Home Forums Hunting & Shooting Hunting Rifles Temperature vs Velocity - Gun Powder

Well this started out as a quick test of two rifles I hunt deer in November with, to see how sub zero temps effects the load specs. I grabbed my 280 Ackley and 6.5 PRC rifles & ammo, and set them outside for hours at -16c (3F) Also had a few rounds of 6.5 Creedmoor I wanted to blow off so set it outside as well. Rifles were really cold, transported to the testing grounds with the heater off in the truck (thank goodness for heated seats). Rifles set in back of truck as I got ready to shoot. -16c (3F) with gusts up to 30km/hr (19mph) Nasty!

My 280 Ackley load is the 160gr Nosler Accubond over 60.0grs RL26. Speeds in the +15 (59F) to -1c (30F) temps I have shot the load at were all in the 2951-2961 fps. Set up the radar, temp -16c (3F) I was pretty surprised when the radar flashed 3100 on the first shot. Five shot average 3057

Next I grab my 6.5 PRC, loaded with 140gr Nosler Accubonds over 55.6grs RL26. Speeds in the +13 (55F) to -5c (23) temps have been 3049-3038 fps. Five shot string at -16c (3F) = 3047. I was expecting less, but now that two rifles with two loads of RL26 didn't lose any velocity in cold temps, had me really thinking. Was expecting below normal speeds.

Now onto the 6.5 Creedmoor. Ammo was 130gr Sierra Tipped Gameking over 42.0grs RL17. Only have shot the load once prior, in +5c (41F) and it did 2749 fps. RL17 is known to be temp sensitive, so I was expecting this one to give 2700 fps or less at -16c (3F) I was surprised when it did 2809 fps! I'd expect that on a hot summer day, not in a nasty winter blizzard.

Back to the 280 Ackley. I had some 165gr Sierra TGK loads done up with Accurate Magpro. Another temp sensitive powder, that should lose velocity in cold weather. In -2c (28F) temps it did 2800 fps. At -16c (3F), 2825 fps

Back to the 6.5 PRC, another RL26 load, but with the 143gr Hornady ELDx. In +10c (50F) to +6c (43F) temps of early summer, it did 2929 to 2942 fps. At -16c (3F), five shot average was 2920. Stable! And a little slower than before, as I would expect.

Back to the 6.5 Creedmoor, 147gr ELD over RL26. I shot this load earlier in the winter at -2c (28F) and it did 2524 fps. At -16c (3F) it did 2546. Another cold weather spike.

One last load to try, in the 280 Ackley. 195gr Berger over RL26. Speeds in +10c (50F) / +7c (45F) were 2655-2674 fps. At -16c (3F) 2692

Cold rifle, did the bore diameter shrink? Causing more PSI? On 5 of 6 loads, I got more speed in the colder temps. I went home and set 8 rifles & ammo outside in temps dipping down to -30c (-22F) , when I shot the next day it was -19c. (-2F) I needed a larger sample size for a retest

Day 2 , -19C (-2F) . Rifles/ammo had been outside for hours. So cold they burned the hands packing them to the truck. Another 10 minute cold ride with a warm bum to the range, where they were set outside in the shade.


