Interesting article in BPCR News

[Boz330]

The latest BPCR News has an interesting article on BP compression. The author does a comparison of KIK, Goex, Goex Express, and Swiss at 0, 1/8, 1/4, 3/8, and 1/2 inch compressions. Of course he can't do every possible combination but I thought that he came up with some interesting results. The thing that struck me the most was he got the best group out of Goex Express and the second best group from Swiss with what I would call a significant amount of compression.
The amount of compression made very little difference in the velocity, ES, SD, or how clean it burned.
He actually built a rifle just for this test. The groups were shot at 100yds and the powder was a volume measurement in the case for each powder. The weight from the lightest, KIK to the heaviest, Swiss varied almost 10 grains for the same volume and velocity was almost 100FPS difference. As the powder was compressed the boolit was just seated deeper in the case.
This isn't any kind of definitive study but just hits on certain points. As most of us have figured out or have been told YMMV, and every gun is as individual as each of us. My one 40-65 with an NEI boolit likes .225 compression with Swiss which sorta goes against the conventional wisdom.

Bob

[McLintock]

Yeah, I thought that was a pretty interesting article also. My best loads for my Browning BPCR in 45-70, had .245" of compression with Swiss 1.5, also outside of conventional wisdom; makes one wonder about conventional wisdom sometimes,eh.
McLintock

[Boz330]

Yeah, I thought that was a pretty interesting article also. My best loads for my Browning BPCR in 45-70, had .245" of compression with Swiss 1.5, also outside of conventional wisdom; makes one wonder about conventional wisdom sometimes,eh.
McLintock

Conventional wisdom seems to go out the window a lot with BPCR, or it seems that way for me. Just when you think you have it figured out a monkey wrench comes out of the blue and proves you wrong.:veryconfu Sort of like hunting, it's the chase.

Bob

[BPCR Bill]

I've been shooting one case lot of Swiss 1.5F for a couple years and both my rifles (a Shiloh 45-110 and a C.Sharps 45-70) are showing best accuracy and least Es with no mechanical compression. Time to get worked into another case of powder this winter, we'll see what happens there.

Regards,
Bill

[JeffinNZ]

I compress 1.5Fg Swiss in my .38-303 0.350 inch and it shoots REAL good.

[Bent Ramrod]

I thought the article was kind of naive, myself. He only shot one five-shot group per compression of a given powder, he was OK with a spread of 3 grains in his boolit weights (estimated from weighing a small sample), he shot his groups at 100 yards and he let the distance between his seated boolits and the rifle's leade vary enormously in order to compress the same volume of powder. I would hope those castings on page 33 were not typical of what he was firing in his experiments; the driving bands are pretty rounded.

If he had maintained his cartridge overall length (with a stack of wads, perhaps) selected his boolits within a grain of weight and fired at 300 yards or so, he might have had some results he could assign to compression alone, although one five-shot group (and his rather debonair treatment of the fouling from the shot strings) would still be a little thin for the rather sweeping conclusions he drew.

I do, however, envy him his test bed. That heavy-barreled Mauser would be a riot to play with.

[Boz330]

As anyone who has shot much BP knows, this can be a labor intensive pursuit. The combinations can literally be limitless. He picked one thing and even that entailed the loading and shooting of 125 rounds. Had he filled the case up with wads that would have introduced another set of variables. I always shoot for group at 300yds myself, but for that number of rounds it would have gotten even more labor intensive. Not disagreeing with you, just saying that it is pretty tough to do a study like this that encompasses everything we deal with. In reality all that he proved is what we all have figured out, this is what his gun will do with this set of circumstances.
As far as a bolt action BPCR, it just ain't right somehow.

Bob

[The Double D]

Who was the author?

[Boz330]

Bob Woodall or Woodfill, he has the British Double rifle, Rook & Rabbit shoot on his farm up in IN. Usually it is during the ML championships, not sure whether it is spring or fall shoot.

Bob