Posted: 12/14/2004 8:05:28 PM EDT
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OK, let me start this out with a disclaimer that there is nothing scientific here at all, but possibly some marginally useful anecdotal information. Secondly, I'd like to put in a shameless plug for Old_Painless' Box O' Truth Thread and the Ammo Oracle if you like this sort of stuff. I took my Oehler 35P chronograph out over the weekend and spent a day hurling lead and copper through it. Mostly, I was looking for rough comparisons of bullet velocity from different barrel lengths. I'm primarily motivated by the idea of building an SBR 9mm AR and was thinking about what barrel length I want. Conditions were sunny, mid 70's and very light winds. The skyscreens were set about 15' downrange. All tests were using 10 rounds minimum per string. 9mm Test First, here are my non-scientific measurements with 9mm. Guns listed are what I had handy at the time. The % change in energy shown is relative to the 5" Taurus as a baseline:  I did a linear regression to guesstimate the energy at various intermediate lengths. Graphically, it looks like this:  I know, there are many variables at play that prevent this from being scientifically sound, but I think it's kind of handy as a guideline. I suspect that if I had other intermediate barrel lengths to try, the curve would look different. I would love to have a single 16" or longer barrel to play with. I'd test fire it and cut it down in 1" increments to build up a really meaningful graph. [I'm happy to accept a barrel donations, by the way  ] I also suspect that the 16.1" barrel is near the point of diminishing returns. My guess is that more testing would show that the trend curves up more in the middle, then levels off..22 LR Test Anyway, I also discovered that a Walther P22 with a 3.5" barrel shoots 36 gr Federal HP's at subsonic velocities. An 18.5" Rossi single shot rifle fires them at 1,204 fps (116 ft-lbs.). A 5.5" Browning Buckmark pistol is 1,040 fps (86 ft-lbs) and the Walther P22 3.5" is 910 fps (66 ft-lbs). .45 ACP Test Then I switched to .45 ACP. I had a full size Springfield M1911 with a 5" barrel and a Springfield V10 Ultra Comp with a 3.5" heavily ported barrel. Ammo was Winchester white box 230 gr. ball. The 3.5" ported barrel delivered a 20% loss in total energy (26% loss with some of my low-powered reloads). Here are the numbers: 5" normal barrel: 827 fps (349 ft-lbs) 3.5" ported barrel: 738 fps (278 ft-lbs) |
This reminds me of the day I bought my Alpha Chrony. I rushed home from the local Sportsmen's Warehouse and started shooting different loads over it. My Nephew comes by about a half our later with his Browning Hi-Power. Wants to shoot some 9mikemike over the Chrony. Very first shot he drills it dead center with a Speer Gold Dot +P+. No more Chrony. Oh well fun while it lasted, even if it was only a half hour. He felt really bad about it. I wasn't upset though. Just told him maybe he needs to practice shootin a bit more.
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Got one better, I was shooting an M-14 at the Schofield Rod and Gun Club range. I was concentrating on my target where the corner of my eye, I see pieces and a large rectangular object flying about 20 meters downrange with a Cease fire being yelled out. I look over and one of the guys had a 45-70 single shot pistol and he hit the chrony dead center. Everyone on the line went down the clean up the carnage, we had a real good laugh about it. The shooter said he had flinched, the .45-70 was killing his hands every shot.
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I do like the idea of the Oehler's brains being separate from the sky screens. I have managed to cut one of the sky screen verticals in half with a 5.56 round.  My brother-in-law took a chunk of plastic out of a sensor housing, but it doesn't affect anything functionally.Now if I accidentally blast the brain box on the bench, then it's time to hang it up for good!
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Ya I hear you there. Nice graphs by the way! |
Thank you, thank you! In addition to graciously accepting a 9mm AR barrel donation for a progressive cut-down test, I would also love to measure M193 before and after hitting various types of walls to measure energy loss. I've been thinking about doing wall penetration tests for over 10 years and Old_Painless beat me to it. Now I dream of augmenting his experiments. |