Topic: AR10 Uppers

[hessmanca]

So a buddy of mine asked me a question that has me stumped............. So I am hoping the knowledge in this group will help.
He has an original Bushmaster BAR-10 with an A2 upper.  He is wanting to swap out the upper for a flat top.  The question is: is there any AR10 upper out there that he can replace his with.  He is hoping to just replace the upper and keep his barrel.  I know most have proprietary barrel nuts and similar items.  If he needs to replace the entire upper is there a company that will match up with his Bushmaster Lower?

Well there it is........... Please help!

thanks
Chad

[broncovan]

Rock River took over that design.  I think they made some pretty significant changes to the lower and a couple changes to the feedramps.  Give Rock River a call and see what they have to say about it.  We could probably get together and see if mine will pin on to his lower.  I don't think I'd want it shot before talking w/Rock River.  They do sell a stripped upper for $160 that you could switch the A2 fwd assist and dust cover over to.

After looking at some BM BAR-10 pics, it looks like mine would bolt right on to his lower.  I know Rock River made some modifications to the original BM designs to minimize feed issues they had early on.  Maybe it was in the feedramps, mine has some pretty significant feedramps compared to a normal AR-15. 

Does his use FAL mags?

[hessmanca]

His does use FAL Mags.  He told me that he spoke to RRA and they told him that they do not make part compatable with any other manufactuor.  But don't know who he actually spoke to. May of been a salesman trying to get him to buy a complete rifle.  He added that they treated him very poorly on the phone.

[JoshAston]

The Rock River rep was sort of correct.  They don't make parts that are compatible with any current production .308 AR.  However, as already stated, the Rock River LAR-8 started life as the Bushmaster BAR-10.  I don't know if the parts are interchangeable, but I'd bet they are.

[hessmanca]

UPDATE!!!!
Broncovan and I went out to the range this morning and set out to determine if a RRA LAR-8 upper would fit and function on a Bushmaster BAR-10 lower.... Here is what we found.

First thing we disassembled the BCG and found that my buddy apparently does not know how to clean a rifle! 
We began by looking at the the BCG and found that they appeared visually identical.  (note: we did not measure them, just visual examination.)  I then noticed that the Bushmaster bolt had a shorter length extractor, which did not extend into the carrier.  The RRA had a longer extractor that did extend into the carrier, similar to a standard AR-15. 

We then removed the bolts from the carriers and found that the rear neck of the Bushmaster bolt had broken off and was flopping around on the firing pin.  The bolt was so dirty that we actually thought it was a completely different bolt design at first.  Then we realized it was broken.  We then test fitted the Bushmaster bolt into the RRA carrier and vice verse.  They did not fit.  Figured that they may of had a slightly different body diameter or had something to do with the length of extractor.

Next we looked at the feed ramps and upper receiver internals.  Everything there appeared the same.  So we slapped the RRA bcg into the Bushmaster and loaded it up.  It fed a round just fine and completely seated it in the chamber, I did a brass check and slapped the forward assist just for grins (all though it was not needed).

Then I clicked the safety to FIRE and bang, bang, bang.  Three rounds perfect.  So a RRA BCG will function in a Bushmaster upper receiver.

We then swapped out the Bushmaster upper with Broncovan's RRA.  After getting the the front pin put in and putting the RRA bcg into the RRA upper, I closed the upper down onto the lower and it was as tight fitting as the Bushmaster.  Both pins fit perfect and the upper and lower mated together like they had come from the factory together.

The combo fired perfectly with two different types of ammo. No failures, jams, hick ups or jerks.

We did not do an extensive firing test as we were primarily wanting to see if they fit and fired together, which they did.

The one thing that we did not check was the Bushamster bcg in the RRA upper due to my buddies broken bolt.

All in all, I would say that the parts are interchangeable, with the exception of the bolts.

Another interesting thing we noticed was the barrel nut on the Bushmaster.  It actually had two rows of teeth on it.  The standard handguards mounted up to the first row and the second was taller and held the gas tube in place.  We could only assume that they did this so that they could use standard HG's they had at the factory, but they needed the extra (taller) row to help support the gastube.  Broncovan's RRA had a free float tube so we could not compare barrel nuts.

I apologize, I did not take photos, I thought of it after the fact.

I hope that this helps those of you out there that have had questions about AR-10 parts.