Buffers & Springs

[tom12.7]

What if you simplify to a further degree and say there are only 2 weights without an internal spring that have different masses and have space to travel in that buffer. Which could preferably be placed in what position?
What position would the weights be when in forward travel? They would be rearward, and have a time delay in collision to the front of the buffer to counter the inertia of the rebounding carrier. How much space is "needed"? It takes time to travel the distance. It does good to counter the rebound, it hurts it if it "chases" rebound forward in terms of "bounce".
So let's look at this further, we know that the lower mass items "bounce" more in displacement when compared to higher mass items in that collision. The BCG and buffer housing is a higher mass than the weights in the buffer. We know that energy is bled from the bounce in the system and we can't just counteract mass with that same mass. If we look at the combined mass with a solid system, as if it was just bar stock, then there is a definite bounce that we want to control or reduce. The magnitute of the bounce diminishes quickly as the energy gets used up, lets say 3-5 cycles. The first cycle has the highest magnitude and it falls off from there quickly.
If the higher mass is towards the muzzle, the inertia of that higher mass doesn't influence as much toward the BCG rebound. The reduced mass behind it has the additional collisions and rebounding.
If the higher mass is behind the lower mass in the buffer, if timed properly by provided displacement of them has a higher inertia to counteract the rebound of the carrier that combination can reduce it well, that's another timing issue. Remember that the net isn't zero, there are losses, and they come quick, 3-5 cycles of "bounce" is about it. In this example the lighter component inside the buffer runs out both ways, but can have the initial reduction in "bounce" by using that lower mass with a higher one as a whole.
While this doesn't sound cut and dry, it isn't, because it isn't.
There are ways to reduce the magnitude of the first "bounce" in the operation that further lessens the same as it cycles to zero.
The frequency, displacement and other items come into play in just buffers alone. Add in other items like internal springs, etc are other variables.
In general, more mass can be beneficial behind the lower mass, but there are examples when the opposite is true. Many things can be in play here.
An anvil doesn't respond differently if mounted to the ground or on a maintained velocity, neither does the swinging pendulum of ball peen hammers posted above. That's just the perspective it. The physics of it remains the same.
Sorry, but this has been a long post on counteracting mass in motion with mass in a different velocity. We know the "end goal" is to reduce the bounce in FA, some things hurt, some things help.

[Joe Mamma]

I'm still not sure how much of a difference things like weight position matter. Once you start looking at that level of detail, I think there are many other factors that come into play like distance between the weights, size of the cavity for the weights, friction between the weights and inner buffer surface, etc.

I do appreciate your post and perspective.

Joe Mamma

[tom12.7]

At that point, it is splitting hairs. More of a difference would be made in observing operation by looking at the stacking (or lack of) of the conventional buffer weights during initial operation versus the position of the platform. Meaning parallel to ground, perpendicular pointing up, and perpendicular pointing down.

[Iraqgunz]

I was just having this discussion the other day at Vltor and I suppose someone else can chime in. With the use of the biasing spring, it would mean that the weights would always be in the same position. All things being equal, it would mean consistent locking and unlocking.

I'm not sure how much of a difference it makes if you have individual weights or one solid weight (loose). But let's say it matters. Then do you think it matters what order the weights are in inside the buffer body (heavy weights up front, or in back, or staggered every other, etc.)?

Joe Mamma

[tom12.7]

The addition of a biasing spring in the A5ish manner is another variable added in. The addition can have many positive attributes. Not only from a consistency standpoint in unlocking, but in over travel time, as it takes more time to compress the spring in the over travel. The base system lacks in over travel time, and base platform modifications to compensate for things do not always equal net positives for all. In locking, the bias spring can have advantages to use inertia with the spring to reduce BCG bounce. The problem I have with that is that it seems one spring cannot do it all as well as dedicated springs for that mass. As in a A5H0 would not use the same spring as an A5H4. I do think the concept is great, and I use their products. I think that an evolution of the concept would be better with internal springs dedicated to their masses or mass range.

[SmugPePe]

About why colt shipped civiy ar with h1 meanwhile socom m4a1 with h2... its because socom would have strict steady diet of hot 5.56 ammo meanwhile civiy would have freedom to shoot much weaker ammo like tula and with heavier buffer than h1 the risk for failure is unacceptable higher for civilian. And about the weight of barrel and bolt bounce yeah accord to physics thats true heavier barrel would be more resist to change in movement causing lighter action mass to bounce more than it would have if it was heavier or the barrel was lighter. But the ammo would be bigger reason for the h1 with civiy colt and that civiy colt wouldn't be ran full auto.

