Is there any benefit to short barreled 7.62 nato?

[Bolt_Overide]

I've seen this bandied about a few times by others, and I just cant get my head around it. Is there something I'm missing?

[Failure2Stop]

Not really.
Once you drop below 14.5" (16" to many), you might as well just go to .300 Blk and retain magazine/gear compatibility.


Typos brought to you via Tapatalk and autocorrect.

[TehLlama]

I think the absolute cutoff is 13" or so (where OAL for velocity is literally worth no gain), but a 14.5" .308 is going to weigh more than a 16" BLK, so I'll defer to the above.

If you're only concern is barrier penetration at closer range, and running suppressed, maybe there's something to a 14.5" .308 rifle, and in some cases some SCAR-H owners report better accuracy after shortening the barrel, but there isn't really antying to gain by going SBR .308

Some people will do it anyway... but like everything else in the gun industry, even if a smarter was has already been found, there's enough people wanting to be different the 'other' solution will get built anyway.

[Bolt_Overide]

Wheres my SR47 jack....

[TehLlama]

Oh, you saw the URX 3.1 Equipped one from last month too? Yeah... my keyboard hasn't quite recovered from the drool dumped on it yet.

[Failure2Stop]

Wheres my SR47 jack....

That purchase order must be around here somewhere...

[Suwannee Tim]

A good way to think about this is to describe the barrel length in calibers which is the barrel length divided by the bullet diameter. For example a 14.5 inch 5.56 mm barrel is about 65 calibers long. A 16 inch 7.62 mm barrel is about 52 calibers long. For standard rifle cartridges barrel length below 50 calibers and certainly 40 calibers gets you well into a regime of diminishing returns. By this reasoning a 16 inch 7.62 barrel is a short barrel.

[Jaws]

A good way to think about this is to describe the barrel length in calibers which is the barrel length divided by the bullet diameter. For example a 14.5 inch 5.56 mm barrel is about 65 calibers long. A 16 inch 7.62 mm barrel is about 52 calibers long. For standard rifle cartridges barrel length below 50 calibers and certainly 40 calibers gets you well into a regime of diminishing returns. By this reasoning a 16 inch 7.62 barrel is a short barrel.

Not a good way to go. The AK round is 7.62mm and 16 inch barrel is basically rifle length. You have to take into consideration the ratio between the chamber and bore volume to have a better idea how much barrel you need.

[Failure2Stop]

A good way to think about this is to describe the barrel length in calibers which is the barrel length divided by the bullet diameter. For example a 14.5 inch 5.56 mm barrel is about 65 calibers long. A 16 inch 7.62 mm barrel is about 52 calibers long. For standard rifle cartridges barrel length below 50 calibers and certainly 40 calibers gets you well into a regime of diminishing returns. By this reasoning a 16 inch 7.62 barrel is a short barrel.

The model is wrong if it considers a 16" 7.62 as "short", and it must think that an 11.5 .300 Blk is unusable.

I would base criticism on performance, not an arbitrary comparison of dimensions that don't have much correlation.

Typos brought to you via Tapatalk and autocorrect.

[Suwannee Tim]

Not a good way to go. The AK round is 7.62mm and 16 inch barrel is basically rifle length. You have to take into consideration the ratio between the chamber and bore volume to have a better idea how much barrel you need.

Which is why I mentioned "standard rifle cartridges" specifically discussing 5.56mm and 7.62mm. Magnums such as the 300 Winchester magnum or small cartridges such as 7.62X39 or 300 AAC do not fall into that class. When thinking about what class a cartridge falls into I like to think about the typical bullet to propellant weight. A standard rifle cartridge for example will have a bullet to propellant ratio of about 3 or 4 to 1. A magnum more like 2 to 1, even 1.5 to 1. In 300 AAC this ratio is 220 / 10 = 22 down to maybe 110 / 20 = 5.5. Dimensionless ratios widely accepted method of making comparisons and can give interesting insights for example the 458 Winchester Magnum will have a ratio of maybe 500 / 80 or 6.25 placing it below a "standard rifle" cartridge. There is in fact a body of engineering knowledge called Dimensional Analysis, Scaling and Similitude.

The model is wrong if it considers a 16" 7.62 as "short", and it must think that an 11.5 .300 Blk is unusable.......I would base criticism on performance, not an arbitrary comparison of dimensions that don't have much correlation.....

Dimensionless ratios have great value in making comparisons of this sort and can produce insights not ordinarily evident. For example, the 5.56mm, 7.62X51, 50 BMG, 20mm, 105mm, 155mm, even up to the 16 inch naval gun are all essentially the same cartridge when judged by the projectile to propellant ratio, projectile length to weight ratio and range to projectile mass ratio It is interesting that such a wide range of guns fall into a narrow range of projectile to propellant ratio.