stubbicatt
Member
I've posted this over at HKpro.com and received no input. I figured you the cognoscenti will have insight.
Guys.
I am trying to duplicate 7.62 NATO loadings with the Hornady 150 gr. FMJ bullets.
So yesterday I took my PTR91 to the range, set up the chronograph maybe 3 or 4 feet in front of the muzzle, which is equipped with a muzzle brake. No errors and readings pretty consistent. Would have put it out further, but the distance seems OK.
So I go online to find out what milsurp velocities should be, and the almighty internet gave a range, but out of the G3 barrel it is supposed to be 800 meters per second, or 2625 fps. See Wiki. (I verified the math on the conversion to fps. here.)
The first five rounds out the 18" tube were South African surplus, and averaged 2792 fps. Notably faster than the Wiki article suggests. OK so far I guess. SD was 35.
Next five rounds were handloads at 2841 fps average. SD 19
Next five rounds, +1 grain of powder over the first five averaged 2898 fps. SD 28.6
Last five rounds, +1 more grain, averaged 2968 fps. SD 24.
No pressure signs on the brass, and all loads below maximum by published data of the powder manufacturer, and data published by the bullet manufacturer.
What gives?
The 18 inch barrel should be a limiting factor on these loads. I would have expected lower velocities than out of a 20 inch barrel, or longer.
1) I think either the chronograph is wrong, or
2) The PTR barrel gets more velocity than a G3?, or
3) The South African Surplus is higher velocity than NATO spec., or
4) I don't know what...
Not sure how to interpret this data, and look for suggestions.
Anybody?
Guys.
I am trying to duplicate 7.62 NATO loadings with the Hornady 150 gr. FMJ bullets.
So yesterday I took my PTR91 to the range, set up the chronograph maybe 3 or 4 feet in front of the muzzle, which is equipped with a muzzle brake. No errors and readings pretty consistent. Would have put it out further, but the distance seems OK.
So I go online to find out what milsurp velocities should be, and the almighty internet gave a range, but out of the G3 barrel it is supposed to be 800 meters per second, or 2625 fps. See Wiki. (I verified the math on the conversion to fps. here.)
The first five rounds out the 18" tube were South African surplus, and averaged 2792 fps. Notably faster than the Wiki article suggests. OK so far I guess. SD was 35.
Next five rounds were handloads at 2841 fps average. SD 19
Next five rounds, +1 grain of powder over the first five averaged 2898 fps. SD 28.6
Last five rounds, +1 more grain, averaged 2968 fps. SD 24.
No pressure signs on the brass, and all loads below maximum by published data of the powder manufacturer, and data published by the bullet manufacturer.
What gives?
The 18 inch barrel should be a limiting factor on these loads. I would have expected lower velocities than out of a 20 inch barrel, or longer.
1) I think either the chronograph is wrong, or
2) The PTR barrel gets more velocity than a G3?, or
3) The South African Surplus is higher velocity than NATO spec., or
4) I don't know what...
Not sure how to interpret this data, and look for suggestions.
Anybody?