temerature change and effects on rifle ammo

[Guy Miner]

Right - temp DOES make a difference. But not such a huge difference at short ranges.

Honestly, if they're off by that much, with that small of a temp change... What would be the difference in point of impact out at 300 - 400 yards? With only a small temp change? It would be huge! And we'd have one heck of a time trying to hit our targets.

Am well aware of the differences in point of impact changes due to temperature - but it's something seen at much longer ranges.

Competed with the good old .308 Win in NRA prone matches for quite a while, enough to wear out a few barrels. That's a lot of .308 shooting, much of it at 600 yards. Time to time, when conditions were particularly hot, or cold, I'd have to make small adjustments in my elevation. Small. At 600 yards. Not big, at 50 or 100 yards.

Been stewing on this thread for a while now, and decided that "the other side of the story" needed to be told before other readers accepted as gospel that a 30-40 degree temp change is going to cause that big of a difference in their point of impact...

I figure we'll continue to disagree - you have your observations. I have mine. They differ.

That's fine, I'd still welcome you at my campfire anytime!

Regards, Guy

 

[Silent Sam]

I'm not a long range competition shooter or ever been a SWAT shooter, just an old hunter. When I asked about the velocity change that only affected elevation and not groups I was alluding to what Guy is saying. He quantified it much better than I could, but for me it just didn't pass the smell test. I shoot different rifles year round where there are four seasons and my experience is that if groups moving are not caused by something mechanical, which for me it almost always isn't, it's my hold, my rest, or just me. I gave up chasing zeros because the more I shot the more I realized my rifles are more consistent than I am.

 

[DrMike]

Thank you for that perspective, Guy. Appreciate the cautionary tone. I've shot for quite a few years here in British Columbia. I don't often shoot in temperatures above 30 C (~86 F), but I do shoot routinely at temperatures ranging from +5 C (41 F) to -15 C (5 F), and for many years I hunted in temperatures dipping to -35 C (-31 F). I'm a little more selective about hunting in cold weather anymore. We did not have all the newer powders that are less sensitive in years past, and I still managed to take game. The powders were originally produced to avoid pressure issues at higher temperatures and had a less pronounced effect on loads shooting in colder temperatures. Because I thought of myself as a hunter and not a shooter, I don't recall ever missing an animal because I used the wrong powder. I don't believe I've ever taken a shot over 350 yards, and the average on ungulates is closer to ~125 yards and bear closer to ~40 yards. Still, advertising sells, and when customers contract for load development, the overwhelming majority ask for temperature insensitive powders. I always inquire about when they are shooting, the purpose of the load and the conditions in which they will be shooting. Perhaps one out of fifty will benefit from the less temperature sensitive powders. It doesn't change anything, the advertising has been effective and they will insist on using a powder that is less sensitive. I'm happy to accommodate them, even when I doubt that they will see the benefit.

 

[LD375]

Guy isn't saying temperature doesn't make "any" difference...he is saying it doesn't make that much difference at the ranges you are shooting.

And he is correct, it doesn't...

As he said...a click or 3-4 at 600 yards, yes...but not anything measured in inches at 100 yards.

Earlier I mentioned parallax...that would cause the group size to remain the same while the group itself moved around depending on how the gun was shouldered.

Also, when scope manufacturers request the temperature for turrets....they are not asking because of powder characteristics, they are asking because temperature affects air density, which affects trajectory.

I have to agree also, also when I sighted in back in march, its was very cold, I was wearing my heavy hunting coat, 2 weeks ago I was just wearing shorts and a t-shirt, could of also been my LOP, and the way I was shouldering my rifle off a sand bag at the bench, either way, I'm still shooting groups well under .5" all day long, and that's what counts to me :grin:

2 more sleeps to go for Black Bear 8)

Lou

 

[preacher]

As long as accuracy stays good, I never had a problem with re-zeroing a load. That's just life for you, ha. That is a really, really nice looking rifle Pard! My SIL's Tikka Lite in 7mm Rem mag is pretty utilitarian in looks, but man will it stack 'em! Good luck to you.

 

[BF375]

I'd agree with everything Guy Miner said. I have sighted in a slew of hunting rifles over the years in temps from 70-80 degrees and then hunted them later the same year in temps from 40F to -25F in Central Canada...but mostly from 0-40 degrees. I have never experienced a change in POI if the rifle/scope were otherwise any good.

Of course I don't bother testing them at 100 yards or under once they are zeroed. I test them weekly at 300 yards because I really don "trust" short range group testing.

I think the entire "temp sensitive" thing ,while it exists to some degree and may be vital to target shooters, is a boogey man for most hunters with most rifles.

I'd leave tomorrow on the most important hunt of my life loaded up with something like R22....but that's just me.

 

[SJB358]

I'd agree with everything Guy Miner said. I have sighted in a slew of hunting rifles over the years in temps from 70-80 degrees and then hunted them later the same year in temps from 40F to -25F in Central Canada...but mostly from 0-40 degrees. I have never experienced a change in POI if the rifle/scope were otherwise any good.

Of course I don't bother testing them at 100 yards or under once they are zeroed. I test them weekly at 300 yards because I really don "trust" short range group testing.

I think the entire "temp sensitive" thing ,while it exists to some degree and may be vital to target shooters, is a boogey man for most hunters with most rifles.

I'd leave tomorrow on the most important hunt of my life loaded up with something like R22....but that's just me.

Same here. Shot during the summer here in Va / NC and never missed an animal with RL19 or 22 in Idaho or Oregon in the Fall. Might've been a little luck but I don't believe it is quite as bad as most make it out to be.

 

[TackDriver284]

Same with the 7 Mag and RL19, I remember my chrono speed in February which was 3100 and it was 65 degrees, a few weeks ago the same load shot at 3175.

 

[Silent Sam]

As long as accuracy stays good, I never had a problem with re-zeroing a load. That's just life for you, ha. That is a really, really nice looking rifle Pard! My SIL's Tikka Lite in 7mm Rem mag is pretty utilitarian in looks, but man will it stack 'em! Good luck to you.

My question to myself would be "Am I re-zeroing or refining a zero?" IOW is it really a change caused by something other than the tightness of the nut behind the trigger or not? One range session doesn't do it for me. If you adjust your zero based on one day's data and then the next time you shoot, say the temp is halfway between the previous two trips, and your groups are now consistent but an 1 1/2" low, what then? Which data set is the anomaly? Are any of them really an anomaly? it's easy to get overly focused on what happens of a benchrest. And unless you are hunting off one i feel it's better to focus on what it takes to get hits from field conditions.

 

[LD375]

As long as accuracy stays good, I never had a problem with re-zeroing a load. That's just life for you, ha. That is a really, really nice looking rifle Pard! My SIL's Tikka Lite in 7mm Rem mag is pretty utilitarian in looks, but man will it stack 'em! Good luck to you.

Well as far as the rifle goes, it shoots lights out day in and day out, I'm not worried about it at all :grin: ..I just had to refine my zero a tweek, no big deal, it could of been the temperature or just me with my cheek weld while shooting in hotter weather than back in march with the extra 1/2-3/4" of clothing as well, cheek weld plays a big role as well, thanks for everyone's input on this topic

Lou