Swapping Bolts

[bobsav21]

I've been bombarded lately with adds from various dealers with killer prices on all sorts of uppers without BCG and Charging Handle.

Was wondering how many people buy " uppers " in various configurations and swap bolts between them.

[Fishinfool]

In theory, bolts should fit any in spec gun. That said, I would personally check headspace with a "go / no go" gauge before firing. Bolts between my Colts & Bushmaster AR15's fit each other without issue. Never tried with my Rock River. My rifles were all bought complete, and my Rock River upper came with a bolt / carrier as part of the package.

Larry

[cyphertext]

Originally Posted by bobsav21

I've been bombarded lately with adds from various dealers with killer prices on all sorts of uppers without BCG and Charging Handle.

Was wondering how many people buy " uppers " in various configurations and swap bolts between them.

Hopefully nobody is swapping bolts between multiple uppers.

New Barrel + New Bolt = GTG
New Barrel + Used Bolt = GTG
Used Barrel + Used Bolt = Bad juju possible

[vipermd]

Parts wear in. The original selling point on 300 BO was you could swap BCG between the 2 guns, sounds great but I prefer to avoid used barrel & used Bolt combination- Bad JUJU as stated by Cyphertext. I have seen many torture tests on AR's, but I do not remember seeing any that would swap bolts during a 10,000 round run. Be Safe,

[Disabled1]

I have bought a few PSA BCG's in my travels. And, I have always installed them without checking head space. But, I have NEVER combined a used barrel with a used bolt. And, I don't intend on it!

[sgtsandman]

I'm going to agree with the bolt swapping though I'm a bit more cautious. I would run a Go/No Go gauge with any bolt swap just to make sure. It doesn't happen often but when tolerance stacking strikes, it's never good. A gauge is cheaper than a damaged rifle and/or person.

[shep854]

Interesting post. I'm thinking about picking up another bolt carrier group as a spare, and I wonder about this. Think 'new bolt-used barrel'

[cyphertext]

Originally Posted by shep854

Interesting post. I'm thinking about picking up another bolt carrier group as a spare, and I wonder about this. Think 'new bolt-used barrel'

Usually GTG... left that one off. Check headspace if you are concerned.

[shep854]

Originally Posted by cyphertext

Usually GTG... left that one off. Check headspace if you are concerned.

Thanks!
If I do this, it will be a top notch BCG.

[hdwhit]

Fishinfool wrote:
I would personally check headspace with a "go / no go" gauge before firing.

I agree 100%.

[Disabled1]

Originally Posted by shep854

Thanks!
If I do this, it will be a top notch BCG.

A Premium PSA BCG, logo or not, will run with ANYTHING out there.

[jaymoore]

Most of the variation will be in the chamber/barrel extension.

And easy enough to check the bolts directly. If you want to be fancy, measure the bolt lug height with a 0-1" micrometer. Then the depth of the face with a depth mic. Subtract the bolt face recess dimension from the lug height to get the effective headspacing dimension for the bolt. Shouldn't be more than 0.002" difference between bolts unless something is really weird! And that is rather less than the total headspace tolerance....

Realistically, you can do it with calipers, unless you are a ham fisted lout, in which case you ought not be measuring important stuff anyway.

ETA: The REALLY direct route would be a set-up like this. (I was replacing the bolt head in a WWI Berthier rifle. Five bolt heads, all within 0.001"/0,025mm of being the same!) :



FWIW, I've been swapping AR parts since the mid '80s and have had yet to find an out of spec bolt. But they've been all from "known makers" or GI. Can't comment on "no name" stuff found at gunshows and the like.

[shep854]

Originally Posted by Disabled1

A Premium PSA BCG, logo or not, will run with ANYTHING out there.

Oh, definitely NO logo. I'm not paying to carry around a billboard. I even blacked out the 'M&P markings on my rifle's mag well.