Ramshot TAC Temperature Sensitivity

[BillW73]

I am using Ramshot TAC in .223. My load is 24.6 grains with a 77 grain OTM. I am shooting this in both a bolt gun and AR. My temperature range that I shoot in is -20 to 70 degrees. Thru out this range I see no signs of pressure or changes on target.
At what temperature range should I start seeing increases in pressure and performance due to temperatures? The hottest I have shot in this summer has been 68 degrees. I left my ammo out in the sun for about half an hour before shooting it. Everything appeared normal to me.
I just don't want to be surprised if I happen to travel somewhere that gets warmer than what I am used to.

Thanks.

Bill

 

[FLIGHT762]

68º in the Summer.? Where do you live? Alaska? Oh yeah, I see. I've had issues with max loads above 80+º. @ 24.6 of Tac, you are at the upper end of that powder / Bullet combination.

 

[ken4570tc in WY]

I just checked the Western Powders load data and your load appears too hot. The maximum load for TAC and a 70gr bullet is in the neighborhood of 24.3 grains. You aren't seeing signs of excess pressure up to this point because of the moderate temperatures you've been shooting at. The risk is that with Ramshot TAC or X-Terminator there is a significant amount of nitroglycerin in the double base powder mix. This makes those powders sensitive and dangerous when overloaded because there will be no gentile warning signs as you approach critical overpressure. This overpressure causes the nitro to explode instead of accelerate the burn rate. If you and the equipment survive, you will at the very least have a blown primer, case head separation or loose prime pocket. You need to back off that load by at least .3 grains. I know this because I did it. Double base powders aren't as nice to give you advanced signs of reaching critical pressure.

 

[Gustav7]

I just checked the Western Powders load data and your load appears too hot. The maximum load for TAC and a 70gr bullet is in the neighborhood of 24.3 grains. You aren't seeing signs of excess pressure up to this point because of the moderate temperatures you've been shooting at. The risk is that with Ramshot TAC or X-Terminator there is a significant amount of nitroglycerin in the double base powder mix. This makes those powders sensitive and dangerous when overloaded because there will be no gentile warning signs as you approach critical overpressure. This overpressure causes the nitro to explode instead of accelerate the burn rate. If you and the equipment survive, you will at the very least have a blown primer, case head separation or loose prime pocket. You need to back off that load by at least .3 grains. I know this because I did it. Double base powders aren't as nice to give you advanced signs of reaching critical pressure.

Might wanna check the load book on their site again.

Max charge for NATO Rated chambering is 24.7gr, at least when i checked it. I’ve ran up to 24.7 in my AR with 77 TMK’s at 85*. There were pressure signs and I backed off to 24.5. I ended up abandoning TAC due to temp sensitivity. I developed the load around 80-90*, and when temps dropped down into the 60’s I was getting 30-50fps lower. Too much swing for me, so I switched over to XBR 8208.

 

[LMT/556]

My TAC temp velocity swing was about 1.5 FPS/degree, meaning 2750 @80° F wound be 2720 @60° F. My 77 OTM load was 24.3 TAC over a Nosler CC w/cannelure. 24.8 was max published but way hot for my chamber Noveske NMm0 .

 

[918v]

TAC is too fast for heavy bullets. Put it under 55gr stuff and it’s fine. Yeah people will argue but 55gr loads are much more forgiving when it gets hot.

 

[Gustav7]

TAC is too fast for heavy bullets. Put it under 55gr stuff and it’s fine. Yeah people will argue but 55gr loads are much more forgiving when it gets hot.

I was wondering about this, because TAC was touted as a pretty insensitive powder for being double base, but wasn't the case for me with 77's. But that makes more sense for 55's.

 

[LMT/556]

I was wondering about this, because TAC was touted as a pretty insensitive powder for being double base, but wasn't the case for me with 77's. But that makes more sense for 55's.

I'm going to try AA2520 for MK262 clone.

 

[Gustav7]

I'm going to try AA2520 for MK262 clone.

I've heard of Power Pro Varmint being a speed devil too. I have some, and thought about trying it.

 

[bunsen27]

I run TAC in my .223Rem bolt gun for 73gr & 75gr ELDM's, both loads are 25.2gr and yield 3025fps & 2980fps. It's definitely a warm load, but I've had zero issues up to 95F or in a hot chamber when hunting PDogs. I am NOT running that at AR-15 magazine length though! My MDT polymer mags allow me to seat to an OAL of 2.550in which makes a HUGE difference.

For a more temperature stable 77gr load I'd look at IMR 8208 XBR.

 

[FLIGHT762]

I've heard of Power Pro Varmint being a speed devil too. I have some, and thought about trying it.

Johnny's reloading bench has a good video on PP Varmint and Sierra 77.

 

[MTRecon]

I use Tac in various bullet weights from 55 to 80grs and from below zero up to around 90 degrees. Only thing I notice it seems to burn less efficiently in the cold. Western 556 Nato load data is where I get best results with Tac.

The pattern in the pic shows up in cold weather only.

 

[ken4570tc in WY]

I use Tac in various bullet weights from 55 to 80grs and from below zero up to around 90 degrees. Only thing I notice it seems to burn less efficiently in the cold. Western 556 Nato load data is where I get best results with Tac.

The pattern in the pic shows up in cold weather only.

View attachment 7425474

Nice snowflake pattern!

 

[clcustom1911]

I'm going to try AA2520 for MK262 clone.

Somewhere leading up to and including 25.20gr of AA2520 does very well with 77's


See what I did there?

 

[MTRecon]

Someone asked me what that pattern means...the first time I saw it was make liberals cry again lol...

 

[Mr Tibbs]

I'm going to try AA2520 for MK262 clone.

LMT/556 and all other’s who are users of A2520, there is recall from Western Powders for A2520 1lb bottles with the lot # 0913192116, this is a limited recall and ONLY applies to this lot # of Accurate 2520

 

[LMT/556]

LMT/556 and all other’s who are users of A2520, there is recall from Western Powders for A2520 1lb bottles with the lot # 0913192116, this is a limited recall and ONLY applies to this lot # of Accurate 2520

8lb and unopened just bought it from Grafs, but thanks for the heads up...2109 061220

 

[sprad05]

I just bought 1lb to play with, but for most of my uses AR Comp seems to be my fave. Low SDs and very little temp sensitivity