AR-15 Buffer weights

[MoBoost]

What's the purpose of the buffer weights. I've heard that removing them will cause anything from busting off the buffer tube to bolt not closing.

I have had mine removed for a year now - and haven't seen any adverse effects - should I expect any?

 

[aestus]

If everything else in your rifle is spec, then functionally nothing. The lack of buffer weights will only increase bolt bounce and felt recoil. Bolt bounce is almost a non-issue for semi-auto anyways. For full auto, limiting bolt bounce is fairly important.

The biggest difference is felt recoil and increased lockup time. A heavier buffer will make the recoil feel softer. This is mainly because the increased lock time will cause a delay in the bolt cycling instead of cycling earlier when gas pressures are higher. This also has a benefit of being easier on the internals of the rifle. Stuck shell casing, ripped case rims, FTE, ect can be associated with not enough lock time before the bolt cycling.

 

[ASP785]

A standard full auto bolt carrier weighs around 8.5oz to a little over 9oz. A JP low mass carrier weighs 6.25oz, as stated on their website. Therefore you take away 2.25oz+ from the system. The 3 steel weights in a standard carbine buffer weigh approximately 1.9oz, which is less mass than the low mass carrier removes. Considering the entire assembly acts as a system (it is all reciprocating mass)...I wonder what those same people spouting falsehoods would say about simply switching to a low mass carrier?

 

[aestus]

A standard full auto bolt carrier weighs around 8.5oz to a little over 9oz. A JP low mass carrier weighs 6.25oz, as stated on their website. Therefore you take away 2.25oz+ from the system. The 3 steel weights in a standard carbine buffer weigh approximately 1.9oz, which is less mass than the low mass carrier removes. Considering the entire assembly acts as a system (it is all reciprocating mass)...I wonder what those same people spouting falsehoods would say about simply switching to a low mass carrier?

Most people I know running the low mass carriers are typically also running adjustable gas blocks to lower the gas pressure and/or running 18" barrels with rifle length gas systems. Makes for a very soft shooting rifle. Not sure if I'd run a JP low mass bcg in a carbine gas, especially in a 16" barrel. Probably would shoot fine, but not optimal.

 

[ASP785]

Most people I know running the low mass carriers are typically also running adjustable gas blocks to lower the gas pressure and/or running 18" barrels with rifle length gas systems. Makes for a very soft shooting rifle. Not sure if I'd run a JP low mass bcg in a carbine gas, especially in a 16" barrel. Probably would shoot fine, but not optimal.

I am not suggesting it is optimal or even desired. However, reciprocating mass in a system is just that, reciprocating mass. Wherever you remove the mass from, your rifle will not die a fiery death because of it; be it the bolt carry or buffer.

 

[Glocktogo]

Too much gas increases felt recoil, muzzle lift and accelerates wear and tear on the gun. Too little gas will cause the last round bolt hold open (LRBH) feature to fail, failure to go fully into battery or a feed stoppage, depending on severity. The most common ways to control gas delivery are adjusting the reciprocating mass weight, adjusting the recoil spring tension, changing the gas system length (new barrel assembly), changing the gas port size in the barrel or using an adjustable gas block. Note that it's exceptionally rare to see a barrel with a gas port that's too small. In most cases, the gas port is either correctly sized, or oversized which overgasses the system.

Most standard carbine length gassed guns are overgassed to increase reliability across a wide range of available loads. For example, PMC Bronze .223 55gr ammo is one of the most underpowered loadings. NATO Spec M855 62gr (AKA, SS109) is loaded much hotter. No manufacturer wants their guns in the hands of poorly instructed shooters using less than ideal maintenance rituals, constantly malfunctioning and giving them a bad rep. So they sacrifice some longevity and extra recoil for 100% function under less than ideal conditions. Some of the 3-Gun rigs are optimally tuned to give the softest recoil with a few select loads.

If one wanted to tune their gun for optimal performance (and I'm not saying this is necessary at all), all you need to do is decide what the lower and upper limits of ammo you're likely to shoot are and go from there. Assuming you have a correctly tensioned extractor (and that's an entirely separate issue in itself), and your carbine is clean and properly lubed (the biggest issue with DI AR's) you can use the ejection pattern to set up gas delivery. Here's a chart you can use.

