Load Details

[Old Jim]

Heres a program I wanted to test against actual feild loads.

http://dragonflybridge.com/cgi-bin/Muzzl...rtridge.pl

The program indicated that 72.0 gr. of 1.5 Sw. would provide 1184 fps from a 30" bbl. using a 530 gr. bullet.

I loaded that exact load, fired 5 shots from my 30" Shiloh Sharps 45/70: Field reading from my PACT @ 15' from the rifle = 1200 fps avg. Not bad, pretty close. Correcting the 15' to the muzzle gets me about 6 more
fps .

Jim

[Dakota Dick]

Kurt

I did not experience that result at Alliance at the 900 and 1000 steel target. Groups were inpacted by shifting winds, but elevations were constant. However, at 900 and 1000 the wind seemed to have more of an effect on the bullet.

what fouling control practice were you using...wet wipe, how many, dry wipe after wet? Still using the 50% water 50% RV antifreeze? That is working well for me.

[Kurt]

I used two wet and two dry with 50/50 RV antifreeze.
I'm going to Milan this weekend for a two day Mid Range match and I will harden up the alloy a little more and change the wad stack.
Brent pretty much used the same load as I did except he had a 1/16 twist barrel with 82 grains of 1.5 swiss with a .060 Walters wad.
My load worked very good at 800 but I did miss some changes in conditions.
I also think a 1.505 long bullet is to much for the .45-70 with a 1/18 twist.
And I also wonder if maybe the .043 wad I was using in a full length sized case might have compressed the wad to much and let the gases get by as the case expanded to the chamber wall.
Brent's chamber is tight and he does not size his brass so it does not alter the wad diameter.
Arnie recovered one of my bullets that told the story of what was going on with the single wad load I used after running out of the three wad stack.
This weekend I will use unsized brass and use a three wad stack again and see what happens.
Here is a pictures of the bullet Arnie recovered for me.
http://www.flickr.com/photos/leadpot/
You can see the bad gas cuts on the side of that bullet.
In the Lodi May 2012 set there are the other three sides of that bullet.

Kurt

[Dan]

Kenny, heck of a lot of info in your last, thanks.

Compression.......385 mark. Presumably inch fractions there? Should I wear an EOD suit when doing that? Sound crunchy does it? -smilin'-

[Dave Roelle]

Gentlemen:

Have there been any attempts to use what could be identified as a "obturating wad"--------------i have designed and used them with success in Milspec Buckshot Shotshell loads we developed for the military.

Velocities and pressures are in the same neightborhood with BPCR ammunition.

Certainly it would be cost prohibitive to develope a wad of this type by the usual means of plastic injection molding.

I had done some work on "compression formed celulose" wads with and obturating end profile to replace the common "homosoap board" die cut wads previously used in varying lengths to adjust loaded shotshell height for proper crimping

I had thought some about press forming something similar for BPCR loading

I appreciate any thoughts and feedback

Dave

[Don McDowell]

Kenny, heck of a lot of info in your last, thanks.

Compression.......385 mark. Presumably inch fractions there? Should I wear an EOD suit when doing that? Sound crunchy does it? -smilin'-

Dan that's our Kenny a shy bemuir fella that won't hardly answer a question...
Did ya happen to pickup on the "2/3rds" less windage bit?
Just a wee bit different than what the expert on the other channel had to say...

[Dan]

Yes sir, I certainly did, and it certainly is a different view that does not surprise. Matter of perspective I hold Kenny's word in high regard on such matters. Was thinking about some of his experiences and reports whilst typing on the other forum, but it's difficult sometimes to make theory and fact congruent. There is seldom enough data to do that in internet forums. I know some 'experts' would disagree.

Some years ago I was reading McCoy's book and one of the things that struck me was that with the passing of time and improved technical capability, the imponderables of ballistic science have grown less murky. The water is still turbid though, here and there. Just a few weeks ago a 16 year old kid in Germany solved a physics problem posed by Newton centuries ago and never solved until now. The kid just turned exterior ballistic science upside down and the future will be interesting.

http://www.foxnews.com/world/2012/05/27/...ac-newton/


What was it they said, "Theory is fine in the absence of fact."??? Works for me...both ways.

[Don McDowell]

Dan I don't even begin to know why the two types of bullets behave so differently but yesterday, once again, at 600 yds, with the paper patch bullets slapping the target around rather rudely, then switch to the grease grooves and they all start striking the bottom and below the target frame..... I did not bother to adjust the sights, but to get those greasers to land in the bull like the patched were would of meant raising the poi nearly 4 ft.....
Oh and with the mild left to right breeze the greasers were landing very near 4ft to the right of center...

[Dan]

Don, you may recall my discussion at the other place about the effect of grease grooves and slight shoulder radius extending outside of the ogive break? This is one of those imponderables that I have no known reference that may resolve the question. The figure I quoted about the low value of shank drag was developed with jacketed bullets which are uniformly smooth in comparison to GG bullets.

Where I'm headed with this should be obvious I think. My mention of probable vortex generation due to grease grooves is the sum difference between otherwise comparable GG and PP bullets, and I suspect it to be quite substantial. Turbulence equals drag in the world of aerodynamics. Question I can't answer is just how much additional drag. Existing BC calculators do NOT take this into consideration, so the only way to fathom the spread is to shoot and compare. I read an illustration the other day about the comparative drag between PP and a .500 BC greaser. I don't believe such a thing has ever been cast of lead. I may be wrong about this but from what I've seen, an average of .300 BC is not to shabby with cast bullets and .400 is sterling. I truly do not know what the top of performance is or could be with large bore lead.

I have no scientific basis for this either, but my sense of it is a BC advantage for PP bullets otherwise equivalent to GG styles could run in the range of .025-.100. Don't quote me on that, it's just a gut feeling. Haven't even tried running the numbers in a calculator, but if someone can provide solid drop data and bullet specs along with MV for a couple of ranges, say 300 and 600 yds, it wouldn't be hard to crunch.

[Don McDowell]

Dan I sometimes think in really simple terms. I got to thinking about the grooves of a bullet and I came up with comparing the grooves with the affects of junk laying in the pickup bed. the vortex coming over the cab will smear things all over the place in the back, but not in the front half of the box, and there have been some tests that indicate the tailgate being left out actually improoves gas mileage (reduces drag) then you can somewhat make the comparison to a pickup with a shell on the box... the vortex drops off the back of the entire thing and nothing to disrupt it from the ogive to the base...