Bbl cutting Q

[The Extractor]

Im a machinist with 10 years exp and I have cut and threaded bbls previously, but none c/l.
I am wanting to shorten my c/l bbl.

Will it mess up the chrome lining if I shorten my c/l bbl ?
Is there a certain technique to it ?

[ChicagoTex]

Not if you have it done by someone professionally experienced with AR barrel cuts like Adco.

[The Extractor]

Im going to rephrase my first post.

[DaBears_85]

Im a machinist with 10 years exp and I have cut and threaded bbls previously, but none c/l.
I am wanting to shorten my c/l bbl.

Will it mess up the chrome lining if I shorten my c/l bbl ?
Is there a certain technique to it ?

The chrome can flake around where it's cut. Barrels are generally cut to size and then chromed for that reason. I would send it to Adco just to be on the safe side, they do excellent work.

It also depends on the rifle itself and wether or not you have any other AR's. If it's on the lower end and and you're just wanting to test your skills I would reluctantly say go for it. That is of couse it's not your only/primary weapon. If it's your only AR and/or it's a top tier weapon I would send it off to be done.

Entering 'chrome lining and bbl cutting' or any variation of those words into the google machine produced alot of results, too many to post here. Also, try using the search function here as this question has to have been asked here before.

[bkb0000]

i wouldn't think so.. just follow your standard RPM and lubrication guidelines for turning 41xx steel. the chrome is bonded to the steel, so it's not going to flake or peel. just my never-done-it-before opintion: if i cut my own, i'd probably turn the crown before threading. that way, if you **** it up, you can just re-turn it. if you **** the crown up after threading, you'll have to re-turn the shoulder and re-thread. i'd also leave the neck the same OD as the thread peaks- that way you can just re-turn the shoulder and re-thread, if it became necessary. helps for centering your indexing device, too.

if you're confident in your ability- go forth, young man. and take pics.

[bkb0000]

The chrome can flake around where it's cut.

it cannot. chrome lining in a bore has zero sheer strength- it's not thick enough nor independent enough from the host steel to pull itself away. and this is even if it wasn't soaked into the surface of the host metal- literally bonded to it.

think apple skin, not orange peel.

[DaBears_85]

it cannot. chrome lining in a bore has zero sheer strength- it's not thick enough nor independent enough from the host steel to pull itself away. and this is even if it wasn't soaked into the surface of the host metal- literally bonded to it.

think apple skin, not orange peel.

Ahh, well it seems I am misinformed. Thank you for squaring me away.

In the interest of honesty and brevity, if I would've double-checked my old notes on this instead of going off memory I would've came to the same conclusion. My apologies...

Nice analogy by the way.

[The Extractor]

I was reading on another forum and they were having flaking issues with the SCAR bbls. but eh. Thank you for the information gents.

[ST911]

Late to the party, but I had and know of many other 20" GI barrels cut back to 16". No flaking, no problems. Done by a good vendor.

[Artos]

do your have a loop or a borescope...would love to know how your first go round comes out.


bkb, how does the quality of the cl come into play??

[MarkG]

Cutting the barrel to length is not so much a problem as crowning it. All of the cutters available from Brownells are only hardened tool steel. Hard chrome is tougher than kryptonite. These crowning cutters tend to chatter when used and leave a ragged crown.I had three carbide cutters made several years ago that cost about $100 each and they are barely sufficient. While I agree that crowning an SBR may be unnecessary, I crown all of my barrels for peace of mind.

[az doug]

I have cut, threaded and crowned several without issue. No flaking etc. to date. I use a carbide lathe tool to crown the bore.

[FJ540MN]

Cutting the barrel to length is not so much a problem as crowning it. All of the cutters available from Brownells are only hardened tool steel. Hard chrome is tougher than kryptonite. These crowning cutters tend to chatter when used and leave a ragged crown.I had three carbide cutters made several years ago that cost about $100 each and they are barely sufficient. While I agree that crowning an SBR may be unnecessary, I crown all of my barrels for peace of mind.


Sounds like a pressure/speed problem. Was this being done on a lathe?

Carbide is harder than chrome, but it's also very brittle and will easily chip if inconsistent pressure is applied (it has to do with how the cutters are scintered and thier bonding alloys fracture).

HSS is plenty tough enough for 41xx steels, especially considering barrels are not hardened. Feed/speed is key to keep from overheating the tool though.

Using a lathe, cutting from the center out (which should be done anyway to eliminate the burr on the bore), there's little risk of flaking the chrome. You may have to hone the cutter though, as most insert tooling is made with a "dull" edge designed to hold up longer under heavier cuts.