custom spring loaded custom weight. Last weekend I did some more testing and was getting good reliability with the weak Tubb 300 BLK spring but my Pact Timer was acting up and wouldn't turn on so couldn't get cyclic rate numbers. It is definitely slower than the 556 Tubb spring but still very flat shooting. I hope to get some RoF numbers for this configuration as well as some suppressed numbers tomorrow. |
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@amphibian ...I have been closely watching your excellent and informative posts with the RDB Guard setup, but have held off on buying the bcg/barrel combo in hopes that Foxtrot Mike reveals another (possibly better?) delayed blowback setup at SHOT 2019 in another week or so.
I really like your objectives of balancing ROF with choppiness. In your testing, have you considered the total mass of each comparative setup? While I don't own an MP5, I held one once and it seemed heavy. "Chopiness" can also be influenced by the total firearm mass with greater mass resulting in less chopiness. Thus, maybe the MP5 is less choppy due to the greater mass. You might consider adding weights somewhere on your setup to help with this. Fortunately, with the RDB setup you can add extra mass to something other than the buffer/bolt (i.e., non-moving parts) and choose what center of gravity or moment arm works best for you. Of course, the downside is a heavier gun to tote around. ;) Thanks again for the superb work! v/r, Esox |
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if you had the pin further forward could possibly use the 2.0 oz steel weight that comes in the Guard tuning kit. So many different scenarios and so little time! I can't say thank you too many times for all your work and dedication to sharing your results. The progress I have made by following your research is huge. Thanks! edit: Tungsten, not titanium. Brain fart. Been having too many of those lately. |
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Quoted: Are you still happiest with the conical spring/washer/.625" diameter x .552" long titanium weight setup? How about this for the titanium rod? Surface scratches an issue? https://www.ebay.com/itm/Titanium-Round-Bar-6AL4V-625-x-6/163145268702?hash=item25fc373dde I can't say thank you too many times for all your work and dedication to sharing your results. The progress I have made by following your research is huge. Thanks! 
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| FWIW, I've been searching for .625" tungsten rod after amphibian posted his results and found this: https://www.kakindustry.com/ar-15-parts/lower-parts/buffer-tubes-and-parts/9mm-carrier-weight-extra-heavy |
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Quoted: Titanium? That's super lightweight. Did you mean tungsten? This one may work. https://www.amazon.com/Castlebar-Polished-Chamfered-Cemented-Tungsten/dp/B07GT3X8TR/ref=sr_1_2?s=industrial |
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Yeah no kidding...I could spend all day tinkering with stuff like this. Let us know if you try out the two springs. |
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The double spring idea is a cool extension to what amphibian put together. Is there room for both springs and still have enough added mass in between? Also wouldn't the outside spring mar the buffer face? Not sure if extended use would mar/damage the buffer face. I've only shot ~50 rounds through it total with nothing noticeable on the buffer. (yet?) I've been meaning to get back to testing but just haven't had the time. |
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Quoted:
@amphibian ...I have been closely watching your excellent and informative posts with the RDB Guard setup, but have held off on buying the bcg/barrel combo in hopes that Foxtrot Mike reveals another (possibly better?) delayed blowback setup at SHOT 2019 in another week or so. I really like your objectives of balancing ROF with choppiness. In your testing, have you considered the total mass of each comparative setup? While I don't own an MP5, I held one once and it seemed heavy. "Chopiness" can also be influenced by the total firearm mass with greater mass resulting in less chopiness. Thus, maybe the MP5 is less choppy due to the greater mass. You might consider adding weights somewhere on your setup to help with this. Fortunately, with the RDB setup you can add extra mass to something other than the buffer/bolt (i.e., non-moving parts) and choose what center of gravity or moment arm works best for you. Of course, the downside is a heavier gun to tote around. ;) Thanks again for the superb work! v/r, Esox |
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Quoted:
