Just wondering if Bushmaster lowers for their XM15E2S 20", 16", Dissipator, and M4 clones are all the same.  

I have a Bush 20" standard Hbar, but I'm thinking of picking up a Bush M4 style upper and then slapping it on the lower to make it an M4gery when I feel like it (probably most of the time since the Hbar's just plain heavy).  Would that be a recommended thing to do?  I would imagine all Bush parts would match well.  Would it shoot worse than the all factory Bushy M4?

By the way, does the lower for their M4 have a different model to note it's specific for their M4gery and not the XM15?

They are identical.  No the upper and lower fit does not have an effect on accuracy.  In my opinion you can build a Bushmaster better in your garage than they can build at the factory.  Dont sweat it.

Actually, there are at least 2 different Bushmaster lowers now.  Machined by different vendors.  Easy to identify by serial # and the logo.  Some have the AR rifle on the snake, some have the bullpup on the snake.

I have seen reference to the bullpup marked AR lowers crowding the lower end of tolerances on some dimensions.

BTW I have seen both, they do look different.

Your eyes are better than mine!  Interesting piece of Bushmaster trivia.  Any idea the change point?

Back to the original question:  there are no different receivers for any Bushmaster model, they're all marked XM15-E2S.  There may have been a marking change or even different machining, but that was an across the board change.

-- Chuck

Interesting....so which one is the newer one?  Or are they being produced concurrently?  I have the bullpup kind.  I always wondered about it since the manual shows Bushmaster logo with AR inside the snake.

I wonder if that vendor's the same one that made the M17S.

AFAIK they all say XM15-E2S on the lower.  My post-ban V-Match does, and so does Dad's A3.  

I've heard that the first 2 digits of the serial number changed when they changed sources for the forgings, but I don't recall which is which or even what the two prefixes are.  Didn't know about the bullpup/AR difference.  I don't know which rifle is in the logo on mine.

IIRC the orginal M17s were Austrailian and Bushmaster bought the rights to the weapon to continue developement here.

FYI that isn't the Bushy M17 on the Snake Logo - its an outline of their ARM pistol.  One of their earlier products - intended as a .223 survival pistol for AF pilots.  Very unique.

ar_wrench, Forest or anybody with information - tell me more. Tomorrow I pick up a new XM15 E2S A3 20". If it has the bullpup/Arm pistol in the logo what should I look for? ar_wrench's comment in the above post about that version having tolerances on the "lower end" on some dimensions has me a little concerned [:(]

If you are getting a complete rifle, assembled by Bushmaster, it should be fine.  Bushmaster uses a mil-spec magwell dimension, but the non-AR-on-snake magwell can be a hair tighter.  Mags still drop free fine, but an out of spec mag (swelled) will hang in these before they will hang in an AR/snake lower.  The difference may be a thousandth of an inch or so, not much.

Also, RR uppers fit tighter to these uppers than the AR/snake uppers.  Again, not much different, and no difference after 200 rounds or so.  

If you are concerned, the only place you might see a tolerance stacking problem is in the fire control group.  Do the function check as outlined in Tweak's FAQ.  If it passes, no worries, if not, it is under warranty and Mr Bushmaster will make it right. I doubt you will find a problem.

ar-wrench:  Thanks for the information. The rifle is new and manufactured/assembled by Bushmaster. I ordered it from a gun shop who is getting it from his normal (large) distrubuter. The distrubuter sent the serial number and Bushmaster said it was made in May 2003.

I'm leaving now to pick it up. I'll be inspecting it very closely for the things you described. Thanks again.