An older chronograph...
Thanks SixShooter, a comment from an actual user. A couple of years ago, I was at our local range and a hunting/shooting acquaintance had one strapped to his rifle barrel a few benches down from me. Between target re-postings I asked him how he liked the magnetospeed. He said as you, "so far so good." I haven't seen him since then, so I wondered how they may have worked for others. Thanks again.
Probably better than 15 years ago now, a good friend and his wife up in Montana invited me and my darlin' up to their place to visit. The wives went shopping and my buddy and I went shooting. I brought my 45/70 Sharps up there, knowing he was going to set up his "Chrony." Because I wondered back in those days what my B.P. cartridge was doing out the muzzle, he was glad to find out, too. He was shooting his Browning High Wall in 38-55, and was curious to see what his M.V. was out of that rifle, also. Both guns' cartridges used GOEX black powder (no duplexing), and cast bullets. So, all set up, he told me to take a shot after carefully setting up his unit, and both of us situating my rifle properly. His unit had a digital readout on it, and right after I took the shot, we both looked at it and it read something like (as I remember it, now) 1153 f.p.s. And just as quickly as we saw the number, the screen went blank, and he couldn't get it working again (NO, thankfully I didn't hit it! Ha!). That was the ONE and only shot I ever took through a chronograph. Nary another one since. That readout was near what I figured (and what others told me I might expect) my 45/70 was doing with the load I was using; 68 grns. of compressed GOEX 2fg, with a 525 grn. Lyman Postell bullet. So with that, I've considered/wondered about chronographs and what's available 15 years later, for use in any RIFLE.
BTW and FWIW:
Back in '02, I was on a forum for B.P.C.R.s and there was a thread going about strictly using black powder in a cartridge, cast bullets and chronographs. Not having a chronograph, I posted a question about muzzle vel. and the load I was using (the above mentioned one, same rifle) and what I might expect out the muzzle for f.p.s. (as here in this thread, just curious). A fellow shooter posted this info, which I tried, and after using a calculator and my lame math, I actually came up with a result, and it was pretty cool how it calculated, so here is that info for GOEX black powder, from back a fair number of years. I haven't tried it since, just haven't had the need. Give it a try if you use GOEX B.P. and cast bullets in an old cartridge just for the little bit of time and curiosity; it might gratify you!
BTW, I'm not sure where GOEX is manufactured these days, nor if any of the process/ingredients have changed to alter the formula. I can only imagine the old STANDARD GOEX black powder is still close to what it was 20 years ago as far as performance. (?)
From the old post, from the old forum, from a fellow B.P.C.R. shooter:
"Here's a formula you can use to calculate your MV, using the bullet weight and powder weight. These came from one of the Precision Shooting Annual Editions. They are for GOEX powder, and 30" barrels."
Fg: MV=2115-[1143 x (log(b/p))]
FFg: MV=2240-[1199 x (log (b/p))]
FFFg: MV=2396-[1320 x (log (b/p))]
b=bullet weight, and p=powder weight, all in grains.
The "log" here is "log to the base 10", and on your calculator it should say "log". Don't use the "natural log", which is abbreviated "ln" on the calculator.
...
This (following below) concluded the post I was given for the formula, and luckily my 45/70 has a 30" barrel.
"I have a chronograph, and in practice, my velocities are within 3% or so (30-40 fps) of what these formula predict. My loads are consistently SLOW compared to this formula, but it does seem to work fairly well, otherwise. It is good for seeing how changing bullet weights and powder granulations might affect the load."
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That's the end of the old post I received a long time ago and using the old standard GOEX black powder for the formula. I might/could imagine there's a calculation that could be figured if a barrel was inches shorter or longer than 30" to make this formula work for a mathematically inclined B.P.C.R. shooter who might be interested...and who doesn't have a chronograph.
