20" rifle upper w/ carbine buffer?

[Blownmotor]

I would like to know if a 20" rifle length upper will function and cycle properly with a standard carbine buffer system meaning buffer tube, carbine spring, and a standrad carbine buffer itself? Or are the gas systems and buffers proprietary to each other. It's going to be a LMT lower with a BCM 20" upper if it even matters. Thanks.

[the poi]

It'll launch the buffer out the back of the stock

[Blownmotor]

Why so? And what can I do to "fix" the problem? ie using rifle length spring and a heavier buffer?

[eaglemike]

Well, the spring, buffer, and tube length are all different for the rifle length as compared to the carbine.....
Launch parts out the back??? Hmmm, not sure about that. I'd suggest wait a bit for Randall or some that has tried this combo to reply....

all the best,
Mike

[1988]

Well, the spring, buffer, and tube length are all different for the rifle length as compared to the carbine.....
Launch parts out the back??? Hmmm, not sure about that. I'd suggest wait a bit for Randall or some that has tried this combo to reply....

all the best,
Mike

I believe that's what the OP is asking if it's OK to use an upper which has rifle length gas with a lower which has carbine buffer system.

It's yes, if I read the question correctly.

[Blownmotor]

It's yes, if I read the question correctly.

Do I need to do any modifications such as different weight buffers or springs in terms of proper functionality and reliability?

[yasushi]

I've shot my rifle, middy and carbine uppers with the carbine lower and had no problems. I also had the rifle upper and lower I wanted to shoot but didn't have the rifle buffer so I installed a carbine buffer/spring and a spacer (to take up the difference) and it fuctioned fine with no issues.

[gunsnrovers]

The Canadians run rifle uppers on carbine lowers. I believe they use an H2 buffer.

[docsmileyface]

Out of stock, but this kit from VLTOR is made specifically as a collapsing stock for 20" barrel lengths. http://www.bravocompanyusa.com/Vltor...a5%20black.htm

[dieselpower]

Out of stock, but this kit from VLTOR is made specifically as a collapsing stock for 20" barrel lengths. http://www.bravocompanyusa.com/Vltor...a5%20black.htm

+1, beat me to it...by 20minutes..LOL

[nelsonstevenj]

I've got a 20" upper with a carbine buffer setup, standard weight buffer. I've got several thousand rounds through it, not 1 issue.

[spareparts]

For kicks I wrote to Stag Arms

My question

Dear Sir or Ma'am:

I currently own your model 3H upper mounted on a Stag lower receiver with a carbine length collapsable stock.

Can I mount a 4H 20" upper to this lower receiver without changing the stock? Would I need to use a heavier buffer?

Reply

Yes, you can put the Model 4H on your current lower. If you have any further questions please contact us again.

Stag Arms

860-229-9994

[Jpach]

Ive run a 24" upper on my LMT Defender 2000 lower with carbine stock. No problems here.

[Blownmotor]

That's what I want to hear. Thanks guys.

[Josh3239]

You need to read up on how the AR15 operates.