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Thread: Velocity loss in a short barrel?



  1. #1
    Marlin Marksman
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    Velocity loss in a short barrel?

    After carrying my GS through the thick stuff today I've decided I REALLY like the short barreled rifles. How much velocity will you lose from the 308ME round out of a 20" tube? I know they're only made in 22 and 24 right now, but I'm thinking shorter is better.

    I'll have to handload for it, using Barnes TSX's only (stupid CA law) so I was wondering if I'd be just as well off with a 30-30 AI?
    While all the oil may be in Texas, ALL the dipstics are in "DC, and Sacramento"

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    Deadeye
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    Velocity loss in a short barrel?

    I believe they state that the loss id typically 50-80 FPS per inch of barrel loss!!!
    njcioffi likes this.

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    Site Contributor - Team Marlin Express Capt'n Super Moderator
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    Velocity loss in a short barrel?

    Probably around 30 fps per inch of barrel.
    IN MEMORY OF PFC JEFFREY ALAN AVERY, 571st MP CO, KILLED IN ACTION 23 APR 07, AGE 19, MUQUDADIYAH, IRAQ.

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    Marlin Marksman
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    Velocity loss in a short barrel?

    OK if I average the posted numbers I get 55 fps per inch loss. From the MLXR 24" barrel, which would be the std for their posted velocity, if I had a 20 inch barrel, it figures to 2440fps. IF that were the case, I could get VERY close to that with a 30-30 AI, I believe. More than likely I could get a 336 in 30-30 and make an AI of it for a lot less money.

    Maybe that's the way to go, fo me anyway. Seriously considering using the pointy bullets anyway and making it a 2 shooter out of it, since it would be a deer rifle anyway.

    I doubt I'd ever get off more than two shots anyway.
    While all the oil may be in Texas, ALL the dipstics are in "DC, and Sacramento"

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    Site Contributor - Team Marlin Express Capt'n Super Moderator
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    Velocity loss in a short barrel?

    I was getting about 2600 FPS out of my 22 inch barrel this summer. One thing to consider about velocity is that it can change from day to day, it can change with temp changes, so it isn't a hard and fast number. It just gets you in the ball park. I don't sweat the numbers to much, it has performed well for me this year, and at this point I have enough faith in it that it will do anything I'll try to do with it.
    IN MEMORY OF PFC JEFFREY ALAN AVERY, 571st MP CO, KILLED IN ACTION 23 APR 07, AGE 19, MUQUDADIYAH, IRAQ.

  6. #6
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    Velocity loss in a short barrel?

    Thanks.
    While all the oil may be in Texas, ALL the dipstics are in "DC, and Sacramento"

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    Sidewinder
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    Velocity loss in a short barrel?

    I always figure 35 fps per inch for the .30-30’s.
    I get an even 2600 fps give or take a few fps for any given day from my 22” barrel 308MX using Hornady ammunition.
    The 20” .30-30AI will easily get 2,500 fps using any of the 150-grain bullets and any powder from Hodgdon Benchmark to Alliant Reloder 15. This gives you many powder options.
    The important thing to remember here is the .30-30AI achieves this level of performance and high pressure. How high? No one knows for certain – I’ll wager Hornady does – but no one has reported any pressure tested load data.
    Comparing the performance of the .30-30AI loaded to high pressure with the .308 Marlin Express loaded at considerably lower pressure is not an “apples to apples” comparison.
    Don’t misinterpret my comments as negative I enjoy shooting and loading for both cartridges. I have three rifles reamed for the .30-30AI cartridge. I have posted a lot of load data using these velocity goals for the various weight bullets in the 20” .30-30AI: 3,000 fps for the 110-grain bullets, 2,700 fps for the 125- 130-grain bullets, 2,500 fps for the 150-grain bullets and 2,300 fps for the 170-grain bullets. I have posted quite a bit of data which exceeds these goals using Alliant Reloder 15 and Hodgdon Varget but I have since come to the realization I was taking unnecessary risks and have reduced my handloads to these original goals which are a significant improvement over factory .30-30 loads and an improvement over all published load data when the 20” barrel is utilized for testing. That was certainly a long sentence!
    The important thing to remember is the .308 Marlin Express is an easier cartridge for the handloader to work with than the .30-30AI. We have not yet fully explored the capabilities of this new cartridge, Someone will ream a Handi-Rifle to .308ME and cut the barrel back, that will make interesting reading if they are a handloader with an inquisitive mind.
    Slim

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    Velocity loss in a short barrel?

    William
    Thanks for the info, very informative, and I agree, yes, you're pushing the AI pressures to approach the ME. However, the cost of the ME rifle vs the 30-30 used is a factor as well.

    As for the Handirifle, I doubt anyone would do it because it's cheaper for them to just get a 308 Win barrel. They're only about $80, plus some fees.

    The barrels on those cannot be setback, like an AI type thing, but on the 30-30 being a rimmed cartridge, the AI works, but leaves a shorter neck.

    I have a savage bolt gun in 243 and have in my possesion, a 308 Win barrel for it and they're easy to swap, but I get tired of the bolt sticking in my side during carry. That is why I'm wondering about these rounds. This will be primarily a deer round, as I have a long action Savage that will soon become either a 338 Win Mag or 300 Win Mag, when I make up my mind. It's currently an '06 which will certainly do the job, but it's longer than I want to carry for deer. Whatever it becomes, it will be my backup rifle for moose, behind my 1895GS.
    While all the oil may be in Texas, ALL the dipstics are in "DC, and Sacramento"

  9. #9
    Tenderfoot
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    Velocity loss in a short barrel?

    Check out the bottom of my post "Cutting down the .308" I ran Hornadys figures through a ballistics calculator, got a rough number for the Ballistic Coefficient of the .308MX in the 24" and then plugged it back into another calculator using a 20" barrel length. The numbers I got where as followed:

    20"
    Range(yrds) Muzzle 100 200 300 400 500
    Velocity (fps) 2560 2346 2142 1948 1766 1597
    Energ(ft.-lb.) 2328 1955 1630 1348 1108 906
    Trajectory -1.5 3.3 1.9 -7.2 -25.5 -55.0
    (230 yd. zero)

    So a 100fps loss at the muzzle from 24"-20"

    Hope this helps.

    -Mack

  10. #10
    Marlin Marksman
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    Velocity loss in a short barrel?

    Mack it does, thanks.
    While all the oil may be in Texas, ALL the dipstics are in "DC, and Sacramento"


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