buffer weight

[Koda]

I guess I just assumed you biult the upper too. My bad.

There have been reports of undersized gas potrts, misaligned gas blocks, defective gas blocks, etc. You may have to dig into that if the spring doesn't solve it for you.

What brand is the upper?

No worries, a lot build their own its a good question.

My upper is a Grendel Hunter, 20in bbl 8 twist.

[montana]

No worries, a lot build their own its a good question.

My upper is a Grendel Hunter, 20in bbl 8 twist.

Factory built does not mean built correctly.. QC problems can occur with any firearm or part.

[v4lu3s]

I ONLY run H2 or heavier buffers in all AR platform. The 2.9-3 oz buffer is less reliable all around and is not used im any military specification. These days I am doing new builds with Vltor A5/BCM Mk2/SOLGW Loyal/Forward Controls length systems. Most every AR is overgassed and I have had what looked like short strokes actually be under sprung under buffer systems where the bolt was slamming back bottoming out and then bouncing so hard that the catch is not getting it nor was it stripping the next round. I only see you then out when the bolt catch got broken off.

[montana]

I ONLY run H2 or heavier buffers in all AR platform. The 2.9-3 oz buffer is less reliable all around and is not used im any military specification. These days I am doing new builds with Vltor A5/BCM Mk2/SOLGW Loyal/Forward Controls length systems. Most every AR is overgassed and I have had what looked like short strokes actually be under sprung under buffer systems where the bolt was slamming back bottoming out and then bouncing so hard that the catch is not getting it nor was it stripping the next round. I only see you then out when the bolt catch got broken off.

The heavier buffers were developed to slow carrier velocity and prevent bolt bounce on full auto..The H 1 was developed to slow carrier velocity on the M4 platform ( allowed more time for the magazine to push the next cartridge into place) and the H2 was developed to stop full auto bolt bounce on the heavier barreled M4A1..The H3 buffer was developed for the now defunct firing port weapon..

With an adj gas block, heavier buffers are completely unnecessary in any semi auto carbine AR if the rifle is well maintained..

Heavier buffers on an over gassed semi auto AR rifle is a band aid and not a cure..Even with heavier buffers, the over gassed system will pound on the firing pin retaining pin and is hard on gas rings..

If the rifle is not going to have an adj gas block, then I will use a heavier spring with a lighter buffer and will only use the heavier buffers as a last resort..

The more reciprocating mass, the more felt recoil..

I personally don't care for the Vltor A5 system and use only the standard carbine length system..

A lot of different opinions in AR world..

[Happy2Shoot]

I use the Xtra-Heavy buffer 8.5oz from heavybuffers.com for a 8.5" 5.56 pistol that I shoot suppressed.

It is smooth, recoil is much improved, and double-taps at 25 yards on a 2 second rotating target are easy. It has an adjustable gas block, but that wasn't enough. I set the gas block to lock back the BCG on an empty mag with one extra click open for a margin of error when dirty or cold or both. With the standard buffer weight I was getting gassed out and my bolt speed was too fast. It would jam on average once per magazine. Usually the jam was a new round wedged in with the spent round in front of the chamber.

If your heavy buffer isn't "bottoming out" on the back of your buffer tube the the extra weight will help with felt recoil. The low mass buffer smacking the back end of the buffer tube is a big problem for felt recoil. Also, the low mass buffers fully compress the spring giving you full spring return at full speed. A high mass buffer may only compress the spring 75%. Given the same (or less) spring compression, a higher mass object will return slower than a lower mass object.

I use their 6.5oz buffer for my 12.5" 5.56 and 6.5 Grendel pistols.

[v4lu3s]

I disagree with many things you say, both from first-hand experience as well as formal education. But like you say there are a lot of opinions and I used to have a lot of opinions until I actually took an AR-15 armorers course from a high-end manufacturer. They AR-15 was never designed to have an adjustable gas block it was never designed to have a light buffer it was never designed to have a light bolt carrier group. The 3 oz buffer is a cost cutting measure for the civilian market. The condition that we call over gas is designed into the system to enable greater reliability however when you go and over gas it and put a soft spring and lightweight buffer you create the potential for a lot of reliability problems. An adjustable gas block is a Band-Aid for a poorly balanced system as well. However where a standard military weight buffer and good spring can cover up for other problems and enhance reliability the adjustable gas block without frequent cleaning almost always gums up carbons up and becomes a permanent setting.

[v4lu3s]

The heavier buffers were developed to slow carrier velocity and prevent bolt bounce on full auto..The H 1 was developed to slow carrier velocity on the M4 platform ( allowed more time for the magazine to push the next cartridge into place) and the H2 was developed to stop full auto bolt bounce on the heavier barreled M4A1..The H3 buffer was developed for the now defunct firing port weapon..

With an adj gas block, heavier buffers are completely unnecessary in any semi auto carbine AR if the rifle is well maintained..

Heavier buffers on an over gassed semi auto AR rifle is a band aid and not a cure..Even with heavier buffers, the over gassed system will pound on the firing pin retaining pin and is hard on gas rings..

