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ammo temp

14 Jul 2014
@ 05:41 pm (GMT)


I was browsing on you tube only to find a guy that has a drop chart with different ambient temps.
so he has an infared thermometer, on different days he has taken the temp on the brass and chronographed it. and matched that with the ambient temp for his drop chart.
so when shooting, ammo is always ambient temp.
(he does appear to be more a gong shooter than hunter)
so obviously his whole point is different velocities in different temps.

does anyone else do this kind of thing?
he was in the u.s of a, so maybe his temps were more extreme than new Zealand ones.
I remember another guy saying to keep ammo close to your body so its always the same temp. but that wouldn't work unless you single feed at the last moment. a round in the magazine wouldn't be body temp. of course the chamber temp would change things again.

the shooter app has options for powder temp and ambient temp but im not sure how they work. or how it calculates the difference on different ambient temp days.

I just thought it was interesting.


14 Jul 2014
@ 06:52 pm (GMT)

Nathan Foster

Re: ammo temp
Hi Jason, I must be a bit basic. For NZ temps, providing I have my ducks in a row- if its a hot summer day, I remove 1 click. If its a cold winter morning or evening with ice, I add one click.

No mucking around, just get on with the job.
14 Jul 2014
@ 07:49 pm (GMT)

jason brown

Re: ammo temp
yeah for me its the kind of missing piece, or the answer why lately iv needed the extra click.
my load was made in the summer, and it shot well. but like I say iv been a click low lately.
I do follow the temp daily for work, so the simple approach might be the answer.
14 Jul 2014
@ 11:53 pm (GMT)


Re: ammo temp
Jason & Nathan I like the simplicity of a click or two for temps with a 10C or 15C change out to 800 yards and further and it works!
The problem I have run into is that I try and run the same gun&load from early Sept with highs in the low 30C right through winter hunting coyotes at -30C,,,,, I have experienced velocity swings of 200 ft/sec from temps,,, 162 Amax at 800 yards is a 26 inch (3.25MOA), pretty extreme case but it was a long frustrating lesson for me to learn, I chased zeros and technique and scope calibration,,,,basically cased my tail for a season. Cheers Aj
15 Jul 2014
@ 01:19 am (GMT)


Re: ammo temp
I did my load work up in summer, id prefur this as if the load is hot, it wont get too hot if I had worked it up in the winter and ambient temps increased as I moved into the summer.
so in theory I should only have to go up a click or two as it gets colder, not down a click at all.
its really just a fluke it worked out that way.

iv only just figured this out. and nathans approach would probably work for me too. I cant believe that I didn't think of this before as to why I needed another click when shooting a target lately.(I thought maybe my zero moved a bit) I adjusted my drops down 50fps which brought it about right, but no thought into why I had to do this.

the infared temp units are about 20-$25 cheaper than I thought, iv always thought one would be handy, iv seem them used on engines and there cooling system and thought they would be handy. I might still get one and have a play. even barrel temps would be interesting.
16 Jul 2014
@ 04:43 pm (GMT)

jason brown

Re: ammo temp
I just thought I would add this short video.
its not the guy I was first talking about but it fits the topic. and reminded me that the h1000 or 2217 I use is suppose to be temp stable. I guess even more reason to take the basic approach.
16 Jul 2014
@ 11:14 pm (GMT)


Re: ammo temp
Jason, yes Tomas's (THLR) video's are both beautifully done and very informational, some if his process are not my first choice but are very sound and he's an excellent shooter! I have been a fan of his videos for a couple years and especially enjoy watching the films with the dogs! Thanks, Adam
17 Jul 2014
@ 08:15 pm (GMT)


Re: ammo temp
This was a very timely thread for me. I have a Rem 5R .308 that shoots extremely well. In March (60 degrees F in Oregon, USA) I had been testing the difference between 130gr TSX and TTSX bullets and I found the TSX shoot 0.5" higher. I repeated the test twice this month (low 90s now) and TSX still shoots 0.5" higher, but both bullets are now shooting 0.6" higher than they did in March. Prior to reading this thread, I would have been clueless as to the cause.
Thanks guys!
17 Jul 2014
@ 09:25 pm (GMT)

Alvaro Piqueras Alonso-Lamberti

Re: ammo temp
Another video about this topic:
18 Jul 2014
@ 01:06 am (GMT)


Re: ammo temp
The "extreme" powders have not preformed quiet so well below freezing as the above video but not sure how cold was cold when they pulled there rounds from the cooler, lol

Looking back at some records from a 7mmSAUM; All shot at 3310ft.
load-rem brass/fed 215/H4831sc 60 grains with 168 Berger.
Feb, 2011 -19C. 2635/2644/2638=.257"
Mar, 2011 -2C. 2758/2778/2753=.585"
Jun, 2011 +18C 2843/2858/2851=.448"

just something to keep in mind. Cheers, Aj


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