Back Bore/Vang/ Others...What's the Difference?

The Vang Comp is a couple mods:

The alterations to the barrel consist of lengthening the forcing cone, back-boring the barrel, and adding compensating ports.

Click to expand...

Any decent shotgun smith can do the work.

I can't say whether Vang's back-boring and lengthened forcing cone are unique in any way. Vang claims their porting acts as a flash suppressor. That does seem true, based on my barrel. Vang's porting certainly does not make the flash any worse, with the loads I have used.

There is lots of data that show that back boring and lengthening of forcing cones will improve patterns. The mechanism for the improvement is less pellet deformation as deformed pellets tend to separate from the shot string due to different aerodynamics than round pellets. Abrupt forcing cones tend to jam the pellets together, causing some to be deformed, so lengthening of the forcing cones reduces that effect. If the final bore diameter is less, that will also reduce the number of deformed pellets. Harder shot, to an extent, will also produce patterns with less flyers. For a given choke constriction, loads with different shot hardnesses can be made to pattern from IC to Full. I have seen some data that suggest that some older guns are actually "over-choked" with modern loads due to the harder shot pellets.

I have never seen any data that suggests barrel porting of shotguns will improve patterns. Not saying that it does not have an effect, and I can see how the porting might help separate the wad from the shot. I just have not seen any data.

I've seen Vang guns produce some pretty impressive patterns in classes. I believe Hans' minstrations are fairly unique - but I'm no gunsmith

If you're generally looking to tighten up buck patterns, you might look into some of the low recoil/tight pattern loads out there. Hornady TAP has patterned very well in every barrel I've seen it go through. I've had good experience with the Fed LE133 and I understand the LE127 is even better.

Hans and his gnomes do good work, but nothing they do is unique to them only. Long cones and backboring have been smithing staples for decades.

I remember coming across a shotgun webpage, mainly for skeet shooters, that did tests on what mods were beneficial to shotgunners.

IIRC they determined that forcing cone was the most beneficial followed by choke work. I don't remember what they said specifically about porting but I wanna say they didn't think it provided any benefit.