Similar rifles, different recoil?

[bb223]

For awhile I have only had one AR, which is a Colt 6920. But I recently built a rifle using a complete BCM lightweight carbine upper and a complete LMT lower, but I added an H-buffer from BCM.

Anyway, I finally got to shoot it today and I noticed it had noticeably less recoil than my Colt 6920 and I was wondering why. I was expecting it to have more because it is lighter.

I haven't changed any parts in the Colt and they both have A2 flash hiders and I was using the same ammo.

The only explanation I could think of was that the BCM has a smaller gas port or something, but I don't know as much about the technical stuff as most of the guys here do, so I figured I'd ask.

It's nothing I'm concerned about and I don't think I should be.

I was just curious as to what causes the recoil difference.

I know it's kind of a goofy question, but thanks ahead of time.

[Cameron]

They should feel the same, but there is something about these BCM carbines that is really good.

Cam

[Scotter260]

I can't speak to the why but I recently had a similar experience.

Changed from a CMMG 11.5" gov't profile upper with a surplus Colt FA BCG to a BCM 11.5" lightweight upper with BCM FA BCG. Same H-buffer used. My Aimpoint, QRP, RAS, AVG, etc. is all the same. I did change my light mount from a 1" scope ring to a V-TAC mount but I assume that's lighter. My old upper seemed to jump more while this new BCM upper barely moves.

Maybe for me it's just the different BCGs. All I know is I sure like my BCM upper.

I look forward to the answers to your query.

[Iraqgunz]

My guess is the lightweight barrel may have a smaller port which is why it feels different. It really shouldn't be too drastic though as there is little difference.

[C-grunt]

Does the Colt have a H buffer?

[Failure2Stop]

I added an H-buffer from BCM.


This would be my first guess, in conjunction with a new/stronger action spring. I have no idea if BCM uses a different gas port size.

[orionz06]

See what items are different between the two that will alter perceived recoil. A smaller port seems likely. How many rounds have been through the 6920?

[C4IGrant]

I would be suprised if there is a smaller GP in the 16" carbine from BCM.

The Colt 6920 also comes with an H buffer, so that's not it.

The only thing left is the buffer spring. BCM might have a stiffer/longer spring and that would change the felt recoil somewhat.



C4

[militarymoron]

shoot both uppers with the same lower and see if that makes a difference.

[az doug]

Most have touched on all the possibilities. You can swap parts and try to find out why.

I contend that you could have two "identical" Colts, or any other brand, and have two different felt recoils. It simply has to do with permissible tolerances. I would not think the difference would be too drastic, but possibly noticeable. New,"identical," cars do not handle, accelerate...the same.

[arizonaranchman]

It's just part of the Magic built into every BCM by Paul's elves!!! :)

[MistWolf]

For awhile I have only had one AR, which is a Colt 6920. But I recently built a rifle using a complete BCM lightweight carbine upper and a complete LMT lower, but I added an H-buffer from BCM.

Anyway, I finally got to shoot it today and I noticed it had noticeably less recoil than my Colt 6920 and I was wondering why. I was expecting it to have more because it is lighter.

I haven't changed any parts in the Colt and they both have A2 flash hiders and I was using the same ammo.

The only explanation I could think of was that the BCM has a smaller gas port or something, but I don't know as much about the technical stuff as most of the guys here do, so I figured I'd ask.

It's nothing I'm concerned about and I don't think I should be.

I was just curious as to what causes the recoil difference.

I know it's kind of a goofy question, but thanks ahead of time.

The lighter rifle will not have less recoil than the heavier one when using the same ammo. It will actually have more free recoil due to having less mass. It's possible the shooter will perceive the lighter weapon to have less recoil due to some difference.

Just changing the recoil pad on my hunting rifle changed it's perceived recoil to something more comfortable. The free recoil remained the same.

Making changes in tube lengths; gas port diameters; speed and/or weight of reciprocating parts; spring rates; powder burn rates; size, shape & geometry of stocks & buttpads; dwell times; weapon weight and/or balance or the muzzle device, will change how recoil feels to the shooter