Excess recoil impulse (from an AR... wth?)

[rotarymike]

So I finally got to shoot the lightweight 6.8 AR I built for my wife yesterday. Thing kicked like a mule - I have a bruise on my shoulder from it.

For comparison, I have a personal 6.8SPC AR that weighs just a little more, and it does NOT kick like that.

light gun is 5.2 pounds on the scale; mine is 6.4 pounds. Same ammo in both, same mags, shot the same day.

Her gun is milspec receivers and most internals, M16 BC, QMS FCG, Magpul CTR stock, Hogue grip, AP Customs 9" carbon FFT, YHM block/sight, an AR Performance 14.5 middy gas barrel with 2" levang type comp perm attached, and a Bushnell TRS25 dot.

Basic difference between hers and mine is full A2 stock, Rock River 16" barrel (lightened), and a flashlight.

Discovered on breakdown that her buffer spring is down to 10", and it has an unmarked 3.0 oz buffer. Am I getting the recip mass hammering the rear of the buffer tube?

 

[rotarymike]

Also bear in mind I usually shoot full power battle rifles so when I say an AR kicks like my Mosin, that is really not a good thing.

 

[Dave29461]

You could try an adj. gas block to reduce impulse if the spring and buffer adj. aren't enough.

 

[rotarymike]

I think I'm dealing with defective or worn parts, along with the wrong buffer. I'm kinda stuck with my gas block because of the welded brake. But, I have seen adjustable tubes.

6.8 isn't that hot a load to overgas a normal mid length system.

 

[Clicker]

You're welcome to try my Enidine hydraulic buffer. It sure smoothes out the 9mm upper.

Off hand I don't know what a new recoil spring measures but perhaps a chrome silicon spring would help, Tubb and Sprinco offer them.

 

[rotarymike]

From what I saw Googling, rifle is 13" and carbine is 11". My other 6.8 uses a rifle length buffer, which is 5.5oz vs this one's 3.0.

 

[PapaBear]

I assume you didn't try swapping buffer/spring combos between the two while at the range?

Does yours have a Leavang on it as well?

 

[rotarymike]

Didn't have the tools to swap stocks and buffer tubes.

It may not be clear from my original post, but my rifle has this:

and this:

hers has this:

and this:

They're not swappable without changing buffer tubes and springs, also.

 

[rotarymike]

Also, yes mine has a levang on it as well. You could say I'm fond of the design, until you try to use a pull-through bore cleaner :evil:

 

[Tigerstripe]

with my machine gun i have an H-2 buffer. there are 3 weights inside. H-2 has 2 tungsten and 1 steel. i had to buy one H-2 but the outer buffer has been beaten to death and i just put the tungsten weights in an $8 buffer so you can take her buffer apart and add tungsten or when i change to 9mm i have to change buffers. the 9mm is longer and heavier.

id bet a 9mm buffer would work.

i also have a longer heavier spring than a regular box carbine.