doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Magna Porting on a hunting gun.

Actual recoil is simply an example of Newton's 3rd law.
Recoil is calculated

E = 1/2 (W / 32) (L x V + 4700 x P / 7000 x W)squared.

E = recoil Energy in ft. lbs.
W = Weight of the firearm in pounds,
L = Weight of the load in grains (this includes the wad, filler, etc),
V = Muzzle Velocity of bullet in feet-per-second,
P = Weight of powder in grains

So you can increase W, decrease V or L and reduce recoil. Nothing else impacts the formula.

A barrel is an efficient engine that is highly directional. What happens with a muzzle break or porting is that you create an engine that has lost some of the directional thrust. You can not reduce the base recoil with a break or porting. You can only alter the directional thrust. True there is a slight loss of velocity, but we are talking about maybe 50 fps.

I don't think anyone has touched on the "mental factor" of shotgun porting. This plays a important part in shotgun shooting.
If the shooter BELIVES something will improve his shooting, it will.
Go to any large clay target shoot and look at what people are useing on their guns. You will see everything from different colored beads and ported choke tubes to trigger shoes and recoil pads mounted upside down. They work for the people useing them because they believe they work.
If the guy that won the Grand American Handicap had a 9/16" nut welded on the end of his gun, you can bet that the next week there would be a lot of guns with nuts welded on them.

Chuck,
Thanx for the idea of porting with an end mill....I have ported many barrels on the mill, but have always used a drill to bore "the indexed" holes....the use of an end mill makes clean up inside the bore a lot easier, and you don't get that raised ring around the hole, that is caused by the tapered point of a drill..


"I ported a 870 trap barrel for a guy that just had to have it done. I advised against it, but he would have either me or some butcher with a hand drill do it. So, I did it by copying my Browning 325 pattern, using a dividing head in my Bridgeport, and used a brand new carbide endmill to reduce the burr, then lightly honed it. The customer was very happy, even after he had shot it. I couldn't figure out why a trap gun needed recoil/muzzle jump reduction.".....Chuck H

Mike,
Glad to have given a tip. I'm lucky in that I have a friend that manufactures endmills and rotary files (burrs). When I need a new endmill, it's usually made custom or laying around.