a few questions...please bare with me

[corey4]

as some of you have seen from some of my more recent threads in this sub forum, i am very new to the AR platform. so please forgive me...

if i have a BCG that has seen some use, and i want a new barrel, should i get a new BCG? if i do the inverse, if i have a barrel with some rounds on it and need a new bolt, should i get a new barrel? if i have both a BCG and a barrel from different rifles that have seen some use, can i mix and match? i would assume functionally it will work, but is there a potential of have a decent combo and then switch the BCG and have the rifle not shoot as good? do they go hand in hand, keep the bolt with the appropriate barrel as the surfaces wear together? if round count matters, what should be the cut off on switching BCG and barrels?

if i were to drop the $$$ for an 18" SPR match barrel, should a new bolt be fitted to the barrel somehow, or is a plain ol' BCG ok?

thanks!

 

[eklarsen]

Your CG will be fine but if you get a new barrel get a correctly head spaced bolt with it to go in your broken in CG. If you are using an older barrel you will want to check the head space or have a gunsmith do it so it is fitted correctly

 

[FatBoy]

I reuse my bolts when I install new barrels. Just make sure headspace passes and you should be fine. You should be able to mix and match, BUT you need to check headspace. How it shoots is luck of the draw, but generally speaking if you have a milspec bolt and carrier with an M4 barrel extension it should function well and will probably shoot reasonably well.

 

[corey4]

why dont you have to check head spacing on a new bolt/barrel? or do they do that when they assemble the rifle? if i get a new bolt and barrel do i have to check head spacing, or just when swapping used bolts and barrels?

 

[eklarsen]

I would check anyway but theoretically if they provide you a bolt that is already headspaced you should be good.

 

[longshot2000]

If you are buying quality barrels and quality BCG (I know, it is relative), you ~can~ check head space, but mil-spec 5.56 is like legos. I have never seen quality parts not fit. I am sure there is an example, but the AR platform is standard. Now, move to a 7.62 platform, and all bets are off. The nature of the 5.56 chamber, bolt and barrel extension, all play into a standard that should fit. You can buy a no/no-go gauge to check-it, but once the barrel extension is on, there is no adjusting.

 

[FatBoy]

as said above. Issue is, how do you tell if it's milspec? If you're buying from a company who sells both there is a chance you're getting a non-milspec. My brother had this issue when I sent him one of my old service rifle barrels. With his Delton bolt it separated cases. Dropped in a Daniel Defense and it ran like a sewing machine. They look identical.

Never hurts to verify.

 

[DrainTheSwamp]

I’ve never worried about headspace when switching bolts or barrels and have never had a problem even with some low end components, although I will advise to just get some gauges and check. I reload so I check my brass and make sure they ain’t expanding excessively.

One of those “do as I say, not as I do” type things

 

[TheOE800]

Matched bolt is a gimmick.

 

[DrainTheSwamp]

Matched bolt is a gimmick.

Ya it’s all spec, so long as everything is in spec nothing bad should happen from what I understand.

Never heard of different spec bolts though.
Maybe from a coating standpoint.

And I believe there are different spec carriers with weight variations

 

[eklarsen]

Matched bolt may be a gimick but improper headspace is no joke.

 

[TonyTheTiger]

And I believe there are different spec carriers

How so?

 

[DrainTheSwamp]

How so?

Guess I shouldnt say different “spec” Just different weight. Still not going to change anything with headspace

 

[TonyTheTiger]

Thats kinda what I thought you were getting at, just wanted to clarify.
With regards to the OP's question, I've swapped bolts, carriers and complete BCG's with the regularity of underwear changes in mid summer. Tested four different BCG's on the same barrel ranging from ultra low mass aluminum up to mil spec steel and never even experienced a POI change, and all the brass came out the same size.

 

[VegasHKShooter]

as said above. Issue is, how do you tell if it's milspec? If you're buying from a company who sells both there is a chance you're getting a non-milspec. My brother had this issue when I sent him one of my old service rifle barrels. With his Delton bolt it separated cases. Dropped in a Daniel Defense and it ran like a sewing machine. They look identical.

Never hurts to verify.

The Del Ton bolt was likely the cause there. That’s not a bolt I’d run in any serious gun. DD, BCM, LMT, various others. Delton isn’t in consideration.

 

[corey4]

so the matched bolts and barrels i have seen have already been head spaced the manufacturer? a few people have mentioned the barrel extension and head spacing. is head spacing set with the barrel extension? is the barrel extension a separate part from the actual barrel? so when someone stated that once the barrel extension has been set, it's set?

 

[FatBoy]

the barrel extension is screwed to the barrel. In my case, the barrels are then chambered to fit the bolt I provide the riflesmith. Then the gas port drilled, everything test fit and paint baked on. The Smith can remove the barrel extension, chop off the barrel threads and start over as long as the barrel is fat enough, tbe gas port isn't drilled and you have enough length to meet NFA laws.

If you buy a pre-chambered Lilja with the bolt (pretty common kit) the HS will be checked against that bolt so there is no concern about it. I wouldn't go so far as to say it's a gimmick, I like the idea. I just don't buy off the shelf stuff anymore.

 

[MarkCO]

so the matched bolts and barrels i have seen have already been head spaced the manufacturer? a few people have mentioned the barrel extension and head spacing. is head spacing set with the barrel extension? is the barrel extension a separate part from the actual barrel? so when someone stated that once the barrel extension has been set, it's set?

The headspace is set by the manufacturer when the barrel extension is threaded onto the barrel. The extension contains the locator pin, feedramps, bolt locking lugs etc. Here is an image of an extension...

https://www.google.com/imgres?imgurl=https://www.brownells.com/userdocs/products/p_080000574_1.jpg&imgrefurl=https://www.brownells.com/rifle-parts/barrel-parts/rifle-barrel-hardware/barrel-extension-parts/ar-15-m4-barrel-extension-prod26946.aspx&docid=xyNKmFyzQd2R1M&tbnid=kVn_t5PewzU_BM:&vet=10ahUKEwiq-9vkkKjZAhVr9YMKHYwrDYYQMwjjASgEMAQ..i&w=400&h=400&bih=917&biw=1406&q=AR15 barrel extension&ved=0ahUKEwiq-9vkkKjZAhVr9YMKHYwrDYYQMwjjASgEMAQ&iact=mrc&uact=8

I have bolts that have gone through a few barrels. I rebuild the bolts when I rebarrel, but a good bolt will last for several barrels. The Carrier will last for several bolts.

 

[corey4]

What do you mean rebuild the bolt? Firing pin, extractor, ejector, spring, o-ring?

What about the face and lugs?

 

[MarkCO]

Springs, gas rings, O-rings, firing pin retainer. Inspect cam pin, extractor, firing pin, and replace if necessary.

 

[SAC]

With a new barrel I always use a new bolt that way the locking lugs are new to both, but you can use an old one. You can't headspace an AR, like said earlier it is set with the barrel extension. Buy a quality barrel and bolt or BCG and you will be GTG. match bolt to barrel is a gimmick.

Scott