Cutting a AR-15 Barrel

[Henryrifle]

I have a 1.25" diameter 26" barrel coming to me and want to turn it into an AR barrel. I have all of the dimensions for the finished barrel but am not sure how to start. I want to turn the the barrel down to 1" diameter or .980".

Can I span 22" or so between the 3-jaw chuck and the live center and use a follow rest to reduce the diameter? Is there a better way to do that?

Thank you,
Henryrifle

 

[derf]

Probably will depend on how big your lathe is, if it's 13-14" swing, should be no problem to turn without a follower. Typically chatter won't occur till you get down to about .750" if you only have 22" exposed. You could also turn half the length at a time if it will fit through your chuck. Use a tool that looks like this...^ and set the feed for .015" per rev, and take .015" per side doc. Run the tool tip above center as far as it will still cut.

 

[wrat]

Not knowing your lathe, i'd say to pull out a tape measure and find out if it'll fit. Or how much will fit.
If this is a little Atlas/Craftsman, you may not have the spindle diameter to put an AR barrel through, either, even turned down.

 

[Henryrifle]

The barrel will fit through the headstock as my lathe has a spindle bore of a little larger than 1.5". The lathe is a 12X36 with a 7" swing over the cross slide, otherwise 12" swing.

The barrel is 416 Stainless. Would I be better off cutting with a HSS cutter or an indexed carbide cutter?

I realize I sound like a total newb, and, I guess I am. I have chambered and threaded several bolt gun barrels but this is the first AR barrel.

I know what to do once I have a barrel that is prepared on the outside--just not sure how to get there in the smartest way.

Thank you again,
Henryrifle

 

[wrat]

The barrel is 416 Stainless. Would I be better off cutting with a HSS cutter or an indexed carbide cutter?

For me, indexable carbide is always the best choice.
But that should ignite a couple of opinions <chuckle>

 

[macardoso]

The barrel is 416 Stainless. Would I be better off cutting with a HSS cutter or an indexed carbide cutter?

I've done well on 300 series stainless with the --GX or --GT type inserts. For example a CCGX or VCGT. These are razor sharp and designed for non-ferrous, but they cut with very little pressure and do great on tough and gummy materials like stainless (albeit with shorter tool life). Finish is really great as well since they cut like HSS rather than plowing through the material.

HSS is great too. Whichever you prefer.

 

[Tozguy]

Just curious Henry, do you want to taper the barrel or will it be cylindrical?

I have chambered and threaded several bolt gun barrels but this is the first AR barrel.

Since you are turning from 1.25 to 1'' or less you have room to experiment with different tools. Why not the same tools you have been using to cut tenons, whether carbide or HSS? My best results on 416SS came with the Diamond tangential holder and HSS bits because of the top rake and ease of sharpening.

 

[seasicksteve]

I would do it 1/2 and 1/2 as Derf suggested. Set up like this I would bet you could pretty much get away with any LH heading turning tool that you have handy 416 cuts real nice. Have you thought about clocking the gas port so it winds up in a groove or splitting a groove and land. I am not convinced that it matters but if you have a preference you want to establish the gas port location and turn all features based on that. The follow rest works well too on the straight turning. I did a couple ar rimfire bbls and used the follow when i buzzed the dia off it worked great.

 

[Henryrifle]

Thank you all for all the advice. I received the barrel today and have, so far, resisted the temptation to get started. I am waiting, likely for 4-5 weeks, on several other parts including a range rod, bushings and a reamer, none of which are necessary to reduce the diameter of the barrel but; I would like to do the job in a series of consecutive steps.

What does raising the cutting edge above center do when turning? I have never tried anything other than cutting at the center or very close to it.

I have read a few opinions about drilling the gas port into a groove but as there does not seem to be a consensus that that is necessary, I am not going to worry about it. Maybe I'll get lucky...

Looking forward to getting started. At 27" long and 1.25" in diameter, that is quite piece of steel. My heavy Palma barrels for F-T/R don't look anything like that.

Thank you all again,
Henryrifle

 

[swiftab]

You asked about why keep the tool bit above centerline. When turning long workpieces, the steel will try to walk up on top of the tool bit. Keeping the tool bit above center prevents this.