Ruger m77 Scout 223, 55gr Hornady SP, 21.8grs IMR 4198. In +20c (68F) to +7c (45F) the load does 2865/2817. Five shots @ -19c (-2F) = 2871 fps
Tikka CTR 6.5 Creedmoor, 130gr Sierra TGK, 42.0grs RL17. +5c (41F) 2749 fps, the day before -16c (3F) spiked up to 2817. Five shots @ 19c (-2F) = 2871 fps
Tikka CTR 6.5 Creedmoor, 147gr Hornady ELD, 45.1grs RL26. -2c (28F) 2524, day before -16c (3F) 2546. Five shots @ -19c (-2F) = 2533
Tikka 6.5 PRC, 140gr Nosler Accubond, 55.6grs RL26. +13c (55F) /-5c (23F) did 3049/3038. Day before -16c (3F) 3047. Five shots @ -19c (-2F)= 3075 fps
Tikka 6.5 PRC, 143gr Hornady ELDx, 53.4grs RL26 +10c (50F) 2942, +6c (43F) 2929. Day before -16c (3F) 2920. Five shots @ -19c (-2F) = 2925
Defiance 280 Ackley, 160gr Nosler AB, 60.0grs RL26. In +16c (61F) 2952, +6c (43F) 2951, -1c (30F) 2961, the day before -16c (3F) 3057. @ -19c (-2F) = 3001 fps
Defiance 280 Ackley, 165gr Sierra TGK, 61.7grs MagPro. -2c (28F) 2800, Day before -16c (3F) 2825, Five shots @ -19c (-2F) = 2800 fps
Defiance 280 Ackley, 195gr Berger EOL, 56.7grs RL26. +10c (50F) 2674, +7c (45F) 2655, day before -16c (3F) 2692. Five shots @ -19c (-2F) = 2677 fps
Ruger m77 Scout 308, 208gr Hornady ELD, 38.4grs Varget. +25c (77F) 2225, +12c (54F) 2193, -1c (30F) 2195. Five shots @ -19c (-2F) = 2215 fps
Ruger No1 300 Win Mag, 175gr Barnes LRX, 75.4grs RL26. +22c (72F) 3125, +18c (64F) 3116, -4c (25F) 3116. Five shots @ -19c (-2F) = 3067 fps
Defiance 338-06 230gr Hornady ELDx, 55.2grs Ramshot BigGame +10c (50F) 2534, -4c (25F) 2543. Five shots @ 19c (-2F) = 2489 fps
Defiance 338-06 250gr Woodleigh PP, 55.3grs Ramshot BigGame +17c (63F) 2482, +5c (41F) 2406, -1c (30F) 2402. Five shots @ -19c (-2F) = 2389 fps
Ruger m77 Guide 375 Ruger, 270gr Barnes LRX, 78.2grs Ramshot BigGame +10c (50F) 2636, +6c (43F) 2623. Five shots @ -19c (-2F) = 2578 fps
Ruger m77 Guide 375 Ruger, 300gr Nosler Partition, 78.6grs Win760 +23c (73F) 2580, -5c (23F)2512. Five shots @ -19c (-2F) = 2550 fps



On 10 of 14 (71% of tested loads) I was seeing equal or greater velocity in cold temps, compared to warmer conditions

I decided to try the same test the next day, but would just leave the ammo outside in the cold. Rifles would be room temperature. Should be able to see if gun/steel temperature is causing the increase in speed

Day 3 test, ammo left outside overnight in temps of -25C (-13F) . Was exactly -19C (-2F) when I shot, same as day before with cold gun/cold ammo.. Rifles were left inside all night, loaded into warm truck (heater set to 22C / 72F) and left inside the idling truck until ready to shoot.

Ruger Scout 223, 55gr Hornady SP / IMR 4198
Cold gun - 2871 fps
Warm gun - 2881 fps

Tikka T3x CTR 6.5 Creed
130gr Sierra TGK / RL17
Cold gun - 2817 fps
Warm gun - 2819 fps

147gr ELDm / RL26
cold gun - 2533 fps
warm gun - 2561 fps

Tikka 6.5 PRC
140gr Nosler Accubond / RL26
cold gun - 3075 fps
Warm gun - 3071 fps

143gr Hornady ELDx / RL26
cold gun - 2925 fps
warm gun - 2909 fps

Defiance 280 Ackley
160gr Nosler Accubond / RL26
cold gun - 3001 fps
warm gun - 3010 fps

165gr Sierra TGK / Accurate MagPro
cold gun - 2800 fps
warm gun - 2814 fps

195gr Berger EOL / RL26
cold gun 2677 fps
warm gun 2671 fps

Ruger m77 Scout 308 Win, 208gr ELD / Varget
cold gun - 2215 fps
warm gun - 2241 fps

