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Posted: 4/27/2001 7:50:49 AM EDT
I was wondering if you change JUST the upper housing, but kept the same bolt and carrier, as well as the barrel and barrel nut, etc, would it still have to be head spaced?


Link Posted: 4/27/2001 7:57:14 AM EDT
You mean just change out the upper reciever?
Say from a a-2 to a3-flat top?
bushmaster sells just the upper receivers in there catalog I think the run for under $150
more economical then buying a complete upper if money is a concern.

I never have though,maybe someone else can give mroe help.

Link Posted: 4/27/2001 8:06:28 AM EDT
To be safe, I WOULD NOT swap bolt and carrier between uppers.

I did it once in ignorance, and got away with it. Not worth it, IMO.

If you can afford another upper, I would think you could afford another bolt / carrier to go with it, that was headspaced for it.
Link Posted: 4/27/2001 9:50:41 AM EDT
I bought the complete upper assembly from Bushmaster, full upper + bolt. I think that the bolt adds about $150.00 to the overall price. But it is worth it, not only because of headspace safety but just having the extra parts is always a plus. If needed, you can carry the extra barrel assembly as a backup. If for some unforseeable reason you get a mechanical breakage, all it takes is a quick pull on the take down pins and you have a fresh clean new rifle/upper that is ready to go.
Link Posted: 4/27/2001 12:01:20 PM EDT
By the way, this is a new rifle, never fired by me.  It was test fired at the factory.  That's why I was wondering that if the ONLY thing that was changed out was the upper housing, would the headspacing be messed up.
Link Posted: 4/27/2001 12:14:05 PM EDT
OK, I'm definitley not a gunsmith, but I believe it sould be OK, IF you have a competent gunsmith check the headspace after the barrel is installed on the new upper.  On the AR, the bolt and barrel interaction is what determines headspace, and since these are the same, it SHOULD be fine.  It is also my understanding that if you put only a new barrel on an upper, you can still use the same bolt carrier, just be sure to use a new  bolt.  Let the flaming begin.
Link Posted: 4/27/2001 12:42:48 PM EDT
i've gotten away with it a time or two myself but sometimes the gastube can be such a pain in the ass that i now let a gunsmith buddy do it rather than mess one up...ive always interchanged bolts and carriers at will but i once had him check the headspace on all my ARs with the different bolts and he says they are good but you NEED to get them checked.  he called me the other day while putting a new gas block on one and a flattop on another and told me of excessive wear i had in one of my flattops that i shoot a bunch--so it doesn't hurt to have an "AR Gunsmith" on retainer....Dick
Link Posted: 4/27/2001 1:24:45 PM EDT
Link Posted: 4/27/2001 2:23:11 PM EDT
i once did depot maintenance on 25 m16a1's and asked if it made a difference to keep bolt carriers with the uppers.  i was told (by a colt armorer who was a specialist on the m16/ar15) these are 'erector set' guns and it does not matter.  on m14's and other guns like that it DOES MATTER - but on m16's "no seat g.i."

i reassembled all 25 weapons with what was there.  some where more worn than others - some looked brand new.  

Link Posted: 4/27/2001 2:35:13 PM EDT
Troy is correct.  You have the same bolt and barrel.  Only the metal that supports them is changed if you only change the upper receiver.  Headspace is unchanged.  It will be fine.
Link Posted: 4/28/2001 8:39:57 AM EDT
Thanks guys for all the information!

Yes, Troy, the ONLY thing that I would be changing out is the upper housing, exchanging the A2 housing for a flattop.  Perhaps a DPMS.  Haven't decided yet if I will get a regular height flat top, or a high rise flat top.

Thanks again!
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