just bought an old rossi

The Rossi Model R92, a lightweight carbine for Cowboy Action, hunting, or plinking! Includes Rossi manufactured Interarms, Navy Arms, and Puma trade names.
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Re: just bought an old rossi

Post by Archer »

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.
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Re: just bought an old rossi

Post by HarryAlonzo »

I think BBTI’s methodology is fundamentally sound, and I don’t think they intend for conclusions that are any more than directional. They were kind enough to do something that none of us would be willing to do - Progressively cut and crown a barrel down to a nub for the sake of science. The article you cite points out the variation inherent in the study of ballistics. With that in mind, I’m hard pressed to fault data that doesn’t exhibit a smooth trend.
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Re: just bought an old rossi

Post by Archer »

I like what BBTI was trying to do. As you say, not a whole lot of us are willing to chop up a barrel inch by inch and chronograph the results. I know when I've spent $100 to $550 or so for a barrel I'm NOT interested in chopping it into bits. Not to mention that popping off 2 or 3 or 10 rounds at each barrel length of 5 or so different kinds of ammunition adds additional expense quickly.

The fact remains that their experiments were generally limited to one barrel and a half dozen kinds of ammo and given the destructive nature were difficult to correct any issues that were not caught immediately during the testing.

I'm not faulting the lack of smoothness in the data. That's something that happens in experimentation.
Even if there is a smooth curve fit to the data it may not be evident when you are plotting FPS against barrel inches.

I am pointing out that the sample chop barrel for .38 and .357 doesn't go above 18". That the velocity curve shows a dip at 17" with both the 16" and 18" barrels showing higher velocity numbers than the 17" barrel chop point. I'll also point out that for several loads the difference in velocity between 15" and 18" appears to be within the accuracy limitations of the chronograph they were probably using and that they didn't seem to test normal to heavy for caliber magnum level loads for a lot of their data.

When you get a spike like the cylinder gap example I cited before that shows a trend that isn't evident in the other dozen ammunition examples I checked it is generally taken to be a problem with the data recording or the setup.

There are a lot of reloading manuals that used a lot of rifle length barrels over the years. When you combine that data it doesn't tend to show a 16" barrel being the ultimate velocity for .357 or .44 magnum level loads.

I've read that Paco Kelly said the ultimate pistol caliber barrel length was less than 16" and after that you simply lost velocity. While that MIGHT be true with true pistol calibers I have generally found that the full magnum level .357 and .44 data doesn't back that up.

Crap happens in experiments. I could give you examples of wind tunnel testing or even flight tests experiments that didn't go at all smoothly.

I think BBTI's experiments got better over time but the expense of the whole thing tended to limit what they could do and the results showed some similar limitations.
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