Are you still happiest with the conical spring/washer/.625" diameter x .552" long titanium weight setup? As mentioned in my previous post, 95% of my testing has been un-suppressed. In my experience, adding a suppressor on a SMG only adds about 30 RPM (you typically see about 200 RPM increase for rifle caliber like on a 556 M16) or so more to the cyclic rate and if anything increases reliability but is dirtier and then it will get more fouled. So I was thinking that putting the suppressor on would be no big deal. To my surprise, adding a suppressor with my spring loaded tungsten weight is giving me a lot of problems. With the 300 BLK spring it is now a single shot with my MK9K. Swapping to the 556 Tubb spring is better but jamming like every 3 or 4 rounds. I have to remove my spring loaded tungsten weight and it is fine but after shooting more with it, I can definitely feel how much smoother it is with it and am disappointed it is not working with a suppressor. I don't like the way the Guard feels with either of my uppers suppressed. I have an early Guard barrel that came with the dual feed ramp extension and that one was testing with the MK9K. While I was using an SWR Trident on my other Guard barrel that has the single feed ramp. They are both bouncy to me suppressed. I feel like my setup unsuppressed have rivaled the MP5's I have tested against. However suppressed, the MP5's kick's the Guard's ass. Not from a sound perspective, Guard sounds fine like the MP5. It is the flatness, smoothness suppressed compared to the MP5 that the Guard is way behind. I've got some things I'm going to try though so not giving up suppressed yet. I was just hoping to have the same buffer/spring/weight setup to use suppressed / unsuppressed but at this point, I think I will have to make changes every time I add/remove the suppressor for optimal performance. |
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Dang. I have been misreading your test. I was up the impression that you were very happy with the guard suppressed. I was all excited about that! As I just posted, I am happy with the Guards suppression. I think it would please 95% of the people out there. I hung up my blowback Colt setups years ago. My buddy brought his blowback Colt setup out yesterday as well. On a Colt M16 lower suppressed. Clocked at over 1000 RPM and bouncy as hell...hideous. Reminded me why I hate that setup. My suppressed Guard with MK9k was clocked at 686 RPM yesterday. Slower than the MP5 and I can still pull singles with it which is better than what I can do with the MP5 but at a cost of being considerably more bouncy than the suppressed MP5. I am just surprised that going suppressed made such a big difference on the Guard. I've never seen these kinds of differences on any other full auto SMG's. Macs, Sterlings, 9mm Styer AUGs, MP5's, Sig MPX's, blowback Colts, etc....none of them turn into a single shot after adding a suppressor. Again, this is only with my spring loaded tungsten carrier weight. Runs malfunction free without it just not as flat as "I" want. I think most people would be happy with where it is. I'm just not most people. Here is the video I did 3 months ago suppressed with Guard and Endomags w/ NO weight. https://www.youtube.com/watch?v=_XaGtM2NT38 
I don't think I was trying to pull singles at the time. Just messing around. 686 RPM. Again, nicer RoF than the MP5 and just as quiet to me, just not as flat as I would like. 
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No not really. The mass would have to be so small it would be of negligible weight. The only way to do it is to drill a hole further forward in the carrier for the cross pin. I did it; will post some pics tonight. Quoted:
No not really. The mass would have to be so small it would be of negligible weight. The only way to do it is to drill a hole further forward in the carrier for the cross pin. I did it; will post some pics tonight. Quoted:
I've got some things I'm going to try though so not giving up suppressed yet. I was just hoping to have the same buffer/spring/weight setup to use suppressed / unsuppressed but at this point, I think I will have to make changes every time I add/remove the suppressor for optimal performance. |
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Yes, have thought about that but note that I've been doing 95% of my testing all un-suppressed. I know that adding a suppressor is going to throw everything off so wanted to get through all un-suppressed testing first. v/r, Esox |
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Quoted: I didn't communicate my message very well. What I intended to convey was: If your entire M16 weighed 40lbs, it wouldn't be bouncy. The MP5 probably weighs more than the M16. Have you considered total gun mass as a variable? v/r, Esox Just need to get the suppressed configuration to my liking.... |
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As promised, here's how I executed amphibian's great set-up using dynamic mass in the Guard carrier. (of note, my big limitation was getting this to work with a Lightning Link)
