Barrel length vs muzzle velocity vs accuracy test

[Koshinn]

Good article and good comments at least the first few that I read. It's interesting how on all but the heaviest bullet the shortest barrel length is the most accurate up to 500 yards and often beyond. HEY MARINE CORPS READ THIS AND ISSUE M4s INSTEAD OF A4s! lol
I wonder if this article will inspire some 13.5"+Surefire brake AR308s. If I had seen this before I built my 18" Noveske+MaTen it would have made me reconsidered my barrel length.

It's peculiar how we as a world of people have been shooting firearms for hundreds of years and we are still bound by old "wisdom"

The article only talks about accuracy. It even acknowledges that terminal ballistics and ethics regarding hunting are not taken into account.

[CC556]

The article only talks about accuracy. It even acknowledges that terminal ballistics and ethics regarding hunting are not taken into account.

It also is assuming you're able to accurately read all the environmentals, and know the true distance to the target. So basically if you're magically able to know all the correct environmental data, the exact wind speeds and directions between you and the target, you can correct perfectly for all that, you know the exact distance to the target, you can apply perfect fundamentals, and you don't care about terminal ballistics then yeah, there's no disadvantage to a short barrel.

As taliv mentioned above, when was the last time you saw any of these "just as good" short barrel rifles at matches where accuracy at long range is important? This article is based on a whole lot of "if" and not a whole lot of real world use.

[caelumatra]

I'm genuinely curious here and not being argumentative.

So he is measuring half accuracy basically, right? If he is, isn't he also measuring the same way for the longer barrels?
For matches is there a requirement beyond accuracy? Is there any reason to have a higher velocity at range? I understand ethical hunting and the need for more velocity in that regard. I am only talking about matches. Is the only need for higher velocity to overcome the wind? Is the higher velocity what you need so that your round is less effected by air conditions between you and the target?

Trident has videos of himself shooting his 10.5 LMT 556 shooting 773 yards consistently and ringing steel.
https://www.youtube.com/watch?v=AcSSwyfZcy0
And we've all seen Haley's videos of ringing steel @ 750 with a 10.5" 300 BLK
https://www.youtube.com/watch?v=tgKjbySsAik (7:00 mark or so)

Even as I post this and rewatch the videos I can see in Haley's video he hits all around the center of the target, but he is using a T1 and most likely not aiming anywhere near the target lol
Is the higher velocity key to make even tighter groups at range? Well I guess the above article answered that. It doesn't.

Again only for matches and again I am genuinely trying to learn.

ETA:
I've not shot long range competitively, what are the types of accuracy one needs to achieve? You mention 13" @ 900 yards Taliv. How small are the targets for LR matches?

[CC556]

Regarding matches, the extra velocity helps make up for error in gauging the wind and/or the distance to the target. This is especially important if you're shooting UKD targets, even at moderate ranges and using the 155 Amax numbers from the link in the first post the extra speed going from the 18" to 26" barrel gets you 13" less drop at only 600 yards, and a little more than 3" less wind drift in a 10mph wind. Chop another ~150fps off that for the 16" barrel or 200 fps off for the 13.5" barrel and those drop/drift numbers get even further apart.

As for videos of guys hitting steel with whatever, it's not hard if you can sit there and shoot round after round and figure out the wind, then video yourself making a bunch of hits. The hard part is when you walk up to a stage and you don't get to fire a bunch of rounds to get on target, then you've got 2 or 3 minutes or whatever to find/range the targets, determine wind, make corrections, then shoot ONLY 1 or 2 rounds on each target.

[taliv]

cael, he's not measuring 'half accuracy' per se. both methods are reasonable ways of measuring accuracy. he's just using the radius (distance from the shot to the center of the group) instead of the extreme spread (two shots farthest apart in the group). It's like comparing G1 and G7 BCs. a bullet might have a .315 G7 and a .630 G1 BC. If everybody is used to hearing G1 BCs (a number in the 600s is great) and I use a G7 BC (number in the 300s) it just doesn't SOUND as good even though it's equal, which is why mfgs still use flat base pistol bullet drag profiles for their VLD match bullets. they sell better that way.
In this case, showing lots of .1 and .2 MOA numbers will make people who don't know any better think "wow, that guy is really good cause those are winning benchrest numbers" when he's really just using different units.


velocity delta in the test in the OP ranged from 195 fps to 535 fps between 26" bbl and 13" bbl.

just running some quick numbers and taking the first column as an example. 168g amax, 2705fps - 2390fps
just as an example, round numbers 700 yard target, full size ipsc 20" wide, 10mph wind.
the 26" bbl has 149" of drop and 47" of wind deflection.
the 13" bbl has 200" of drop and 58" of wind deflection.

let's say the actual wind is 7mph and you guess 5mph, so you've got 2mph of uncorrected wind.
with the 26" bbl, that's 9.4" which means you hit 1/2" from the edge of the target.
with the 13" bbl, that's 11.6" which means you miss 1 1/2" off the target.

if you were shooting at 600 yard f-class targets, the x ring is 3" diameter and the 10 ring is 6". at 600, one mph of wind is 3.3 vs 4.1 inches for 26" and 13" bbls respectively. so either is going to put you out of the 10 ring if you can't read the wind REALLY well, but wind is variable and doesn't come in discrete 1.0 mph increments

these numbers might sound pretty close, i mean, it's only an inch difference, right?? but consider one of them is really 20% better than the other, and the top shooters are separated by a point or two, or maybe just x count, statistics will catch up with you over 60 record shots. 20% less wind drift is a pretty dang big advantage.

for practical matches with UKD targets, you have to consider ranging error, where you mil or laze the target at say, 700 yards but it was really 723 yards. reference the numbers above and you'll see the 26" bbl is shooting 50" flatter at 700 than the 13" bbl.

in other words, higher velocity is more forgiving for both wind and range estimation errors, for any type of shooting you do where 1st round hits are important.

by way of comparison, cartridges that don't suck, like the 6Creedmoor shooting a 105g berger at 3150 fps would have 94" of drop and 23" of wind. so basically twice as good as the 308 with 13" bbl. And at 600, a 1mph wind is 2" of drift, so barely out of the x ring.

[TiroFijo]

You guys are a tought audience

I think the article was more geared towards making people realize that if you have a 308 with a 16" or even shorter barrel you not necessarily have a short range rifle. With the current adoption of many 7.62 NATO semiauto precision rifles (LMT, Knights, LaRue, HK, etc.) with 16" barrels that have proven very capable up to 800 m we all know that here, but many people don't. Everything is a compromise, but just until a few years ago similar rifles had at least 20" barrels, and a decade ago even longer.

[caelumatra]

Thanks guys for the responses. Very informative