doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Choke Modification Methodology ?

Perhaps someone could enlighten readers on how fixed chokes are "opened." While it is obvious that some type of reamer is used, more detail would be appreciated.

1. Since shotgun bore sizes vary so much (12 gauge from .710 to .750 ?) the reamer probably has some mechanism to stay centered in the bore at the outset. How is this done?

2. The choke reamer tool must be adjustable to cut a specific amount. How is that done?

3. Supposedly that last inch or so of the barrel should be the same parallel "new" diameter. How does the gunsmith cause that to happen?

4. Is this reaming process performed from the breech/chamber end of the barrels using a long rod?

Hope this query isn't too basis....

There are a number of ways to bore chokes , we all have our preferred methods and those of us who do it have built up a collection of tooling over our lifetimes .
There is no one tool or reamer and most people who do choke work will use a degree of honing to get a specific size and to finish .
I bore chokes with specially made long shafted and piloted reamers from breech to muzzle ,taking the metal out in stages and finish hone .

These may help you understand.

https://www.youtube.com/watch?v=l6yrnJIyjtU

https://www.youtube.com/watch?v=bR0KtitH7bU

Pete

Midway video opening up a Parker makes it look easy, factory single barrel like a M12 or 870 it is. They are round inside and out machine made not filed down to finish. Indexing inside on the bore is a viable option. Besides mess it up new barrel is easy to obtain

Hand made double gun its not a simple job. Have seen way more Parkers messed up opening than done right. Thin at the muzzle out of round rough inside etc. plus you loose those nice long chokes Parker was known for. Other makers same thing.

Set up needs to be rock solid, true, and take metal off very slowly on a nice double, something few gunsmiths are set up to do, guessing not a half dozen in the U.S. That can do it right. One of the shotgun magazines had a photo of a English hone set up recently. Massive sliding bed on a lathe that could be dialed in perfect & compensate for the hand finished barrel

Better to buy a nice SXS choked like you want than alter my opinion. Not all will agree though.

Boats

Here it scanned



Outfit that that will do the job. Lot different than Midways turn a reamer with a tap wrench. Heck I can't run a tap true without setting up in the lathe or drill press, much less a choke reamer free hand.

Boats

I will note that chokes without parallels are nothing new. Lefever as well as several other makers were using "Taper choke" which meant the entire length of the choke was a cone with no parallel section, some of them beginning well back into the 1800's.
Adjustable reamers have been offered to the trade for many years with the instructions to use from the muzzle & take very light cuts at a pass & let them follow the parallel.
On the taper choke there is no parallel to follow. I worked as a machinist for over 35 years & will assure you. I don't care how good you "Think You Are" you cannot align an unguided reamer with the bore.
As rocketman said it truly matters not whether the reaming is done from the breech or muzzle as long as the reamer is aligned with the bore. It also matters not whether the reamer is hand or power driven. In the linked video the reamer was inserted from the breech with a bore fitting bushing on the shaft. In this case the reamer itself will center in the cone with the bushing keeping it in line. The fact that the reamer was turned with a heavy tap wrench is of no consequence.
To ream from the muzzle does require a more elaborate set-up as both the barrel & reamer, for a satisfactory job, must be held in alignment.

All good stuff except the bit about taking metal off slowly. Ideal cutting speeds are many times the average gunsmith's use of cutting tools. There is a some rationale for going slowly. Like when your setup is weak. But taking it off too slowly will not yield as good a surface finish. Few gunsmiths are good machinists and few machinists are good gunsmiths.

I have cut hundreds of chokes over the years, for myself and for my clients. I insert an adjustable reamer from the breech end and place a bushing in the bore and another in the chamber. The barrels are held in a milling vise mounted on the compound of my lathe. I flood the bore with coolant and use the power feed on the lathe to move the barrels over the reamer. The set up is rigid enough but the reality is when the reamer is bushed it wants to stay true to the bore. Reamers by nature want to center themselves unlike an endmill which is happy to cut on just a portion of its cutting surface. I like the power feed on the lathe. You can set it fast to remove the majority of the material and very slow for the final pass which leaves a very nice surface finish. I know a very good gunsmith who cuts chokes by hand with a large tap wrench. It is not for me but the gentleman has been getting excellent results with his method for many decades.

I agree with Chuck, few machinist are good gunsmiths and vice versa.

Getting the open job to center is going to depend on the gun as well as the man doing the job. Thing about a lot if not most nice doubles is they were hand filed outside after the bores were choked and finished. Hand work they are not always true outside to inside muzzle to breech.

To be concentric at the muzzle spot you index your lap or reamer would have to be concentric with the muzzle. Filer or the man that choked the gun did not take that into consideration when finishing the barrels.

Other factor is how the finished job is going to look at the muzzle. Have two Parker VH's both factory choked. One is .040 and .033 other is .019 & .014 If you look at the muzzles it's almost impossible to tell one barrel from the other. Reason is the barrels were filed to finish and Parker was looking for a certain thickness at the muzzle. If the tight choked gun was opened to match the open choked gun result would be paper thin muzzles.

Case in point good gun shop near me has hundreds of vintage doubles. You can go down the racks and spot the poor open jobs easily and there are a lot of them. He prices the guns accordingly.

There are shops that can do the job and do it well, some of the best will refuse a job if on inspection they think it's not going to be sucessful It's a personal choice and have no argument with anyone that wants to alter chokes or has had good choke jobs done. Just consider the altered resale value, cost of the work. risk it's not going to come out right vs the cost of buying another gun choked like you want.

Boats