doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com I read it in a magazine...

Just read all recent posts. Yes, as Mike suggests, I meant that the total payload would only differ by 2% and I defy anyone to tell the difference in anything, recoil or otherwise, with a 2% change in total ejecta.

I think there is something in the equation that assumes that the increase in powder is an increase of the same type of powder that was in the baseline load. Are you guys implying that the "equation" knows whether the added percentage of powder is actually ten more grains of powder or ten grains of filler? Some powder has a big percentage of coating to slow the burn rate, and some powder probably has filler in the mix that is not even attached to the powder grains in the form of a coating. How does the "equation" know? If you added ten grains of sand to your 15 grains of powder, would it increase the recoil as much as your equation suggests? I don't think I am the only reader who is doubting the the correctless of the equation.

No, just as 10 grains more lead shot has less effect. The key is the assumption that X grains of powder, any powder, is converted to X grains of gas. And that gas, unlike the lead shot or sand, accelerates to 2-3 times the speed of the shot the instant the blockage (projectile) clears the muzzle. That sudden back thrust of gas adds more to the recoil than an equal mass of sand would. A muzzle brake redirects that gas thrust to pull the gun off your shoulder, thus reducing recoil.....as I understand it.

If it was the same "type" of powder, whatever that means, it would give more velocity.

I've seen the same difference that Mike mentioned between recoil formulas for rifles and formulas for shotgun. They do not come up with the same answers. I don't remember shy, but that's probably why they have two different formulas.

Well, that's enough for me... I'm going to have all my barrels ported.

The one factor the formula does not address is the burn rate of the powder. Which takes us back to the example referred to by Thomas, in which supposedly the only difference in loads was a faster-burning vs a slower-burning powder. All else being equal, including total weight of ejecta and velocity, does one produce more "felt recoil" than the other? This is probably where we need another of those "finding out for myself" tests. Except in this case, because we're talking about "felt recoil", we're pretty much stuck with relying on the opinion of the individuals selected as test shooters. Thus subjective, and always open to questioning and debate.

A gun could be mounted in a rest with the butt against a stationary stop with a sensor between the butt and the stop to measure and record the force of recoil between different loads.

Mike, what would be the difference between ten grains of sand and ten grains of inert coating on the grains of a slow burning powder? I think we all know that not every grain of weight in gunpowder is gas producing, or at least I thought that everyone knew that. How does the equation know the difference between actual gunpowder and inert filler or coating? Jim, no, I'm not neccesarily hardheaded, I just don't believe it is a legitimate equation when used to compute recoil. Jim Legg, I guess I am offending your idea of "discussion", so I will write less and read more.

Murphy: The computer program doesn't care if the powder burns 100% or not. The key is that 100% of the weight of the original powder charge is ejected from the bore at whatever velocity the equation uses.

The 'mass' of the ejected material is what counts along with the velocity. As long as the stuff is flying out the bore at gas speed, it matters not what the stuff is or how it got accelerated.

The equation is valid with black powder also, and we know that much of black powder generated 'gasses' are actually solids. These particles are carried at gas velocity, at least until the pressure is relieved and they hit still air.

In a kenetic energy calculation the velocity is given a squared value, thus the dramatic increase in energy when the speed goes up.

Dean,
Send me all your Parkers and I'll port them for you. I've ported some trap guns for customers when I was gunsmithing. I may have to think about how to do it with your Parkers. That may take quite a while. I'll have to shoot the guns to get the actual "felt recoil" baseline, probably over a long period of time and variety of shooting situations. This could take a bit of time as well.

More to this thread's topic. The device at this web link is shows a force/time curve that cuts thru most of the questions, positions, suppositions, and head scratching. Recoil is broken down into to characteristics, force and time. Be-all-end-all? Nah. But it's a lot better'n that test I saw a couple decades ago in a magazine where they measured how far the gun moved with some weight attached to it. That simply measured energy under the time/force curve...total energy.
http://www.shootingsoftware.com/recoil.htm