AR-15 Bolt Swap Outs

FPrice

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I don't recall any threads asking this specific question.

If you put a new BCG into your AR-15, are there any recommended preparations or actions you should take prior to firing the rifle?

Based on my limited experience I would make sure it is cleaned well, lubed carefully (not too much), and move it back and forth with the charging handle to see if it seems to move smoothly.

Just want to make sure that I am not missing anything.
 

76Too

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99.95% of the time, there’s never going to be an issue...and if there is, it’s likely due to manufacturing tolerances being off.

I’ve admittedly never headspaced an AR build, but you’re technically supposed to and probably should...but if it were me I wouldn’t bother (probably the only kind of gun on the planet I’d say that about too, because otherwise I’m kind of a stickler about headspace).

that said...god hates cowards. Shoot the damn thing 😂
 
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Tinkermatic

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Headspace gages maybe and make sure it's the right bolt for the cartridge your shooting .

Load it up and shoot it .

This!
This past July, I was sold a brand new in box 5.56/.223 complete BCG from a reputable company (or so I thought) that was assembled at the factory with the wrong caliber bolt.

I did exactly what OP described; clean, lube, reciprocate, it even ran (and ejected) snap caps with no issues. Lock up was fine, ran smoothly, no reason to be even a little concerned. However, at the range with live ammo, repeated failures to extract led to closer inspection and the determination (with the help of NES) that I had a 7.62 or 6.5 Grendel bolt.

The company sent me a proper replacement after providing photos, but it took 2-1/2 months to receive thanks to increased demand. It runs flawlessly and is a very nice nitride BCG, but needless to say, I won’t be purchasing from them again.

A closer look goes a long way.
 
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teamRR

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Don't be a cheap hack about it, if you are going to assemble your rifles in pieces buy the following, there is no excuse - do it right. These are not the cheapest prices just a quick lookup, total is $125:

View: https://www.amazon.com/5-56mm-NATO-MAX-Headspace-Gauge/dp/B01MZ55FZ0/ref=mp_s_a_1_3?dchild=1&keywords=5.56+headspace+gauge&qid=1606594851&sprefix=5.56+hea&sr=8-3


Quality 1/16 punch for ejector removal:

View: https://www.amazon.com/565-Series-Parallel-Pin-Punches/dp/B06Y5SY16Z?th=1&psc=1


Ejector removal tool:

 

1903Collector

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I've put together a few ARs. I just show the rifle off a little bit, get a friend real exited about shooting it, offer them the opportunity to christen it, and then I stand back and close my eyes. 60% of the time it works all the time.
Or......strap it to a table and tie a long string to the trigger, hide behind your truck and pull! Yes I did this many years ago when I built my first upper and didn't know any better!
Seriously though I would just headspace the new bolt just to make sure it's on the up and up
 

FPrice

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I've put together a few ARs. I just show the rifle off a little bit, get a friend real exited about shooting it, offer them the opportunity to christen it, and then I stand back and close my eyes. 60% of the time it works all the time.
Or......strap it to a table and tie a long string to the trigger, hide behind your truck and pull! Yes I did this many years ago when I built my first upper and didn't know any better!
Seriously though I would just headspace the new bolt just to make sure it's on the up and up

Some people just have to do things the hard way.

I have a "Go No-GO" gauge arriving in todays mail.
 

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Do you know how to properly lubricate an AR BCG? If not, check this out View: https://www.youtube.com/watch?v=6EuiUhPLifA


A headspace gauge is a nice thing to have, but truthfully, in all my years of owning/building rifles I only ever check headspace with the older surplus rifles that I own / have worked on.

My advice - lubricate the bolt, rack it back and forth a few times to ensure it spreads evenly, and then go put 10 rounds through it and see how it performs compared to before.
 

FPrice

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Do you know how to properly lubricate an AR BCG? If not, check this out View: https://www.youtube.com/watch?v=6EuiUhPLifA


A headspace gauge is a nice thing to have, but truthfully, in all my years of owning/building rifles I only ever check headspace with the older surplus rifles that I own / have worked on.

My advice - lubricate the bolt, rack it back and forth a few times to ensure it spreads evenly, and then go put 10 rounds through it and see how it performs compared to before.

I enjoy watching those guys, they seem to have their chit in one sock.

