I bought the "heavy carbine" Odin adjustable buffer for the SP1 conversion M16.  Minimum weight 3.0 oz.

My M16 has a brand new 6920 upper on it & carbine buttstock.  I inspected the FCG and everything looks used but OK condition-wise.  I installed new springs.

The buffer tube is mil-spec dimension.

It runs perfect in FA using a Colt C buffer or Colt H1 buffer, with either a stock carbine spring or the tubbs flat wire spring.  I'm getting ejection at 3:00 to about 4:30 with both the C and H1.

When I tried the Odin Adjustable buffer, it would run OK in semi, but not in FA.  It appears that the hammer would not cock back.  Open the gun, the hammer is forward.

No matter what buffer weight or spring I used the Odin would not run in FA.  It did not appear to be binding up in the buffer tube at all.

This was with Federal American Eagle 55 gr FMJ.

This is very mysterious to me.  It's just a weight, so how could it not work?   I'm a new guy to tinkering with this platform, but I doubt that I used the product incorrectly.  There isn't much there to screw up.

That’s hammer follow from bolt bounce.

The OW Adjustable 9mm buffer is a bit tricky to use.  When installing the weights, one needs to follow the recommendations on the packaging to match the weight used with the caliber, and buffer tube length.
Also, the OW buffer assembly has three screws.  The screw that sets the depth to ensure loose fore/aft motion of the internal weights must not be screwed all the way down as the weights need to "rattle" to provide the anti-bounce effect required for full auto firing.  A second screw is used to hold the fore/aft adjustment screw in place and can be tightened firmly.  And the third screw is used to hold the buffer tip in place, but if one attempts to tighten that screw firmly, the screw will go through the buffer tube wall and into the buffer tip.
As you probably know, loose screws and firearms don't do well together, so one typically tightens screws on firearms as tight as possible.  What I have done on the OW Adjustable 9mm buffer that I have is install the three screws to the proper settings and use a generous amount of nail polish to at best hold the screws in position; or at worse, provide an indication that the screw(s) are coming loose.

And FWIW, I've only used an OW Adjustable 9mm buffer in 9mm and .45 ACP full auto ROF testing.  As it did not produce as low ROFs as did the best hydraulic buffer, I now keep the OW buffer as a backup with a semi auto .45 ACP AR-15.

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Best of luck.
MHO, YMMV, etc.  Be well.

When I used the Odin buffer, the weights rattled a little inside, but that was with the big screw tightened down snug.

It's a shame it doesn't work right out of the box, because it's actually a pretty good idea, and it seems well made.

Considering that the gun functions well with the Tubbs spring and standard spring with the Colt C buffer and H1 buffer,

I figure that I'll just get a Colt H2 buffer as well, try that and call it good.

My understanding is that Colt uses either a carbine length or rifle length gas tube, and that the M4 has an H1 buffer and the M4A1 has an H2.

My semi-auto 6920 came with the H1.

I'm also going to change the whole FCG out with Colt parts, just to be sure everything is 100% GTG.

Thanks.

I just read up on bolt bounce a little.

1. Would it be correct to say that a heavier buffer generally reduces bolt bounce?

2. Would it be correct to say that a stiffer recoil spring reduces bolt bounce?

I mean "within reason" for both.

From what I've read, it appears that the Tubbs spring and H2 buffer are favored by some for a carbine length gas tube like on the 6920 upper that I have on the gun.

Also,

3.  Is it possible to get a out of battery discharge from the M16?   I've heard about AR15s slam firing, I don't know the circumstances.

Thank you for that information.

I'll screw it together again and see how much it rattles relative to the Colt buffers.

Haven't tried the Odin or different springs, but have tried various weight buffers, the MGI rate reducing buffer, and Kynshot hydraulic.
I prefer the Kynshot for rate of fire and smoothness of operation.

Amphibian has done a lot of testing for smoothness and rate of fire, but his tests haven't really helped me much as I like to run old school with a 20" upper and iron sights.
Although I have been meaning to talk to Helix gunsmithing in St. Louis to see if they could modify a 20" upper with standard front sight base with a valve to adjust gas.
I know there is a gas tube available that is "adjustable" but it has several different orifices and can't be micro adjusted.

RCA

I had the Odin in mine, but once I got the Kynshot it was put into one of the semis.  I can’t recall how it was set up in mine with the Tubbs spring.

