Barrel length question

[Harter]

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 .

[JeffreyDeGraff]

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.

It’s been my experience, that over bore cartridges are affected more by barrel length.


JTD