[Broken External Image]

Keep in mind the above chart is set up for an upper with a brass deflector. Overgassed guns will have a lot of brass marking on the deflector and undergassed guns will have almost none. If you're using a slick sided carrier, the red area will likely be undergassed and overgassed will be indicated by your brass landing 3 lanes over.

Let's say for example that you want to set up to shoot any ammo you can find on the shelf at the LGS (good luck with that!) in a 16" carbine with carbine length gas. Acquire a supply of PMC Bronze 55gr. Then decide how you want to change the gas volume. The cheapest ways are to use heavier springs or heavier buffers. On the Spring side, Sprinco makes three different spring weights http://www.sprinco.com/tactical.html as does Wolff http://www.gunsprings.com/index.cfm?page=items&cID=2&mID=1&dID=79#490

In a standard carbine receiver extension, there are four different buffer weights you can use, standard; H1; H2 and H3. All of them have the same number of weights. A standard has 3 steel weights. An H1 has two steel and one tungsten. An H2 has 1 steel and two tungsten. The H3 has all tungsten weights. Rather than buy all four buffers, you can buy an H3 and with your standard buffer, mix and match weights for the desired result.

As you play with the setup and get pretty close to the desired ejection pattern, do a LRBH test with the PMC Bronze. To do this, put one round in the magazine, hold the rifle loosely and fire. If the bolt locks back, repeat this 4 more times. Then repeat the same test holding the rifle at 90, 180 and 270 degrees. If at any time the LRBH fails, you're probably undergassed and need to use a lighter spring or lighter weight combination in the buffer.

Like I said, if your gun is functioning 100%, none of this is necessary. However, if you shoot for speed or plan to fire 10K+ rounds out of the gun, optimizing gas delivery is beneficial. If your gun isn't functioning correctly and you've ruled out lubrication and other setup issues, this might help.

FWIW, I don't run low powered ammo in my Bravo Co. 14.5" LW Middy, so I have it set up to shoot soft with an H buffer. If I'm ever forced to utilize low powered ammo, I have a standard buffer in the kit to swap out for the H. With the BattleComp 1.5, H buffer and standard Colt buffer spring, the gun barely moves when fired, making follow up hits very fast. Hope this gives some insight on the AR-15 gas system!

 

[1911user]

Great post G2G!

 

[technetium-99m]

A standard full auto bolt carrier weighs around 8.5oz to a little over 9oz. A JP low mass carrier weighs 6.25oz, as stated on their website. Therefore you take away 2.25oz+ from the system. The 3 steel weights in a standard carbine buffer weigh approximately 1.9oz, which is less mass than the low mass carrier removes. Considering the entire assembly acts as a system (it is all reciprocating mass)...I wonder what those same people spouting falsehoods would say about simply switching to a low mass carrier?

Using a JP low mass carrier in a carbine length 16" gun will probably get you an unreliable rifle. The light JP parts should really only be used if you plan on turning down your gas. Just so you know there are a few 3 gunners who use standard weight carriers and buffers with rifle length gas systems and do well. The comp used also has a lot to do with it.

 

[technetium-99m]

Here's a clip of brass flying out of my 3 gun AR. I turned the gas up just a bit after this although it ran perfectly for quite a while (my surefire 60 rounder has never held the bolt open).

https://www.youtube.com/watch?v=KpoGqLfz0r0

 

[ASP785]

Using a JP low mass carrier in a carbine length 16" gun will probably get you an unreliable rifle. The light JP parts should really only be used if you plan on turning down your gas. Just so you know there are a few 3 gunners who use standard weight carriers and buffers with rifle length gas systems and do well. The comp used also has a lot to do with it.

Just so we're clear, the OP stated he had removed his weights and hadn't had seen any adverse effects. He also commented that he had heard people say in doing so, the buffer tube could burst off, to the bolt not closing. Those statements are false. That won't happen. The OP didn't provide any other specifications, so we don't know whether he is running a rifle system with tuned gas, mid length or carbine. The entire point of my statement was routed in the fact that it does not matter where you remove mass from a reciprocating system, be it the carrier or buffer, it all still acts as a system. Without knowing any of the other specifications, it would be very difficult to comment on the reliability of the rifle.

I have never tried using a JP low mass carrier in a carbine system so as I stated above, I am not saying it is wanted or even desirable, only on the fact that it will not destroy your rifle.