June 19, 2013, 10:15 PM | #1 |
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Barrel length
Most of the data I have seen for 9mm reloading is based on a 4 inch barrel. My XD-9 has a 5 inch barrel. Does this even matter? Do I have to adjust powder loads at all?
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June 19, 2013, 10:48 PM | #2 |
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The difference is very slight. I doubt you would notice it very much, if at all. When you work up your load, you will probably find the most accurate load is going to be below the max level. I prefer accuracy over speed any day.
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June 20, 2013, 05:24 AM | #3 |
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No.
No.
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June 20, 2013, 06:42 AM | #4 | |
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Quote:
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June 20, 2013, 07:02 AM | #5 |
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Thanks for the input. I was pretty sure barrel length was not a major issue, but being a newbie to reloading, wanted to be sure.
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June 20, 2013, 10:42 AM | #6 |
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4" is just the SAAMI standard pressure/velocity test barrel length for this chambering. All commercial ammunition velocities are reported for SAAMI standard test barrel lengths except as noted, and for the few where there is more than one SAAMI standard test barrel length (some pistol rounds, particularly where rifles are made for them as well) then which test barrel length was used should be specified.
In your case you should see about 4½% to 6½% increased velocity over a 4" barrel, depending on bullet and powder used. That's small enough that gun-to-gun chamber tolerances can make as much difference in some instances, so there's no guarantee you'll actually realize the increase as compared to the test barrel velocity reported. It's just the difference you would see if you cut your own barrel down to 4" after testing at 5". As the others have said, there's no effect on peak pressure.
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June 20, 2013, 09:56 PM | #7 |
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Whatever the change of velocity will depend on the burn rate for the powder you are using, which BTW, you haven't mentioned. With faster burners than W231 the difference will be pretty insignificant, but if you're using something from the medium-slow group like Silhouette, HS-6 or 3N37, you'll see a significant increase. I didn't mention Power Pistol because I don't use it because its got nasty muzzle flash. The powders I mentioned are spherical and will meter better anyway.
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June 21, 2013, 06:56 AM | #8 | |
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guess again?
Quote:
This statement is not entirely true; it is an assumption. The asumption is that a longer barrel will automatically provide higher velocity. Extensive chronograph testing proves this untrue. Normally (ha! I spit on that word!) a longer barrel shows an increase, but NOT always.
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June 23, 2013, 02:52 PM | #9 | |
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Now if you were to tell me you saw no difference in velocity between a particular short barrel gun and some other, longer barrel gun in the same chambering, that's perfectly believable. As I mentioned before, chamber-to-chamber differences can easily account for bigger velocity differences than the percentages I gave. One time I was testing some match ammo in different club-ownded Garands, and had individual rounds in one rifle differ by 200 fps from individual rounds in another rifle. That was about 8% difference just due to headspace, throat, and bore conditions in the rifles. In handguns the percent difference can be even bigger because each thousandth of an inch of chamber dimension difference represent a bigger percent difference in expansion ratio in a short straight wall cases than it does in a bottleneck rifle case. So, unfortunately, the only way you can say for sure that extra barrel length is not getting you anything in your particular gun is to start cutting the barrel down and measuring the velocity change that results. Comparison to another gun won't tell the tale.
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June 23, 2013, 04:24 PM | #10 | |
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June 24, 2013, 12:03 PM | #11 |
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57K,
It appears you're making an assumption that difference in terminal performance is the only measure of significance to the shooter. If, instead, it's trajectory calculations, the difference will have similar significance for both the fast and slow loads (not much, as it turns out for normal target ranges to 50 yards).
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June 24, 2013, 06:34 PM | #12 |
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First off, with the example I used with a 115 gr bullet in 9mm, who's gonna be loading above the 1150 FPS level that's more than typical with a 4" barrel using a fast burning powder? in a 5" barrel with your QuikLoad statement of a 4.5% increase that's 1204 FPS. Any number of medium/slow powders will give 1200 FPS and even higher at STANDARD 9mm pressure of 35,000 PSI/33,000 CUP from a 4" barrel, so with the 6.5% increase from your own statement, from a 5" barrel that velocity would increase to 1283 FPS which I actually understated at 6.3% because the actual difference would be 6.6%. That's simply basic math! As far as performance with a conventional cup and core 115 gr. JHP in 9mm, I'd much prefer 1283 FPS/420 FT/Lbs of KE to 1204 FPS/370 Ft/lb load. I don't need to rely on QuikLoad to tell me that!
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June 26, 2013, 02:37 PM | #13 |
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I guess we're just destined to talk past each other.
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