Hi yall.  I'm going to be buying a used Bushy 11.5" barrel with the pinned 5.5" FH from the EE.  I just bought a new bolt/ carrier for another rifle, which I will now use with the newly acquired upper.  I was under the impression that the bolt/ carrier could be dropped in and ready to go (no headspacing required), but now I'm questioning myself.  Or is this only safe to be done with a brand new (factory) upper?   Sorry for the noobe ??, but I have yet to learn about headspacing.  I hope this is clear

Thanks in advance

--VT

www.ar15.com/forums/topic.html?b=3&f=4&t=261587

The "headspace" on an AR15/M16 is set by the armorer that mounts the barrel extension to the barrel.

That said I use a "new" b/bc/ch on every "new" upper and make certain that they stay together.

YMMV, but to do otherwise is just plain dumb, IMO.

Here you have a used upper (no b/bc/ch and no idea of the round count or use possibly) & your asking if it's okay to place a "used" b/bc/ch (same condition NO idea of round count or use, possibly) in the upper.

More than likely, you'll be alright.

I would never have bought the upper in the first place, and take those that sell uppers without the "original" b/bc/ch, that came w/ the complete rifle or upper as idiots, best avoided, (sorry, but it's just my way of seperating the wheat from the chaff).

Mike

ps - at the very least I would pull out my "GO"-"NO-GO" gauges and check the headspace before I shot the thing............


ETA - metal parts working in close proximity to each other over the course of time tend to "take a set" or "wear-together" this is the reason for my opinion expressed above. Is it more expensive, yes most certainly, but then I'm worth it and prefer my rifles run 100%, (heck, I have 2 new bolts, a new carrier & charging handle in my spare parts kit and would much prefer to replace a "broken" old bolt w/ a new one, than a used bolt of un-known condition, in my uppers).

IMO these folks that think mixing and matching parts (so closely related) is a-okay are probably destined for a KABOOM post at some time in their lives.

Quoted: Here you have a used upper (no b/bc/ch and no idea of the round count or use possibly) & your asking if it's okay to place a "used" b/bc/ch (same condition NO idea of round count or use, possibly) in the upper. More than likely, you'll be alright.

Thanks for the replies guys.  The upper (Bushmaster) is said to have about 200 rnds threw it, the bolt/ carrier assembly is brand new from Bushmaster.

Thanks again,

--VT

IMO these folks that think mixing and matching parts (so closely related) is a-okay are probably destined for a KABOOM post at some time in their lives.

Nope.  Not likely.

I thought the Bolt carrier had nothing to do with Headspacing, I thought it was all related to the Bolt and the Barrel. Am I mistaken?

Im curiously because I put on a CMT upper with Denny's 16" WOA with pre headspaced CMT bolt. The bolt is in a Bushmaster Carrier.

Bolt carrier has ZERO to do with headspacing.

And Kabooms are not caused by headspacing.

Kabooms are caused by

   (1) Obstructed bore.

   (2) Case head separation.

   (3) High Primer

   (4) Certain power conditions, including having too little powder.  5.56 cases cannot be "double charged".  And even if filled all the way, there are few rifle powders that could cause a kaboom.  It would take a completely wrong powder... pistol powder, for example.

But Kabooms are not caused by headspace.

I swap bolt groups all of the time and have never had a problem.  That is what the M16/AR15 is designed to do.  The worst thing that could happen is it would not cycle.

Quoted: Bolt carrier has ZERO to do with headspacing. And Kabooms are not caused by headspacing. Kabooms are caused by    (1) Obstructed bore.    (2) Case head separation.    (3) High Primer    (4) Certain power conditions, including having too little powder.  5.56 cases cannot be "double charged".  And even if filled all the way, there are few rifle powders that could cause a kaboom.  It would take a completely wrong powder... pistol powder, for example. But Kabooms are not caused by headspace.

Add Out of Battery to the list.


Thanks,

What you want to do before you fire this upper is have someone with the correct headspace gages test the upper with your new bolt.  If the gage says "OK," then go for it!  If the round count is accurate, it probably will pass with flying colors.

As for not getting the original bolt and carrier, who cares about the carrier when it comes to either headspace or wear-the BOLT is what wears or doesn't, and the carrier is just what holds it while it works.  But I would be curious why the seller was keeping the bolt...

Quoted: IMO these folks that think mixing and matching parts (so closely related) is a-okay are probably destined for a KABOOM post at some time in their lives. Nope.  Not likely.

Then your a fool, as the mindset of those that do not understand the value of a properly set-up AR15/M16 (ie. new bolts w/ new uppers and keeping them together throughout their life) is the same stupidity that ALWAYS gets one in trouble.

They are same as folks that fail to realize the danger of bullet "set-back", so they aren't attune to the indications; when it occurs.

They are the same as folks that fail to recognize the "squib" round when it occurs.

They are the same as folks that  think using pistol powders for loading 223/5.56 rounds is a viable accepted reloading practice.

They are the same as folks that think saving a few bucks by shooting sub-standard ammunition in their 1K rifles, instead of quality ammunition is an okay thing, (I mean "heck, it shoots" is all that matters to them)

They are the same as folks that spend thousands of bucks on ARs, mags and ammo, but fail to realize the importance of a spare buffer retain pin spring.

They are the same as folks that think reduced course HP matches actually compares to the skills developed by shooting full range HP matches, (200, 300 & 600 yards).

YMMV, but some of us just can't settle for "good-enough" we require "best" in our choices.

Mike

I'll respectfully disagree with Mr. Wilson.  As others have noted, headspace in the AR-15 is controlled by the installation of the barrel extension, not specifically by the bolt & bolt carrier.  Provided all parts are correctly dimensioned, you can safely swap bolts & carriers without fear of disaster.  That said, checking headspace with gauges is a good idea, simply to ensure that headspace is where it should be.  There may be accuracy & reliability considerations that would make it worthwhile to keep an upper & its bolt & carrier united throughout their lifespan, but it is not foolish or reckless to swap components.
Best of luck.
--Snowbound

tag

Quoted: Quoted: IMO these folks that think mixing and matching parts (so closely related) is a-okay are probably destined for a KABOOM post at some time in their lives. Nope.  Not likely. Then your a fool, as the mindset of those that do not understand the value of a properly set-up AR15/M16 (ie. new bolts w/ new uppers and keeping them together throughout their life) is the same stupidity that ALWAYS gets one in trouble. They are same as folks that fail to realize the danger of bullet "set-back", so they aren't attune to the indications; when it occurs. They are the same as folks that fail to recognize the "squib" round when it occurs. They are the same as folks that  think using pistol powders for loading 223/5.56 rounds is a viable accepted reloading practice. They are the same as folks that think saving a few bucks by shooting sub-standard ammunition in their 1K rifles, instead of quality ammunition is an okay thing, (I mean "heck, it shoots" is all that matters to them) They are the same as folks that spend thousands of bucks on ARs, mags and ammo, but fail to realize the importance of a spare buffer retain pin spring. They are the same as folks that think reduced course HP matches actually compares to the skills developed by shooting full range HP matches, (200, 300 & 600 yards). YMMV, but some of us just can't settle for "good-enough" we require "best" in our choices. Mike

I am not any of those thing listed, nor a fool, but am a turd.  My 5.56 headspace gauges sit in thier parts drawer with no use for the past 10 years or so (other then when I play with 5.56 AK's).  The thing is I NEVER found a AR bolt/barrel combination that had the headspace out of spec, so quit checking them.  But then again, I only have Colt/USGI barrels and bolts, so YMMV.