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Clark · October 1, 2013, 07:03 AM

I have threaded a number of old shotguns barrels to take screw in chokes.
I bought the rem choke reamer, bushings, and tap.

Another thing to look out for, is shotgun bores that are off center. This really is a problem. Cut an inch off the end of a shotgun muzzle and you can often see it with the naked eye.

I find I can do a barrel much faster [not that time matter much for some old retired guy] if I make a drawing of what the reamer is supposed to do, and cut some of the metal out of the way with a boring bar. Then the reamer, then the choke tap. Some guys tell me my reamer is dull if I do that. It is not. I am reaming slowly and it fills with chips. The boring bar.. I can run the lathe at high r.p.m.s.

There are some straight forward cautions from Brownells:
http://www.brownells.com/UserDocs/Mi...stallation.pdf

CREW-IN CHOKE INSTALLATION REQUIREMENTS
Before accepting a barrel for machining to accept screw-in chokes, you must measure the outside diameter (O.D.) to determine
if there will be sufficient wall thickness after machining. “Mike” the O.D. of the barrel and the O.D. of the tap for the particular
gauge. Subtract the O.D. of the tap from that of the barrel, divide by 2, and this will give the wall thickness after machining,
providing the O.D. of the barrel is concentric with the inside diameter (I.D.). A sample calculation appears below.
Barrel O.D. (12 Gauge) .850"
Tap O.D. (12 Gauge) Win-Choke™ – .814"
.036" ÷ 2 = . 018" Wall Thickness
We DO NOT recommend installations in barrels where the resultant wall thickness will be less than .015", providing the I.D. of
the barrel is concentric with the O.D. If the I.D. is not concentric with the O.D., you will have to make your own decision as to
whether the installation will be safe. In addition, you CANNOT install screw-in chokes in barrels whose inside diameters (I.D.)
exceed the following dimensions:10 ga. - .780";12 ga.- .735";12 ga. Thinwall- .728";16 ga.- .666";20 ga.- .624". Exceeding these
dimensions WILL CAUSE DAMAGED CHOKE TUBES and there is a GREAT POSSIBILITY OF CAUSING A BARREL BLOW-OUT!
Check EVERY installation before firing to make sure the tube does not protrude into the bore. Back-bored or jug-choked barrels
are usually NOT suitable for screw-in choke installation.

http://www.midwayusa.com/product/938...nwall-12-gauge

Specific Choke Types:

Tru-Choke for use with barrels that are too thin for Win-Choke. Outside diameter .020" smaller than Win-Choke.
12 gauge .795" - 44 tpi, accepts standard Tru-Choke tubes. 20 gauge .675" - 44 tpi

Tru-Choke thinwall for over and under, lightweight single shot, side by side with thin barrels. 0.020" thinner than standard Tru-Choke tubes.
12 gauge .775" - 44 tpi, accepts thinwall style tubes only.

Win-Choke for threading barrels to accept original equipment tubes from Win-Choke, Mossberg AccuChoke, Weatherby, Browning Invector.
12 gauge .814" - 32 tpi. 20 gauge 11/16" - 32 tpi.

Rem-Choke barrels will accept Rem-Choke and Remington factory tubes.
12 gauge .814" - 32 tpi.

October 1, 2013, 07:03 AM	#19
Clark Senior Member Join Date: December 4, 1999 Location: WA, the ever blue state Posts: 4,678	I have threaded a number of old shotguns barrels to take screw in chokes. I bought the rem choke reamer, bushings, and tap. Another thing to look out for, is shotgun bores that are off center. This really is a problem. Cut an inch off the end of a shotgun muzzle and you can often see it with the naked eye. I find I can do a barrel much faster [not that time matter much for some old retired guy] if I make a drawing of what the reamer is supposed to do, and cut some of the metal out of the way with a boring bar. Then the reamer, then the choke tap. Some guys tell me my reamer is dull if I do that. It is not. I am reaming slowly and it fills with chips. The boring bar.. I can run the lathe at high r.p.m.s. There are some straight forward cautions from Brownells: http://www.brownells.com/UserDocs/Mi...stallation.pdf CREW-IN CHOKE INSTALLATION REQUIREMENTS Before accepting a barrel for machining to accept screw-in chokes, you must measure the outside diameter (O.D.) to determine if there will be sufficient wall thickness after machining. “Mike” the O.D. of the barrel and the O.D. of the tap for the particular gauge. Subtract the O.D. of the tap from that of the barrel, divide by 2, and this will give the wall thickness after machining, providing the O.D. of the barrel is concentric with the inside diameter (I.D.). A sample calculation appears below. Barrel O.D. (12 Gauge) .850" Tap O.D. (12 Gauge) Win-Choke™ – .814" .036" ÷ 2 = . 018" Wall Thickness We DO NOT recommend installations in barrels where the resultant wall thickness will be less than .015", providing the I.D. of the barrel is concentric with the O.D. If the I.D. is not concentric with the O.D., you will have to make your own decision as to whether the installation will be safe. In addition, you CANNOT install screw-in chokes in barrels whose inside diameters (I.D.) exceed the following dimensions:10 ga. - .780";12 ga.- .735";12 ga. Thinwall- .728";16 ga.- .666";20 ga.- .624". Exceeding these dimensions WILL CAUSE DAMAGED CHOKE TUBES and there is a GREAT POSSIBILITY OF CAUSING A BARREL BLOW-OUT! Check EVERY installation before firing to make sure the tube does not protrude into the bore. Back-bored or jug-choked barrels are usually NOT suitable for screw-in choke installation. http://www.midwayusa.com/product/938...nwall-12-gauge Specific Choke Types: Tru-Choke for use with barrels that are too thin for Win-Choke. Outside diameter .020" smaller than Win-Choke. 12 gauge .795" - 44 tpi, accepts standard Tru-Choke tubes. 20 gauge .675" - 44 tpi Tru-Choke thinwall for over and under, lightweight single shot, side by side with thin barrels. 0.020" thinner than standard Tru-Choke tubes. 12 gauge .775" - 44 tpi, accepts thinwall style tubes only. Win-Choke for threading barrels to accept original equipment tubes from Win-Choke, Mossberg AccuChoke, Weatherby, Browning Invector. 12 gauge .814" - 32 tpi. 20 gauge 11/16" - 32 tpi. Rem-Choke barrels will accept Rem-Choke and Remington factory tubes. 12 gauge .814" - 32 tpi. __________________ The word 'forum" does not mean "not criticizing books." "Ad hominem fallacy" is not the same as point by point criticism of books. If you bought the book, and believe it all, it may FEEL like an ad hominem attack, but you might strive to accept other points of view may exist. Are we a nation of competing ideas, or a nation of forced conformity of thought?