Ok, help me out with burning rate

[singleshotbuff]

Gentlemen,

I have read the posts in other threads about determining the burning rate of pulldown milsurp powder. I think I have it right, but I'd like some more experienced guidence.

The "donor" ammo is 7.62X54R, yellow tip, heavy ball ammo. Steel case, 180 (+/-)gr fmj bt. I pulled down 20 rds of the ammo and weighed the powder charges on an electronic scale. The average was 47.4grs, and the charges were surprisingly uniform. There was less than 1/2gr variance. Anyway, this ammo chronographs 2405 f.p.s. from my M44 carbine. I figure this to be 50.7 f.p.s. per grain.

Looking at my load & chronograph data, also using a 180gr bullet, 48grs of IMR-4320 gives 2383 f.p.s. out of the same gun. I figure this at 49.6 f.p.s. per grain.
50grs of IMR-4320 gives 2520 f.p.s. for 50.4 f.p.s. per grain.

The pulldown powder is even a stick powder with a physical appearance identical to IMR-4320. Equal weights seem to occupy the same volume.

Are these figures (50.7, 49.6 & 50.4) close enough to conclude that this powder has a very similar burning rate to IMR-4320? I hope so as 4320 is one of my favorite powders in several applications.

Are there other tests that I can/should conduct to verify my inference of this powders burning rate?

All help is appreciated.

SSB

[felix]

SSB, you've already suggested it. Try it in another gun! ... felix

[Buckshot]

.............Just for fun disassemble 5 milsurp factory rounds and substitute the same grain weight charge of 4320 and re-seat the slug. Put the milsurp powder into 5 of your cases with your 180gr slugs. Shoot both over the chronograph and see. Neither load appears to be 'warmish'. Should be an interesting test.

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

[omgb]

Go here: http://www.loaddata.com/articles/index.cfm There's burning rate chart for all of the popular canister powders. It's in PDF and it's free to the public. This might be of help in determining what can be substituted for what.

[singleshotbuff]

Gentlemen,

Yesterday (since I couldn't browse this board [smilie=1: ) I loaded 15 test rounds. All used a Graf case (7.62X54R), WLR primer and a Hornady 180gr bullet. I loaded 5 rounds each with 46grs of IMR-4320, 46grs of this pulldown powder and 46grs of IMR-4350 (just for comparison). I then ran them over the chronograph.

The 4320 averaged 2099 f.p.s and the pulldown averaged 2308 f.p.s. The 4350 was slower as expected (I don't have the # in front of me here at work). Based on this I think the pulldown powder is close enough to 4320 that I can use that data as a starting point. 9 f.p.s. is probably less of a variation than I would get by changing lots of 4320.

Today after work, I plan to do some testing of this powder in 8X57mm Mauser. I'll post the results on monday. I'm sort of enjoying this research into pulldown powders!

SSB

[sundog]

SSB, you've lost me on the velocity comparison. Looks to me like 200 fps, not 9. That's NOT close.

I'm not sure that you're theory on X fps per grain is all that safe a way to look at it. Without knowing what the stuff is, you could run into pressure spikes going one way and squibs going the other. Burn rates are relative, not a constant. Change components and you have to start over. Do not assume that it will work the same in another loading! Milsurps are most often designed for a specific purpose and while they may resemble a cannister powder, they may be something different. Unless you have a potful of the stuff, I'd just use it for fertilizer (or shot the way it's already loaded). sundog

[swheeler]

209 fps is quite a difference, at least a couple spaces faster on the charts.

[singleshotbuff]

oooops,

That should have read 2299 & 2308. Sorry, trying to post and work at the same time.

SSB