Chambering a barrel blank, gunsmithing question.

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Dr.K
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Chambering a barrel blank, gunsmithing question.

Post by Dr.K »

Curious,

I ordered some barrel blanks for 9mm, and a chamber reamer in 9mm luger.

I'm going to make one of those inserts that goes into a 20 guage break open, and thread the end of it for suppressor use.

This will be my first time to cut a chamber in anything, but I don't think it will be too far fetched of a task.

Should I just use the reamer, or rough out the chamber first with a boring bar? I understand the headspaceing issues.

Any tips?

Thanks.
Kyle O.
Tony M.
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Re: Chambering a barrel blank, gunsmithing question.

Post by Tony M. »

Dr.K wrote:Curious,

I ordered some barrel blanks for 9mm, and a chamber reamer in 9mm luger.

I'm going to make one of those inserts that goes into a 20 guage break open, and thread the end of it for suppressor use.

This will be my first time to cut a chamber in anything, but I don't think it will be too far fetched of a task.

Should I just use the reamer, or rough out the chamber first with a boring bar? I understand the headspaceing issues.

Any tips?

Thanks.
For a cartridge like the 9mm, I wouldn't bother with boring the chamber before hand. If you were chambering a large diameter bottleneck cartridge, that would be different. As long as the pilot is the right size for the bore, it should be a pretty easy job.

ETA: Make sure you're using good cutting lube. That makes more difference than people realize. It preserves the tool and makes the job easier.
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Re: Chambering a barrel blank, gunsmithing question.

Post by Capt. Link. »

Dr.K wrote:Curious,

I ordered some barrel blanks for 9mm, and a chamber reamer in 9mm luger.

I'm going to make one of those inserts that goes into a 20 guage break open, and thread the end of it for suppressor use.

This will be my first time to cut a chamber in anything, but I don't think it will be too far fetched of a task.

Should I just use the reamer, or rough out the chamber first with a boring bar? I understand the headspaceing issues.

Any tips?

Thanks.
You should have a TGP bar to set the headstock then a Lathe bar to dial in the tail stock.A floating reamer holder and gauges are standard.Its not hard but best done the first time with a Elmer.PM me!
Last edited by Capt. Link. on Tue Dec 24, 2013 10:38 am, edited 1 time in total.
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Re: Chambering a barrel blank, gunsmithing question.

Post by rqlasl »

I did the exact same thing with a old Hopkins & Allen 12 ga. Converted it to .44 mag. I used a chamber reamer and a good cutting oil.....I rented the chamber reamer, go no-go gauge and a pilot bearing for the job. Came out perfect and its a tack driver!.......I'm guessing you were inspired by Enfields build?

Any Q's let me know....Good luck and be safe

Don't take it shorter than 18 inches, technically its still a shotgun and falls under the barrel length restriction for that.

I must have gotten really lucky!....Did my chamber by hand with the reamer and a t-handle and it came out perfect......Threaded it 16x1LH.

Really quiet with .44 special loads.......Working on a nice 300gr subsonic .44 Mag load in the mean time.
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Dr.K
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Re: Chambering a barrel blank, gunsmithing question.

Post by Dr.K »

I just saw one of those non rifled inserts, and thought I could improve on it. Rifled blank was only $40, and I have a gunsmiths lathe.

Is enfield's on this forum? I like that guys stuff!
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Re: Chambering a barrel blank, gunsmithing question.

Post by Baffled »

Cut sloooowwwwwwly and use gobs of lube, as stated. Be sure to withdraw as needed to clear the flutes.

Maybe it's just me, but I'd pre-bore to 0.015" undersized, then ream. Reamers are finishing tools. Also, if possible, leave the barrel long. Do the chamber first. If successful, turn the muzzle end. If not, you have barrel stock available to try again.
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Re: Chambering a barrel blank, gunsmithing question.

Post by Stachi »

But Reamers with a Pilot need a Diameter that the Pilot can ride in :) Pre-Boring it will remove the Guide Bore for the Pilot, or am I mistaking?
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Re: Chambering a barrel blank, gunsmithing question.

Post by rqlasl »

Enfield557 ......Look Under Complete Builds, He Did One In 32 Acp.......I NeveR Would Have Thought To Try tillTill I Saw His Build.....Ejector Was The Real Trick On Mine. He Has A Video On Youtube....
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Re: Chambering a barrel blank, gunsmithing question.

