w-w760 is it tempature sensitive?

[Ironworker]

Shooting a max load in my 22-250AI at 75 degrees with 44 grs of W-W 760 no problems. If I shoot that same load in 95 degree heat will it cause problems?

[PaulS]

What happens in your rifle is likely to be different that what would happen in another rifle. All ball propellants are fine in their "normal" heat range but if you get the cartridge warmer than that pressures do rise. Ball powders are generally more sensitive to extremely cold temps - they tend to detonate at temps below -20F.

[victorcharlie]

I load W760 in my 30.06.  I noticed that while shooting it last week, the point of impact changed low and right by about an inch.  Although I'm not 100% about what caused it, the temps were in the 90's.

[Old Syko]

If a 20* ambient temp difference is going to cause pressure problems your load was outside proper pressure parameters to begin with.  44gr. of 760 is at or beyond safe pressure limits with any slug available in this round.  I would predict a dim future for the firearm and shooter at some point.

[Grumulkin]

Winchester 760 is the same powder as H414.  You can look at a bottle of H414 and if it says it's an "Extreme" powder then it's deemed to be relatively temperature insensitive.  I don't happen to have a bottle of H414 around right now or I'd tell you.

Unless I was running at the ragged edge of a maximum load, I wouldn't hesitate to shoot cartridges in 95 degree as opposed to 75 degree weather.  My practice is to load for accuracy and not for velocity or maximum loads so in most cases, I'm not running at the ragged edge of maximum.

Also, a change in the area of impact of bullets over a few days doesn't mean the powder is to blame.  It could be but factors like scope, stock, barrel, humidity, etc. can all come into play here.

[Dave in WV]

H414 is not an "Extreme" powder. How temp sensitive W760 is I don't know. Keeping your ammo out of direct sunlight on hot days will help keep your chamber pressure down.

[John R.]

Win. 760 is indeed temperature sensitive. I used it for years in my 7mm/08, because it shot the highest velocity. After shooting and chronographing from early fall to the dead of winter, the velocity changed about 75 fps. I started using Varget (which is an extreme powder) and haven't noticed near the velocity change that I did with W760.

[Graybeard]

VERY SENSITIVE to heat. I put together some max or near max loads one fall for use during deer season in my Remington Model Seven in 7-08 that shot into 3/8" groups and I loved it. The next summer I fired some and pressures were so high it locked the bolt when fired a couple times and then I decided I needed to stop and pulled the bullets and have never used that load again. It worked nicely in cool weather but was definitely way too much in hot weather so I decided it best not to keep them around. Shame too as they sure were accurate in that rifle.

[Ironworker]

According to latest Sierra manual 44.5grs of W-W760 is max so I'm .5 below that. My BBL is a 5R cut rifled 8"twist. This load produces 3,900 +Fps.I live in the SF Bay area of Ca ( east of the horrible city) I'll be mounting an offensive against hopefully a regiment of war squirrels in the central valley next Saturday. Long range weather for-cast predict 95 degrees. I just don't want my bullets to bounce of these squirrels and gain a tactical advantage.

[MnMike]

I don't use 760 but I have tried 748 in my 7-30 Waters. It is a great powder for summer - very accurate, but will not do so well during deer season here in the frozen north. I went to Varget.

Good luck

mike

[jhalcott]

 Ironworker, you are right on the edge with that load. I suggest that you keep your gun AND ammo out of the sun as much as possible. keeping the ammo in a cooler is not a bad idea either. I have used a similar load in the 22-250 with 55 grain bullets on ground hogs. If the bolt gets "sticky" at all ,it's best to have a second gun handy while you allow the 22-250 to cool in a shaded place. The alternative is shoot till you ruin the 22-250!

[Bob A]

I'll be mounting an offensive against hopefully a regiment of war squirrels in the central valley next Saturday. Long range weather for-cast predict 95 degrees. I just don't want my bullets to bounce of these squirrels and gain a tactical advantage.

I know our California Ground Squirrels have a world wide reputation for throwing back bullets that bounce of their armor plating  but don't believe it. People have been known to kill them with a single shot 22lr.  I use a Handi Hornet and haven't had a  bullet thrown back at me for years.

Good luck and stay cool

Bob A

[Ironworker]

Found out the war squirrels waved the white flag and have  regrouped in their base camp. ( Numbers have greatly diminished) So rather then pay $ 150 bucks for guide fees . I find some other place to mount an attack................ My load of 44grs of w-w760 is hot. Last Saturday I dropped the load by 1 1/2 grains, and lost only 60 fps. from 3,910 to about 3,850 FPS. I bet my BBL will no the difference ?

[Old Syko]

If max velocity is what you're looking for, and it appears that it is, try to work up a load using H380.  If you want accuracy try lowering your 760 charge even more.