Overall layout. New pin hole drilled further forward in carrier. I used a 1.4oz steel weight in between two 20# wave springs with a .125" thick 17-4 SS washer up front (prob a little overkill). Carrier has been cut for link:  The mass itself. It started life as a Grade 8, 5/8" bolt from Ace Hardware. I measured different ones in the store using calipers and the unthreaded portion was pretty much right at .625". I got one that had ~2" of unthreaded shank and chopped it up. Because the mass comes much further forward due to the new hole location, the bottom is clearanced. Additionally, I cut a channel in the top to allow a guide pin to ride in it to prevent the mass from rolling/rotating laterally in the carrier and possibly damaging the LL paddle. (scratches are from test fitting) 
Guide pin in carrier which prevents the mass from rotating: 
As it all sits in the carrier. Rear spring is not captured; entire assembly held in by buffer face.  As mentioned, because I'm using a link, clearance is very important. The paddle needs to be well clear of everything but the carrier trip face. After profiling the bottom of the mass, the one thing I couldn't mess with were the springs. The forward spring was potentially going to be an issue. So I ended up shortening a paddle to clear it. Spring (and washer) would get a little too close to the paddle for my comfort: 
Short paddle next to unmodified one:  I've tested the set-up in both 45 and 9mm. (~50 rnds each) Because I didn't shoot them with the old set up first, immediately change it to this new one, then re-shoot, it's really hard to say if it made a vast difference. I "think" it did, but it also may have been placebo since I had very high expectations going into it. Plus I was rushed, going back & forth between calibers, etc. When I have more time or better yet, someone else with an unmodified Guard willing to go shooting with me, I could do a true side-by-side comparison. What I did notice however was the limited shooting I did do was enough to shorten the springs. Without something there to prevent coil lock, they are getting fully mashed (with some force) on each shot. This is where I could see conical springs being a little better application vs wave springs. This is about what the setup looked like before testing (held in place with finger): 
And now this: 
So I've lost quite a bit of spring tension. Worst of all I can hear the weight moving back and forth now. I think next step will be to try it with conical springs. |
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60-Driver, nice work. I don't envy the additional work you guys w/ RLL's have to deal with.
I think the steel 1.4 oz may not be enough to make much of a difference but as you mentioned, it is mangling your springs so you know it must be doing something just may be hard to perceive the difference. You also lost some weight milling out your carrier and adding an additional hole for the longer weight. Do you have a timer that has built in RoF capabilities that you can use? I noticed you are using a standard roll pin. Make sure you keep an eye on that. Typically spring tension pins are used to secure the weights on these which I think are considerably stronger. I have had one shear apart before using a really heavy tungsten weight in 7.62x39. I was thinking that if one were to go through the trouble of adding another hole forward like you did, to use a bushing for a smaller pin (so not to remove too much weight and retain strength of weight) and then slot the weight. This would prevent the weight from rotating and keep it from failing out when you remove the upper off the lower. I would slot it so the pin never bottoms out on the forward or rearward stroke unless the upper is removed from the lower. |
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Quoted:
As promised, here's how I executed amphibian's great set-up using dynamic mass in the Guard carrier. (of note, my big limitation was getting this to work with a Lightning Link) Overall layout. New pin hole drilled further forward in carrier. I used a 1.4oz steel weight in between two 20# wave springs with a .125" thick 17-4 SS washer up front (prob a little overkill). Carrier has been cut for link: https://i.imgur.com/vHyPsokl.jpg The mass itself. It started life as a Grade 8, 5/8" bolt from Ace Hardware. I measured different ones in the store using calipers and the unthreaded portion was pretty much right at .625". I got one that had ~2" of unthreaded shank and chopped it up. Because the mass comes much further forward due to the new hole location, the bottom is clearanced. Additionally, I cut a channel in the top to allow a guide pin to ride in it to prevent the mass from rolling/rotating laterally in the carrier and possibly damaging the LL paddle. (scratches are from test fitting) https://i.imgur.com/eF3fnZ4l.jpg https://i.imgur.com/qYlxk0Fl.jpg?1 https://i.imgur.com/8AszsCjl.jpg Guide pin in carrier