black powder compression

[sabbatus]

i see many different recommendations as to the amount of compression of black powder in the cartridge.  I know that each rifle/cartridge/load can act differently so there is no magic number or amount that works for everyone.  What i am wondering is what is the maximum amount of compression that is safe for a black powder load.  i am shooting 45/70 in a handi rifle.  still trying different bullet/wad/powder combinations.

[boommer]

THAT'S  a good ? Till the case bulges!!! compression is what tweaks your burn rate so lets say you use 2f and you compress it heavy, you are moving closer to 3F by crushing the granules smaller. NO matter how much you compress you don't have to worry about chamber pressure with black.

[boommer]

To ad this, my loads, None of my loads go over 1/4" compression in Swiss, Goex or KiK .PRIMERS NO magnums, paper over the flash hole will change burn rate, , bullet tension will change it some. Just get the bullet set up on the lands at over all length and a soft bullet and that will help you A LOT!

[John Boy]

the Black Powder Cartridge News -2009 Fall - "Some Black Powder Compression Data" article by Bob Woodfill:
Caliber - 45-70
Lyman 457124
Constant volume of FFg powder used
Compression tested: 0" - 1/8" - 1/4" - 3/8" and 1/2"
Best 3 Shot Groups 100yds ... 5 shot groups were tested also, with the same compression values except for Goex (1/4") and Schuetzen (1/2")
Goex - 0.62" with 1/8" compression
Goex Express - 0.26" with 1/4" compression
Schuetzen - 0.61" with 1/4" compression
Swiss - 0.56" with 1/2" compression
KIK - 0.65" with 0" compression

PS: It pays in spades to buy a subscription of BPC News magazine to find loading data tests like this and much more!

[longcaribiner]

how does one get a three shot group with 45 caliber bullets that measures a quarter inch?

I load my 45-70's for my 1884 trapdoor by loading a 457125 bullet ontop the greease cookie and powder in a 45-90 tong tool.  I feel the powder crunch as the bullet is seated to 45-90 OAL.  I think it amounts to a 3/32 of an inch compresion of the 2f.

[boommer]

That's easy, group size is measured from center to center, so you just measure from your two farthest spread bullets from outer cut from bullets and say your useing a 50 cal slug .500 so to center of bullet is .250 and your outer bullet cuts is 1' spread  this would be a half inch group or if your outer bullet cut spread is .750  this would give you 1/4" group.

I don't know if this helps you, I'm terrible at explaining things on paper. Maybe somebody else can put a diagram up that knows how to work one of these puters.   

[longcaribiner]

That's good shooting no matter how measured.  I also see alot of folks giving measurements of three shot groups.  I had a scholarship to college shooting a target rifle, and according to our coach, a group of less than 5 shots didn't count.  I also took notice that Harry Pope normally referred to 10 shot groups. 

Is there some rule of three?

[Ray Newman]

"Is there some rule of three"?
---longcaribiner

Origin of the "Rule of Three" -- most rifles (and some shooters) can only shoot 3 shot groups before things start to deteriorate.

IMO, you’re right on the 10 shot groups....

[John Boy]

I also took notice that Harry Pope normally referred to 10 shot groups.

And he charged an extra $2 to make the barrel shoot MOA at 200yds!
Three shots is not a rule of thumb, yes 10 is a better indication of group accuracy.  Most folks shot 5 though and remove any fliers from the group size.  Also, a true indication of a bullet accuracy is the group at 200yds.  If one plans to use the bullet for long range (800 - 900 - 1000yds) then 500 yds is a good indicator of accuracy  Why?  Because some bullets are dynamite groups at 200 yds, but won't go to sleep shooting long range

[RMulhern]

how does one get a three shot group with 45 caliber bullets that measures a quarter inch?

I load my 45-70's for my 1884 trapdoor by loading a 457125 bullet ontop the greease cookie and powder in a 45-90 tong tool.  I feel the powder crunch as the bullet is seated to 45-90 OAL.  I think it amounts to a 3/32 of an inch compresion of the 2f.

longcaribiner

I think you're compressing the powder with the bullet and that IMO is a big NO NO! You will deform the bullet and more than likely it will not want to chamber! Even if it does....the bullet may not offer the best accuracy being deformed!