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W-W 760 Tempurture sensitive
- Thread starter Worker
- Start date
L
Larry Elliott
Guest
I can only offer my experience from maybe 18 or 20 years ago when I got ahold of some H414 that was marked "surplus powder". I'd worked up a load with H414 for both a .22-250 and .243 I had then that was a good load and safe at the temperatures I worked up the loads for - warm in Seattle, but not for Eastern Montana. Took the loads to Eastern Montana to shoot prairie dogs where the temp was 15 to 20 degrees warmer. They were all too hot. On returning to Seattle I found that it took 1.5 gr more powder to achieve the same pressure signs in the .243, and I found that I couldn't get enough more powder in the .22-250 case.
This is relevant because H414 and W760 are the same powders only differing in labels, and with lot to lot variations. That from a Hodgdon rep.
This is relevant because H414 and W760 are the same powders only differing in labels, and with lot to lot variations. That from a Hodgdon rep.
T
taxman
Guest
I cannot vouch for the 760, but I can on the H414. I shoot a .243 with 55 grn Sierra BLK's. Super accurate, but 1 to 1.5 grains difference on a hot day can make you very nervous the first time around. I have since backed off the load to where it is safe most of the time.
K
keithcandler
Guest
Larry, it has not been my experience that 760 and 414 are the same...
It always takes more 414 to achieve the same pressures and velocities in my 22/250, 22/250 AI, and 243's.
Worker, quite a bit of the "temp sensitive" thing comes from the fact that when you are working up a load at the range you are sitting underneath covered benches. When you go out hunting, you are not covered, meaning that the ammo is exposed to the sunlight's heat.
When I was shooting thousands of p. dogs a year, I lived in S. ca were I worked up loads in 70-75* temps. When I got to S. Dakota, on the first trip, we shot off the ground either off the ground or off a bench. I did notice that my loads were too hot because often the ammo was hot to the touch when I chambered the rounds. I built a camper shell for the truck, put a 50"x50" hatch in the top of the camper shell, and also installed a re-tractable awning over the top of us while we were shooting. While we were shooting underneath the awning, we had no pressure problems at all, even though it was still hot, but the ammo did not get hot because we kept it out of direct sunlight.
We hunted coyotes all across Ca, Arizona, Nv, and Mexico. We never had any pressure problems due to hot weather, but leave the ammo out in the sun, and look for pressures to go up as the cartridge gets hot to the touch!
If you leave your ammo exposed to direct sunlight, then I recommend H4895 for the 55g bullets, but you will not get the velocity of 760.
It always takes more 414 to achieve the same pressures and velocities in my 22/250, 22/250 AI, and 243's.
Worker, quite a bit of the "temp sensitive" thing comes from the fact that when you are working up a load at the range you are sitting underneath covered benches. When you go out hunting, you are not covered, meaning that the ammo is exposed to the sunlight's heat.
When I was shooting thousands of p. dogs a year, I lived in S. ca were I worked up loads in 70-75* temps. When I got to S. Dakota, on the first trip, we shot off the ground either off the ground or off a bench. I did notice that my loads were too hot because often the ammo was hot to the touch when I chambered the rounds. I built a camper shell for the truck, put a 50"x50" hatch in the top of the camper shell, and also installed a re-tractable awning over the top of us while we were shooting. While we were shooting underneath the awning, we had no pressure problems at all, even though it was still hot, but the ammo did not get hot because we kept it out of direct sunlight.
We hunted coyotes all across Ca, Arizona, Nv, and Mexico. We never had any pressure problems due to hot weather, but leave the ammo out in the sun, and look for pressures to go up as the cartridge gets hot to the touch!
If you leave your ammo exposed to direct sunlight, then I recommend H4895 for the 55g bullets, but you will not get the velocity of 760.
Last edited by a moderator:
Sun light
I'm thinking of bringing a cooler along and put the ammo in there. Today with W-W760 and a 55gr bullet I was getting 3,900+ . I also shot some Berger 55gr Match with same powder charge I was getting 3,980 FPS but!!!! Bullets fragmented in flight before the 100 yard line. Why were the Bergers faster?
I'm thinking of bringing a cooler along and put the ammo in there. Today with W-W760 and a 55gr bullet I was getting 3,900+ . I also shot some Berger 55gr Match with same powder charge I was getting 3,980 FPS but!!!! Bullets fragmented in flight before the 100 yard line. Why were the Bergers faster?
K
keithcandler
Guest
Bullets vary in dia.....
there are a couple of dimensions to consider:
1. dia of the pressure ring on the very back of the bullet
2. Dia of the shank
3. how much bearing surface does the bullet have
I made 6 mm bullets that were fat, .2436 pressure ring and .2433 shank, and they were very fast. I think that they sealed the gases behind the bullet more than skinnier bullets as the bullet obturated in the lands.
there are a couple of dimensions to consider:
1. dia of the pressure ring on the very back of the bullet
2. Dia of the shank
3. how much bearing surface does the bullet have
I made 6 mm bullets that were fat, .2436 pressure ring and .2433 shank, and they were very fast. I think that they sealed the gases behind the bullet more than skinnier bullets as the bullet obturated in the lands.
T
Thunderbolt
Guest
Have learned my lessons on W760 and its counterpart H414 long ago. Wild pressure swings with temperature changes and lot to lot batches. What ever you do don't let a round with this stuff heat soak in a warm chamber that can happen in varmint hunting conditions.