Changing ammo to maintain zero across temps

[b6graham]

My money is on Applied Ballistics being 1000% better at it than y'all!!

I hope you're Trolling and really not that stupid!!!

You said it yourself earlier that you can have 30-40 fps speed differences in the same box of ammo.
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not even comprehension this time. just lack of reading skills.

between DIFFERENT LOTS OF AMMO is what i said

MV temp tables are cool. and in theory work. but this is rimfire. and you're assuming there is no zero shift. even something like where the ammo is stored; ie. on body under coat versus in magazine in gun can make a difference in FPS

the best solution is record MV at different temps and dope the rifle to confirm ballistics. but that's not always possible

 

[RTH1800]

honestly, trying to match ammo to the temperature to keep zero sounds like a lot more work than figuring out what your dope will be on 1 lot of ammo for any given temp....

at most i could see having a "winter lot" and a "summer lot" of ammo.....but saying "im going to shoot Eley tenex at 80*, and Lapua midas at 70* and eley black box at 60* and Lapua polar at 50*" sounds like a fuck ton of work.


personally i like to reduce as many variables as possible, and the brand, and more specifically, the lot of ammo, is the biggest variable we have in rimfire.

I agree with you about reducing variables. I seldom switch ammo brands. My go to ammo is Eley Tenex or Match. It of course varies in velocity. My interest was to see if anyone had compensated for temps by changing AMMO LOTS not brands, bullets, lubes etc.

This question has stirred a lot of misconceptions and apparent anger. Sorry I ask. I will let the computer nerds play with thier ballistic programs and video games now.

 

[BisSilent]

not even comprehension this time. just lack of reading skills.

between DIFFERENT LOTS OF AMMO is what i said

MV temp tables are cool. and in theory work. but this is rimfire. and you're assuming there is no zero shift. even something like where the ammo is stored; ie. on body under coat versus in magazine in gun can make a difference in FPS

the best solution is record MV at different temps and dope the rifle to confirm ballistics. but that's not always possible

I agree!!

 

[...]

I agree with you about reducing variables. I seldom switch ammo brands. My go to ammo is Eley Tenex or Match. It of course varies in velocity. My interest was to see if anyone had compensated for temps by changing AMMO LOTS not brands, bullets, lubes etc.

so with different lots of the same ammo, i havent seen much significant change in zero, mostly changes in group size.

ammo tends to respond pretty similarly to changes in temperature, regardless of lot #, from what ive seen

 

[RTH1800]

I agree on a small velocity change at 50Y. At 100Y and a 50 FPS average velocity change can be over an inch in vertical POI.

I also agree that ammo responds in a similar manor over temp range. More so when utilizing the same ammo brand and type. That is why I am considering simply utilizing hotter ammo in colder weather.

My initial question was if anyone has tried this. It was not worth the effort of posting. I will simply do the work and post data in case anyone else cares to read it.

 

[Seymour Fish]

Not sure how to say this. I’m not interested in your ideas other than using ammunition to maintain point of impact in changing temps. And yes 80 FPS is the 8/10 of an inch at 100 yards.

RTH, If only it were simply linear. Your accuracy node may fall apart with a big delta in MV. Finding a lot # of hotter ammo which is equally as accurate as your standard, but at low temps, is a journey of time, $, and ability to catch the temps you are interested in. Staying within an ammo brand will save time cleaning and re-seasoning between different brands. Consider bi-athlon types for the extreme cold end of the Range. J.Bell on here knows shooting rim fire in the cold and likely could help. I say go for it.

 

[RTH1800]

Thank you. I ask the question here due to the huge knowledge base on the hide.
I will start getting my baseline readings soon as it is 97 degrees here yesterday and will remain hot for a while. Then as we move into fall and winter I can get the other data.
Thank you,
RTH

 

[Seymour Fish]

I think the simple answer is yes, use the hotter ammo, as it would possible reduce one of the many different variables when shooting in warm vs cold temperatures.

Off the cuff, I can think of at least 4 different variables, some of which you have no control over, that will effect your poi. In general, I think the only way you're going to come close to the same point of impact in various temperature situations is from your dope. Nothing is better than practice.

1. Air density- cold, dry air being more dense than warm, moist air; use 'hotter" ammo in the winter to reduce the loss in velocity when shooting in colder, denser, more resistant air. This is where a ballistic calculator may be of help.
2. Keep your ammo warm to help reduce the variance in velocity caused by the temperature sensitivity of the powder and to keep the lube soft.
3. Does your rifle shoot differently when it's cold vs when it's warm? Maybe try a barrel tuner to mitigate changes in velocity and/or harmonics due to temperature changes. Keep your firing pin dry so the oil on it doesn't slow down ignition speeds.
4. Do you hold the rifle differently when you're wearing gloves and a heavy coat?

The tuner thought is a good one, assuming a platform that allows some positive compensation, will allow at least a 40 FPS delta MV to hit the same POI, at a given distance. Nice comprehensive post dude