A5 BUFFER
Frequently Asked Questions — The VLTOR A5 Recoil System
The gas system decides how much energy comes in. The A5 decides what happens to it.
// The Short Answer
Same energy, longer runway, lower peak.
A carbine buffer system has to absorb the bolt carrier’s energy, stop it, and send it back — and it has to do all of that in a short tube with a short, stiff spring. The A5 does the same job over three quarters of an inch more travel, using a full-length rifle action spring instead of a carbine spring. Spreading the same energy across more distance means lower peak force at every point in the cycle, which the shooter feels as a softer, longer, more progressive push instead of a sharp slam. The buffer itself is longer too, which allows four internal weights instead of the carbine’s three — and those weights are what stop the bolt bouncing when it returns to battery. The system was developed by VLTOR in 2009 at the request of the U.S. Marine Corps, who wanted the smoothness of the rifle-length system without giving up an adjustable stock. That is the same thing we want on a precision rifle, which is why it’s our preferred configuration.
// Three Parts, One System
It isn’t a heavier buffer. It’s a different set of physics.
Plenty of people try to fix a harsh-cycling AR by fitting a heavier carbine buffer. That helps, and it is not what the A5 is. The A5 changes three things at once and they only work together: a receiver extension three quarters of an inch longer, a full rifle action spring rather than a carbine spring, and a longer buffer carrying four internal weights. Take any one of them away and you have something else.
The extra travel and the rifle spring do the obvious work. A rifle spring has more coils and a lower rate, so the force it applies rises more gradually across a longer stroke instead of stacking up hard at the end. The carrier is slowed over a greater distance rather than stopped over a short one, and everything in the recoil path — buffer, spring, extension, receiver, and your shoulder — sees a gentler curve.
The four weights do something less obvious and more interesting. They are uncoupled — free to move inside the buffer body rather than being part of it. When the buffer stops, they keep going for an instant and then arrive, exactly like the shot inside a deadblow hammer. That trailing impulse is what kills bolt bounce: instead of the carrier rebounding off the barrel extension when it returns to battery, the internal mass arrives just behind it and holds it there. Making a buffer heavier adds mass. Making it an A5 adds timing.
| The system | Specification |
|---|---|
| Receiver extension | 3/4″ longer than carbine · 7-position · impact-extruded 7075-T6, hard anodized |
| Action spring | Full-length rifle spring — not a carbine spring |
| Buffer | 3/4″ longer than carbine · four internal weights (carbine carries three) |
| Internal design | Uncoupled weights in a cascading deadblow arrangement — addresses bolt bounce |
| Weight options | A5H0 3.80 oz · H1 4.56 oz · H2 5.33 oz · H3 6.08 oz · H4 6.83 oz |
| H number | How many of the four internal weights are tungsten rather than steel |
| Default | A5H2 — the standard starting point for most configurations |
| Stock compatibility | Standard Mil-Spec M4 / AR-15 collapsible stocks |
| Origin | Developed by VLTOR in 2009 at U.S. Marine Corps request |
| Critical | A5 buffers must never be fitted to a standard carbine extension — see Q 08 |
// Questions We Get Asked
What does each of the three parts actually contribute?
They’re often described as an upgrade kit. They’re better understood as one mechanism with three parts:
- The longer extension gives the carrier more room to be slowed down in. Energy absorbed over a longer distance means a lower peak force, which is most of the softer impulse you feel.
- The rifle spring has more coils and a lower rate, so its resistance builds gradually across that longer stroke rather than stacking hard at the end of a short one.
- The four-weight buffer carries more mass than a carbine buffer can, and carries it uncoupled — which is what handles bolt bounce rather than simply making the rifle sluggish.
Is three quarters of an inch really enough to matter?
On a stroke that short, yes. A carbine system has very little travel to work with, so adding three quarters of an inch is a meaningful percentage increase in the distance available to slow the carrier down. Combined with a spring that resists more gradually across that distance, it changes the shape of the whole impulse rather than just its size.
What’s wrong with a carbine spring?
Nothing, in a carbine system it was designed for. But it’s short and relatively stiff, so its force climbs quickly and stacks toward the end of travel — and it’s the part of the system most people notice when it starts to wear. A rifle spring in a longer tube gives a flatter, more consistent force curve across the whole stroke.
