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

Come on guys! What's this fixation you all have on FUNCTION? No FASHION sense? I suppose not a one of you has a maroon-anodized Double Auto? (well, it IS a DOUBLE GUN, ain't it?).

Well, it does reduce the aerodynamic drag during the swing by allowing air to pass thru the holes thus lowering the base area drag.

Normal formula for estimating recoil velocity, from which is then derived recoil energy, adds total total wt of ejecta plus 1½(?) times the powder charge times muzzle velocity. The 1½ may be arbitrarily modified according to muzzle pressure. A .30 cal magnum rifle for instance firing a 150gr bullet ahead of 75gr powder, obviously has a charge wt ratio .5 (powder to bullet). A 12ga shotgun with 1 1/8oz shot, 35grs of wads, ahead of a 26gr powder charge has a CWR of .05, notice this is a factor of only 1/10 (.1) that of the mag rifle. It should be quite obvious a muzzle brake is not going to have the effect on the shotgun it does on the magnum rifle. In fact the benefit reaped will be small indeed, but it is real & "Measurable". Extremely funny noone seems able to feel it, but so many can feel a forcing cone, which has no measurable effect. In both cases assuming actual velocity unchanged. Shoes I guess what a good "Promo" salesman can accomplish.

Miller,
I know you're probably not referring to me on feeling of recoil reduction on forcing cones, and I never could feel anything about that either. But, I have done long cones on several guns for what I believe to be pattern improvements. In my very small test, I saw what I believed to be pattern improvement. Until someone shows better evidence to the contrary, I'll stick with my story.

But back to the calculation of the the effect of muzzle breaks. It seems to me that pressure would have more to do with the effectiveness of a given break than the payload velocity. Once the payload leaves the barrel, the hot gases/powder escape at velocities much higher than the payload. So I believe a very slow payload with an extremely high pressure could reap comparable benefits or better than a light, high velocity payload with moderate pressures.

Chuck; No was not referring to you. I can see a distinct possibility of pattern improvment brought about from less deformed shot. I believe you are right about the presure at muzzle. Of course the wt of the powder charge determines the weight of gases exiting, which plays a part s well as the exit velocity. Of course if we could actually determine the exact exit velocity for any individual shot we could exactly figure recoil. Generally speaking the higher the CWR, the slower the burn rate of the powder will have to be to maintain acceptable chamber pressures, therefore the higher will be the muzzle pressure. The .30 cal magnum even with the 150gr bullet would normally burn a slower powder as well as have a much smaller expansion ratio than would a .458 mag with a 500 gr bullet, thus would likely have a higher muzzle pressure. The 500 grain buillet is 3.333 times heavier than the 150gr, but would have a similar wt powder charge, so the percentage of the recoil from the exiting gases is a smaller proportion of the total recoil. Those guns which have the highest percentage of their rcoil produced by the exiting gases reap the largest benefits from muzzle brakes/porting etc. They also of course produce the largest increase in side blast.

I believe there is a big difference between Magnaporting and a muzzle break. Has any one bothered to read the claims on the Magnaport site? They talk about felt or perceived recoil. http://www.magnaport.com/sgun.html

I have a Marlin 1895 45-70 with 26" octagon barrel ported by Magnaport. I was shooting hot lever action reloads. I could not tell the difference after the port job. My final solution was to drop the load down a few grains.

I have a custom Mauser 375 H&H Ackley Improved with a 26" heavy barrel. I had it built with a removable break. I can certainly tell the difference with the break on and off.

Given the porting I have seen on shotguns, I would have to say that I doubt it would make much of a difference. I think stock fit makes more of a difference.

Pete,
I agree. I'm sure the physics say it works on a shotgun...how much, and whether or not it is discernable or improves a person's shooting is much more subjective. A well fit stock and adjustment of the load to the shooter/gun capabilities should be all that's needed and has the potential to fix more dramatic recoil effects.

One can I presume call it whatever they desire. There are two ways it can reduce recoil. First is by reducing overall work done by the expanding gases, resulting in a reduced velocity of the shot load. This affect would be less than a reduction of the bbl length to the point where the ports start as not all the gas is diverted. 2nd is closely related ie the gases themselves are diverted from exiting the muzzle, thus not adding to the recoil. "IF" the ports do this then they serve as a "Muzzle Brake", "IF" they don't act as a muzzle brake, they don't reduce recoil, elementary. If you look at the scenario I gave on the load, which was weighted a little on the powder charge, most target loads will use less than 26 grs powder, "IF" the entire powder charge were diverted & not allowed to escape the muzzle forward the max reduction possible would be less than 5%. These little ol holes aren't going to anywhere near that effecient.
"Surgical Precision", I can assure you I'm no surgeon, but I have operated an EDM machine. "Some" of what they say is "Partial" truth.

Leave theories alone! Once I was in blind with one guy with magnaport double. He didn't shoot no one goose, but made me deaf!

Miller,
"Surgical precision" should be easy enough with some of the new CNC EDM machines, ... and besides, a surgeon is "eyeballing" everything anyway. They do surgury on the wrong people all the time, how precise is that? But heck, that gas don't care how precise the holes are located or sized, just that there's enough area to get out in approximately a direction you want and enough gas to make a difference.