How temperature sensitive is TAC really?

[Scout21]

I'm reading mixed reports on the temp sensitivity of TAC. Some say it's super sensitive and others say it's nearly as stable as Varget.

I'm wanting to load some 110 or 130 grain Barnes TTSX for my .308 Win. using LC brass and TAC because it seems to give great velocity compared to other listed powders. The problem is that I would like to use it for deer hunting where the temps could be anywhere from 20 degrees F to 80 degrees F, depending on the time of season. I'd also like to be able to use it for hog and coyote control on the farm year round, meaning potentially shooting in 100 degree F heat.

Is it feasible to have one load worked up to use year round using TAC, or am I better off sticking with Varget? I'm not looking for absolute pinpoint precision; keeping my groups within an inch relative to POA is fine by me.

 

[2ndtimer]

I haven’t tested TAC for differences in temperature in .308 Win., although I have some loaded with 125 gr Speer TNT’s. But I did do a comparison of TAC, X-Terminator and Hodgdon Benchmark (labeled as an “Extreme Powder”) in my 26” barrel Rem 700 in .223 Rem with Nosler 40 gr Tipped Varmageddon. In warm temperatures, they were very close in velocity, but when tested at 30 degrees, both the ball powders, TAC and Exterminator, lagged by over 200 fps compared to the extruded Benchmark. Accuracy was still fairly comparable, with a slight edge to the ball powders, but I was very surprised at the velocity edge provided by Benchmark.

Again, not sure if this would carry over to the .308 Win., but I did not expect the results.
These we’re 5 shot groups at 100 yards from a rest.

 

[jmr40]

From 20-80 degrees isn't enough of a temperature swing to worry about IMO. The most temp stable powders will show velocity changes of about 1/2 fps for every degree temps change. The least stable, around 2 fps. You'd be looking at around 100 fps difference between 20-80 degrees. Unless you start pushing the range past 400 yards that isn't going to change trajectory enough to matter. And a 110-130 gr bullet in a 308 is a short to moderate range load anyway.

You can get 3100 fps with 130's using TAC with a max load. I stopped at around 3050. The only issue with very high temps is that a load at, or above listed max might be dangerous. But once again you're only talking about 20-40 fps more velocity at 100 degrees at most. If you're concerned about heat stay away from loads pushing the red line.

 

[Walkalong]

From 20-80 degrees isn't enough of a temperature swing to worry about IMO. The

Depends on the application.

 

[kcofohio]

Recently I came across a chart that had several powders for .308W and 223 applications. I haven't been able to find it so far. But TAC seemed to a bit below average on in gaining fps per degree than most. CFE223 and H355 were higher on the list. If I come across it again I will post it.

 

[BushMaster-15]

I'm reading mixed reports on the temp sensitivity of TAC. Some say it's super sensitive and others say it's nearly as stable as Varget.

I'm wanting to load some 110 or 130 grain Barnes TTSX for my .308 Win. using LC brass and TAC because it seems to give great velocity compared to other listed powders. The problem is that I would like to use it for deer hunting where the temps could be anywhere from 20 degrees F to 80 degrees F, depending on the time of season. I'd also like to be able to use it for hog and coyote control on the farm year round, meaning potentially shooting in 100 degree F heat.

Is it feasible to have one load worked up to use year round using TAC, or am I better off sticking with Varget? I'm not looking for absolute pinpoint precision; keeping my groups within an inch relative to POA is fine by me.

This will answer ALL your concerns ;


https://ultimatereloader.com/2022/04/01/extreme-powder-temperature-testing-varget-vs-tac/

 

[IALoder]

I did a little bit of an experiment with some of the powders I like to use for "blammo ammo" 62gr fmj's in .223. between 10° and 90° TAC was well behaved for a ball powder. It was right at .7fps per degree, second best ball powder I tested. It could be very different in .308 though.

Edit: found my notes with temp/velocity numbers, changed to match

 

[Walkalong]

This will answer ALL your concerns ;


https://ultimatereloader.com/2022/04/01/extreme-powder-temperature-testing-varget-vs-tac/

From the link.

 

[Ranger99]

Just me- unless it's affecting accuracy,
it's not something I'd fret over
( unless you're strictly chasing velocity)

 

[GeoDudeFlorida]

From the link.
View attachment 1163931

In all seriousness, if it’s -70 outside, I am not going hunting. Ditto for 130. I don’t care about the powder, my body doesn’t react well to those temperatures.

The turning point for both powders is 70F. The difference in delta isn’t that much but without knowing the loading data for each it’s hard to judge significance. Are they both max loads? Min loads? The velocity difference is significant so I’d also like to know the pressure of each. Knowing the slopes of each line where they break at 70 would tell the tale. It’s not really a good chart for trying to interpolate the slopes.

 

[FROGO207]

Have not used TAC in 308 but in 223 I have used it from -10* to 98* with no noticeable change of impact on target at 100 YDS. Did not measure the velocity at extremes but being on target is what I care about in the end.

 

[kcofohio]

Though this is not the same one as I found before, it may be of help. The one I had seen had CFE223 listed.

 

[BushMaster-15]

OK Temperature is one of a few aspects which collide with accuracy . Person who sights in at Sea level or a few hundred ft. above ,at 85 Deg. F. in gonna get and awful surprise at 17 Deg. and 9400 Ft. elevation !. Shooting at elevation air density is less ,thus equates to less MOA than Sea Level to stay on target . Most Not all , Hunting guides prefer their clients to " Sight-In " at least around base camp and IF one is hunting Sheep ,Tar ,Chamois ,they had better know angle of accent and angle of decent trajectory . Just a guess on MY part but believe those factors account for 80+% of MISSES in hunters who DON'T understand the effects .

STANDARD CONDITIONS

ELEVATION	STD. TEMP. F.	STD PRESS. ABSOLUTE
0	59.0	29.92
500	57.2	29.45
1000	55.4	28.99
2000	51.9	28.07
2500	50.1	27.65
3000	48.3	27.21
3500	46.5	26.79
4000	44.7	26.37
4500	42.9	25.96
5000	41.2	25.54
5500	39.4	25.15
6000	37.6	24.76
6500	35.8	24.37
7000	34.0	23.99
7500	32.2	23.61
8000	30.5	23.24
8500	28.7	22.88
9000	26.9	22.52
9500	25.1	22.17
10000	23.3	21.82

 

[Slamfire]

From a logistical standpoint, especially during the chaos of war, it does not make a lot of sense to have "hot weather" only ammunition and"cold weather" only ammunition. (I have no idea how the latest 80 Kpsia 6.8 X 51 ammunition will perform at 120F) And since rifle ammunition was used in aircraft machine guns, at high enough altitude things do get -70 F.

Poor bastards flying B-24's and B-17's were flying unpressurized, un heated airplanes, at 40,000 feet. They got very cold in those things. The bow and waist gunners were using 50 cal's, primarily because the beastly Huns became too hard to disable with 30 caliber cartridges.

Early in the war, the Brits were using 303 in their Hurricanes and Spitfires. As I understand, the cock pits in those planes were also unheated. You can imagine the machine guns and ammunition in the wings, also got very cold.

Consistent velocity was very important when firing machine cannon shells through the propellers! Get the the timing off, and I am sure some one lost a propeller blade. Or a gun. The 20mm Oerlikon was a advanced primer ignition (a delayed blowback) cannon.

A hangfire that reached peak pressure after battery would mess up the timing. Then the mechanism would eject a round at pressures high enough to burst the sidewalls.

That would cause a lot of trouble. Timing was always an issue with that sort of mechanism.