Post by rqlasl »

Sorry, tried to post from my phone and the format changes
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Re: Chambering a barrel blank, gunsmithing question.

Post by Baffled »

Stachi wrote:But Reamers with a Pilot need a Diameter that the Pilot can ride in :) Pre-Boring it will remove the Guide Bore for the Pilot, or am I mistaking?
I think it depends upon the length of the pilot, but I may be very mistaken as well. I've only reamed .22LR chambers, and it's only a little bit of metal that comes off. I was looking at it from a machinist's POV; it's a reamer, therefore, 0.015" would be a good amount to cut. Too much can dull and overload a reamer.

You are correct in that the pilot MUST contact the rifling to be correctly guided.
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Re: Chambering a barrel blank, gunsmithing question.

Post by 57fairlane »

Stachi wrote:But Reamers with a Pilot need a Diameter that the Pilot can ride in :) Pre-Boring it will remove the Guide Bore for the Pilot, or am I mistaking?
You're right . . . the 300 blk barrels I've done I let the chamber reamer do all the work.
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Re: Chambering a barrel blank, gunsmithing question.

Post by Tony M. »

Stachi wrote:But Reamers with a Pilot need a Diameter that the Pilot can ride in :) Pre-Boring it will remove the Guide Bore for the Pilot, or am I mistaking?
Yeah, that's a big part of why I didn't recommend the pre-bore. The larger diameter rifle chambers I generally pre-cut, either with a boring bar or a roughing reamer, then when possible I use a pull through reamer to maintain concentricity.
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Re: Chambering a barrel blank, gunsmithing question.

Post by Fulmen »

It shouldn't be a problem to bore out the chamber so that the pilot will engage the bore before the reamer cuts. And strictly speaking a bored hole should be as concentric as the bore, right?
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Re: Chambering a barrel blank, gunsmithing question.

Post by Dr.K »

I'm thinking I'll just push the thing in there without pre-boring.

I mean, were talking 9mm luger, there is not a lot of stuff to take off outside the bore diameter. My blanks should be here today, thanks for the advice everyone, If some unforseen head scratcher pops up, I'll surely ask my favorite group of folks on the internet what to do! :D
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Re: Chambering a barrel blank, gunsmithing question.

Post by Fulmen »

I was speaking in general terms, for something like a 9mm or 300BLK I wouldn't bother boring.
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Re: Chambering a barrel blank, gunsmithing question.

Post by Stachi »

For bigger Calibers there's always a Rougher or an old dull Finishing Reamer.

But, for what it's Worth, we're not Talking Production Reaming. A good Quality Reamer will do more Chambers than anyone of us Privateers may ever needed, if treated properly. Than there's still Regrinding.

That's just my Opinion :) There've been People that totally bored out or even drilled Chambers and these Things are Working. Not that I'd promote this Way of Chambering.
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Re: Chambering a barrel blank, gunsmithing question.

Post by Baffled »

Stachi wrote:.

That's just my Opinion :) There've been People that totally bored out or even drilled Chambers and these Things are Working. Not that I'd promote this Way of Chambering.
I've often felt that if you have a good lathe, nice boring bars, and the necessary measuring equipment, it wouldn't be hard at all to bore a straight-walled chamber, like just about any pistol round, .30 carbine and other straight rifle rounds, and the like.

In fact, it'd give you great control over chamber size, with potential accuracy implications. But it obviously must be approached intelligently and with an understanding of head space, any necessary rim relief, etc. Also, any cuts for extractors need to be done, and that's not something a chambering reamer can do.
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Re: Chambering a barrel blank, gunsmithing question.

Post by Fulmen »

In principle I agree, and my friend whom I share shop with proved that by turning the Morse taper on a new spindle for the old mill. But he had a gage to check against, without that it is a practical impossibility to measure a conical bore accurately. You can't measure a cone accurately without an exact depth at the point of measurement, and while that shouldn't be impossible (I've never done anything like that), I suspect it would be quite time-consuming. Once you put that much work into it I suspect it would be simpler to make a reamer.
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Re: Chambering a barrel blank, gunsmithing question.

Post by Tony M. »

Baffled wrote:
Stachi wrote:.

That's just my Opinion :) There've been People that totally bored out or even drilled Chambers and these Things are Working. Not that I'd promote this Way of Chambering.
I've often felt that if you have a good lathe, nice boring bars, and the necessary measuring equipment, it wouldn't be hard at all to bore a straight-walled chamber, like just about any pistol round, .30 carbine and other straight rifle rounds, and the like.

