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[ARCHIVED THREAD] - Thoughts on the CMMG Guard? (Page 25 of 25)
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you don't need any special tools, a small pin punch to drive out the roll pin and vise to hold the bolt. However you will probably need a new roll pin as the original is probable beat up. Put bolt in the vise with the roll pin hole facing up, start the pin but not enough to block the plunger. put the spring in followed by the plunger the use a spent case or a dummy round and hook the rim under the extractor and use that a as lever to push and hold the ejector down, then with the other hand tap the roll pin in. |
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So today I had the time to configure my returned from CMMG pistol. 8 inch barrel slimmed, tacom 2 port comp, CMMG Lower, standard 223 carbine spring and buffer. Eotech. Great news it is back to the soft shooting gun Fell in love with.I'm a lefty brass hits me in right shoulder. I know that sounds annoying but when it throws at that spot I don't have FTE's, hardly any dot dance. The bolt is not slamming on the open or close. Now let's hope it lives beyond the 1000 round mark. |
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Just posting an update that the new MK10 spring in my .40SW died yesterday around the 1K mark. Ran close to 600 rounds at a SMG match. On the first two stages, it was flawless. Next stage I had 3 FTE's (Failure to Eject)s. I thought it may have had something to do with some new reloads and so went back to the same loads I ran in the first two stages and then I had at least 6 or 7 FTE's. I'm done with the spring loaded ejector at this point. As mentioned before I already gave up on the spring loaded ejector for 9mm. BTW, there were 3 guys at the match that bought the CMMG Guard in 9mm after seeing mine like 6 or 8 months ago... They all run them in semi but they all have several thousand rounds through theirs with no issues and very happy with them.....So YMMV. |
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I hope I'm not jinxing myself here, but I'm at about 3k rounds give or take and my 8" guard pistol has only ever had FTE's when using a brass catcher. It"s never happened without it. The FTE issue must have something to do with rate of fire as I rarely rapid fire mine( I can count the # of mag dumps on 1 hand). |
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Quoted: I hope I'm not jinxing myself here, but I'm at about 3k rounds give or take and my 8" guard pistol has only ever had FTE's when using a brass catcher. It"s never happened without it. The FTE issue must have something to do with rate of fire as I rarely rapid fire mine( I can count the # of mag dumps on 1 hand). There are other running them in full auto like me and even using the same buffer/tube/spring I am and are supposedly beyond 4K rounds on the original spring. |
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I have a thread here discussing issues I had with my 8" CMMG RDB upper with an ADM lower. CMMG supplied some bolt components and at one point a new bolt assembly; while the situation improved there we still ammo loads with persistent failures (to eject). I've attached a spreadsheet image, but don't necessarily expect anyone to look it over. The bottom line is that the carrier assembly from my original "Guard" 16" rifle runs the SBR configuration flawlessly, or as close as matters. The new carrier assembly not so much. At this point I have a configuration that will work in competition environments, but no way I would trust a new similar build for defensive use: I see 300BLK in my future. CMMG has been good to work with and I'm going to update them and see what happens. The strange thing is that the carrier assembly that came with the 8" upper runs flawlessly in my older 16" (Glock) CMMG rifle.Attached File |
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Sorry to hear this. Fingers crossed. I'm at 600 rounds with the Mk10 replacement springs they sent me with no hiccups yet but my confidence in it is just not that great. If the first replacement spring dies as well I have the second one but then what after that? As much as I don't like the idea I may have to sell the upper but.......... I'll be selling it dirt cheap and crystal clear to the next owner what issues these have had and what to expect. I just couldn't in good faith screw someone over like that. I'm watching for how the MEAN roller delayed shapes up. It sounds promising but until there is some real world data out there from honest end users we shall see. Hoping it turns out to be a good setup and worthy of obtaining one. At least @amphibian 's secret sauce buffer/spring/tube combo has worked out fantastically paired with my 5.56 upper so this journey hasn't been a complete wash. I'm sad because I really wanted to like the CMMG RDB system. |
| I've finally resolved my 9mm 8" Guard ejection issues. In the end a replacement ejector spring appears to have solved the problem. It's interesting that the complete bolt assembly provided by CMMG didn't work, but the original bolt with new extractor and replacement ejector spring now functions 100% with everything from extremely soft reloads up to factory ammo. I probably stretched out this exercise more than necessary by inadvertently swapping the two bolts. I do have an occasional light/no strike and I've seen this with both my ADM and BCM lowers; I'll exercise some OCD on the side of cleanliness and see how things go. The innards do get dirty and the "no strike" occurs on what feels like a completely normal cycle and trigger reset so a buildup of some sort would seem to be involved. |
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Originally Posted By rdtompki: I've finally resolved my 9mm 8" Guard ejection issues. In the end a replacement ejector spring appears to have solved the problem. It's interesting that the complete bolt assembly provided by CMMG didn't work, but the original bolt with new extractor and replacement ejector spring now functions 100% with everything from extremely soft reloads up to factory ammo. I probably stretched out this exercise more than necessary by inadvertently swapping the two bolts. I do have an occasional light/no strike and I've seen this with both my ADM and BCM lowers; I'll exercise some OCD on the side of cleanliness and see how things go. The innards do get dirty and the "no strike" occurs on what feels like a completely normal cycle and trigger reset so a buildup of some sort would seem to be involved. Interesting. I thought I was the only one seeing light strike issue. It's maybe 1 every 200 rounds. Better if I keep it clean I've found. Tried a few things but haven't had a chance to shoot this upper in awhile. |
