I'm trying to help a friend sort out his bolt bounce issues. Whenever we try to use the CAR stock & Shorty uppers we have light primer strikes following the first shot. Between the two of us we have the following buffers...

Colt H Buffer - fail
1pc 9mm Buffer - fail
H3 buffer - fail

Is there something else we can try? Is there another buffer we should try?

So far the buffer experiments have been free. I'm reluctant to tell my friend to go buy a $100 item only to have it not work.

Yes, runs perfect on semi.

With the car stock it passes the lock back on empty mag test...but won't run due to light strikes after first round.

With the rifle stock/buffer it doesn't always lock back on the empty mag test...but runs better. We actually stuck a Popsicle stick behind the mag which forced the mag forward and reduced "short stroke" issues. During the Popsicle stick test it ran reliable, but SLOW.

The car buffer spring has a couple thousand rounds through it.

No one cure is the same for another 16's bounce. The design of this rifle makes bounce issues. First off I have found the buffers are one way to try to cure bounce, and complete uppers are the other. The barrel ext. and the carrier are to blame for the harmonics of the bounce.(just like leting a steel ball bearing hit a concrete floor it bounces) Use a different longer or shorter barreled upper(friends or one of your own try to keep it a shorter barrel under14.5")to see if the m16 will run with car stock.

If it wont run than its going to take some chedder to get it figured out, unless you live in NW Ohio. I have been down this road not too long ago and have purchashed extra and low power hammer and recoil springs, bcm H enidine mgi buffers, Lower parts kit(for timming), lots of ammo, and a high speed camera. One of these combos will work. I will help you if your in my area. I have all the parts and camera to get it figured out. A hammer retarder would be the cats ass for this issue, while slowing down your ROF.

Put the gun back to standard 20" configuration. Totally stock, no heavy buffers, crap hung on the gun etc. Then work backwards.

At this point you have a gun that doesn't run, and have no idea what the problem is. Throwing in different variables complicates things.

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We haven't tried many different ammo types. We have tried multiple uppers...one 5.56x11.5", and one 5.45x10".

We installed a Wolff extra power hammer spring in the lower so we could run 5.45 surplus ammo, but have not replaced any other springs. Maybe we will give that a try next.

When hand cycling everything seems to be timed perfect.

I sure wish I was closer to Ohio...I really appreciate the offer.

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I do know the extra power hammer spring may make the hammer follow problem worse. What happens with that spring is it decreases the lock time of the hammer. So with bolt bounce the hammer will hit the carrier as its bouncing back. I know that the ammo you want to use people say it has a military primer and needs the extra power spring.
I have no experiance with this ammo so I would give up on it for now and get the 556 to run first. Its a long shot to offer any help through the internet but my only combo of parts that could help your friend out would be to order a MGI or Enidine buffer, JP enterprises 5lb trigger hammer spring set(or the 4lb but it may be to light for the 22 conversion or bolth their only $10), Tubb CS or MGI flatwire extra power recoil spring, and some ammo.

This is about a $200 gamble from Midway. I would only use the Tubb or Mgi extra power recoil spring with your H buffer. Then try the MGI or Enidine buffer with the standard reciol spring. The Mgi and Enidine buffers are probley to heavy with extra power recoil springs to cycle with out short strokeing. Oh and by the way you may have short strokeing problems anyways because of your gas port size. Port size for the 11.5" barrel I think is .081 Do check the port size before ordering!

Doesn't spikes make a heavier buffer with tungsten shot in it? That might be worth a try.

But a friend-of-a-friend went the bubba route, pulled out his buffer spring, pulled it until it was permanently stretched out a little bit, and put it back in. While I did go at the bubba-ness... I have to admit, it did work.

Go back to the OEM hammer spring, leave the CAR stock tube on with a "normal" weight carbine buffer and spring. See if it will run in that configuration with the original 20" upper. If not, the carbine stock is the issue. If so, then likely it is trying to run a short barrel that may be the issue. If it runs, try installing the rifle stock/buffer assembly and then using the shorty upper. If it runs only one of the two ways that helps narrow it down. If it runs both ways that also helps narrow it down.

As said, there are lots of variables, and you can flounder around in the dark trying to guess at which it is, or you can go back to the point where it worked and try one thing at a time.

[ETA] also, what length shorty upper(s) are you trying?

The advise about returning the rifle to original spec, then working towards the carbine set-up.....very good to follow.

Also look at the firing pin protrusion,
http://www.brownells.com/.aspx/pid=26477/sku=080-216-013/Product/AR-15-M16-Firing-Pin-Gauge

If the firing pin is at the ragged edge of being close to minimum, I could see to failing to get a solid hit when the bolt is moving into lock-up faster.

Any updates clikclikpull? Hows your friends 16 running or not?

Is it a COLT UPPER ? AND what length?

Get a spikes tactical ST-T2 buffer. It has a tungsten powder in it which acts like a dead blow hammer when it locks into battery.
I've used this on a few problem rifles with excellent results.
http://www.spikestactical.com/new/z/lower-parts-spikes-stt2-heavy-buffer-p-201.html

If it's failing with the 9mm and H3 buffer, then the buffer isn't your issue here. I would first check the timing of the auto-sear with the short upper. If it's good to go, then I would try a new hammer spring.

I have the AA pdw upper and it wouldn't run until I put an h3 in it. Tried colt b and x to slow it down some. B worked good, x didn't.

JP makes a carrier weight insert that can also help.