Ruger no1 300wm 175gr LRX / RL26
cold gun - 3067 fps
warm gun - 3063 fps

Defiance 338-06
230gr ELDx / Ramshot BigGame
cold gun - 2489 fps
Warm gun - 2515 fps

250gr Woodleigh PP / Ramshot BigGame
cold gun - 2389 fps
warm gun - 2399 fps

Ruger m77 375 Ruger
270gr LRX / Ramshot BigGame
cold gun - 2578 fps
warm gun - 2579 fps

300gr Nosler Parition / Win760
cold gun - 2550 fps
warm gun - 2556 fps


Average speed of cold rifle = 2713 fps
Average speed of warm rifle = 2720 fps
.003% change. I think it's safe to say the temperate of the rifle plays a very minimal role in velocity of the ammunition.

Interesting results Mark. Did you notice any change in where they shot, i.e. same point of impact when cold out? Some of those velocity jumps are significant, I would not be surprised if POI changed somewhat.

Wow! Ton of good data. Thank you for that.

Very cool, thanks. I shot my 6.5CM the other day after sitting out in temps down to 2F. With RL26 and RL16 there was no meaningful difference. Good powders!

Interesting data below. Ignition consistency suffers in the cold on average. But that doesn't explain to me, the increase in velocity. Just shows a sloppiness of velocity

223, Dominion small rifle primer (Russian manuf.)
Standard deviation of 27 fps at +7c, and SD of 36 @ -19c

6.5cm, CCI 450 small rifle magnum primer (Lapua brass 147gr ELD load)
SD of 11 fps at -2c, SD 26 fps at -19c

6.5cm, Fed210M large rifle (Alpha brass 130gr TGK load)
SD of 4 fps at +5c, SD of 9 at -19c

6.5 PRC, Fed 210M large rifle
SD of 11 fps at +13c, SD of 25 at -19c (140gr AB RL26)
SD of 9 fps at +10c, SD of 17 at -19c (143 ELDx RL26)

280 Ackley, Fed 210M large rifle
SD of 9 fps at +6c, SD of 14 at -19c (160 AB RL26)
SD of 22 fps at -2c, SD of 25 fps at -19c (165 TGK Magpro)
SD of 8 fps at +10c, SD of 28 fps at -19c (195 EOL RL26)

308 Win, Fed 210M large rifle
SD of 21 fps at +12c, SD of 46 fps at -19c

300wm, Winchester Large rifle magnum primer
SD of 11 fps at +18c, SD of 12 fps at -19c

338-06, Fed 210M large rifle
SD of 10 fps at +10c, SD of 6 fps at -19c (230 ELDx BigGame)
SD of 8 fps at +17c, SD of 22 fps at -19c

375 Ruger, Fed 215 large rifle magnum primer
SD of 7 fps at +10c, SD of 11 fps at -19c (270LRX BigGame)
SD of 16 fps at +23c, SD of 12 fps at -19c (300NP W760)

On average, SD in warmer temp (+9c avg) was 12 fps. In cold (-19c), 21 fps. That's 75% more velocity variation when temps dropped 32 degrees Celsius

I didn't shoot for groups. My range is only accessible by foot for most of the winter and it's 1/4 mile haul in. So I just fired these offhand at a snowbank. I am sure group size can vary in hot to cold

I have braved the Texas heat in the Summer for load development. It was sweaty, hot & humid. But, at least I was in the shade in my t-shirt. On the other hand, when it's freezing cold & you are all bundled up, the recoil is much easier to deal with, especially with the heavier bullets.

Good information. I hope some one knowledgeable on the topic has an explanation. Is the bore a smaller diameter? Is the barrel steel less flexible? Is the powder undergoing delayed ignition and acting more like a duplex load. Is there a change in air density? These are just guesses that hopefully motivate some one in the know to respond.

It is also interesting that R26 is relatively stable at low temperatures but not high. Did you compare magnum to standard primers?

I like the cold weather data, thanks a great deal pard!

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