How accurate are ammo manufacturer's claimed MV numbers?

B

Bart B.

New member
Unclenick,

If 21.75" is a sort of magic number, I think it's only for that warehouse yard range, barrel and specific load for the rifle used.

7.62 NATO M80 ammo used in 1000 yard Palma matches has to be shot in barrels at least 30 inches long to keep them super sonic in cooler temperatures.
 
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B

Bart B.

New member
Generic said:
There’s a perfect length barrel for all loadings, after which additional barrel length is a detriment to MV,
Click to expand...
I've never heard of this.

Does it apply to all barrels?

According to ballistic data from Sierra Bullet's gurus, such rifle barrels need to be at least 36 inches long.

Why shoot bullets as fast as possible?

What if such bullets leave at the wrong place on the muzzle axis vertical swing angle where slowest ones exit at lower angles to the line of sight than faster ones?
 
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O

old roper

New member
Here is where I got number.

SECTION II – PROCEDURES
CENTERFIRE RIFLE
REFERENCE AMMUNITION:
PERIODIC ASSESSMENT
SAAMI VOLUNTARY PERFORMANCE STANDARDS

varies from the Raw Average by more than plus or minus 50 fps in velocity OR
plus or minus 3,500 CUP/psi in pressure, the pressure or velocity data from that
(those) station(s) should be discarded. The mean pressure and velocity data
should be recalculated omitting the discarded data. The new mean is the
“Corrected Average”. If the mean pressure value of a station is outside of the
limits as defined above, but the velocity is in, the pressure data should be dropped
and the velocity data retained. The converse is true as well. Using the Corrected
Averages, the Inclusion Limits are determined as follows:
VELOCITY: MEAN = Same as Corrected Average
HIGH = MEAN + 50 fps
LOW = MEAN – 50 fps
PRESSURE: MEAN = Same as Corrected Average
HIGH = MEAN + 3,500 CUP/psi
LOW = MEAN – 3,500 CUP/ps
 
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