If the rifle is not going to have an adj gas block, then I will use a heavier spring with a lighter buffer and will only use the heavier buffers as a last resort..

The more reciprocating mass, the more felt recoil..

I personally don't care for the Vltor A5 system and use only the standard carbine length system..

A lot of different opinions in AR world..

The lighter buffers were developed as a cost-cutting measure for the civilian Market. And heavier buffers do not create or have anything to do with heavier recoil they reduce recoil by having more mass because it slows the cyclic rate, and the buffer weight moves slower because the laws of physics. When you impart the same energy to a heavyweight versus a lightweight the lightweight always moves much faster. A standard spring and a 3 oz buffer is far more likely to bottom out in a Carbine length receiver extension and that is where you will definitely feel more recoil.

An adjustable gas block is also a Band-Aid for a poorly balanced system. The system was designed to be over gassed for reliability, but the system was also designed around a four to five and a half ounce of buffer from the get-go.

If you look at a military M4 they run a heavier buffer than the 3-oz civilian buffer. With a carbine length gas system with a heavy bolt carrier group. They are over gas but they are reliable.

Obviously it's the internet but I've spent 15 years building ARs as a hobby. The only thing I've learned through that is the more I learn the more there is to know so I finally recently went and took a certified armorers course from Sons of Liberty Gun Works and learned more in the first 4 hours that I had in the past 15 years.

[biodsl]

If the rifle is not going to have an adj gas block, then I will use a heavier spring with a lighter buffer and will only use the heavier buffers as a last resort..

A standard spring and a 3 oz buffer is far more likely to bottom out in a Carbine length receiver extension and that is where you will definitely feel more recoil.

Then you agree with Montana; a stronger spring is better approached than a heavier buffer?

[montana]

The lighter buffers were developed as a cost-cutting measure for the civilian Market. And heavier buffers do not create or have anything to do with heavier recoil they reduce recoil by having more mass because it slows the cyclic rate, and the buffer weight moves slower because the laws of physics. When you impart the same energy to a heavyweight versus a lightweight the lightweight always moves much faster. A standard spring and a 3 oz buffer is far more likely to bottom out in a Carbine length receiver extension and that is where you will definitely feel more recoil.

An adjustable gas block is also a Band-Aid for a poorly balanced system. The system was designed to be over gassed for reliability, but the system was also designed around a four to five and a half ounce of buffer from the get-go.

If you look at a military M4 they run a heavier buffer than the 3-oz civilian buffer. With a carbine length gas system with a heavy bolt carrier group. They are over gas but they are reliable.

Obviously it's the internet but I've spent 15 years building ARs as a hobby. The only thing I've learned through that is the more I learn the more there is to know so I finally recently went and took a certified armorers course from Sons of Liberty Gun Works and learned more in the first 4 hours that I had in the past 15 years.

The original CAR15 used by SOG during the Vietnam war used the standard buffer..It was used in the first civilian Colt carbine.. I gave the reasons for the increase of buffer weights used in the M4/M4A1 and cost cutting was not one of them..I tried the VltorA5 on my daughters rifle and she was not impressed and neither was I.. I returned it back to a standard receiver extension..

Heavier buffers do create more recoil impulse, which is why competition rifles use lighter carriers ( less reciprocating mass equals less recoil).. The caveat is the gas (ammunition type) has to match the recoiling weight/force being used..If an AR is over gassed, a heavier buffer is beneficial if there is no method to adjust the gas, but it is a band aide approach when it is possible to adjust the gas/ammunition to the rifle.. I have found it is better to increase recoil spring strength with a standard buffer than to use a heavier buffer with a standard recoil spring to mitigate recoil impulse..

An adjustable gas block will only restrict the available gas, not increase it.. The difference between military rifles and civilian rifles is the plethora of different ammunition being used by civilians compared to the military's smaller set of ammunition standards..



I'm not going to despair SOLGW or anyone else..I have great respect for Mike Mihalski SOLGW, Chad ( who I met personally at a Colt armorers class and call him friend) from SOTAR, Caleb from Brownells and others, but I don't agree with everything they say..By the way, none of these gentlemen agree 100 percent with each other..That said, I will take the Pepsi challenge with my rifles against anyone when it comes to recoil management..

Different builds require different approaches when building an AR rifle, whether it is reliability, accuracy, recoil management or combinations of each..Choose your poison!

[LRRPF52]

I ONLY run H2 or heavier buffers in all AR platform. The 2.9-3 oz buffer is less reliable all around and is not used im any military specification. These days I am doing new builds with Vltor A5/BCM Mk2/SOLGW Loyal/Forward Controls length systems. Most every AR is overgassed and I have had what looked like short strokes actually be under sprung under buffer systems where the bolt was slamming back bottoming out and then bouncing so hard that the catch is not getting it nor was it stripping the next round. I only see you then out when the bolt catch got broken off.

