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ufo
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31.03.2014 16:51

Vliv délky hlavne na ustovou rychlost a precizi

300 Winchester Magnum: How Does Barrel Length Change Velocity- A 16″ 300 Win Mag?
What happens when we cut down our 300 Winchester Magnum from 24.25" to 16.25"?

zdroj

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Did recoil, muzzle flip, or muzzle blast change?
Firing the rifle with the 24.25 inch barrel was pleasant (for a belted magnum) with minimal muzzle rise. Recoil and muzzle blast increased significantly when the barrel reached 20.25 inches in length and again below 18.25 inches. The 16.25 inch made my shooting buddy laugh. He said the ground 15 feet in front of the muzzle was blowing around. I developed a mild headache from the 50 rounds of ammunition I shot, despite wearing both ear plugs and muffs.
Did the point of impact shift as the barrel was cut?
Yes, it did, but less then expected. I did periodically make scope adjustments to utilize different parts of the target, but in general, groups were within 1 inch of the group fired with the previous barrel length. In some cases, the point of impact was unchanged.
How much did weight change as the barrel was cut?
Weight of the rifle, including bipod, optic and mount was 18.28 pounds with a 24.25 inch barrel. Weight decreased 1.82 pounds to 16.46 pounds with the 16.25 inch barrel. Keep in mind almost two pounds came off the muzzle end. The rifle became easier to handle at the expense of decreased ballistic performance and increased recoil, muzzle flip and blast.
What are the possible sources of error?
Possible sources of error include:
- Small sample size.
We only chronographed 5-rounds at each barrel length, a greater number of rounds would provide more reliable results.
- Heavy trigger.
The factory 700 trigger was turned all the way down to 4 pounds, 12 ounces. A few of the larger groups contained one flyer (see some samples in the photos above). While this wasn’t an accuracy test (hacksaw cut crown), I personally feel the larger groups would have been smaller with a lighter trigger.
- Sawzall induced stress and vibration.
If you haven’t used a reciprocating saw to cut a barrel off, you haven’t lived. That said, it shook the rifle violently for extended periods of time. I don’t see how that can be good for accuracy. The screws holding the Viper Skins actually fell out onto the shooting bench. One of us sat on the rifle other while the other cut the barrel. The hacksaw was far less violent, but still required one of us to sit on the rifle while we cut it. I should note that the scope held it zero and worked well despite the harsh conditions we caused.
- Only one type of ammunition was used.
While the Gold Medal 190 grain ammunition is a good standard for testing, it doesn’t represent heavier bullets and slower burning powders which will show greater benefit from longer barrels.

So what did we learn?

What was the average velocity loss per inch?
39.6 ft/sec. See the table above for specifics. Longer may not necessarily be better. While the longer barrel has a milder recoil, and less muzzle rise with superior ballistics, the short barrels aren’t as wanting as you would think. This is especially true for typical big game hunting applications where the maximum point-blank zero may be used. This doesn’t mean I don’t think a 16 inch 300 Winchester Magnum is silly, because it is, I just think there may be some merit to moderate barrel lengths for this cartridge.
Are short barrel magnums a good idea?
I don’t think so. I am unsure what a short barrel 300 Winchester Magnum gives you that a long barrel 308 or 30-06 won’t. A mid length barrel, say 22 inches, offers better external ballistics, terminal ballistics, less muzzle flip and a reduced blast. I think my next 300 Winchester Magnum will be at least 22 or 23 inches.
Isn’t a 16″ 300 Winchester Magnum basically a 24″ 308 Winchester?
Basically, yes. While my personal experience loading the 190 SMK in a 24-inch 308 provided slower then published results, according to the reloading manuals I referenced, 190 grain projectiles from a 308 with a 24 inch barrel will have a similar velocity. The 17-inch 300 is similar to a 30-06. Keep in mind, the 308 or 30-06 would be far more pleasant to shoot, use cheaper brass, less powder and have a shorter powder column and are theoretically more accurate since they do not headspace off of a rim.
A small change in barrel length may or may not have much effect on velocity. Some cuts reduced muzzle velocity significantly, while some did not, and in one case, a small (3 ft/sec) increase was noted. Personally, I would prefer a shorter barrel IF velocity and accuracy were identical. This is an instance where I wish I had shot 10 rounds per barrel length to increase the reliability of my results.
Does a rifle’s crown affect accuracy?
This was the million dollar question today. I’ve read a series of similar experiments where the shooter intentionally damaged his crown to see how it affected group size. This wasn’t the primary purpose of this experiment, however. But, I was able to shoot a series of sub MOA groups with a hacksaw cut crown. I would say in those cases, the crown didn’t matter; but in the larger, over 1 MOA groups, the crown clearly had a negative impact on accuracy.
What about a 26″ 300 Winchester Magnum?
I don’t know. Looking back, I wish I had a 26 inch barrel to start with. Published velocities seem to have a 26 inch barrel pushing 190 Gold Medal at 2900 ft/sec, which, doesn’t seem to be much of a gain. However, with some of the newer, slower burning powders, there may be some benefit to the 2 additional inches of barrel length especially with heavier projectiles. The 190 is old hat for the many 300 Winchester Magnum shooters. Heavier projectiles and slow powders offer promising long range potential, filling the gap between the 308 Winchester and 338 Lapua/338 Norma.
Do short rifles look cooler?
Yep, they sure do. The rifle looked cooler the shorter you cut it.

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Radek07
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07.08.2019 9:37

Re: V-AR 15

Nemáte někdo šikovný odkaz na tabulku s energií střely v závislosti na délce hlavně u 223 či 308?

Na netu je to většinou už pro určitou délku hlavně.

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Quirinus
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07.08.2019 10:36

Re: V-AR 15

Nevím jaké délky hlavně tě zajímají, třeba ti to bude stačit.

.223 tady:
http://www.ballisticsbytheinch.com/223rifle.html

.308 tady:
http://bulletin.accurateshooter.com/201 ... el-length/

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