Long range semi auto caliber.

[Salt Works Rifles LLC.]

I would like to propose a question.

What would you consider the best long range semi auto caliber and why?

[dc2allday]

Define long range

[Salt Works Rifles LLC.]

Define long range

Let's break it down

1200 yards + caliber . (that should put you on the cusp)

1200 yards and closer caliber.

[nick]

Define semiauto. Pretty much anything can be fired out of a semiauto firearm. Or did you mean something that fits an AR10/155?

[kcstott]

Define long range

Yeah exactly

how long is a piece of string??

0-300yds/M soft target =.223 Hard target =.308
0-800yds/M =.308
600-1200yds/M = .300 win mag
800-1700yds/M = .338LP mag/ .408, or .416
1700+yds/M .408, .416, 50 BMG, 510 DTC

Keep in mind at the lower in of the scale the .243 win, .270, are very good and very underrated rounds

Seal snipers are issued four weapons currently
the Mk12, Mk11 a bolt gun (M91A2) and a Barrett 50

so it depends on where you are going and what you intend to shoot and how far that target is to determine what weapon to bring.

[Salt Works Rifles LLC.]

Define semiauto. Pretty much anything can be fired out of a semiauto firearm. Or did you mean something that fits an AR10/155?

Good point, but the mag being the limiting factor of your OAL some calibers will perform better in semi auto.

[JMP]

Also, consider the shape of the cartridge. Especially for most semiautomatic platforms, you do not want a shoulder angle that is too steep or you may run into feeding issues. You'll probably want a cartridge that has the canonical 20 degree shoulder angle; whereas, some more modern wildcat cartridges are built with a steeper shoulder angle to give the case a bit more capacity and/or efficiency.

[Salt Works Rifles LLC.]

Also, consider the shape of the cartridge. Especially for most semiautomatic platforms, you do not want a shoulder angle that is too steep or you may run into feeding issues. You'll probably want a cartridge that has the canonical 20 degree shoulder angle; whereas, some more modern wildcat cartridges are built with a steeper shoulder angle to give the case a bit more capacity and/or efficiency.

Don't you think the 30 degree angle or thereabouts, seems to provide a more stable push from all sides to eliminate a yaw before entering the rifling? As opposed to a less sharp angle or no angle at all, where there is a greater change to gyrate as the tip of the bullet attempts to enter the rifling which also lies at an angle. I assume therefore that the pushing effect is more even, provided the convergence happens inside the length of the neck at some specific point. So, the ratio of the shoulder angle to the neck's length, will determine the point of convergence, which may be an important parameter in obtaining a sweet spot.

[JMP]

Don't you think the 30 degree angle or thereabouts, seems to provide a more stable push from all sides to eliminate a yaw before entering the rifling? As opposed to a less sharp angle or no angle at all, where there is a greater change to gyrate as the tip of the bullet attempts to enter the rifling which also lies at an angle. I assume therefore that the pushing effect is more even, provided the convergence happens inside the length of the neck at some specific point. So, the ratio of the shoulder angle to the neck's length, will determine the point of convergence, which may be an important parameter in obtaining a sweet spot.

I believe it is a case by case issue. Many factors can induce a yaw. It's that I would personally recommend staying away from a more steep shoulder angle only in semiautomatics since they are not manually fed. They should feed more reliably with a more tapering in the shoulder. Semiautomatics are inherently less accurate/precise than bolt action rifles, so I'd stick to what's known and works. .308 Winchester is about the most I'd care to go in a semi. The very large semis like the Barretts are more geared toward anti-materiel rather than precision. For long range accuracy, you'll want a bolt action.

[kcstott]

Oh lord Here comes the shoulder angle debate.


All things being equal case shape has zero to do with accuracy of the round. The case simply holds the powder, primer, and bullet

[JMP]

KC, steeper shoulder angles are commonly introduced to get more capacity when you are limited by the size of your action and boltface. The only reason I brought it up is for semis. Some platforms rely on the feed ramp to guide the cartridge into the chamber with the shoulder, and they'll jam the should pretty hard. This can be an issue with steeper shoulders.

[kcstott]

KC, steeper shoulder angles are commonly introduced to get more capacity when you are limited by the size of your action and boltface. The only reason I brought it up is for semis. Some platforms rely on the feed ramp to guide the cartridge into the chamber with the shoulder, and they'll jam the should pretty hard. This can be an issue with steeper shoulders.

that I agree with it was the "more stable push from all sides to eliminate yaw" that caught my eye

There are still some benchrest guys that believe case shape makes a difference down range.

The thing is no one can separate the variables to such a fine degree that they could prove that case shape has anything to do with accuracy.

If you stacked all the variables up it would be an endless list of thing that change to effect where your bullet goes and how fast it gets there.

Case shape even if it did have an effect on accuracy would be so slight that a slight change in barrel temp would negate it

[Fjold]

I'm shooting the 260 Rem in my AR10. But unless you single load the limiting actor is magazine length which typically means that you have to use lighter (shorter) bullets as a compromise on BC versus case capacity.

For the AR 10 type rifle, the largest case capacity possible combined with the smallest bore to use long for caliber bullets, would be best.

In this case the 260 would be better than the 308 but the 243 would be an improvement on that. But the 22.250 Ackley Improved shooting 90 grains bullets may be the best.

[spamsucker]

Fjold brings up a good point. For the most part, not all but most, semi auto platforms have mag length limitations that don't favor long high BC VLD projectiles.

Perhaps shifting the debate towards that of platform instead of caliber would be useful. Other than the mag length issue I've always had stunning performance from AR platform rifles. I don't know of many other platforms that so readily lend themselves to the creation of a consistent sub-MOA rifle.

[highpower790]

Maybe not the best platform,but a couple times a year Ill take out my M14 for matches at Sac Valley.