...interesting take on powder sensitivity...

wildgene · May 16, 2016

...a lot of things go into altitude density, colder air is thicker, higher elevation is thinner, 50% relative humidity is a lot less water vapor @ 40* than @ 80*. Consistency is a hallmark of accuracy, but might there be a line that stepping over bogs us into "anal retentive". For most hunting cartridges when we start to get on the low end of velocity, energy, bullet performance, let's say 2000fps/1500ft.lbs/ 500-600yds., a loss of 100fps MV would give you less change in POI than missing your wind call by 2mph...

http://www.rifleshootermag.com/accuracy ... fleshooter

Dwh7271 · May 16, 2016

That's interesting Gene. Thanks!
You're right about the wind call also IMO.

Horsethief · May 16, 2016

Loads developed in the late summer usually don't perform the same as in the coldest months, so checking the 100 or 400 yard scope settings for your long-range rifle is a great thing. Such a check can reveal if you've got a much different load at hunting season than you had during load tests.

I have no doubt RL-22 is not going to work as well as H-1000 or another temperature resitant powder. That's probably by Alliant Powders now has temp insensitive powders, RL-17, RL-23, and RL-26. By the way, RL-26 is close to the burning speed of H-1000.

kraky1 · May 16, 2016

The way people post pictures of groups with a very slight powder changes it would sure seem that a 100 FPS change would throw a gun into a terribly different accuracy node.
I guess if you had a gun that didn't mind that big of a swing you've got a heck of a gun and better never sell it!

Guy Miner · May 16, 2016

kraky1":3a7zj581 said:
The way people post pictures of groups with a very slight powder changes it would sure seem that a 100 FPS change would throw a gun into a terribly different accuracy node.
I guess if you had a gun that didn't mind that big of a swing you've got a heck of a gun and better never sell it!

Yes.

The loss of 100 fps may only result in a tiny change in elevation data...

But sometimes the accuracy goes to pieces!

Guy

Dwh7271 · May 17, 2016

Guess that kind of highlights the OCW method of load work up.

Guy Miner · May 17, 2016

Dwh7271":ynavf8yb said:
Guess that kind of highlights the OCW method of load work up.

Hmm. I don't know if it does or not, since we're discussing how temperature extremes affect the load...

Dwh7271 · May 17, 2016

Ok.
OCW highlights a series of loads having the same area of impact. For example, a made up loading that 39 gr through say 39.6 gr may have the same impact area on the target. We decide 39.3 is the right load for example. Although 39 gr and 39.6 gr are slower and faster than our charge we load, the impact area is roughly the same(albeit not the group size). So although the drops may slightly differ, the area in which the bullet will impact should be predictable even if it's slightly faster or slower than our "good" load. Seems to me that particular method might help when potentially dealing with temperature swings.
That was my point. Sorry I wasn't a little clearer.

http://optimalchargeweight.embarqspace.com/ocw-instructions/4529817134

Guy Miner · May 17, 2016

Might. I understand your thoughts. Be interesting to try!

I've seen some darned good loads, come apart accuracy-wise, when temps fall considerably. Don't know if the OCW method would mitigate that, or not.

Guy

Polaris · May 17, 2016

Most sporting powders originate from military innovations. I believe this is the case with the temp insensitive powder, granddaddy of them all, Varget by ADI. In addition to requiring precision in 7.62 sniper rifles at extreme range in southern hemisphere climes, I believe part of the driving force was to develop consistent pressures, i.e. not spiking extremely high... in a very hot GPMG chamber.

As anal as American sport shooters tend to be, the concept was a natural sell. Unless you are shooting BR or possibly F-class, the change in POI from old fashioned powders vs newfangled powders will be far smaller than shooter induced error. You can get into trouble working up very hot loads in colder weather. You are already pushing the limits of pressure and then firing in conditions that will increase it.

You can shoot tiny groups off a bench until you erode so much rifling that the rifle won't group anymore. Go ahead, can be a fun hobby in itself. Just understand that if you're approaching MOA groups, you are exceeding the field accuracy potential of a rifle/shooter combination. You'll never notice +/-1" at 400. Don't be afraid to go out and use the good oldies.