Filler (COW?) to simulate shorter barrel

[freedomlives]

Does anyone know/guess how far off using an inch or two of COW/Corn Meal/etc. over the powder in my muzzleloading pistol to simulate a shorter barrel would be?

My derringer is .45 caliber with a 4.5" barrel, which is at the upper limit of being concealable for carry. I've written an article for a Slovak magazine about guns for self defense as well as an accompanying website I'm starting (which my dear wife will translate soon, hopefully before the magazine hits the press). I want to include some data on powder loads vs. muzzle energy, but my gun is really atypical of what someone buying these derringers would get. Most would get a maximum 3.5" barrel, if not shorter.

When I go to the range to test different powder loads, I intend to add an inch and two inches of some sort of filler over the powder load so that the bullet travels the equivalent distance as though it were in 2.5" and 3.5" barrels.

I know from previous testing that when my gun is loaded with 1.5grams of BP I get a muzzle energy exceeding that of a 9mm Makarov (which over here is considered by many to be going "big guns"), but also a bit of kick from shooting it, and I'm not so sure that a lesser load would give the same power. For me, this isn't an issue, because I don't mind the kick much, but a small woman carrying such a gun might mind, so I want to find the optimum load.

Anyway, now that I've rambled a bit, the point of my question is:
Will the approach of adding 1" of COW or some similar filler (as we don't have COW here), approximate a 3.5" barrel or would it drastically change the ballistics?

[curator]

Adding an inch or so of cream of wheat would change the load's ballistics considerably. Not only would the filler add to the weight of the bullet, but the compression-sealing provided will cause a much more efficient burn of the powder charge resulting in more velocity even though the bullet is closer to the muzzle. Sorry to be a "wet blanket." In the world of pocket pistols, an inch more or less of barrel length does not mean much in terms of velocity. If you are using FFFg granulation, I doubt an extra inch (3.5 vs 4.5") would account for more than 20-30 fps, if that. A tighter or loser parch can cause more than that, as can a slightly fouled bore.

[fouronesix]

Yah, seems like the best, most direct way to get where you want to go (and I'm not exactly sure where that is) would be to use a chronograph along with some well designed testing procedures (scientific method). Especially important if you will be publishing the results.

[freedomlives]

It would be funny (and great!) if adding inert material between the bullet (a 200 grain .45 R.E.A.L.) and the powder actually increased velocity.

The main thing I want to determine is what is the optimal powder charge. The insufficient instructions that come with the gun state that it can be loaded with 13 to 23 grains of Vesuvit LC (made by Explosia, the same Czech company that makes Semtex), which is an ungraded black powder that I think is perhaps just what's left over after sorting out grains for military and blasting grades. It is cheap at least, about $12/pound.

The "optimal" charge given is 18 grains. Whether this is really optimal, I don't know. If anything, it is the midpoint between minimum and maximum.

Given that the company doesn't really give complete instructions on loading the gun for carrying for self defense, while the main point of these guns is precisely that, I'm suspicious how muct testing went in to find the optimal powder load. Also, there is no indication of whether that load would be for a patched round ball, unlubricated bullet (none of the bullets sold for the gun, even by the company) have lube grooves filled with anything, or a properly lubricated bullet, of whatever weight.

Anyway, out of curiosity now I'll see if whatever inert filler I find at the supermarket tomorrow increases velocity when I get a chance to go to the range and test.

[greywuuf]

What if loading the filler first...before the powder charge....that would effectively shorten the barrel.

On reflection....it might be a little hard to actually ignite the powder through 2" of corn meal.


Never mind.

homeland defense begins at home.

[nanuk]

It would be funny (and great!) if adding inert material between the bullet (a 200 grain .45 R.E.A.L.) and the powder actually increased velocity.



I remember reading a thread where subbing COW equally grain for grain for powder kept the velocity the same even after a noticeable reduction in powder.

increased weight of projectile, increased pressures, keeping velocity the same...

anyone else remember reading this stuff?

[freedomlives]

When I finally get to the range, I'll try several variations and see! But it sounds really counter-intuitive...