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EOD3
10-02-2008, 2:39 PM
As I understand it, a heavier buffer will slow cycling and reduce the ejection distance. Is there any downside? Will I need to change/modify the spring?

aplinker
10-02-2008, 4:20 PM
Heavy buffers are for very short carbines and eroded/mis-drilled gas ports.

They're an artificial reduction to the cyclic rate and not the best way to do it, but sometimes necessary.

Going heavy increases recoil - due to a larger reciprocating (moving) mass.

The down side is you rifle will become finicky and short stroke with lighter loadings, lighter bullets, etc.

EOD3
10-02-2008, 4:59 PM
Thanks guys,

Is there a good way to reduce the "fling the case" distance and/or take it easy on the brass?

aplinker
10-02-2008, 5:54 PM
Thanks guys,

Is there a good way to reduce the "fling the case" distance and/or take it easy on the brass?

buy a bolt gun. :p

You can do it, but you'll be interfering with the system.

A heavier spring or buffer could, as would an adjustable gas block. Again, though, you're taking the wide tolerances out of the system. If it's a range gun, I'd get an adjustable gas block - you can tune the system to your load and even use a lighter buffer to reduce recoil.

Josh
10-02-2008, 9:11 PM
Heavy buffers are for very short carbines and eroded/mis-drilled gas ports.

They're an artificial reduction to the cyclic rate and not the best way to do it, but sometimes necessary.

Going heavy increases recoil - due to a larger reciprocating (moving) mass.


How exactly does an increase in moving mass increase recoil?

cal3gunner
10-02-2008, 9:43 PM
Are you trying to reduce recoil? Is your rifle for self defense or just for shooting at the range and competition?

If the rifle isn't for just self defense and you want the softest shooting AR, you can change a few things. Right now I'm running a MSTN QCB Muzzle Brake, a JP adjustable gas block, a light weight bolt carrier, a rifle length stock with a carbine length spring with an A2 buffer. Don't forget to lube your buffer spring. The gun shoots soft. Whe shooting at longer distances its really easy to see the hits and at close range its really easy to double tap targets.
If I was using this as a battle rifle, I would rather live with the recoil and oversprung rifle to guarantee reliability. But for just shooting at the range, customize to your hearts content.

FMJBT
10-02-2008, 11:20 PM
How exactly does an increase in moving mass increase recoil?

Because all that extra mass ends up impacting at the end of the buffer tube which is held against your shoulder. The bolt carrier and buffer may take a bit longer to get there than the lighter standard buffer, but will arrive with more inertia.

REDHORSE
10-02-2008, 11:51 PM
Thanks guys,

Is there a good way to reduce the "fling the case" distance and/or take it easy on the brass?

I carry 3 different carbine buffers in my range bag (stand carbine, "H" M4, & 9mm heavy buffer). So, I have a buffer on hand when I change uppers/ calibers.

Heavier buffers do change ejections pattern. The direction and how far it's ejected from the shooter.

As for felt recoil, the heavy buffer actually seems smoother to me.

Depending on the ammo, if it's on the weak side, you risk short stroking. But, with factory ammo that I've tried, I haven't had any short stroking issues, but your rifle may differ (too many variables). The factory Remington ammo seems to have a weaker ejection pattern than Winchester factory ammo when I use the 9mm buffer with .223 ammo.

The 9mm heavy buffer with my 5.56 upper (16" bbl, carbine gas tube length, improved style carrier) shooting factory Walmart Remington 55 gr FMJ, ejects within a foot of me to the 1:00 clock position.

I also have different buffer springs, but I'm not sure which one I have in there. I just have a small box with several bugger springs and install it. I've never sorted out the carbine springs.

I do not have a chrome silicon. Although the chrome silicon my friend has does seem to have a small effect too.

Pics of different buffers:
http://www.biggerhammer.net/ar15/buffers/

AR15.com vendors have a couple more custom buffers: like the 9mm Q-buffer, etc..
http://www.ar15.com/forums/topic.html?b=7&f=125&t=263131&page=1

Josh
10-03-2008, 7:07 AM
Because all that extra mass ends up impacting at the end of the buffer tube which is held against your shoulder. The bolt carrier and buffer may take a bit longer to get there than the lighter standard buffer, but will arrive with more inertia.

Yes it impacts the rear of the tube but at a slower speed and acceleration so it will hit with less force.

if we use F=ma and see that the force used to push the buffer back is the same no matter the mass of it becuase the same round generating the same chamber pressure pusing the same bullet is being used. Then the only thing that changes is mass and to keep force equal acceleration must decrease with an increase in mass.

now if we take recoil to be more a function of impulse vs pure force which is why if you use a softer recoil pad the gun recoils less due to a longer impulse. The larger mass of the buffer will slow down the action of rifle and spread out the time from the recoil of the bullet and the impact of the buffer.

With the extra weight of the buffer added to the rifle there is increased inertia and the rifle overall is more inclined to resist the movement from the recoil of the round being fired.

