gunDriller
9th February 2016, 07:22 AM
When I first got into looking at the spectrum of calibers above 308, one thing that was quite striking was how 300 Winchester Short Mag was close to the top of the pile.
I wasn't thorough enough in checking out other calibers.
I did find a few that shoot faster than the 300 WSM.
To keep things 'apples to apples', I am considering velocities for only the 150 grain bullet.
300 Remington Ultra Mag (300 RUM) ... 3515 fps ... 6.51 grams IMR 7977 powder
300 Weatherby Mag ... 3437 fps ... 5.36 grams IMR 4831 powder
300 WSM ... 3248 fps ... 4.39 grams IMR 4451 powder
7 mm WSM ... 3197 fps ... 4.57 grams Winchester Supreme 780 powder
7 mm Rem. Mag ... 3081 ... 4.41 grams Winchester Supreme 780 powder
Specs from
http://www.hodgdonreloading.com/data/rifle
*Asterisk* type performance -
I discard the velocities for "Suprform" powder. Hodgdon/ Hornady claim great things for it.
But, if you read the reviews at MidwayUSA, the message is, "avoid Suprform".
The only time I've gotten a 10% increase in speed, it was with a 5.56, and an over-load of Magnum Pistol powder. It shot a few inches high at 200 yards, definitely an indicator of a significant speed increase. It also created an over-pressure condition that damaged the bolt and blew the contents of the magazine all over the floor.
I was wearing safety glasses and a welding mask when this happened. That does look a little strange at a shooting range. :)
I think of the task of propelling the bullet as being a little bit like shuffle-board.
You need one long sustained push to get higher velocities.
The pressure peaks at approx. 60 kPsi, then at the tip of the barrel, right before leaving the rifle, it's down to 8 kPsi. What the chemists & engineers at the firearms companies work night & day on is to increase the pressure after the initial peak, without increasing the maximum pressure, so that the bullet is really given that nice long SUSTAINED push.
I think there are 2 ball-games going on when you look at a list of powder burn rates like this -
http://www.reloadersnest.com/burnrates.asp
A - give re-loaders a wide variety of burn-rates.
B - MAXIMIZE revenues, by giving re-loaders way more variety than they actually need, and promoting some powders (e.g. Suprform) with some pretty audacious claims. If it is true that Hornady & Hodgon did a bait-and-switch on the Supfrom powder - selling the bullet with one proprietary powder, calling it "Suprform", then selling a different powder with the same name ... well, I wouldn't be surprised.
And I don't believe the claims until I test them (just got a Chronograph, to measure bullet velocity.)
Added 7 mm Rem. Mag to the list.
I wasn't thorough enough in checking out other calibers.
I did find a few that shoot faster than the 300 WSM.
To keep things 'apples to apples', I am considering velocities for only the 150 grain bullet.
300 Remington Ultra Mag (300 RUM) ... 3515 fps ... 6.51 grams IMR 7977 powder
300 Weatherby Mag ... 3437 fps ... 5.36 grams IMR 4831 powder
300 WSM ... 3248 fps ... 4.39 grams IMR 4451 powder
7 mm WSM ... 3197 fps ... 4.57 grams Winchester Supreme 780 powder
7 mm Rem. Mag ... 3081 ... 4.41 grams Winchester Supreme 780 powder
Specs from
http://www.hodgdonreloading.com/data/rifle
*Asterisk* type performance -
I discard the velocities for "Suprform" powder. Hodgdon/ Hornady claim great things for it.
But, if you read the reviews at MidwayUSA, the message is, "avoid Suprform".
The only time I've gotten a 10% increase in speed, it was with a 5.56, and an over-load of Magnum Pistol powder. It shot a few inches high at 200 yards, definitely an indicator of a significant speed increase. It also created an over-pressure condition that damaged the bolt and blew the contents of the magazine all over the floor.
I was wearing safety glasses and a welding mask when this happened. That does look a little strange at a shooting range. :)
I think of the task of propelling the bullet as being a little bit like shuffle-board.
You need one long sustained push to get higher velocities.
The pressure peaks at approx. 60 kPsi, then at the tip of the barrel, right before leaving the rifle, it's down to 8 kPsi. What the chemists & engineers at the firearms companies work night & day on is to increase the pressure after the initial peak, without increasing the maximum pressure, so that the bullet is really given that nice long SUSTAINED push.
I think there are 2 ball-games going on when you look at a list of powder burn rates like this -
http://www.reloadersnest.com/burnrates.asp
A - give re-loaders a wide variety of burn-rates.
B - MAXIMIZE revenues, by giving re-loaders way more variety than they actually need, and promoting some powders (e.g. Suprform) with some pretty audacious claims. If it is true that Hornady & Hodgon did a bait-and-switch on the Supfrom powder - selling the bullet with one proprietary powder, calling it "Suprform", then selling a different powder with the same name ... well, I wouldn't be surprised.
And I don't believe the claims until I test them (just got a Chronograph, to measure bullet velocity.)
Added 7 mm Rem. Mag to the list.