Fixed choke

I have a semiautomatic shotgun that has a fixed mod choke from the factory. I'm aware I can get it fitted for truchokes. But I want to install a permanent fixed choke in it. Probably going with a full choke(long rang squirrel gun). Any advice ot measurements would be greatly appreciated. I have lathe and milling machine experience.

There is no set diameter of choke bore at the muzzle. The amount of constriction that is made is dependent on both the general bore diameter before the choke as well as the choke diameter. Generally .040 constriction will give a full choke pattern in a 12 ga. Barrel.

I understand bore to choke restrictions. Just wondered about how to hold the permanent choke in place.

If I understand, you want to bore out a recess at the muzzle and then permanently install a piece that has a full choke? Sounds like a difficult process. Yes, I have see that some gunsmiths offer that as a service for thin barreled guns that need a choke. Silver solder or soft solder comes to mind to hold it. Several options that would appeal to me more that one come to mind also

Stan Baker, the guy who invented the screw in choke system, used to expand the last couple inches of the barrel where the choke was installed. He made a collet die that expanded the barrel in a similar fashion as exhaust pipes are done. He then bored it true and threaded for the choke tubes that he also made.
I have a Remington 1100 trap gun that Stan installed choke tubes in while he was still a one man shop in Federal Way Wa. He made winchokes for Winchester and within one year after he did mine he had 85 employees and a new shop.

An interesting project you are tackling. Post pictures if you can. We like those kind of projects.

this has to be one of the oddest requests ever. You'd have to probably bore out the muzzel then swage in a piece then hone to a full constriction. Big bucks. What kind of gun? Can't you just buy a full choke barrel?

The gun is a beatup remington 1100 I got a good deal on. I agree I could just buy a new barrel, but that would take all the fun out of it.
Besides look at the smithing forum, we wouldn't have the great customs like hondo44 and sharps 40 has on here. It's realy a learning project. Im gluing the busted stock, smoothing the deep gouges is the action, rust blueing, and I figures sense I'm doing all that, might as well do some barrel work. I would love to make a 1" bull barrel, but taking the rib off has me nervous.

Your problem is obviously you need to increase the constriction. Tough to do

most of the ones being built now are spot welded (rem.)
With remington ribs, cut the rib at the posts,removing the rib than cut the posts.
Cleaning up what is left of the posts take time with a file and a hard polishing wheel,draw file to remove the wrinkles and get a good blended surface. (pasted from shotgun world)

If it were my gun, I would use a brake cylinder hone to open up the bore behind the
choke to form what is known as a jug choke. Remington barrels are normally thicker than most barrels and the difference between modified choke and full choke will only be a few thousandths on each side of the barrel. A brake cylinder hone with a drill extension should be able to open up that bore in a relatively short time. Hone and pattern,hone and pattern. That is how gunsmiths have done it for many decades.

I was thinking of reaming out .800" and swag ing a choke tube in. Then maybe back boring or sleeving the entire barrel and starting from scratch.

constriction difference is probably .020 total at the diameter. so .010 on each side. typical bore size is .740 Industry standard -Briley
CYL: 0.000
SK: -0.005 - - - - .735
IC: -0.010 - - - - .730
LM: -0.015 - - - - .725
M : -0.020 - - - - .720
IM: -0.025 - - - - .715
LF: -0.030 - - - - .710
F : -0.035 - - - - .705

Interesting side note; Have you ever seen the trap barrels they made back in the late 70's to early 80's that were sold for the Remington870 and 1100.
They had 12 ga. Chambers and we're bored from the chamber forward to 10 ga.
I had a friend who shot one at our local gun club. That gun
,when using normal trap loads,had a super soft report and recoil and ground up clay targets as good as any gun I have ever shot. Hit every bit as hard as my Ljutic and in the 1100 the recoil was so soft as not to be believed.
There is hardly anything that has not been tried and done when it comes to custom shotgun bore work. Do your thing and take photos and post a report if you will.
Have fun!!!

I wish you knew the bore and choke size!!

Sorry, I do not. Maybe that info can be found on the net? I don't remember who made them or what they were called either but it is real,not a pipe dream I swear!

The late 1980's and 1990's 870 and 11-87 trap guns were .745" again from shotgun world

I'm trying to decide exactly what I want from the barrel work. Parts want to make it a gun trap gun, other parts wants to make a stock appearing card shoot barrel.

I'm with Chuck on this. Googe "Jug Choke." You can open up the portion of the barrel behind the existing choke with a cylinder hone. This is the method for adding a choke to smoke poles and it works.

You DO NOT silver solder on barrels; soft solder only.