Though its only a few ounces difference and i doubt anyone truly notices the change with their shoulder and if they do its mostly psychological.

cal3gunner
10-03-2008, 1:21 PM
Though its only a few ounces difference and i doubt anyone truly notices the change with their shoulder and if they do its mostly psychological.

Its not so much the kick of the rifle I and other people are trying to get rid of. Its gaining the ability to be able to see your hits at distance through the scope. When shooting steel plates at couple hundred yards in competition, you want to see where your hits and misses are that way you can adjust.

After changing the buffer it might not seem like a lot of difference, but when you start changing springs, adjustable gas blocks, lightening the bolt carrier, and so forth. It is very noticable when comparing to a stock rifle.

redcliff
10-03-2008, 1:49 PM
Yes it impacts the rear of the tube but at a slower speed and acceleration so it will hit with less force.

if we use F=ma and see that the force used to push the buffer back is the same no matter the mass of it becuase the same round generating the same chamber pressure pusing the same bullet is being used. Then the only thing that changes is mass and to keep force equal acceleration must decrease with an increase in mass.

now if we take recoil to be more a function of impulse vs pure force which is why if you use a softer recoil pad the gun recoils less due to a longer impulse. The larger mass of the buffer will slow down the action of rifle and spread out the time from the recoil of the bullet and the impact of the buffer.

With the extra weight of the buffer added to the rifle there is increased inertia and the rifle overall is more inclined to resist the movement from the recoil of the round being fired.

Though its only a few ounces difference and i doubt anyone truly notices the change with their shoulder and if they do its mostly psychological.

One thing not considerred in the above though is that the heavier buffer delays the openning of the bolt, which causes it to unlock when there is a higher gas pressure if I'm not mistaken. Therefore more pressure would cause the bolt to accelerate rearward faster wouldnt it?

REDHORSE
10-03-2008, 6:56 PM
One thing not considerred in the above though is that the heavier buffer delays the openning of the bolt, which causes it to unlock when there is a higher gas pressure if I'm not mistaken. Therefore more pressure would cause the bolt to accelerate rearward faster wouldnt it?

What? :confused: I would think the chamber pressure would be less. The longer the bolt stays locked (we're just talking milli-seconds here), the pressures should be decreasing.

I don't know what all the speculation is all about. I've run my various buffers in my carbine. All with my 5.56 & 9mm uppers. They all function with any of the three buffers I have.

• standard carbine buffer = ~2.9 ounces
• "H" M4 carbine buffer = ~3.77 ounces
• COLT/RRA 9mm heavy buffer = ~5.47 ounces

Changing buffers have to some degree:
• changed felt recoil. IMHO having less recoil with the heavier buffer.
• changed the brass ejection pattern: it's direction, distance from shooter, and the velocity of the brass coming out of the ejection port.


If you don't want to take the chance of wasting money, buying heavier buffer that won't work with your specific AR15. Borrow or invite fellow CG.net to the range and have them bring the various buffers and just try out.

ar15barrels
10-03-2008, 9:10 PM
Learn about how the action works before you fool with it...

www.ar15barrels.com/prod/operation.shtml

Josh
10-04-2008, 12:57 AM
Its not so much the kick of the rifle I and other people are trying to get rid of. Its gaining the ability to be able to see your hits at distance through the scope. When shooting steel plates at couple hundred yards in competition, you want to see where your hits and misses are that way you can adjust.

After changing the buffer it might not seem like a lot of difference, but when you start changing springs, adjustable gas blocks, lightening the bolt carrier, and so forth. It is very noticable when comparing to a stock rifle.

I agree and with a heavier buffer it will increase youre ability to see hits through
the scope and keep it on target though it probably feels the same to your shoulder. IMO the main factor in the ar15 and keeping the sights on target through the shot is the 2nd impulse of the buffer striking the end of the tube.

I asked the question on how a heavier buffer affects recoil just to see what the responses were and to see if there was anything i could learn. Applying a bit of basic statics and dynamics seems to clear most things up.

EOD3
10-04-2008, 12:03 PM
Thanks for the input guys. I'll be mounting a 10X mil-dot with the intention to shoot out to 600 yards. It would be nice to stay on target well enough to see the misses however, my concern at the moment is maximizing brass life. Given the skyrocketing price of components, I need all the reloads I can get.

ar15barrels
10-04-2008, 1:00 PM
Thanks for the input guys. I'll be mounting a 10X mil-dot with the intention to shoot out to 600 yards. It would be nice to stay on target well enough to see the misses however, my concern at the moment is maximizing brass life. Given the skyrocketing price of components, I need all the reloads I can get.

The first thing to do to help keep on target is to put on a good muzzle brake that is biased upwards to keep the muzzle level.
Even better is to tune the brake so that there is no muzzle rise.

That's how my 3gun AR is setup.
It makes double taps really easy...