putting together a build using a Daniel Defense DDM4V7 16” complete upper. For fun I asked ChatGPT to recommend buffer system components. It came up with BCM MK2 (A5) Receiver Extension, VLTOR A5H2 Buffer, Geissele Super 42 Rifle Spring, and a MilSpec castle nut. Thoughts from the real experts? Thanks!

I very recently invested in an A5 tube, A5H2 buffer (same as carbine H3 overall weight), and a Sprinco rifle spring. I intended to post a report of sorts, but it may never happen.

I had known of the A5 system for at least a couple years, but never felt compelled to try it. It seems to have recently become the "standard" for some of the higher-end factory rifles, so I got one to see what the deal is.

I did as objective of a comparison I could do, swapping otherwise identical lowers back and forth on two different uppers.

There was no especially noticeable "wow" performance difference.

Both uppers were suppressed, and deliberately built to utilize a silencer. The other lower was equipped with a carbine H3 buffer and Sprinco red spring.

Of course there are performance aspects that don't reveal themselves in the confines of my limited test.

Considering my experience so far, I would not encourage anyone to go out of their way to go the A5 route. Though it certainly can't hurt, if you'd be employing spendier buffers and springs anyway, and you're starting from scratch.

Good luck finding VLTOR buffer parts. Get this BCM kit and be done. I put it on a Mk12 system and it works well. Very high quality with typical BCM fit and finish.

https://bravocompanyusa.com/bc...ion-system-mod-1-t2/

First, watch this video:



Regardless of which A5 receiver extension you choose for best compatibility with your chosen buttstock, my rule of thumb is this:

Mid-length gas system, 16" barrel, I use the A5 H2 buffer

Carbine-length gas system, 16" barrel, I use the A5 H3 buffer

And yes, for years, it has been difficult to find A5 components. When I was gathering parts a few years back, I monitored Midway USA every day and eventually got the buffers I needed.

FYI, Magpul's UBR gen2 stock uses an A5-length receiver extension. All you need is an A5 buffer and rifle-length action spring (which is the spring used in all A5 receiver extensions.)



16" barrel, carbine-length gas system, Magpul UBR gen2 stock, A5 H3 buffer, Colt OEM rifle action spring

quote:

Originally posted by KSGM:
Of course there are performance aspects that don't reveal themselves in the confines of my limited test.

IMO, tunability is the chief advantage for the average shooter.

Here's an excellent explanation of the A5 system, which I found online years ago:

Think of it this way:

The rifle spring is in a tube shorter than a rifle tube.

This increases the pre-load on the BCG versus a rifle setup. The preload is higher than a rifle, but lower than a carbine setup.

The rifle spring when fully compressed has the same load no matter what, but the length of the A5 buffer isn't *exactly* the same as the rifle one, so it compresses a bit farther.

The solid load of the A5 system is higher than for a rifle, but lower than for a carbine.

All sounds good doesn't it? Basically, it takes more to unseat the BCG than a rifle, but not near as much as a carbine, and the spring is soaking up more energy but doesn't require as much force to bottom out.

Now, the real kicker is that the difference in loads between pre-load and bottomed out is smaller than with a carbine.

What does that mean?

A spring increases it's load linearly (in a perfect world). Which means the first inch might take 2 lbs to compress, the second inch takes 4 lbs, etc. The A5 system doesn't 'stack' as quickly. This means that for variances in the initial BCG velocity (based upon loads, gas system, etc) the BCG responds similarly. This provides consistency to the system. It also extends the shot-to-shot time, meaning you're doing the same amount of work over more time, which means more energy dissipated. This means more time for the gun to do it's thing, and also since the 'recoil work' is the same (mass times muzzle velocity = recoil momentum) but the buffer system is taking longer to deal with that work, means a lower applied force. This results in a 'softer' feeling recoil impulse. It also equates to consistency.

The carbine runs into issues because it is trying to accomplish too much, too fast. When the buffer bottoms out in the tube, it transfers more recoil - when it doesn't, it short-strokes. The A5 system reduces these potentials because more energy can be absorbed by a rifle spring and the whole system is slowed down due to the increased pre-load.

Okay, so it slows things down - this will increase the probability of short stroking, right? Wrong - the pre-load is higher, but because the final compressed load is lighter, the rate is lower. This means that a lighter loading will still cycle the gun, because while it takes more force to unseat the bolt, the spring doesn't 'ramp up' as fast with regard to applied BCG force. Neat, huh?

Basically, it brings rifle-type operation to a carbine-type platform while only increasing the overall length of the system by less than an inch.

VLTOR also claims some internal voodoo with regard to the buffer which they claim helps the operation of the buffer with regard to bolt-bounce. This only affects full-auto guys though, right? Wrong. Bolt bounce contributes to inconsistent chambering of the next round, which leads to a reduction in accuracy. Though VLTOR doesn't claim it publicly, I've heard tell that the system has proven to tighten groups on otherwise well-shooting weapons. I don't think it will turn a turd into a match-grade rifle, but when you're exhausting all possibilities in the pursuit of accuracy - one has to admit, eliminating bolt bounce is just making the rifle that much more precise.


Regarding the "internal voodoo" of the A5 buffer, it's pretty neat:

The Vltor A5 buffer features an internal biasing spring that keeps the internal tungsten and steel weights stacked against the front face of the buffer. This mechanism ensures that the weights are always in the same position when the gun starts its unlocking and cycling processes, providing consistent mass and improved energy transfer.

Key functions and effects of the internal spring include:

Consistent Cycling: By preventing internal weights from scattering, the spring ensures the rifle overcomes the same mass in the same way every time, reducing bolt bounce and smoothing the recoil impulse.

Enhanced Reliability: Testing indicates the biasing spring allows equivalent or higher mass to travel rearward with higher velocity compared to standard buffers, effectively widening the operating envelope of the AR platform.

Efficient Energy Transfer: The spring pushes the "dead blow" weights against the rear of the Bolt Carrier Group (BCG), creating a more efficient transfer of energy and making it easier for the gun to cycle its mass.

It is important to note that not all A5-length buffers contain this internal biasing spring; generic "A5 style" buffers from other manufacturers may lack this patented feature and will not offer the same level of forgiveness or reliability as Vltor or BCM buffers.

I chose the A5 system on my HK wannabe with Noveske 13.7 barrel. I assumed that barrel was heavy on gas; and other factors pushed me to the A5 system. I went with an A5H2 buffer which seemed to be the recommended option, and it works even full auto so far (all full power 5.56.) It also came with an A5H1 which also worked the only time I shot it.

I wondered if it would run because it feels noticeably different than a carbine system. The way it's described above makes perfect sense. It's got a "firmness" that is immediately evident. I like the author's detailed account of exactly what's going on and why. It seems to match some of what I thought could be happening.

This message has been edited. Last edited by: Slippery Pete,

It's good to see ya, Pete

Yes sir, the feeling's mutual. Gotta check in with the good guys.

Thanks all. I had no trouble finding the buffer, so I’ve ordered these parts and look forward to competing the build.

Which buttstock are you using? This determines which A5 receiver extension you choose. Did you watch the video I posted?

Yes, I watched the video - thanks for posting. I’m using a B5 Enhanced SOPMOD stock.