Throat reaming 40SW nitride barrel

[gloob]

I have never reamed a throat before. Everything I have found says that a HSS reamer costs about $45.00, but it won't do nitride. And a carbide reamer costs about 10x as much.

I just happened to find a suitable 40SW conversion barrel for a project, and it is on closeout for a good price but is nitride coated. About $70 cheaper than what I can find for an equivalent barrel in stainless.

I want to elongate the freebore so that I can load 40SW extra long, and work up some loads for it. (In a 10mm handgun).

How impossible is this idea? I can turn a brass rod to 401.5 in diameter until it just barely slides into the freebore. Then I can put a 10-20 degree shoulder on the end and put PSA sandpaper over that part. Or glue regular sandpaper, if need be. And carefully trim so that it doesn't touch the rest of the freebore.

Then turn it slow with a drill, cleaning and adding a bit of oil, regularly, until my dummy round fits in. Reapply sandpaper and repeat about 1 or 2 dozen times? Or is this simply not possible?

Alpha Wolf barrel, SBN coated RC 60. On sale $119 at Midway.

[Outpost75]

Nitride barrel will just make a mess and get ruined if you try to ream it. Even with carbide.
Wears out diamond hones quickly too.

[gloob]

Thanks. Any guesses if silicon carbide sandpaper could do this in a reasonable fashion (as in only having to reapply it 20 times or so)? I think the execution of my plan might make the freebore too large, but I can be careful in that respect. I can shape the plug to make it reach long enough, first, but leave the freebore 1 thous too small. Then try to sand it out to full diameter, more carefully, after.

[DougGuy]

Well, you are in luck! I have a 40 caliber carbide reamer with LOW miles on it, it will throat that aftermarket barrel nicely. Send me a PM, and a reminder about the first week of January when you would like to ship it. I STRONGLY recommend waiting until first week of 2024 to send it.

Sandpaper? Glue? DRILL? Any of the Bubba school of kitchen table gunsmithing MAY work, but you have no way of insuring concentricity like a piloted reamer will.

[Randy Bohannon]

Send it to Doug and you will be rewarded with a barrel perfectly executed.he did my Dan Wesson CCO 45 ACP and it shoots very good. Target was shot using 5.0 gr. Bullseye 230 gr. cast bullet from a RCBS mould.

[gloob]

I was hoping for an answer to my question, but it's good to know where to find a smith with the proper tools, already.

I thought the taper of the plug-lap would keep the leade concentric, along with the base ground to a nice slip-fit to the existing freebore. Same as how a normal throat reamer does it?

I could also grind down a mandrel to a slip fit and temporarily glue it into the muzzle end of the barrel to spin it in my 1/2" lathe, along with a steady rest towards the chamber end of the barrel. Then spin the barrel instead of the lap. If I'm lucky, Alpha Wolf bores are concentric with the OD enough for the steady rest to work. If this spins true, I could even use a die grinder and a diamond bit to break thru the worst of the nitride coating if the sandpaper takes too long. I figure I could bore and turn a brass bead to slip and glue over the shaft of the diamond bit so that it can only cut most of the leade lands without going all the way to the freebore. Then finish it with lap.

I'm sure DougGuy does a great job and possibly even at a great price. I might prefer to have a cheap project. I've done similar projects with good enough tolerance and finish to what this requires. Just haven't dealt with nitride coatings before.

[Outpost75]

DougGuy is the man! You will be happy!

[ulav8r]

Black nitride is not a coating, it penetrates the metal a few tenths.

[gloob]

Black nitride is not a coating, it penetrates the metal a few tenths.

Oops. I meant surface treatment.

I think the B in SBN means Boron, and according to google boron nitride is harder than boron carbide. And boron carbide is harder than silicon carbide.

I guess a solid silicon carbide reamer can force its way through a few tenths of SBN without too much trouble, but silicon carbide sandpaper might not do the job! I guess I'll have to hope I can get the barrel to spin true on my lathe to get at it with diamond.

And the barrel sale has to last a bit longer until I pull the trigger, else I'm not going to stomach knowing I missed out!

[DougGuy]

I had to dig and dig in my archives to find this FB post so I could respond to this thread in a proper way.. I have already done the work you want done years ago, it's nothing new.. 10mm on the left, 40S&W on the right.

Attachment 321034

3/31/2015: A nice pair of .400" Lone Wolf barrels for Glock, after throating for use with .402" cast flat point boolits. The owner wanted to seat long in the case on the .40 S&W so it would have the same case volume as the 10mm, and the 10mm barrel needed a little throat work since both these barrels had nice generous throats from Lone Wolf, but they were only .4015" in diameter. Now, as you see them in the photo above, they are finished out at .4025" and will accept .402" boolits without issue.

THIS, is the RIGHT WAY to solve the problem of tight throats, NOT seating deeper in the case to compensate for it!

[littlejack]

Another vote for DougGuy. He throated three barrels for me, and honed my SS Ruger chambers. Doug done a great job. Great turn around and fair price. But, it's your choice.

[Plate plinker]

Great now I have an idea to burn up an extra Glock barrel.

Your nothing but a bunch of enablers!