Are all buffers equal? Carbine buffers vs. rifle length buffers, etc....? If I have a carbine that doesn't cycle correctly (failure to feed / failure to extract). Could a buffer make a difference?

No, not the same and yes, could make a difference, but a weapon should not be so finely "tuned" (i.e. sensitive) that the buffer will make a big difference.

However, more info (rifle, barrel length, gas system, ammo, nature of failure, etc) is needed in order assess actual cause; you don't want to treat the symptom.

+1 We need more info about your AR, like component brands, barrel, gas system, BCG, buffer weight/ type, buffer spring, mags, ammo, etc, and detailed description of your procedure before and what happened during failure.

My former and current carbine and midlength gas system carbines with good military surplus ammo and good mags all work fine with standard carbine buffer up to the heaviest H3, even with 9mm buffer.

Here are the typical carbine buffer weights, note some manufacturers use slightly different weights.

BUFFER WEIGHTS:

Standard Rifle - 5.1 oz

Standard CAR - 2.9 oz

H CAR - 3.8 oz

H2 CAR - 4.6 oz

H3 CAR - 5.6 oz

9mm CAR - 5.5 oz (made of steel)

Ok, the "rifle" is a MILES rifle. Bushmaster lower / Armalite upper. We converted them from A2's to flat tops due the sighting system we use. I haven't weighed the buffers, but I'm going to go out on a limb and say that the buffer and spring are the standard buffers that came with a Bushmaster 20" barrel rifle as these weapons were all once Bushmaster A2 20" live weapons before being converted. Standard DI gas system. Barrel length - I have some that are 20", most are the 16" M4. Magazines are the standard stamped type with the green follower. Ammo - M200 Blanks.

The MILES weapons system for those that may not know.........your taking a rifle that was designed to run at pressures of 65,000 + PSI and dumbing it down to around 14,000 PSI. The malfunctions that we experience commonly are failure to feed or failure to extract. Without any doubt I can say that extractor issues have been ruled out. I have been told that 4 things will make a MILES rifle NOT run. Ammo, Magazines, Friction, and Air pressure.

So far I have eliminated magazines as being an issue. I have also eliminated friction. Each and every time before the MILES rifles are issued for use the BGC is checked to ensure that there is proper gas tube / gas key alignment, almost to a point that if you were sliding the BCG in and out blindfolded you wouldn't even know when the gas tube entered the gas key. I'm pretty anal about it. Also, they get lubed up....WET! WET! WET!

So that leaves us with Ammo and Air Pressure. This is where it gets dicey. When looking at air pressure issues on a MILES rifle the first thing I suspect is the gas tube abd the BFA (blank firing adapter). Well, we replaced the gas tubes and the blank firing adapters. Should be no issues there. That leaves us with ammo. The ammo that we are forced to buy (due to contractual obligations) is without a doubt 2nd run blanks that the goverment wouldn't accept. BUT, we did get our hands on some of the "good stuff" and some of our MILES rifles won't even run on it either. Still experiencing failure to feed / failure to extract.

Here is where it even gets more interesting.......As stated above, I have some MILES that have a 20" barrel still. Some I have converted to the 16" M4. Those that I have converted to the shorter barrel run like a sewing machine when fed the "good stuff" and some that still have 20" barrels run like a sewing machine no matter what blank ammo I feed it (the good stuff or the 2nd run stuff). And about half of the 16' M4 that I have may as well be considered single shot wonders no matter what blank ammo I feed it. Understand my frustration?

That's when I thought about the buffers and what impact they may have. Any suggestions?

When you say you converted rifles to carbines, do you mean full conversions with stock and buffer, or are you running 16" uppers on rifle lowers?

Do you have a non-MILES weapons to try your ammo in (w/BFA, of course)?

I'll ask our armorer, but it's been quite a while since any one I know ran MILES.

I stepped in as armorer after this was all done. The conversions. So I'm playing a guessing game right now. They all have the 6 position collapsible stocks. And yes, I have a non-Miles weapon to run blanks through, but the barrel would not be ported like a MILES weapon. Please do check with your armorer. Put me in touch with him if he thinks he can help!

I would say not enough gas or too much action spring.  Buffer shouldn't make that much difference.  Sounds like my Stag when I put in a spring that was too stiff and tried to run Wolf.

Weighed random buffers today on a calibrated scale. 2.9 to 3.0 ounces. Most of the MILES will not run on the 2nd run blanks that we get. Took a leap of faith and took the worst running MILES I had and drilled the gas tap (gas return, (whatever you want to call it) in the barrel the same size as the hole in the A post, thus increasing the return pressure. Problem solved.