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Posted: 8/29/2006 8:47:09 AM EDT
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This heavy buffer reduces recoil thing to me? In most 3 Gun rifles that I have handled and seen built by well known builders, a lightened carrier and lightened buffer are used...the reasoning is that by reducing reciprocating mass, the recoil impulse is lessened. This is sometimes also coupled with reduced gas flow, but not always. (yes, I know that reducing gas makes the weapon very sensitive to ammo selection for reliablity...does that lead to...) ....Then, I see others post here that they use heavy (9mm) buffers to achieve the same effect. These two approaches seem to be at odds with each other...please enlighten me! B |
The heavier the action and buffer, the more energy it absorbs due to inertia. It takes more energy to move it the same distance as a lighter buffer. Thus, less energy makes it to your stock/shoulder. Anyone who says a lighter buffer/carrier reduces recoil has no idea what they are talking about. PS I am a physics grad student  ETA: In reality, the actual total recoil energy stays the same regardless of buffer. What you are reducing is the "felt" recoil. |
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are you sure they aren't using light hand loads? which means they need lightened bolt carriers, standard carbine buffers, etc... for the AR to function properly... the lightened recoil is just a direct effect of the underpowered ammunition... for a hotter load like XM193 or similar, adding extra mass to the buffer in an otherwise stock rifle helps to use up the excess energy during the cycle (takes more energy to move more weight, less energy reaches the shooter)... |
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Typically, comp rifles are fired with standard 223 ammo, not 5.56. I can see that there is a breakover point somewhere in there where a heavier buffer would hold down bolt velocities and lower felt recoil and this would override the advantage of lighter components and lowered reciprocating mass. There is no doubt in my mind that lighter components going forward into battery give a much different recoil impulse to the rifle... Thoughts? B |
| Heavy buffers are used to reduce cyclic rates in carbines. Is the "H" buffer marketed as a recoil reducer? During a range trip I have tried both in the same SA carbine and noticed no difference in recoil but I wasn't really looking for a reduction in recoil; was more or less just trying different things out... |
You're still not getting it, lower reciprocating mass doesn't change recoil for the better assuming that you are using the same ammo load. The mass might be lower, but that causes it to reciprocate faster, and kinetic energy increases with the square of velocity, but only linearly with mass. It's one thing to use lighter mass in combo with lighter loads, but by itself ligher mass only increases felt recoil. |
There's not enough weight difference in an H buffer to noticibly reduce felt recoil. Try a 9mm buffer. But even then, the % change is not huge. |
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Doesnt the weight of the BC and or Buffer also change the "ejection timing"?...ie.. where your brass is landing after ejection. 1 thru 5 oclock Quite a few reliable builders have stated on here ARs should eject toward 4 or 5 oclock. My 6.8 caliber ARs eject toward 2 oclock. I have been thinking about experimenting with H2 or 3 buffers and or tungsten inserts in the BC. |
Right that's my point Phoebus - I have always been under the impression that heavier buffers were used to throttle back the cyclic rate. im my opinion they have nothing to do with recoil. Now the hydraulic buffer or some of those gizmos maybe but increasing the mass alone, should have little effect, as you stated. i think we're saying the same thing. 
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Yup I personally have found the 9mm buffer to make enough of a difference for me that I used them in my carbines (to soften that snappy carbine gas system), but it's a matter of personal perception. |
A quick re-read of Hatcher's notebook shows that the state of recoil theory way back then was entirely based on momentum, not kinetic energy. I don't know that anything has changed. Therefore, if you used a lightweight bolt, carrier and buffer to decrease recoiling mass by 20% compared to standard, the velocity of the system at rearmost impact would have to be 25% higher than standard to give the same felt recoil. I don't think the increase would be that much. This is partly because the gas system vents to atmosphere as soon as the carrier has achieved sufficient rearward inertia, and lighter moving parts will accelerate and open those vents faster than a heavier system would, reducing total thrust they receive. Also, once the vents are open, the carrier proceeds rearward by inertia, resisted by the action of the recoil spring. A lighter recoiling mass will be decelerated by the spring faster than a heavier one would, and by the time the buffer bottoms out in the tube, transferring its energy to your shoulder, a greater proportion of its energy has already been transferred though the spring, making the blow lighter. |
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Don't forget that those using JP rifles with lightened carriers are typically tuning their gas settings for reliability with a specific load which gives them versatility that others don't neccesarily have. Changing the carrier/buffer on a rifle that doesn't have an adjustable gas system isn't likely to give the shooter results that are very noticeable. It's one thing to have the gas port opened up for proper functioning with a higher mass carrier/buffer, turning around and using that same setting with the same ammo but with a lower mass carrier/buffer is going to pound the action pretty good with the additional cyclic rate. I've experienced it with my own JP gun going from shooting light bullet but relatively hot loadings to heavier bullets that are still pretty warm. You can tell a difference in what is going on with the carrier, considering that the gun is set to be virtually recoiless with the light bullet loads you do notice a difference if you switch out for heavier ammo if you keep the same gas setting. |
This is almost always coupled with a reduced gas flow. Otherwise, the carrier would unlock too fast and the recoil would be more harsh from the faster cycling. The AR is generally over-gassed. That's done for reliability sakes. Adding the heavier buffer just changes the TIME of the recoil pulse, slightly lengthening it. The physical amount of energy to the shoulder is very similar, but taking it slower makes it not feel as bad. Reducing the amount of gas ALLOWS you to also reduce the amount of reciprocating weight, thereby also reducing recoil. That's the two different principals at play here. Hopefully that explains why both lighter OR heavier buffers can be said to reduce recoil. It's for two different reasons. |
Thank you, that's what I've been trying to say, rather unsuccessfully 
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What I find interesting is that anyone ever felt the need to "lighten" the recoil of a 5.56!!! Now that's funny. I'm just kidding, I can see the reasons behind it for competition and such. I remember seeing a big marine shooting on the TV once and he had and A4 with an ACOG. It showed him shooting and I swear I didn't see any recoil impulse at all. He must've been hanging on pretty good. |
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