Paper patch in 30-06: with and without a GC

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mtngun
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Paper patch in 30-06: with and without a GC

Postby mtngun » Mon Feb 04, 2008 6:10 pm

from the old forum, some parts were lost in the move to the new server so the thread seems to ramble:

Today I tried paper patching a 165 gr hollow point.

This bullet started out as a conventional lubed bullet, more or less a loverin design, that I had shot last year and it shot about as well as anything, 4" with full power loads, except the velocities were low, barely 2700 fps if I remember right.

I sized it to 0.3015" in a push thru sizer. I started out sizing the bullets dry, but that required a fair amount of effort, so I applied just a little Wonderlube solvent. I often use Wonderlube as a case lube, so you would think it would work for sizing bullets. Instead, it made things worse, and a bullet got stuck in the die. After hammering out the bullet, I tried moistening the bullets with Felix lube, and sizing was easy after that.

On half the bullets, I installed a gas check, while the other half did without. After heat treating, all were patched with 0.0026" paper, coated with Rooster Jacket, sized to 0.3107", and then dusted with mica.

The load was 58 gr. IMR 4350. Quickload predicted 53753 psi at 2826 fps.

With gas checks, only 2697 fps. 3.9" average for three 5-shot groups at 100 yards.

Without the check, 2707 fps, 5.4" average.

The difference in accuracy is not statistically significant, but I think I'll stick with gas checks, just to be safe. Overall performance with the paper patch was very similar to the conventional lubed version of this bullet -- same low velocity, same 4" groups.

How to explain the missing 100 fps, considering this rifle produces "normal" velocities with jacketed bullets?

Maybe Quickload just isn't very good at predicting for high velocity cast????? There isn't a heck of a lot of data out there for high velocity cast, so maybe it plays by different rules.

Or maybe the bullet is getting damaged and leaking pressure?

Pressure trace may help answer the question, but today the strain gage wasn't working right on this gun, and gave bogus numbers.');

How to explain the missing 100 fps, considering this rifle produces "normal" velocities with jacketed bullets?

Maybe Quickload just isn't very good at predicting for high velocity cast????? There isn't a heck of a lot of data out there for high velocity cast, so maybe it plays by different rules.

Or maybe the bullet is getting damaged and leaking pressure?

Pressure trace may help answer the question, but today the strain gage wasn't working right on this gun, and gave bogus numbers.


Dan,

Send me that there apparatus and I will figure it out for ya.

Maybe you need to try some softer bullets if you want higher pressure. Quickload does not accout for twist rates or bore friction. Still, my Quickload predicts within 50 fps with everything tested. I do have to lop off 1/2" of barrel for wheelers to keep it within the 50 fps limit.

One thing is for sure, you must not be getting any secondary pressure spikes or it should be higher. Figure that contraption out soon. Do you have any city ordinances about poping one off in the air at night?

Incognito,
Quickload has usually been very reliable for me, too -- with the notable exception of high velocity cast -- which is why it really bugs me when a load is 100 - 200 fps slower than Quickload says it should be.

I'm not sure if anyone knows what effect a secondary spike has on a cast bullet. I don't remember Charlie Sisk reporting any correlation to accuracy or velocity in his testing of secondary spikes with jacketed bullets, just minor problems like blowing the muzzle off the barrel. But lead bullets might be different. That's what makes them so interesting.

I tried an air cooled WW paper patch bullet a few weeks ago and it shot very poorly, 8" groups if I recall. Reminds me of the time a feller from back East sent me some of his soft bullets to try in my '06 -- had a hard time keeping them on the target. Maybe my rifle is bass ackwards, I dunno. :?

Thanks for visiting, Bass ....... I mean, Incognito.

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Re: Paper patch in 30-06: with and without a GC

Postby mtngun » Sun Feb 10, 2008 5:10 pm

............
To start with, let's think about whether or not the paper can handle rotational forces. True, paper has a very high tensile strength, much, much, higher than lead. But, conventional wisdom -- and I will be the first to be question conventional wisdom -- says that the paper is cut by the rifling, exiting the muzzle like confetti (and usually burned by the muzzle blast, so I haven't been able to recover any paper downrange to verify this). Now if the paper is indeed sliced lengthwise by the rifling, then it can't directly carry any rotational force, can it? More likely it is transferring the rotational force to the adjacent lead, and the paper only serves as a thin barrier between the lead and the barrel, much like a lube is supposed to do.

