Pressure at low temp???

[Maple57]

So it was not as cold today but did an experiment. Left rifle and ammo outside about -27. Shot a shot. Not pressure like yesterday but bolt handle felt a bit stiffer than normal to lift but could just have been from cold. Brass did not show excessive pressure signs. Brought rifle and ammo inside for a few hours till room temp. Shot it. Bolt handle easy to lift. I need to run 2 more checks with warm ammo and cold rifle and vice versa.

Nothing I have read says hybrid 100v is terribly temp sensitive. At this point I am thinking it is one of 5 things. 1)Barrel contracting in cold (although I am having a hard time believing this), 2)Lubalox???coating on the CT bullets responds poorly to extreme cold, 3)click-bang-sizzle-boom (possible but I have never had that problem with these primers although I usually only hunt with Retumbo at these temps as I am usually after bison with a .375) 4) a bad one slipped through the reloading process 5) Case seperated. I wish I had not dropped it. Tempted to go back with a metal detector

I went back and reweighed all the cartridges loaded as well as some older ones that are the same loading and they are all the same so if it was a reloading error it was a one off.

What if we drop all assumptions and consider this with no pre conceived causes?

Cold weather delays ignition... sure, but what if the load is just too hot?

Lots of factors can contribute to random pressure spikes, like throat angle and jump.

If the bullet is seated too close to jam, you can get random pressure spikes.

If the brass is resized differently, you can get very different max pressures.

If the brass is not all the same weight or brand, or the neck length has not been trimmed, you can get binding.

Could be the load is just border line too hot, maybe just dial down the load.

How old is the powder... powder gets lighter with age and old powder can have higher energy by weight than when new.

Powder lots can vary ... that's why when you get a new lot of powder, you need to re-develop loads

Go back to the basics and forget about blaming the temperature for the problem and just work to eliminate the dangerous over pressure condition.

 

[Rayleigh_Scattering]

>2.5 gr over max load in nosler book

I never go near the high end (I can miss just as reliably with the starting load) so I have no first-hand experience with this, but if you're pushing past max load I understand that both sings-of-dangerous-pressure and hyper-sensitivity-to-small-variations are exactly what you're expect to see.

Aren't they?

 

[todbartell]

I've experienced higher speeds in cold weather in a few different loads. Here's a post of mine from 2 years ago

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. 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 with gusts up to 30km/hr. Nasty!

My 280 Ackley load is the 160gr Nosler Accubond over 60.0grs RL26. Speeds in the +15 to -1c temps I have shot the load at were all in the 2951-2961 fps. Set up the radar, temp -16c. 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 to -5c temps have been 3049-3038 fps. Five shot string at -16c = 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 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. 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 temps it did 2800 fps. At -16c, 2825 fps

Back to the 6.5 PRC, another RL26 load, but with the 143gr Hornady ELDx. In +10 to +6 temps of early summer, it did 2929 to 2942 fps. At -16c, 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 and it did 2524 fps. At -16c it did 2546. Another cold weather spike.

One last load to try, in the 280 Ackley. 195gr Berger over RL26. Speeds in +10c / +7c were 2655-2674 fps. At -16c 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 -30, when I shot the next day it was -19c. I needed a larger sample size for a retest

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

 

[nof60]

So todays not very accurate test confirms tod bartells post above and totally surprising as I thought pressure always dropped as powders got cold. Cold gun warm ammo no signs of pressure. Warm gun -30 ammo bolt handle a wee bit sticky.

So....when shooting this rifle, or any others that I am pushing max loads through if this cold weather nonsense becomes a thing will load down for it. Short term will be taking a different rifle out for the rest of this hunt. 7mm-08 or 30/06 or .375??? Hmm, wonder if i can use this to justify a new .280 Nosler or 7mmSTW to the wife????

 

[nof60]

>2.5 gr over max load in nosler book

I never go near the high end (I can miss just as reliably with the starting load) so I have no first-hand experience with this, but if you're pushing past max load I understand that both sings-of-dangerous-pressure and hyper-sensitivity-to-small-variations are exactly what you're expect to see.

Aren't they?

Well I did not start at max load and work up. Start low and work up. Watch for pressure. OK to keep going till you see pressure, than back off. Also I am not loading for max velocity, I am loading for max accuraccy and that just happens to be the node with this rifle. And it is a Mark V action which is pretty strong as well as built to jump a fair bit to the lands. But you are 100% correct that playing in the deep end is more sensitive to small changes. What the heck, you only live once and thats enough if you do it right. Faster horses, older whiskey, younger women and hotter loads. Results may vary.

 

[Neilm]

Possibly the Labrador does not like cold weather?

 

[Dogleg]

Faster horses, older whiskey, younger women and hotter loads. Results may vary.

Speaking of varying results (and with apologies to cowboy philosophers) years of research and solitary reflexion I believe that mix is wrong.

“Faster women, older money, younger horses and more whiskey” is a better combo. ;}

 

[nof60]

Speaking of varying results (and with apologies to cowboy philosophers) years of research and solitary reflexion I believe that mix is wrong.

“Faster women, older money, younger horses and more whiskey” is a better combo. ;}

I'm afraid I know nothing of old money and am too old to run or get bucked off so "Slower women, older horses, younger whiskey and fast money"??

 

[Dogleg]

I'm afraid I know nothing of old money and am too old to run or get bucked off so "Slower women, older horses, younger whiskey and fast money"??

You have given me much to think about. There is an undeniable appeal to fast money; but younger whiskey must to considered on a case by case basis. In extreme cases it can lead to older women and no money.

 

[jsquig]

Any chance that taking the gun from somewhere nice and warm to the cold might have led to some condensation inside the barrel?

 

[Rayleigh_Scattering]

>risk

No worries. We've all got our second half-eternity of oblivion coming, and I'll be the last one to tell another adult male how to run their lives. Bad manners. Worse; it might end up making me responsible for another mammal.

In my own reloading I've always stuck to the lower end, partially because my practices and tooling are not ideal, and partially because I already struggle with recoil sensitivity. I know that +- a few % of powder in the lower 1/3 range is no big deal. At the high end that same sloppiness could get me into trouble.

Good on ya for getting out there and having fun with it!

>condensation

Or snow in the action. Had a bugger of a time with that in November. Fresh snow coming down off the trees got into everything.