I know what you mean. 18” does seem really short.
It is very frustrating to make informed decisions like this because you don’t have any concrete numbers until after you spend the money. But I feel like you are headed in the right direction. I hope I was able to help a little.
When you get your barrel and work up a load, I would sure appreciate if you would start a thread with your findings. I’m very curious and I’m sure it may help someone else down the road.
JTD
I appreciate the insights for sure. It gave me a few things to think about certainly.
I’m also looking at a type of rifling that is alleged to increase muzzle velocity as well. So every little bit helps I guess.
I’m super excited to get it all put together and figured out. And I’ll happily share data once I have it.
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Long ago there was an arsenal test done with an 06 and a 36' barrel reduced 1" at a time down to about 6" . Ammo was from 1 lot of GI M2 and fired at 100 rounds per step . From 36 down to 26" there were steady , although not a perfect curve , velocity gains . It basically flat lined down to 22" where there was a jump up of about 25 fps at 20" it began a similar slowing to the gains from 36" down . 22-23" was called optimum barrel length . 1935 Model of 1906 cal 30 M2 , 150 gr FMJ and a powder likely similar to IMR 4350 or Win 748 . Full case or very nearly so .
Of course if you change powder burn class from fast mag to slow standard speeds , bullet weights , bore contact , composition or length , barrel finish , bullet core , or any one or more of about 50 other things within the 145-165 gr bullet class that could change the "optimum" barrel length by 2" .
While it's nice to use thumb rules they don't always jive with actual results .
The article and associated table in the middle of the Speer books "why ballisticians get grey" shows how things don't always match up well . They use 357 in 30+ revolvers 2 of which are just weird . A 2" example is actually faster than one of the 6" examples .
That’s very interesting.Originally Posted by Harter
It’s been my experience, that over bore cartridges are affected more by barrel length.
JTD
That’s way cool, and exactly the kinds of research I’d want to do if I had time and money to.
But really what I’m hearing is that in the 20-26” range, velocity is basically as fast as it can be. Beyond that on either end, it drops off a bit.
And given the hugely complex discussion of powder burn rates, bullets weight/makeup, rifling, and everything else… it’s basically guess and check. As an engineer, that annoys the snot out of me. There should be a way to solve this mathematically, but perhaps there’s just too many unknowns.
All this considered, I decided to 3D print a mockup of my suppressor that allows me to artificially see various barrel lengths. I’m leaning toward the 18-20” range as a balance between ideal length for ballistics and ability to move through the woods.
I really appreciate the insights, it’s a fascinatingly complex problem.
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So, this is on topic but a different monster.
I have an 1896 krag in the original 30-40 krag. Is has been sporterized and the original barrel chopped from 30” to 22”. My velocities are almost 300fps lower than what the manuals say. 300fps loss from 8” shooting loads that are hovering around 45k psi.
I acquired the rifle in the condition it is currently in. It would have been nice to compare velocities before and after the barrel was chopped.
JTD
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