Which brings us back to the observation that my patched bullets shot just like their lubed counterparts, minus the leading.

But to make a point, let's pretend that the paper does not tear, and that it is indeed able to carry 100% of the rotational forces. OK, so does that mean only the paper jacket rotates, while the lead does not? Of course the lead rotates, because the paper transfers the rotational forces to the lead. The lead does not escape the rotational forces, they are still there, 100%. The same logic applies to the relationship between a gas check and the lead bullet. It even applies to the relationship between a jacketed bullet and its lead core -- the lead core feels the rotational forces, too, only the copper jacket serves to spread the forces over the entire surface of the lead core, instead of being concentrated at particular areas as is the case with our cast bullets.

Maybe I didn't do an adequate job of explaining it, but if you don't trust me, trust Issac Newton. Newton's second law says that any mass that is accelerated, must feel a force equal to mass times acceleration. So any lead bullet, or lead core that is accelerated rotationally, will be stressed rotationally, paper or no paper, check or no check. Any lead bullet or lead core that is accelerated in a forward direction, will be stressed in a forward direction. There's no way around it.

That doesn't answer all of your questions, or all of my questions, either.

To answer your other question, my hi-vel cast groups usually open up as more shots are fired, presumably due to fouling, with a little shooter fatigue thrown in, too. The GC paper patch groups were consistent, if you can call 4" consistent.

My next step? Get the strain gage working right and retest some of my old cast loads. I already know they aren't accurate, but I'd like to see what the pressure looks like before I move forward. Whatcha wanna bet they have secondary spikes, and I'll have to switch to a faster powder?

In fact, even if there are no secondary spikes, I may switch to a faster powder anyway, because the evidence is starting to whisper in my ear that the cast bullets are not providing enough resistance to make the 4350/RL19 speeds burn efficiently. More on that later.

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Re: Paper patch in 30-06: with and without a GC

Postby mtngun » Sat Feb 23, 2008 8:03 pm

Dan,

When you paper patch, do you use hardened bullets?

You want the lead to obturate in order to seal better. When I recovered the good ones you can't even distinguish the grease groove they obturated so much. In fact the base of the bullet was a bevel base as-cast, but after fireing the base gets formed into a very slight hollow base.

If the powder simply burns the base of the patch off that would be no big deal. It's when the powder gases blow by between the paper and the bore that really chews up the paper. Obturation is absolutely critical with paper patched bullets.

I think 100% density loads have some effect on obturation, I don't quite understand it though. I speculate that without the airspace in the case the powder immediately behind the bullet acts as a filler and seals the caseneck, throat and bore from blow-by gases while the pressures are low. By the time the powder has all been burnt, the pressures have built up to cause sufficient obturation to seal the bore.
.................................................
It's been a while, but I seem to remember that I tried both air-cool WW and heat treated WW for my paper patch experiments, and the heat treated bullets did better, though neither did particularly well.

Obviously there are many other possible variables, like the type and thickness of paper, bullet diameter, and bullet design, that I never played with.

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Re: Paper patch in 30-06: with and without a GC

Postby nobade » Sat Mar 20, 2010 6:23 am

I tried PP in my M1 Garand a couple of weekends ago. #308241, 150gr. plain base roundnose bullet, cast from air cooled wheelweights (quite soft) sized to .309, patched with 9# onionskin, sized to .309 again with paste wax for lube, loaded over 47gr. IMR 4895. Didn't chronograph them, but they tracked with the sights to 500M and had no trouble hitting the highpower silhouettes off the bench. They have to be seated plenty deep to easily chamber without resistance, but I was pretty impressed at how well the old M1 worked with PP! BTW, no paper in the gas system and it functioned normally. I didn't try feeding from the magazine, only single loaded it. Don't know what the trip from the clip to chamber would do to my patches.


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