6.5cm ban?

[Pete]

I see it stated that a 22LR will travel approx. 1.4kms when fired at an angle of 30 degrees to the horizontal, and likewise, a 308 will travel 4kms.
So how do they establish these values, do they conduct a practical experiment (though maybe not quite as I described, ),or is it done mathematically?

Pete

[Martiniman]

Don’t know if you served but mil ammo has a stock number and various codes on the side of the container meaning you can be assured there’s a level of QC gone into it before sqauddies light up the targets. 6.5 Creedmoor is yet to be adorned with the same NATO treatment meaning the only numbers to go on the ammo’s performance are from the supplier - assuming they will be give up their own data or sell it. Asides, it will be a some VTI’s working out the envelope of the round over the coming months no doubt applying analytical data and comparing it to actual. Be an amazing job to work on.

[Pippin89]

I see it stated that a 22LR will travel approx. 1.4kms when fired at an angle of 30 degrees to the horizontal, and likewise, a 308 will travel 4kms.
So how do they establish these values, do they conduct a practical experiment (though maybe not quite as I described, ),or is it done mathematically?

Pete

It is pretty straightforward to do mathematically. To calculate the time in the air, the forward travel is irrelevant. All you need to know is how fast it is moving up and down. Lets say a .308 leaves the barrel at 800m/s (2624ft/s) at an upward angle of 30°. The vertical component of the velocity is 800 x Sin(30) or 400m/s. Simple Newtonian calculations state the bullet will reach the top of its arc at roughly 41 seconds into the flight, and therefore, come back to earth another 41 seconds after that. So a 1 minute 22 second flight time. From that, the forward component of muzzle velocity is 800 x cos(30) = 692m/s, and they know the ballistics coefficient and can calculate the deceleration in forward velocity and use a bit of calculus to determine how far the bullet has travelled. I doubt very much that they would actually test it, although I am sure someone has somewhere.

I did a rough fag packet calculation with a 0.4BC for 155gr .308 bullet at 900m/s (2950ft/s) and came to ~3200 meters. I assume they have used a tail wind for a worst case scenario to get to 4000m. If I get bored later I will work out what tail wind would give that range

[Pete]

I get the maths, and on reflection, it might be difficult to test fire at a range calculated to be the maximum attainable.
The target would have to be pretty big, and the wind very light.

Pete

[Mattnall]

it might be difficult to test fire at a range calculated to be the maximum attainable.
The target would have to be pretty big, and the wind very light.

They have done something similar at Yuma in the past. Not a very practical exercise generally, though, I would think.

[Alpha1]

All very interesting I have decided to re barrel my Ruger precision 6.5 Creedmoor in .308 a simple solution because I can do this my self. The 6.5x55 rifle I have could also be rebarreled in .308 I have a suitable barrel blank but it will need threading and chambering I am not sure I can be bothered to be honest the way shooting on MOD ranges is going is it worth the effort. Or should I just bin it.

[Mattnall]

All very interesting I have decided to re barrel my Ruger precision 6.5 Creedmoor in .308 a simple solution because I can do this my self. The 6.5x55 rifle I have could also be rebarreled in .308 I have a suitable barrel blank but it will need threading and chambering I am not sure I can be bothered to be honest the way shooting on MOD ranges is going is it worth the effort. Or should I just bin it.

There are other non-MoD ranges in the country you know.

I guess it depends upon how keen you are on your shooting - shooters will find a way.
Don't give up so easily.

[Pete]

The piece about this in the current NRA journal very specifically refers to "6.5 Creedmore", and that it's a temporary ban until the calculations are done to the satisfaction of the military.
Judging by the wailing & self-flagellation on this and other forums, this may have been lost in the translation, somewhere along the line......

Pete

[Mattnall]

Oh Pete,

But, but, but...it's all a conspiracy!!!!!
They've all got it in for me!

[Pete]

Ah yes, "Carry on Cleo"...

Pete