A reloading question on different barrel lengths.

[41bear]

I have a question for all of you other reloaders out there. In going over my 45/70 notes I noticed something very strange. I got two different velocities out of a 24” barrel and an 18.5” barrel. I know you are going to say that is what is supposed to happen but not this way, I say.

Marlin 24” barrel loaded with 300 gr. Bullet, WW brass, CCI primer, and H322 velocity ave. of 2014 fps.
Marlin 18.5” barrel with same load – 1891 fps a difference of 123 fps.

Now I change only the case and the primer to Starline and federal 215 and this is what I get:

24” – 2152 fps and the 18.5” 2089 fps only a difference of 63 fps

I go to a 405 gr. Woodledge and load one batch with WW and CCI and my velocity ave. is 1639 fps in the 24” and 1508 fps in the 18.5” barrel for a difference of 131 fps.

Ok now same bullet, same powder, but Starline case and federal 215 primers and I get a velocity ave. of 1787 fps out of the 24” and 1736 fps out of the 18.5” for a difference of only 51 fps.

All of these loads were loaded on the same day; 5 shots per load, and shot a week later all on the same day. The only thing I can figure is that the Federal primer is burning the powder much better but at the time I didn’t notice any unburned powder. As a side note both loads are starter loads for this powder and bullet weight. Have any of you seen this sort of difference before, and do you have any idea what may have caused it?

[Chuck 100 yd]

Some primers are not right for some powders and The chrono is the only way to find this out.
I shot 46gr. Reloader 7 in my .444 with 240gr. Hornadys and CCI 200
primers and got ES`s of over 400fps. (load from Speer #14)
Changing only the primer to Rem. 9 1/2 gave ES`s of 60 ( per Alliant web site)

[J Miller]

From the experience I have with Starline brass, it's thicker than the WW brass. This will decrease the case capacity, and increase pressure and sometimes velocity.

Nothing unusual here, any time you change components you change the equation and get a different answer.

Joe

[41bear]

Some primers are not right for some powders and The chrono is the only way to find this out.
I shot 46gr. Reloader 7 in my .444 with 240gr. Hornadys and CCI 200
primers and got ES`s of over 400fps. (load from Speer #14)
Changing only the primer to Rem. 9 1/2 gave ES`s of 60 ( per Alliant web site)

I understand and agree but my question centers on the fact that going from a 24" barrel to an 18.5" barrel normally would lose about 25fps per inch, right? Thats what I got with the WWcase CCI primer but changing to the Starline case/Federal primer the difference in velocity loss is cut in half to about 12 fps per inch and remains consistent with that change.?

[JReed]

25fps per inch is just a guide not a hard rule. I dont see any thing overly odd with your numbers. With the changes in your primers and the change in brass it makes sence.