What is bolt bounce, and why should I care?
When the carrier slams back into battery it can rebound slightly off the barrel extension — bouncing rather than settling. It’s a consistency problem more than a reliability one on a semi-auto, but consistency is the entire point of a precision rifle. The A5’s uncoupled internal weights arrive a fraction of a beat late and hold the carrier forward, which is exactly what a deadblow hammer does.
Which buffer weight do I need?
A5H2 is the standard starting point and suits most 14.5–16″ builds in carbine or mid-length gas. Lighter H0 and H1 suit soft-ported barrels and heavily gas-tuned rifles that would short-stroke on more weight. Heavier H3 and H4 suit short barrels, overgassed rifles, and suppressed use. We select and test yours as part of the build rather than shipping a default.
Does it help with a suppressor?
Considerably, and it’s one of the main reasons we like it. A can raises port pressure and drives the carrier harder, which is precisely the condition a longer stroke and a more progressive spring are best at absorbing. Paired with an adjustable gas system, you can turn the input down and manage what remains more gently — two ends of the same problem.
Will my stock still fit?
Yes. The A5 extension takes standard Mil-Spec M4 and AR-15 collapsible stocks — that compatibility was the point of the original design, since the Marine Corps wanted rifle-length smoothness without giving up adjustability. It’s a seven-position tube, so you keep the adjustment range you’re used to.
Can I put an A5 buffer in my carbine tube?
No — and this is the one item on this page that is a safety matter, not a preference. A5 buffers are longer and are designed only for A5 receiver extensions. Fitting one to a standard carbine tube can damage the firearm and injure the shooter. The A5 is a system: extension, spring, and buffer together or none of them.
Does it make the rifle more accurate?
Not mechanically — your barrel and ammunition decide group size. What it changes is how much the rifle moves while you’re shooting it and how consistently it returns, which affects your ability to spot impacts and get back on target. That’s shooter-facing, and it frequently shows up on paper for reasons that have nothing to do with the barrel.
Do I still need adjustable gas?
They solve different halves of the same problem, and we fit both on our precision rifles. The gas system controls how much energy enters the action. The recoil system controls how that energy is absorbed and returned. Tuning one without the other gets you partway; doing both is why our precision builds cycle the way they do.
Does it add length or weight?
A little of both, and it’s worth naming. The extension is three quarters of an inch longer, and the buffer weighs more than the carbine part it replaces. On a precision rifle already carrying an optic, a bipod, and often a can, that’s a trade most shooters take gladly. On a build where every ounce is being counted, tell us and we’ll talk it through.
Which of your rifles use it?
It’s our preferred recoil configuration, and where it sits depends on the build:
- Standard on builds designed around it — the QUATTRO 15MB ships with the VLTOR A5 as delivered.
- Optional on rifles that ship with a carbine assembly, including the SOTM4 RECC·E and the Monobloc series, where it’s offered for shooters who want the longer, more progressive stroke.
- Part of a larger recoil package on our large-frame precision builds, where the A5 architecture is combined with other recoil components as a tuned system rather than a single part swap.
// What The A5 Does Not Do
It manages energy. It doesn’t decide how much arrives.
- It doesn’t fix an overgassed rifle. It absorbs excess more gracefully, which can mask the problem. Gas port, gas setting, and buffer weight all have to be right together.
- It isn’t a drop-in buffer. The extension, spring, and buffer are one system. See Q 08 — this one matters for your safety, not just your performance.
- The wrong weight causes real problems. Too heavy and the rifle short-strokes or fails to lock back; too light and you’ve given up most of the benefit. Weight selection is part of the build, not an afterthought.
- It doesn’t shrink your groups. See Q 09. Barrel and ammunition set your accuracy ceiling.
- It doesn’t eliminate maintenance. Springs are wear items and buffers get dirty. A better system still gets inspected and eventually still gets a new spring.
// What You Get
Your build record names the recoil system — extension, spring, and the specific A5 buffer weight your rifle was tested with — alongside the gas setting it was tuned at. Those two entries belong together, because neither one means much on its own: the buffer weight was chosen for that gas setting, and the gas setting was found with that buffer in the rifle. If you change your configuration significantly — a different barrel, a can you didn’t have before — tell us and we’ll tell you whether the pair still suits it.
More runway. Lower peak.