Slowing down AR15 bolt cycling

G

Geezerbiker

New member
It feels like I'm getting excessive pounding as the bolt hits the stops with my M4 style upper. Other AR's I've fired felt a lot smoother but that was a long time ago when I shot them... The lower receiver has an A2 stock and buffer. I weighed the buffer and it's heaver than most of the so called heavy buffers.

There are 2 things I'm considering. There's one heavier buffer at Midway for 53 bucks and a Tubbs flat wound spring. I'm not sure if I want to pop 53 bucks plus shipping for a buffer. I'm considering drilling out the one I have and pouring in a lead core. If I screw it up, a standard replacement buffer is only 15 bucks.

What say you guys?

Tony
 
1

10-96

New member
The first things that come to my mind might be an adjustable gas block or (hold onto your hat) a LIGHTER buffer. As said on here by others, seldom is a 16" bbl seen being under gassed- usually they're over gassed. So along that line of thought, I suspect that maybe the severe thumping you're feeling is the mass of the heavy buffer doing what it was designed to do. The rubber thing at the end is designed to bottom out, and the heavier the buffer is, the more energy it's going to carry rearward. I've played with that stuff before, even going with a carbine buffer in a A-2 lower.
I'm not seeing a lot of availability for a pig tail gas tube (to ease dwell time)- but I think an adjustable gas block and a factory or lighter buffer would be a sound starting point.
 
G

Geezerbiker

New member
I should have mentioned that the gas block on the PSA upper is riveted on. I'm not sure I want to mess with that. Otherwise I'd already have an adjustable gas block on order...

Tony
 
Z

zukiphile

New member
How much does your buffer weigh?

Your A2 buffer should have space for seven weights. If it's an ordinary one, it should have five steel weights and some sort of spacer for the other two.

I have altered buffer weight by replacing the spacer with steel weights and substituting tungsten weights. It can be very effective in taming the secondary impulse you feel from hard cycling. Some people don't like that because of the muzzle dip that comes when the bolt closes.

I agree that an adjustable gas block can also reduce that impulse; it can also permit you to make the buffer much lighter if you are also using a good adjustable gas block. I've a rifle with no weights in the buffer and a lightweight carrier that recoils very gently too.

I would not recommend a lighter buffer all by itself for a rifle that is already cycling too hard. You'll have very high bolt speeds. If you use a buffer with no weights and an adjustable gas block, you'll start with the gas all the way off and slowing open the gas block until you get function and them lock back on an open magazine.
 
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G

Geezerbiker

New member
It didn't come with any weights. It's very possible that it's not a standard A2 buffer. I'll look up more info on how to remove the gas block and to see what I can find out about the A2 buffer and weights.

Tony
 
9

9x19

New member
Tony, here's a picture I picked up a long time ago, it may help clarify what zuki' was saying.

vnLCOKV.jpg
 
G

Geezerbiker

New member
Thanx 9x19. That picture makes it clear where the weights go. I'll try popping the pin out and looking inside later this week.

I had forgotten where I got the stock and buffer assembly and had to look it up. It's a Trinity Force stock set and I got it from Midsouth Shooters' supply. I like the stock and if they ever have more of them, I'll get one for my next build.

Tony
 
S

stagpanther

New member
It feels like I'm getting excessive pounding as the bolt hits the stops with my M4 style upper.
Click to expand...
What do you mean by "hits the stops?"--are you talking about the buffer end meeting the buffer tube end--or the carrier impacting somewhere on the ears/buffer collar on the lower receiver? If you are seeing any kind of impact damage to the lower in those areas--chances are very good you have a mismatch between your buffer's and buffer tube's lengths.
 
M

MarkCO

New member
Less gas. Always the best answer. Ways to go about that are an adjustable gas block, or possibly an adjustable gas key on the carrier. I am not a fan unless that is the only way to cut back excessive gas.
 
H

HiBC

New member
I don't know you,and I am not "sending you down a path"

You make your own decisions about what you DIY.

First,if your barrel AND muzzle device combined come up to 16 or 16.1 inches,

Thats a pretty good indicator that if you took the muzzle device off,the barrel would e about 14.5 inches. That would be a BATF problem.The way they get around it is to make the muzzle device permanently attached.

If the total length muzzle to breech face is 16 inches,or 16.1 ,the muzzle device is not coming off.Which would mean your gas block is not coming off.

If your barrel is 16 in + without the muzzle device,likely its removeable.

I doubt your gas block is riveted on. More likely it is held on by tapered pins.

Those an be knocked out,and your gas block removed. But do not throw your gas block away!! And don't lose the pins. The way they are drilled and reamed results in less than interchangable parts.

AFAIK, you are not going to find an adj gas block that goes on with the tapered pins.

You can find them that use setscrews or clamp screws. What you may find a problem is you now have two transverse slots through your barrel where the taper pins were.

I do not have your solution, as I never considered that acceptable for me.

