How was this pistol barrel indicated?

lowCountryCamo · Apr 21, 2014

I was reading an article about threading the barrel of a .22 berretta and could not picture how both ends of this barrel was indicated. It is held in a spider jig in the 4 jaw. I understand a riffle barrel is dialed in with a rear spider with an indicator at either end, but in this instance the chamber end is inaccessibly with a dial. Here is the picture and below is a link to the article. Thanks.
Threading a Beretta 21A

Zahnrad Kopf · Apr 21, 2014

Far as I can see, one cannot. Best you can hope for is to pin the bore and indicate radially as well as longitudinally. Cross your fingers and engage the feed. That's as good as it's gonna get.

Artv · Apr 21, 2014

lowCountryCamo said:
I was reading an article about threading the barrel of a .22 berretta and could not picture how both ends of this barrel was indicated. It is held in a spider jig in the 4 jaw. I understand a riffle barrel is dialed in with a rear spider with an indicator at either end, but in this instance the chamber end is inaccessibly with a dial. Here is the picture and below is a link to the article. Thanks.
Threading a Beretta 21A

View attachment 105471

That is a good jig you have for doing this job. Put the proper indicator rod in the bbl and set up with two indicators on the rod, one at the muzzle, and the other at the far end of the rod. If you only have one indicator, put the stand on the saddle and run back and forth. Use the screws nearest the chuck to adjust the runout on the end of the rod. Use the screws nearest the muzzle to zero out the indicator nearest the muzzle. You will need to replicate the threads for the suppressor you have, but most times they are just too big for a .22, so you'll probably have to cut a converter to match the two. You might also have to do some cutting to get a little more barrel exposed.

Art

lowCountryCamo · Apr 21, 2014

I don't see why the chamber could not be held in the 4 jaw and muzzle in a live center. Anyone see a problem with this? Gonna be doing this op for a good friend and don't want to miss anything obvious. Thanks.

wesg · Apr 21, 2014

Indicate at the muzzle, and as far in as you can reasonably reach. Get those both within a couple tenths. How much better do you need it to be? It's just a crappy pistol to begin with.

lowCountryCamo · Apr 21, 2014

wesg said:
Indicate at the muzzle, and as far in as you can reasonably reach. Get those both within a couple tenths. How much better do you need it to be? It's just a crappy pistol to begin with.

Never said couple tenths. .001 TIR would be plenty close I think. Just seems between chuck and center is simple and easy, which is why I asked. Thanks.

Artv · Apr 22, 2014

lowCountryCamo said:
I don't see why the chamber could not be held in the 4 jaw and muzzle in a live center. Anyone see a problem with this? Gonna be doing this op for a good friend and don't want to miss anything obvious. Thanks.

I can see where there might be problems. You can put a center in the headstock if you have one that will fit the chamber, and run between centers. That is assuming your lathe is level and the tailstock dialed in. You can go with the 4J, but just make sure it isn't causing a big cone shaped runout; you don't want the suppressor to telegraph any setup problems. I wouldn't worry too much about accuracy, it is a .22 with a 2.5" bbl.

gunwrench · Apr 22, 2014

I would either run it between centers using a faceplate and dog or, if it was going to be a potentially recurring job, maybe fabricating a brass or aluminum mandrel to hold in the chuck.

MilGunsmith · Apr 22, 2014

Use a range rod and indicate in two locations on the rod, or use a Grizzly rod and indicate the rod in at least two locations. The bore needs to run true and square to the threads or you can have baffle strikes. I do a lot of suppressor work, and you need to treat the muzzle threads as if they are a benchrest chamber.

300sniper · Apr 22, 2014

MilGunsmith said:
Use a range rod and indicate in two locations on the rod, or use a Grizzly rod and indicate the rod in at least two locations. The bore needs to run true and square to the threads or you can have baffle strikes. I do a lot of suppressor work, and you need to treat the muzzle threads as if they are a benchrest chamber.

^This.

It doesn't matter what the chamber end is doing as long as the threads are parallel and concentric to the last part of the bore.

michiganbuck · Apr 22, 2014

“We dial indicate these tiny barrels just like we do larger center-fire rifle barrels to ensure the threading is perfectly concentric to the bore.”

He doesn’t say he indicated the other end of the barrel in the article so as Zahnrad suggested a close fitting pin may have been set in the bore to indicate from IMHO.

http://accurateordnance.com/cgi-bin/imcart/read.cgi?article_id=16&sub=4

Test pin in the bore being very close fit to indicate off seems good and as you noted they could not indicate through that spider.. Being a gun shop he might have such a pin..

