Paper Patched vs. Grooved Boolit

[Marlin Junky]

I haven't had a chance to shoot PP boolits yet and here's something that puzzles me about the whole concept:

It's obvious to me when I hit my grooved boolits cast of BHN 13 to 14 metal with too much pressure because they generally "pattern" like a scatter gun opposed to group like a rifle. What I don't understand is how a BHN 5 to 6 cylinder of Pb wrapped in paper can withstand enough pressure to get it going 2200 fps and group like a grooved/lubed boolit over twice as hard.

MJ

[shooter93]

I haven't moved them 2200 fps but around 1900 with no troubles...large caliber bullets....Believe it or not the paper patching actually adds some strength to the bullet, if the are ptched to the right size they fit the rifle so there will be no blow by, they have almost zero neck tension, there is no lube failure and the bullet never touches the lands and grooves...only the paper does. All those thing contribute. And they make very impressive hunting bullets. Powder fouling becomes your biggest problem even with smokeless especially in smaller calibers of 30 or below. When faster velocities are desired it works well to switch to groove paper patch bullets....one made for th purpose not standard grooved bullets.....stronger papers and wiping the patch with several differnt high tech lubes. Speeds to 2700 fps have been reached that way. Paper patched bullets are neat to mess with and in plder type calibers the also look rel neat.

[Buckshot]

............Good paper is very tough stuff. If you could get it straight and attached to them both you could pull another car with a sheet of paper. It is not so much that it's hard, thinking of hard as like in metal, but it is in fact very tough and tenacious stuff. It is also a pretty good insulator.

I've tossed paper patched boolits in the pot along with other scrap slugs and everything melted away except the patched slugs. They just bobbed around happily on the surface until I began pushing them down with the fluxing spoon so the exposed noses would begin melting. Then you end up with a bunch of slowly charring empty paper cylinders :-)

I realize and read of Col Harrison's experiments with patched booits, used toward velocities considered pretty fast for cast, but IMHO I beleive the real reason for being of the paper patched boolit is to allow the user to launch a very soft cast lead boolit to velocities they wouldn't normally be shot at. And to also eliminate barrel leading after rapid successive shots.

My reason for thinking this way is due to the fact that most all the world's major militaries from the 1870's to the advent of smokless used paper patched boolits. Since the only propellant at the time was BP, they weren't trying to create accurate projectiles going say, 2700 to 3000 fps.

...............Buckshot

[pdawg_shooter]

I have been paper patching for years now. Most of the bullets I use are grooved. I reduce them to bore dia. plus .0005/.001 In a Lee style die. Wrap them with 2 wraps of 16lb paper and lube them after drying with any lube handy. I then run them through a die .001 to .002 over groove dia and load. My hunting alloy runs 12 to 12.5 BHN and in 30 cal I take them over 2700 with no problems. In 40 or 45cal I keep them around 2400. I loaded some 50/50 W.W. Linotype bullets to 3314 in a 300RUM with good accuracy. To hard for hunting though. Kind of fun to play with.

[Marlin Junky]

Paper, like anything else has grain and the grain of a patch runs parallel to the axis of the bore, right? There can't be that much resistance to compression or obturation in that configuration. Are the pressure levels required to reach 2200 fps much lower with a PP boolit than they'd be with a grooved boolit at 15 BHN?

MJ

[felix]

MJ, if the pressure, is all summed up incrementally "under the curve", the velocity of the projectile should be the same. Peak pressure is a function of ignition characteristics primarily. If the softer boolit expands a lot, the peak pressure is going to go up. If the powder type burns faster because the peak is higher and is long enough, then there would be less energy under the curve remaining to push the boolit. ... felix

[Marlin Junky]

Felix,

I understand the soft lead of a PP boolit is retaining its shape normal to the bore's axis because the paper is very strong under compression but what about the base itself? It would appear distortion parallel to the bore's axis would be greater with a paper patched BHN 6 boolit than it would with a BHN 15 boolit wearing a gas check and therefore the fired PP boolit's base would no longer be square (with respect to its axis).

MJ