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Aust

Back boring and forcing cones on a Saiga 12 barrel

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I went to a local gunsmiths today to show them my S12 barrel to discus lengthening the forcing cones, as Ive had this done before to trap guns with the benifit of reduced recoil and a more consistant patern spread.

 

Whilst on the subject he measured the std barrel which turned out to be 0.720 ID

 

He comented that this was quite tight and that the gun may benefit from back boring upto 0.729 or greater

 

Obviously this would remove the chrome lining but as I clean my gun after every use this is not an issue for me

 

Just wondering if anyone had back bored their barrel to reduce recoil and improve the shot pattern?

 

The gun smith in question has all the proper equipment and has done allot of barrel honing over 1000 now so knows his stuff

 

He told me not to bother about forcing cones as much as the chokes and bore size for pattern / recoil

 

Any thoughts?

Edited by AustenW

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He proably knows his suff but how many of the guns he worked on had chrome bores? i would be concerned at the possibility of the chrome lifting in the area directly in front of the machined area.i have seen pictures of chrome lifting from s12 gas ports, its only a tiny disturbed area and the pressure and gas wash are lower there due to the distance from the chamber.

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Both back boring and lengthening the forcing cone will help with felt recoil and generally help the pattern.

 

Some times the improved / tighter pattern are seeing is just for having the same choke now constricting from a .73 or bigger to .69 in full instead of the earlier .72, in a way you’ve made your choke .01 tighter.

 

Easy way to tell is go shoot the same ammo out of a Mossberg 835 and a 500, the 835 is majorly back bored.

 

http://www.vangcomp.com/

Edited by 20-Mags

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Just be careful in what you do the saigas are tempermental and what ever you do may effect the cycling of your gun.

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He proably knows his suff but how many of the guns he worked on had chrome bores? i would be concerned at the possibility of the chrome lifting in the area directly in front of the machined area.i have seen pictures of chrome lifting from s12 gas ports, its only a tiny disturbed area and the pressure and gas wash are lower there due to the distance from the chamber.

Good you mentioned this. Plating adheres best when its can wrap around slightly radiused edges..for whatever reason a square edge really lends to chipping. Im not saying it WILL start chipping imediately..but its likely that it will begin to. Ask your smith if he considered this possibility already.

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American 12 Gauge Cylinder Bore is approximately .725 so your gun is definitely a cylinder bore. Nothing tight about that. I would question a gunsmith who told me this is quite tight. Don't take my word, look up standard dimensions for shotgun bores. European and American standards are a little bit different, but not much.

 

I have back bored several barrels and will never do it again because of the inconsistency of the steel used in the barrel. Many of the barrels have hard/soft spots and will cause ripples inside the barrel during the machining. Very few, that I have worked on, will cut consistently.

 

Back boring is generally done to lighten up a barrel and when the math/cut is done properly you can turn a cylinder bore gun into a Modified/IM, etc. As long as there is a constriction at the end of the barrel, you will have a choke, subtract the constricted end from the back bore and compare the numbers on a shotgun choke diameter chart and that is approximately what your gun barrel is choked to.

 

Back boring a Saiga barrel will not give you that much gain per cost. On a trap/skeet gun absolutely, where the weight will make a big difference on the swing/balance of the gun, but seriously, not a Saiga with a magazine hanging out of it!

 

I believe you have asked about forcing cones in a prior thread and as I said , the Saiga 12 does not have a typically tight forcing cone. Not enough to worry about or spend the money on reaming as it will not make that big of difference.

 

Just have the barrel reamed for screw in chokes and be done with it.

 

Jack

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