45-70 - barrel length/velocity.

[prosper]

Well, I've used surplus WC-735 powder in a lot of cartridges now and it performs nearly identically to H322 by weight in almost all cases, including the 222, 223, 308, 30-30 and 7.62x39. But not my 45-70. There, it seems to perform somewhere between 4198 and 322. I get slightly better speeds out of it than listed for an equal weight of 322, by 2-3 grains or so. However, my 45-70 has a 32" barrel, so I'm wondering if maybe that accounts for the difference, as most load data for the 45-70 was developed in much shorter barrels, usually 24".

With straight-walled cases, I've usually found losses due to barrel length to be rather minimal, but I'm sure that 10 or so additional inches must make a measurable difference.

Any thoughts?

 

[hs4570]

My 22 inch #3 Ruger gets pretty close to the same velocities claimed by the reloading manuals useing Re7/Imr3031/Imr4227/Imr4198 all bullets.......and Unique/A2400 for slow heavy 500 gr loads.......

I 'd guess with a 32 in barrel you should gain some speed......how much do you gain over "book" speeds with this gun useing your "other" powders/bullets/loads...chrono wise

I believe there is a point of diminishing returns once you go beyond a certain barrel length regardless of powder type or amount.....and speed may in fact be less in 32 in.vs. say 28 in

I Know quite a few 45/70 shooters, however , 24 inch length is max I've come accross...... this is one of the old Marlin 45/70 s circa 1970 ish...he stated he gained maybe 30-40 fps on avg over his shorter tubed Marlin 22".....

I guess it all comes down to how much brl. length does it take to consume all the fuel and at what point is the rest of the brl. causing drag.....

..if pos. can you post some of your 32" velocities....after the other gents have their say.........thx


hs4570.......your mileage may vary

 

[Boomer]

Prosper -

I think that for the benefit of all at CGN you should conduct an experiment. Load up 50 rounds or so - and after each 5 round group, cut an inch off that barrel - then fire another 5 shot group. I am sure we would all be interested to see the change of velocity at each step of the experiment! Hell, if you were a real pal, you would also crown the barrel after each cut, and see if there was a measurable change in accuracy, as the barrel shortened.