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@amphibian - Weird question: I noticed on your site that you experimented with a 5.45x39 bolt with the CMMG barrel, how was the headspacing on that? Just as bad? I consider myself a basic assembler, not really a smith. I'm looking to do a straight pull build with a 5" barrel and a BCA side charging upper (in my head I'm imagining a super short and quiet suppressed upper compatible with my SBRs/pistols with my Endomags), so I'm hoping that pairing the 5" barrel and upper with the 5.45 bolt will achieve what I want. I'm assuming you didn't shorten the lugs and just created that slope? Will it even chamber unmodified? I'm also reaching out to deadshot to see what they can do. |
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Quoted: @amphibian - Weird question: I noticed on your site that you experimented with a 5.45x39 bolt with the CMMG barrel, how was the headspacing on that? Just as bad? I consider myself a basic assembler, not really a smith. I'm looking to do a straight pull build with a 5" barrel and a BCA side charging upper (in my head I'm imagining a super short and quiet suppressed upper compatible with my SBRs/pistols with my Endomags), so I'm hoping that pairing the 5" barrel and upper with the 5.45 bolt will achieve what I want. I'm assuming you didn't shorten the lugs and just created that slope? Will it even chamber unmodified? I'm also reaching out to deadshot to see what they can do. Regarding suppressing the 5" read my post here: https://www.ar15.com/forums/Armory/suppressed-45acp-CMMG-Banshee-5-barrel-vs-8-barrel/20-511852/ |
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Quoted: Headspacing was the same using the 5.45 bolt. You can drop an unmodified bolt in a CMMG RDB 9mm setup for a single shot setup. Works fine. Cheaper than getting a custom bolt action supppressed 9mm. Regarding suppressing the 5" read my post here: https://www.ar15.com/forums/Armory/suppressed-45acp-CMMG-Banshee-5-barrel-vs-8-barrel/20-511852/ Interesting read, thanks for the link, and thanks for the info. I'm actually finding that the occasional 147 from a few different brands (Federal Syntech, Speer Lawman, and Browning BPT) are going supersonic (confirmed with a chrono, I was surprised) in my 8 inch CMMG barrel/bolt build. I actually bought 158 IMI RN to keep backyard shooting quiet-ish. If I ever get into reloading that'll probably fix the super issue, but for right now I'm looking at the 5" to keep the velocity down. I've been pretty happy with my can (Dead Air Wolf), but I'm thinking about a GSL Phoenix to really do something silly. |
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Quoted: Interesting read, thanks for the link, and thanks for the info. I'm actually finding that the occasional 147 from a few different brands (Federal Syntech, Speer Lawman, and Browning BPT) are going supersonic (confirmed with a chrono, I was surprised) in my 8 inch CMMG barrel/bolt build. I actually bought 158 IMI RN to keep backyard shooting quiet-ish. If I ever get into reloading that'll probably fix the super issue, but for right now I'm looking at the 5" to keep the velocity down. I've been pretty happy with my can (Dead Air Wolf), but I'm thinking about a GSL Phoenix to really do something silly. Don't know if you've seen all my posts on the Gemtech MK9K, GSL Phoenix and the Curtis Tactical CT9KS. I would go with the CT9KS over all those options. Shorter than the MK9K / Phoenix. Lighter and completely serviceable and NO ALUMINUM like the MK9K and Phoenix. Documented here: http://www.c3junkie.com/?page_id=244  |
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Quoted: I reload all my 147, and I reload it hot. 3.7Gr of Titegroup (max charge is 3.6). That is still subsonic even out of a 10" UZI barrel here in FL. Don't know if you've seen all my posts on the Gemtech MK9K, GSL Phoenix and the Curtis Tactical CT9KS. I would go with the CT9KS over all those options. Shorter than the MK9K / Phoenix. Lighter and completely serviceable and NO ALUMINUM like the MK9K and Phoenix. Documented here: http://www.c3junkie.com/?page_id=244 http://www.c3junkie.com/wp-content/uploads/2020/05/300BLK-A5-9mmKynshot-40SWBolt-CT9KS-1024x389.png The only thing better than that can is the bixler mount! |
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Quoted: Interesting. I thought I was the only one seeing light strike issue. It's maybe 1 every 200 rounds. Better if I keep it clean I've found. Tried a few things but haven't had a chance to shoot this upper in awhile. Quoted: Originally Posted By rdtompki: I've finally resolved my 9mm 8" Guard ejection issues. In the end a replacement ejector spring appears to have solved the problem. It's interesting that the complete bolt assembly provided by CMMG didn't work, but the original bolt with new extractor and replacement ejector spring now functions 100% with everything from extremely soft reloads up to factory ammo. I probably stretched out this exercise more than necessary by inadvertently swapping the two bolts. I do have an occasional light/no strike and I've seen this with both my ADM and BCM lowers; I'll exercise some OCD on the side of cleanliness and see how things go. The innards do get dirty and the "no strike" occurs on what feels like a completely normal cycle and trigger reset so a buildup of some sort would seem to be involved. Interesting. I thought I was the only one seeing light strike issue. It's maybe 1 every 200 rounds. Better if I keep it clean I've found. Tried a few things but haven't had a chance to shoot this upper in awhile. Turns out the firing pin hadn't been properly heat treated and was badly mushroomed on the hammer end with some obvious damage on the striker. New FP and all is well. Bryan (CMMG) says he has never seen that; must have been an escape in the supplier's factory. |
[ARCHIVED THREAD] - Thoughts on the CMMG Guard? (Page 25 of 25)
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