OT : The barrel may not run true by itself between centers because chamfers may not be dead true, *but with running true between centers would make the job easy. A barrel length between centers mandrel seems good or a shouldered stub center plug for each end... but to make same to make a pin would be about the same effort..

It dosen't have to run .0000 as you said

ButchC · Apr 22, 2014

I dont know how they would indicate the chamber end on that set up.
I wasnt class 3 but had one class 3 customer who brought me such work. I think mainly so he had a good reason to spend an evening at the shop.
How I preformed short barrel muzzle threading was to chuck a suitable piece of stock and turn it to a good fit for the chamber. The muzzle end then ran in the steady rest with the bore indicated and centered using a purpose built 4 bolt spider. Drove it with a lathe dog or occasionally other creative means. Didnt take half a day to set up the lathe nor the part in it and as far as the customer and I could tell, plenty good enough. Plinking out back of the shop with his "toys" was usually fun times.

Bruce Nelson · Apr 22, 2014

Use a tenth indicator to indicate the circumference and the face. When these are as close to zero as you can get, the hell with it.

CarbideBob · Apr 22, 2014

I do not make guns so most likely I'm missing something but I'd do not understand the problem.
Buy something like one of these:
Test Indicator Kits | MSCDirect.com
Co-ax indicator.

While only good for a thou. or so it will put you 5-6 inches down in the hole.
How do you indicate a 6 inch long bore straight and square to the quill in the B-port?
Think about this, not square to the table top, not to the knee, but true to the quill travel.
Seems like the same type of problem.
Bob

JNieman · May 8, 2014

Bruce Nelson said:
Use a tenth indicator to indicate the circumference and the face. When these are as close to zero as you can get, the hell with it.

That is a great way to induce baffle strikes in suppressors or possibly shoot off a muzzle brake for closer-bore muzzle devices.

You never go by external features. Ever. I don't care who made the barrel or the blank, bores are often not concentric to the outside, and on top of that, the bore may not even be straight inside the barrel. It may take a curved path through the barrel, or simply canted.

Range rods. They exist for a reason. MilGunsmith has it right.

When I did barrel work for precision rifles with high-class barrels that I expected better manufacturing from, I would run the chamber out the back of the headstock, indicate the chamber and the range rod that runs out the muzzle in two places. Checking the chamber was simply a backup to double check my setup. I've put suppressors on 338LM rifles which always had that "If I screw this up, it's gonna be one expensive-as-hell replacement.." and with that setup procedure, I witnessed great results.

I wouldn't start cutting on a barrel if it still had 0.001 TIR or worse. It typically didn't get long to half that number.

Butch Lambert · May 8, 2014

JNieman said:
That is a great way to induce baffle strikes in suppressors or possibly shoot off a muzzle brake for closer-bore muzzle devices.

You never go by external features. Ever. I don't care who made the barrel or the blank, bores are often not concentric to the outside, and on top of that, the bore may not even be straight inside the barrel. It may take a curved path through the barrel, or simply canted.

Range rods. They exist for a reason. MilGunsmith has it right.

When I did barrel work for precision rifles with high-class barrels that I expected better manufacturing from, I would run the chamber out the back of the headstock, indicate the chamber and the range rod that runs out the muzzle in two places. Checking the chamber was simply a backup to double check my setup. I've put suppressors on 338LM rifles which always had that "If I screw this up, it's gonna be one expensive-as-hell replacement.." and with that setup procedure, I witnessed great results.

I wouldn't start cutting on a barrel if it still had 0.001 TIR or worse. It typically didn't get long to half that number.

Mr Nieman,
You are correct as is milgunsmith.The 8 screw spider in the 4 jaw is great. My indicator rods are for ea. caliber and use my reamer bushings. Put 2 indicators on it and you are good to go. Suggesting that some one indicate the OD and face will do nothing. Ain't no barrels made that the OD is concentric to the ID.

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How was this pistol barrel indicated?

lowCountryCamo

Stainless

Zahnrad Kopf

Diamond

Artv

Aluminum

lowCountryCamo

Stainless

wesg

Titanium

lowCountryCamo

Stainless

Artv

Aluminum

gunwrench

Plastic

MilGunsmith

Stainless

300sniper

Hot Rolled

michiganbuck

Diamond

ButchC

Aluminum

Bruce Nelson

Stainless

CarbideBob

Diamond

JNieman

Titanium

Butch Lambert

Titanium

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