Brownells Gun Techs and debunkers of misguided firearm myths Caleb and Steve usually keep things light. But today they delve into a heavy topic: the common belief that an AR-15 chambered for a “heavy” caliber – .300 Blackout, .350 Legend, .450 Bushmaster, etc. – requires a heavier buffer. Heavy caliber = heavy buffer…. Seems logical, right? Actually, NO. The AR-15 bolt / carrier system is designed to handle a certain amount of gas pressure, and the gas port up front on the barrel is drilled to provide the right amount of gas flow to cycle the gun reliably with a standard 3 oz. buffer. A blowback-operated pistol-caliber upper in 9mm Luger, .40 S&W, or .45 ACP DOES require a heavier buffer to manage the higher pressure of the direct-blowback gas. An AR-308 has a heavier bolt / carrier group, so it needs a heavier buffer to push the BCG back into battery. Sometimes, a heavy buffer is needed to tune your system for short barrel lengths, to slow down the cyclic rate on a full-auto AR-15. A heavy buffer can also be used to slow down the recoil impulse to reduce felt recoil – but the gas flow has to be adjusted to work with that heavier buffer. Most of the time, the standard 3 oz. buffer works just fine. So the myth is BUSTED. You do not need a heavier buffer on an AR-15 chambered in a heavy caliber.
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What buffer weight for 7.62 upper
Wouldn't a heavier buffer in a select fire AR result in a slower cyclic rate?
You guys sound like politicians!
There’s no reason to use anything but standard buffer. Then why do they make optional sizes? Because you may need a different size to tune your rifle. To make it run better. Well then, that solves that, myth busted, no need for anything other than standard size buffer.
I guess no one can say you got it wrong.
You start off saying all you need is a standard buffer, no need to use a heavier buffer. Then you ask why do they make different size buffers and you answer is it’s to tune your system and you rattle off several reasons why you’ve used different size buffers. The. You say myth busted, no need to use anything other than standard buffer. WTF?
Thanks, answered my question before I asked it.
Isn't it true that most rifle are over gassed. To make sure they run on all ammo types? And how is this theory affected by 7.5" short barrels with large cal. Bullets?
Also doesn't heavier buffer weights save wear and tear on an over gassed rifle? If so is that just bolts? or includes extractors and bullet casings?
Thanks again guys much appreciated
I have BCA 18" 450 bushmaster with midlength gas tube and have trouble feeding the third round ejection wise is good and around 4-5 o'clok I replace the buffer spring about 2" longer than my standard ar spring still have same problem thank you
Apparently, Diamondback uses a light buffer in the DB15. When I threw a .350 Legend upper on it worked ok with FMJ and XP rounds, but the heavy 180 soft points were causing no really hard ejection like the gun was over gassed. I got another lower (poverty pony) and put it together with all low end milspec parts, it ran all of them perfectly.
Heads up fellow shooters. If you purchase any Brownells products on Optics Planet you have no warranty. I notified both that I would warn you. Joe Harris
X39 Ars need a word
Great video
Black rifle coffee co mug in the lower left corner!
Off topic question. Is it necessary to epoxy bed a scope mount or a scope in its rings on a precision rifle? And if not, is there a circumstance which might cause it to be needed?
What buffer would you recommend for 300blk 8” to run subsonic rounds
I have a 16" .300 Blackout with a carbine gas system. I am trying to get it to reliably cycle sub-sonic ammo with a TiON suppressor. I have tried a fixed gas block, an adjustable gas block, an H1, H2, and H3 buffer, and just about every combination but it just will not cycle. On the recommendation from a smith, I cut a recoil spring down and it would USUALLY come back to battery, but every 4th or so round, it would not.
When I use the same setup but with my 8.5" barrel (again, .300 BO, sub-sonic, suppressor, and any weight buffer and a fixed gas block), the weapon cycles perfectly … magazine after magazine.
Is it just impossible to use sub-sonic ammo and a suppressor on a 16" .300 blackout? Thoughts on what to try next?
Thanks Brownells for putting this video out! I’ve been searching through the forums, and asking the gunsmiths I know for the answer to this very question! Jerry Miculek just released a magnetic buffer that is designed to dramatically reduce recoil out of an AR-15 (he said in the announcement video, “for MSR’s chambered in 223/556 & 300blk”).
I am recoil sensitive after being disabled in the line of duty, and even though it already has relatively little recoil, I’ve been wondering if I could put that buffer in my 6.5 Grendel to further reduce felt recoil. From your explanation, sounds like I can without a problem!
Yep agree. All of my AR's have either rifle buffers or H3 carbine buffers. Three of them are 5.56 X2 and one 6.5 Grendel that I run Geissele Super 42 H3 buffer and springs in. Two others are a LR308 in 6.5 Creedmoor and and another 6.5 Grendel that run rifle buffer and springs. All are reliable and they don't tear up brass like they did with lighter buffers.
No mention of ammunition type… e.g subsonic vs supersonic ?? 300BLK usually has a pistol length gas tube. Standard buffer weight works well with subsonic ammunition. H or H2 works well with supersonic.
Perhaps it is past time for me to chime in with my .02012 cents. There are a lot of great companies serving we firearm enthusiasts. Brownells has proven themselves to be a cut above most of them. Smyth Busters is a GREAT source of information to be sure. If they don't answer you question in one of their videos, just give them a call.
But it goes beyond that. This past Monday (05/03/2021), I ordered a BCG from another well known, great company. After placing the order, I was informed delivery would be 12 to 14 weeks. So, I came over to Brownells and ordered the same BCG and it arrived yesterday.
Brownells inventory, service, personnel and Smyth Busters all work together to provide a great company with which to do business.
Just installed a spring from a Chevy 1500 and a train buffer. AR runs like butter now.
I run H1 buffers in all my carbine length rifles, and they all have mid length gas systems. For my MK18 I use the H3 buffer and the LMT enhanced BCG. Works like a charm. I may use an H2 buffer for an 11.5” build
This is the most in depth description of AR15 buffer tubes available.