which prevents the mass from rotating: https://i.imgur.com/aL9rUGVl.jpg https://i.imgur.com/pRwOKKCl.jpg As it all sits in the carrier. Rear spring is not captured; entire assembly held in by buffer face. https://i.imgur.com/NsdZl0jl.jpg As mentioned, because I'm using a link, clearance is very important. The paddle needs to be well clear of everything but the carrier trip face. After profiling the bottom of the mass, the one thing I couldn't mess with were the springs. The forward spring was potentially going to be an issue. So I ended up shortening a paddle to clear it. Spring (and washer) would get a little too close to the paddle for my comfort: https://i.imgur.com/Z5QY4Bvl.jpg Short paddle next to unmodified one: https://i.imgur.com/OzIXU57m.jpg?1 I've tested the set-up in both 45 and 9mm. (~50 rnds each) Because I didn't shoot them with the old set up first, immediately change it to this new one, then re-shoot, it's really hard to say if it made a vast difference. I "think" it did, but it also may have been placebo since I had very high expectations going into it. Plus I was rushed, going back & forth between calibers, etc. When I have more time or better yet, someone else with an unmodified Guard willing to go shooting with me, I could do a true side-by-side comparison. What I did notice however was the limited shooting I did do was enough to shorten the springs. Without something there to prevent coil lock, they are getting fully mashed (with some force) on each shot. This is where I could see conical springs being a little better application vs wave springs. This is about what the setup looked like before testing (held in place with finger): https://i.imgur.com/Y72602Xl.jpg And now this: https://i.imgur.com/fwwx3ptl.jpg?1 So I've lost quite a bit of spring tension. Worst of all I can hear the weight moving back and forth now. I think next step will be to try it with conical springs. |
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Quoted:
60-Driver, nice work. I don't envy the additional work you guys w/ RLL's have to deal with. I think the steel 1.4 oz may not be enough to make much of a difference but as you mentioned, it is mangling your springs so you know it must be doing something just may be hard to perceive the difference. You also lost some weight milling out your carrier and adding an additional hole for the longer weight. Do you have a timer that has built in RoF capabilities that you can use? I noticed you are using a standard roll pin. Make sure you keep an eye on that. Typically spring tension pins are used to secure the weights on these which I think are considerably stronger. I have had one shear apart before using a really heavy tungsten weight in 7.62x39. I was thinking that if one were to go through the trouble of adding another hole forward like you did, to use a bushing for a smaller pin (so not to remove too much weight and retain strength of weight) and then slot the weight. This would prevent the weight from rotating and keep it from failing out when you remove the upper off the lower. I would slot it so the pin never bottoms out on the forward or rearward stroke unless the upper is removed from the lower. Quoted:
60-Driver, nice work. I don't envy the additional work you guys w/ RLL's have to deal with. I think the steel 1.4 oz may not be enough to make much of a difference but as you mentioned, it is mangling your springs so you know it must be doing something just may be hard to perceive the difference. You also lost some weight milling out your carrier and adding an additional hole for the longer weight. Do you have a timer that has built in RoF capabilities that you can use? I noticed you are using a standard roll pin. Make sure you keep an eye on that. Typically spring tension pins are used to secure the weights on these which I think are considerably stronger. I have had one shear apart before using a really heavy tungsten weight in 7.62x39. I was thinking that if one were to go through the trouble of adding another hole forward like you did, to use a bushing for a smaller pin (so not to remove too much weight and retain strength of weight) and then slot the weight. This would prevent the weight from rotating and keep it from failing out when you remove the upper off the lower. I would slot it so the pin never bottoms out on the forward or rearward stroke unless the upper is removed from the lower. That said, I don't have a shot timer but I think it's a very useful tool for this sort of testing. I absolutely think it would help dialing in the smoothness. Good to know about the pin! Will switch it out with a tension one. Quoted:
Dang. I love to tinker and tweak but you guys take the cake. Good for the rest of us to be able to follow along.
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[ARCHIVED THREAD] - Full Auto CMMG Guard Tuning (Page 1 of 4)
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