The XM177E2, Colt 653 M16A1 Carbine, Colt 723 M16A2 Carbine, Colt 727 M16A2 Carbine, and early M4A1 and M4 Carbines all had 2.9oz to 3.0oz buffers up through about 1996.

I’ve done CQM ranges where I burned through 1100rds in maybe 4 hours with the earlier M4 pre-SOPMOD barrels and buffers.

The primary purpose of the different buffer weights are to correspond with the barrel mass to counter carrier-bounce in FULL or BURST Automatic fire modes.

M16A1 and M16A2 have heavier barrel mass than the early Commandos.

The 653 had the lowest mass of all the 14.5” guns because it was pencil profile.

Early 723s had the same profile, but 1/7 twist to fire M855.

727 had the XM4 barrel profile with the M203 step cut and heavy forend, which was eventually used on M4/M4A1 production from 1994-2003.

The M4 carbines used all of the different buffer weights, depending on year of manufacture or update.

It started with standard buffers 2.9-3.0oz 1993-1997.
Then went to H in 1997, and H2 in 2003.

If you have a heavy barrel profile like on the SOCOM M4A1 pipes, the H2 buffer is meant to counter carrier bounce. Carrier bounce is primarily a full auto concern.

You can run 2.9oz buffers with extra power action springs and they run great in 6.5 Grendel. That’s what is in my 12” Grendel right now, which I’ve been shooting regularly since 2017 as my primary choice of my 7 Grendels.

I spent several years prior to that focusing on the 17.6” Lilja barrel build, and from 2009-2014 focusing on the 16” AA Grendel build.

I did use a Spike’s ST-T2 buffer in the 16” MLGS Grendel, which worked very well.

I’ve tried a lot of different combinations in 16” MLGS Grendels from AA and Lilja, and all were pussycats with a standard carbine and spring set-up.

I do like the ArmaLite/Vltor A5 RET system as well.

[montana]

The primary purpose of the different buffer weights are to correspond with the barrel mass to counter carrier-bounce in FULL or BURST Automatic fire modes.

The main reason for the added weight (H buffer) in the M4 was the adoption of the M855 bullet that had a different ogive than the M193 bullet that was causing feed malfunctions, not bolt bounce..

The original fix was the addition of feed ramps in the upper receiver.. Colt then added a tungsten weight to slow the carrier down to allow the magazine time to present the cartridge for proper feeding..Colt maintained the feed ramps as a redundancy for proper feeding and to keep the M4 TDP as Colt intellectual property when the government tried to claim ownership..

https://youtu.be/DYf-MLMODhA?si=zdMg_5I9DaHqUGYc&t=755

[LRRPF52]

The main reason for the added weight (H buffer) in the M4 was the adoption of the M855 bullet that had a different ogive than the M193 bullet that was causing feed malfunctions, not bolt bounce..

The original fix was the addition of feed ramps in the upper receiver.. Colt then added a tungsten weight to slow the carrier down to allow the magazine time to present the cartridge for proper feeding..Colt maintained the feed ramps as a redundancy for proper feeding and to keep the M4 TDP as Colt intellectual property when the government tried to claim ownership..

https://youtu.be/DYf-MLMODhA?si=zdMg_5I9DaHqUGYc&t=755

They had been shooting millions of rounds through Colt 723s an 727s with extended feed ramps from 1985-1993 until M4A1s were adopted in JSOC in 1994. The extended feed ramps were part of the M16A2 carbines (723, 727, 733) already in the 1980s, along with 1/7 twist for M855. The ogive on M855 is actually more easy to chamber in short throats than M193, since M193 is tangent ogive, and M855 is secant.

Extended feed ramps were introduced on the Colt 723 due to the 2 decades of prior of experience with the CLGS XM177, XM177E2, and RO653 14.5” M16A1 Carbines, which exhibited faster cyclic rates. The increased cyclic rate would sometimes beat the magazine spring lift of the cartridge stack, and slam projectiles back into the case when the meplats hit the inside lower edge of the upper receiver, just below the barrel extension feed ramps. M855 run at 5.56 pressures with the heavier bullet would increase the cyclic rate, especially in hotter ambient temps.

This is where the extended feed ramp design change was made on the carbines. The Colt 723 and 727 laid the core operating system design for the XM4, which began development in the 1980s. Here’s an older Colt brochure on one of the 723 showing the addition of extended feed ramps in the 4th bullet point down.



Here’s another older brochure showing the first configuration of the Colt 723 and 733 Carbine and Commando. There were several different variants of each of these, mainly with different barrel profiles and upper receivers for the 723. Initial uppers lacked the brass deflector, while the newer Abu Dhabi C7 upper with deflector was introduced around 1987 if I recall. Some guys had them and some didn’t in Panama in 1989. The 727 was standard with an A2-looking upper, but had extended feed ramps inside. The 727s all had the stepped profile barrel with heavy fore end with a cut for the M203 bracket. This barrel profile was not on the original 723s, but became more common towards the later years of 723 production and barrel changes by Unit armorers.

[montana]

Thanks for the correction on the bullet ogive not being the problem, makes sense..