[zeus100]

How so?

6920 is a carbine gas system on a 16" barrel. A bit different animal than the M4 or M4A1, too.

though both are carbine gas, I dont see how barrel weight has anything to do with BCG travel rates. Isn't the 6920 a semi-auto only where the M4s are select fire? having buffers with slightly more weight in these M4s likely slows the burst/FA rate enough cunt hairs to make a difference. ??

[AR15barrels]

though both are carbine gas, I dont see how barrel weight has anything to do with BCG travel rates. Isn't the 6920 a semi-auto only where the M4s are select fire? having buffers with slightly more weight in these M4s likely slows the burst/FA rate enough cunt hairs to make a difference. ??

The 16” length vs the 14.5” length matters.
Barrel diameter at the gas port matters but 6920, m4 and m4a1 are all the same barrel diameter at the gas port.
0.625” barrels run smaller gas ports than 0.75” barrels.
0.875” and 0.936” barrels run bigger gas ports than 0.75” barrels.
It’s not ONLY the gas port size that restricts the gas but also the LENGTH of the gas port in the barrel which is why different barrel diameters at the gas port behave differently.

[1168]

though both are carbine gas, I dont see how barrel weight has anything to do with BCG travel rates. Isn't the 6920 a semi-auto only where the M4s are select fire? having buffers with slightly more weight in these M4s likely slows the burst/FA rate enough cunt hairs to make a difference. ??

While the bolt is moving forward, the gun isn’t perfectly static.

[lysander]

A few things:

1) H6 Buffer - The H6 buffer has six tungsten weights in it, each slightly less than half the size of the regular weights. The weights and spacers take up more space, but they should still move within the body. Each of the “half-tungsten” weights weigh about as much as a regular steel weight. Therefore, the action of the H6 closely mimics the action of the rifle buffer with five steel weights. This is slightly better than the H3 for rifle-length barrels with carbine receiver extensions, if you are going to do a lot of full-auto shooting. You not see any difference at all if you stick to semi-auto only.

2) Buffer Assembly, P/N 13004468 - The H2 buffer (P/N 13004468) was not introduced because of the heavy barrel, it was introduced because of excessive bolt bounce in the M4A1. In 1999, APG began to report light strikes and failures-to-fire especially when shoulder firing, this is 1999, two years before the heavy barrel is designed and 2-1/2 before it gets a NIIN. This issue had not shown up earlier because most of the development testing and all of the lot acceptance testing was done in a hard mount. Some shooters are not as “rigid” as other shooters and allow more rifle movement during full-auto shooting. The heavy barrel and the H2 buffer are actually parallel developments.

In fact, the H2 buffer (P/N 13004468) completely supplanted the H1 (P/N 9390023) in both the heavy and light barreled M4s.

3) Biasing springs - They completely reverse the intended purpose of the weights in the buffer. The whole point of the loose weights in the buffer, is that during the forward acceleration of the bolt during counter-recoil, the weights will, observing Newton’s Laws, slide to the back of the buffer body tube. Then when the bolt impacts the barrel extension, and begins to rebound off it, the buffer weights impact the front of the buffer body and the rebound is cancelled out. The physics of this can be demonstrated by Newton’s Cradle.

Biasing the weights forward means the weights will impact at the same time as everything else, and the carrier will rebound. Fortunately, is only an issue in full automatic fire, and even then is highly depended on ammunition and how the gun is held during firing, so most people won’t notice the problem.

Testing has shown that a solid steel 5.73 oz buffer is so bouncy getting a three-round burst off is near impossible. However, when the Army says bolt bounce is a problem, they usually mean a dozen times in a thousand rounds they had a failure-to-fire malfunction. (Personally, one of my .308s has a solid 5.4 ounce steel buffer, works fine, but slow motion video shows some nasty bounce.)

On the positive side, biasing eliminates a variable in AR operation. The weights themselves may bounce around inside the buffer body, you don’t know where they are when the gas starts pushing the carrier rearward. So, their weight may, or may not, be part of the recoiling mass until well after unlocking. If all three weights are aft, you will definitely see an increase in initial bolt velocity. That will be an interesting thing to drop into the AR model . . .