Re: just bought an old rossi
Posted: 18 Jul 2021 17:01
I like the 20" length barrel.
A quick word on BBTI. I like their testing BUT sample sizes tended to be pretty small and their real world examples were very limited. The only rifle barrel in their real world examples was the Winchester 94AE 16" barrel and the only longer real world barrel they tested was an 18" revolver barrel with cylinder gap losses.
All of their .357 Magnum ammo examples were factory ammo optimized for handgun barrel lengths. Same can be said for their .38 SP ammo selection only moreso. Admittedly you don't typically optimize .38 with rifles in mind and you certainly don't buy it off the shelf.
Their .38 SP and .357 Magnum results for 16", 17" and 18" barrel lengths don't even form a reasonable or reliable trend so there was something else going on there that they didn't account for. The data presented for velocity results lists only light for caliber bullets and not a lot of them.
Another example of a graph that doesn't make sense is the cylinder gap test with Black Hills .357 Magnum CNL load (basically a .38 SP cowboy load in magnum brass) where there is a definate 200 FPS spike in the data at 16" for no cylinder gap but smoother curves with actual cylinder gap. Something happened to create that spike and it is not addressed at all in the data report.
Based on those kinds of things, and comparing their results to the published results in several reloading manuals, I tend to take BBTI reduced data with a grain of salt.
I think this article also sheds some light on the variation you can get from gun to gun and regarding barrel length and ammo choices. https://www.leverguns.com/articles/ballisticians.htm
Just looking at the variations between the Colt Python and Smith 19 data for 6" barreled guns indicates the variations that can occur 'when everything else is the same'. Note also the gain in velocity between the Wichester 92 with a 20" barrel vs. a Marlin 1894 with a 24" barrel.
A quick word on BBTI. I like their testing BUT sample sizes tended to be pretty small and their real world examples were very limited. The only rifle barrel in their real world examples was the Winchester 94AE 16" barrel and the only longer real world barrel they tested was an 18" revolver barrel with cylinder gap losses.
All of their .357 Magnum ammo examples were factory ammo optimized for handgun barrel lengths. Same can be said for their .38 SP ammo selection only moreso. Admittedly you don't typically optimize .38 with rifles in mind and you certainly don't buy it off the shelf.
Their .38 SP and .357 Magnum results for 16", 17" and 18" barrel lengths don't even form a reasonable or reliable trend so there was something else going on there that they didn't account for. The data presented for velocity results lists only light for caliber bullets and not a lot of them.
Another example of a graph that doesn't make sense is the cylinder gap test with Black Hills .357 Magnum CNL load (basically a .38 SP cowboy load in magnum brass) where there is a definate 200 FPS spike in the data at 16" for no cylinder gap but smoother curves with actual cylinder gap. Something happened to create that spike and it is not addressed at all in the data report.
Based on those kinds of things, and comparing their results to the published results in several reloading manuals, I tend to take BBTI reduced data with a grain of salt.
I think this article also sheds some light on the variation you can get from gun to gun and regarding barrel length and ammo choices. https://www.leverguns.com/articles/ballisticians.htm
Just looking at the variations between the Colt Python and Smith 19 data for 6" barreled guns indicates the variations that can occur 'when everything else is the same'. Note also the gain in velocity between the Wichester 92 with a 20" barrel vs. a Marlin 1894 with a 24" barrel.