One interesting bit of advice they give is to NOT put any lube in the three vent holes on the bolt. But I have seen several other videos in which the individual does say to put oil in those holes. But these guys explain why they have their position. The others just seem to tell you to do it and move on.
 

teamRR

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Along the lines I was saying, the right way to do it, which is about 15 minutes start to finish being as careful/slow as one can be, remove the ejector and extractor, reassemble the BCG, check headspace, sanity check how the end of the carrier aligns with the end of the upper while you are at it (this is not gauged, just should about line up with a closed bolt), put your BCG back together, good to go provided operationally every feels OK.

You can also do the same w/ the stripped bolt before the barrel is installed, however I like to see headspace workout with the barrel and whole BCG involved, which is doing it under actual timing/alignment.

Sure you can do nothing and probably be OK but if you want to build good rifles this is part of it, just like properly torqueing/timing/shimming your barrel nut, staking the castle nut etc etc. For me, if I am going to assemble my own stuff I want the QC as good or better than a complete rifle from a competent manufacturer.
 

1903Collector

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Along the lines I was saying, the right way to do it, which is about 15 minutes start to finish being as careful/slow as one can be, remove the ejector and extractor, reassemble the BCG, check headspace, sanity check how the end of the carrier aligns with the end of the upper while you are at it (this is not gauged, just should about line up with a closed bolt), put your BCG back together, good to go provided operationally every feels OK.

You can also do the same w/ the stripped bolt before the barrel is installed, however I like to see headspace workout with the barrel and whole BCG involved, which is doing it under actual timing/alignment.

Sure you can do nothing and probably be OK but if you want to build good rifles this is part of it, just like properly torqueing/timing/shimming your barrel nut, staking the castle nut etc etc. For me, if I am going to assemble my own stuff I want the QC as good or better than a complete rifle from a competent manufacturer.
Do you find you have to use shims on the barrel nut often? Just curious. In my experience the sweet spot is around 50-55 ftlb for alignment with the different barrel nuts I have used. The only barrel nut I ever came close to 85ftlb was a standard nut/delta ring type.
 

teamRR

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Do you find you have to use shims on the barrel nut often? Just curious. In my experience the sweet spot is around 50-55 ftlb for alignment with the different barrel nuts I have used. The only barrel nut I ever came close to 85ftlb was a standard nut/delta ring type.

Depends - on an Aero w/ the integral mounting point for the handguard, no - those are the easiest I have done, you can time them but really makes no difference as the gas tube clears the nut at any timing.. A standard mil spec barrel nut, maybe a little. A BAR nut, yes, and maybe alot of shim since you only have a correct timing every 90 degrees.
 

1903Collector

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Never used the BAR nut, but looking at it yea, I can see where some shims may be needed..LOL. I just did a LaRue LAT on a .458 SOCOM upper and boom, 55ftlb and it was lined up.
 

PatMcD

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Buy your parts from reputable sellers and it won't be an issue. I've swapped bolts between rifles, old bolts on new barrels, new bolts on old barrels, a buddy's bolt on my barrel, et, etc, and never once put in a headspace gauge to check it. I have no hesitation because I know our parts come from WOA, Keystone, Compass Lake, or Brownells and are therefore in-spec.
 

teamRR

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Never used the BAR nut, but looking at it yea, I can see where some shims may be needed..LOL. I just did a LaRue LAT on a .458 SOCOM upper and boom, 55ftlb and it was lined up.

It's great when it works that way for sure. I seem to have seen a couple that lined up at about 27 lately - perfectly as far off as you can get :)
 

teamRR

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Buy your parts from reputable sellers and it won't be an issue. I've swapped bolts between rifles, old bolts on new barrels, new bolts on old barrels, a buddy's bolt on my barrel, et, etc, and never once put in a headspace gauge to check it. I have no hesitation because I know our parts come from WOA, Keystone, Compass Lake, or Brownells and are therefore in-spec.

Again, in all likelihood it will not be an issue, but why assume?

If the barrel tolerance is one way, the bolt another, you can potentially have problems. As things wear, headspace goes up.

Those aren't brands I tend to know or hear about as top shelf, but even if it was say JP (ie your $300 BCG's).. why spend all the $$ just to take shortcuts? Its one thing to try something at the range once, but if a BCG is going to live in there why not spend 15 minutes doing it right?
 

enbloc

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I've put together a few ARs. I just show the rifle off a little bit, get a friend real exited about shooting it, offer them the opportunity to christen it, and then I stand back and close my eyes. 60% of the time it works all the time.
It's funny cuz it's true... [rofl2]
 
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