In fact, it'd give you great control over chamber size, with potential accuracy implications. But it obviously must be approached intelligently and with an understanding of head space, any necessary rim relief, etc. Also, any cuts for extractors need to be done, and that's not something a chambering reamer can do.
Technically possible, but I've always just made custom reamers instead of trying to deal with the issues of a tapered bore etc. Reamers are really easy if you've got a lathe and a cutter grinder, but they aren't bad with a lathe and a milling machine with a spindex either.
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Re: Chambering a barrel blank, gunsmithing question.

Post by Stachi »

Technically one could easily bore out simple (read: almost Straight, preferably Pistol-Caliber Chambers) on almost any Lathe with a Compound Slide. It's a no-brainer Adjusting the Angle to give a Taper on a known Distance with a Dial Indicator. On a CNC-Lathe it's even more easy, but maybe a Test Piece needs to be chucked up and machined first to check for Fit. CNC's may be badly alligned too, especially those who run Hard Production on High Strength Steels. Headstock Misalignment results in wrong Angles and tapered Diameters.

As for the totally drilled out Chambers, this seems to have been done with .22lr and the Like. Grinding the Drill's Edges to a Radius may give a better Surface. I've never done this with a Chamber, but with other Production Parts and it worked out quite well.

Nothing of those Methods compares to a correctly reamed Chamber, of Course! I'd not pre-bore or Drill on that 9mm Chamber, but simply go slow, back out often and apply plenty of cutting Oil.
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Re: Chambering a barrel blank, gunsmithing question.

Post by WarbirdsCustomGuns »

Dr.K wrote: This will be my first time to cut a chamber in anything, but I don't think it will be too far fetched of a task.

Should I just use the reamer, or rough out the chamber first with a boring bar? I understand the headspaceing issues.

Any tips?

Thanks.
Do it right & use the reamer made for the job.
It only takes 15 minutes to chamber a 9mm barrel.
With pistol calibers on average only about .025 is taken off each side & the reamers last for 1000's of barrels so wearing it out won't come soon.




Baffled wrote:
I've often felt that if you have a good lathe, nice boring bars, and the necessary measuring equipment, it wouldn't be hard at all to bore a straight-walled chamber, like just about any pistol round, .30 carbine and other straight rifle rounds, and the like.

In fact, it'd give you great control over chamber size, with potential accuracy implications. But it obviously must be approached intelligently
I see lots of Elmer fudd there.

There's a thing called SAMMI specs.
Deviate from that at your own peril.
All straight walled cases have a taper & for good reason.
The case mouth must seal when fired & to prevent ruptured cases.
Also prevents gas blow back that can make you blind permanently.

A couple of things you guys haven't mentioned.
I'd love to see you try to cut the freebore & throat & get it perfect.
Any variance on that will get you in a heep of hurting.





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Re: Chambering a barrel blank, gunsmithing question.

Post by Baffled »

I see lots of Elmer fudd there.
"Elmer Fudd" is using a drill to chamber.

Given that I can (and have) made my own reamers in the past, I'm going to go out on a limb here and say that I believe I can successfully bore a 9mm barrel using the correct tools, and with a bit of care.

YMMV; yes, it's not for everyone.
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Re: Chambering a barrel blank, gunsmithing question.

Post by Stachi »

Boring out a Chamber (a Chamber doesn't necessary mean a .50BMG Chamber..) on a Lathe is totally doable. I could do it on my CNC Lathe for most Pistol Calibers, to Spec on the First Shot. I'm a Machinist by Trade and I've done much more complicated Stuff than this. I've already stated that I'd not pre-bore it nor would I use any other Ways of creating the Chamber. I'd use the Reamer which the OP already seems to have on his Hands. I also stated that the Reamer will do 100's of Chambers without getting Dull when used correctly, even without pre-boring.

I've seen Chambers created just by Drills used in Poacher Guns (it's illegal to Hunt and posess Firearms, unless you've got an expensive Hunting License, where I come from) that worked. Yes, straight walled .22lr Chambers created by a Drill-Bit. If someone in here can't imagine that it'll work, thats not my Fault.
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Re: Chambering a barrel blank, gunsmithing question.

Post by Baffled »

I think the valid point is not to attempt it without

A) Experienced and quality machining technique; and
B) Understanding some cartridges are far less forgiving than others.
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