Instead of getting an H2 buffer, use one of your tungsten weights in the H1 and make sure it works.  It would suck to have another part you don’t need around unless you’re wanting to tinker with other ARs.

I’d ditch the OW buffer. Three set screws to loosen under fullauto use sounds like a big liability. My M16s have standard carbine springs with h2 or h3 buffers and run great.

I bet your counterweights don’t have enough travel distance inside the buffer to act as a dead blow hammer and resist bolt bounce. Adios that silly buffer.

In general it’s not possible to have an OOB discharge in an M16. With hammer follow, the hammer is dropping at a time that the firing pin cannot ignite the primer.

At the risk of sounding like a dick did you bother to read all the info that amphibian provided in your other thread?

I've run hydraulic buffers for years, first one was an Enidine I bought used and it eventually failed. I bought a couple Kynshots and they've been solid.

Finally went with amphibian's A5 / Kynshot RB5007 setup and I'm sold. It delivers a very smooth recoil impulse and slower cyclic rate. If you want a cheap A5 tube look at the PA10 308 buffer tube (#506797) from PSA they're about $20 but you'll probably have to email or call to order one as it doesn't come up when searching their site.

The only downside I've experienced is that the bolt catch is more difficult to release (with one finger in an ambi lower w/DIAS) when it is locked back which I assume is due to the hydraulic pressure of the buffer along with the recoil spring. It also takes more effort to overcome the hydraulic action of the buffer when you manually lock open the bolt.

One thing that I noticed when testing various recoil spring/buffer combinations (in a carbine length buffer tube with 16 in. bbl. 5.56 and .223 Rem ammo) was that proper LRBHO was not always achieved.  Sometimes no LRBHO could be had and other times the bolt catch would latch on the carrier, not the bolt head.  I limited ROF testing to only configurations that provided correct LRBHO.

With 9mm M16 shooting, I don't have the LRBHO.  The Sylvan Arms (Glock mags) and VM Hytech (Uzi mags) magwell adapters don't provide LRBHO capability.  So the potential choices of recoil spring and buffer is more broad.

MHO, YMMV, etc.

I read every word that was written in the other thread and I appreciate the advice from everyone.

I got the Tubbs spring on amphibian's advice.  

At this point I'm still in basic mode, just looking to get a spring and buffer that will let the 6920 upper on my M16 reliably eat all the bulk ammo that I will buy for it.  As opposed to the higher end scientific gunsmithing.

I would also be reluctant to use a spring and buffer that failed to LRBHO properly.  Technically, that would count as a malfunction, wouldn't it?

I understand the slow cautious approach but in this case the setup outlined by amphibian just flat out works. I ran a rifle stock & buffer for years on my SP1 because I was afraid I'd mess up the gun.

I reload most of what I shoot except 22LR of course and I've not experienced any function issues related to the buffer system.

It runs with NATO spec stuff, Wolf 223, cheap Russian 7.62X39 along with a variety of my 55 & 62 grain FMJ reloads and even frangible reloads. Just for fun I ran a mag of my subsonic 230 grain coated cast lead reloads through it one afternoon - again no issues.

Good luck with your quest.

That's a good idea.

It guess it wouldn't hurt to have the H2 laying around, it seems to be fairly useful, I might shoot zippier ammo at some point.

I only have the Fed Am Eagle right now

H2. Done.

Completely agree with this. I was using an H2 + Tubbs but decided to try Kynshot-RB5005 and have never looked back. Absolutely fantastic with 556 and the CMG 9mm upper using Endo mags.

Isn't that model for an AR10?

My 2 cents....  If you look at my site, I test all kinds of buffers / springs.  I really don't care what model is 'intended' for what.  If it breaks, I don't mind buying another one if the performance is worth it and I am using outside of the design parameters.  
A good example is the RB5007.  When I started testing it for the CMMG RDB system and told them how happy I was with it, they didn't seem to care.  Then years later, you see videos on their site recommending it for the CMMG RDB system.  I also did the same for RB5005.  I do prefer the RB5007 over the RB5005 but don't want to get too off topic on the reasoning.  I run the RB5007 for 556 which I typically is softer shooting than a straight blowback 9mm so I think it will work just fine.

Another example is the Geissele SSF.  It is not supported for use in pistol calibers and I don't blame them.  They have no idea how well tuned something is.  If I break my SSF, I won't go crying for a replacement.
If you look at how smooth my tuned 9mm is, it is way smoother than most other 9mm configurations as well as most 556 configurations as well but again the vendor has no idea how well an end customer's setup is tuned.