Maybe someone offers the service of making your original gas block adjustable. Or maybe even drilling a tiny vent hole. I don't know.

I'm simply suggesting the devil is in the details,and you find solid answers to these questions BEFORE you start in on your upper.

A shooter beats a basket case every time.
 
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G

Geezerbiker

New member
I can feel a secondary recoil that I think is the bolt or buffer hitting the stops. The buffer and tube came with the Trinity Force A2 style stock.

I should have said the block was pinned, I do recognize that but I'm still hesitant to knock them out. First off I'm not sure which direction to tap them out from and I'm concerned that I might damage something.

PSA listed it as a 16" barrel and I removed the flash hider and replaced it with a muzzle brake. It could be possible that the brake is part of the problem. I can see how it might change the pressure curve.

PSA lists a tungsten buffer weight for 15 bucks and a flat wound buffer spring from Midway is 24 bucks if I remember correctly. If these 2 things would smooth out the bolt cycling, it's a reasonable amount of money to do so. Also it's been 30 years since I fired another AR15 but it sure seemed to have less recoil than mine and I don't remember it having anything that felt like a secondary recoil.

Tony
 
K

kymasabe

New member
I'm curious what kind of BCG you're running. I had an AR that cycled a little too fast because the NiB bolt carrier group I was running was so slick. I pulled it and put in a simple phosphate one and slowed cycling nicely.
Next...wouldn't it be easier to get a heavier weight buffer spring rather than trying to Richard around with an adjustable gas block?
 
B

BobCat45

New member
There is a company that sells gas tubes with various gas port diameters to use instead of an adjustable gas block. It is: https://blackrivertactical.com/WP/BRT-EZTUNE-Gas-Tube-Configurable-Carbine-p103167251

Note that I have zero personal experience with this solution, just want to point out another option.

I obviously do not understand what is going on, because I find it difficult to see how your 16" carbine can be overgassed if you have an A2 stock, buffer, and spring, unless the gas port in the barrel is much larger than it should be.

I've read (that is to say, I do not "know" - this it is hearsay) that the carbine length gas system should have a 0.062"-diameter port, while the rifle length system should have a 0.093" port.

Wishing you a good outcome with this. You have an interesting problem and you will gain substantial understanding of the gas system function figuring out what is out of balance.
 
I

imashooter

New member
Bold replaces quote marks.

I'm considering drilling out the one I have and pouring in a lead core.

I should have mentioned that the gas block on the PSA upper is riveted on.

It didn't come with any weights. It's very possible that it's not a standard A2 buffer.

First off I'm not sure which direction to tap them out from and I'm concerned that I might damage something.

Based on the above, not sure if you even know what you have.

Don't know what you're doing.

Seek a smith experienced with ARs.
 
S

stagpanther

New member
Bold replaces quote marks.

I'm considering drilling out the one I have and pouring in a lead core.

I should have mentioned that the gas block on the PSA upper is riveted on.

It didn't come with any weights. It's very possible that it's not a standard A2 buffer.

First off I'm not sure which direction to tap them out from and I'm concerned that I might damage something.

Based on the above, not sure if you even know what you have.

Don't know what you're doing.

Seek a smith experienced with ARs.
Click to expand...
We all start someplace, no harm in asking questions.
 
G

Geezerbiker

New member
imashooter said:
Bold replaces quote marks.

I'm considering drilling out the one I have and pouring in a lead core.

I should have mentioned that the gas block on the PSA upper is riveted on.

It didn't come with any weights. It's very possible that it's not a standard A2 buffer.

First off I'm not sure which direction to tap them out from and I'm concerned that I might damage something.

Based on the above, not sure if you even know what you have.

Don't know what you're doing.

Seek a smith experienced with ARs.
Click to expand...
The next time you feel the need to be and A-hole, keep it to yourself.

When I started asking questions, I assumed the buffer was a solid part except for the nylon end and 9x19 politely educated me on their construction. I came here to learn more about how to slow down the cycling without replacing the gas block. Others have helped without being jerks about it...

Tony
 
M

MarkCO

New member
BobCat45 said:
I obviously do not understand what is going on, because I find it difficult to see how your 16" carbine can be overgassed if you have an A2 stock, buffer, and spring, unless the gas port in the barrel is much larger than it should be.

I've read (that is to say, I do not "know" - this it is hearsay) that the carbine length gas system should have a 0.062"-diameter port, while the rifle length system should have a 0.093" port.
Click to expand...

Almost all production ARs are overgassed. Some of that is because folks run steel cased dirty ammo that needs more gas into the system to operate.

The buffer, spring, BCG weight, gas rings, gas tube length, gas port size, charge weight in the case, powder burn rate, projectile weight and dwell time are all integral to the system tune. Even the shooter has an affect. When you think of each component as a part of a system that needs to be tuned, much like an engine, the voodoo starts to vanish.
 
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