I ran into the same problem with a 16” I had shortened to 14.5”.  It would run with a standard carbine buffer but didn’t have enough ass to hold open on the last round with the Kynshot.  It would lock open on the carrier, but not the bolt face…about the travel distance of the buffer piston.  I love the feel of the buffer and opened up the port from 0.063 to 0.067.  Four thousandths was enough to make it right.

In my case, I tune my uppers to the one lower, as I have no other SP1 pattern lowers to top with my creations.  That might not be the answer, but it’s one of many possibilities.

Interesting.  The KynSHOT RB5005 was one of several buffers that did not provide proper LRBHO in 5.56 use for my set up [16 in. 5.56 bbl., standard length buffer tube, so the RB5007 and RB5015HD could not be tested].  What did work, and what I use for 5.56 (and .223 Rem), is the RB5000HP with a Sprinco red spring (that I've found to perform about the same as a standard Tubbs flat wire spring, but is a lot easier to put in and take out).
For 9mm, I use a B & T AR9 buffer and standard AR carbine recoil spring (no LRBHO, so no spacer).  With a straight blowback, 17.1 oz. BCG and 5.5 in. 9mm barrel, the average ROF is 655 RPM.  To me, trying to get any lower ROF isn't worth what it would cost.

MHO, YMMV, etc.

I looked your site over and I see that you have done a ton of very detailed testing.  There is an impressive amount of very useful information.

Seeing as how I have the regular coil spring, the tubbs spring, the carbine buffer and the H1 buffer that I swiped from my semi auto 6920, I was curious to see how an H2 would work.

Sort of as a baseline set of data.

Yesterday I used the tubbs spring and a new Colt H2 buffer and Federal American Eagle.  I measured the approximate center of the empties with a carpenter's tape and they are landing, on average, at 4:06 PM with the H2.  According to my calculator.

That's with a new 6920 upper on it.  

I didn't think to bring the 20" upper that came on the gun originally.  The gun originally came with a 20" upper, C buffer and regular carbine spring, and I would imagine that the empties would eject more towards 3:00 PM with that setup.  I'll try it next time.

I like to tinker, I'll try the hydraulic buffer, etc, eventually.

One thing that has been missing in this discussion, and I am amazed that “amphibian” didn’t mention, the gas supplied to the mechanism. The system needs just enough gas to activate the LRBHO, but no more than that. Extra gas pounds the buffer into the end of the receiver extension (buffer tube). Of course with great mass (heavier buffer) the system might need a little more gas to lock back. A heavier spring causes more gas to be needed to overcome the stronger spring, but then that heavier spring will tend to slam the carrier into the barrel extension harder, which will tend to make greater bolt bounce.

The gas port in most barrels are larger than needed because the manufacturer wants to be sure that the upper runs with dirty underpowered ammunition. OP, if you want your Colt 6920 upper to run with your carbine receiver extension, I am sure a H1 with a standard carbine spring should work. It will tend to run fast and pound the receiver extension. If you want it to run slower, softer, with better control, add a .308/Vltor receiver extension, Kynshot 5007 buffer, and install a good adjustable gasblock to the barrel of your upper. Be aware that all adjustable gas blocks are not full auto rated. Good luck with your M16 project.

Scott

ETA, a standard carbine buffer to too light for full auto use. They work fine in a semi auto, but will tend to cause bolt bounce issues with a carbine length upper.

amphibian is the expert in all buffer matters. Based on his research, I went with the RB5005 because it worked with carbine tubes and I already use the Tubbs in all my ARs. Knock on wood, I haven't had any LRBHO problems except on the last round of the Mean arms upper though I think the new mags might fix that but I still have to test it with that buffer. I am with you in regards to ROF, I could care less and am only looking for smoothing recoil.

I'll get around to the more fancy options sooner or later, I like to tinker with stuff.  It's nice that there are so many excellent products and so many scientific-minded users.

I kind of suck at shooting it, but I've only shot maybe 10 or 12 mags and just dicking around.  It jumps and vibrates a lot more than my Thompson or UZI, that's for sure.

If I can eventually pass the paper plate test at 100 yards, that would make me happy.  

And the 6920 upper has excellent accuracy.  Actually kind of amazing.