Superformance Temp Sensitivity

[General RE LEE]

I had a great day at the range with Superformance out of my 6.5 CM. I got .2" group with 130 grain Berger OTM 2828 FPS and .3" group 140 grain Sierra Tipped Game King 2901 FPS. Both loads had SDs around 9-10 and ES under 20. This is a hunting rifle.

Temps today were 85 degrees. With 2828 fps out of 130 Berger OTM and 2901 out of 140 grain Sierra tipped Game King with Superformance, how much velocity loss can I expect this November and December in Tennessee 25-50 degrees hunting temperatures?

 

[Carlos88]

2900fps with a 140 in a Creedmoor? Wow.

 

[CMP70306]

When I used it in the PRC it was around 150 fps from 30 to 80 but I found out the other way. I loaded them to 3150 fps during hunting season but when to shot them in the summer they spiked to 3300. I loaded it for years in the 30-06 but never noticed because I only ever shot those rifles in winter and I didn't have a chronograph at the time.

 

[General RE LEE]

2900fps with a 140 in a Creedmoor? Wow.

Yep max load for sure I wasn't going any higher.

 

[BallisticsGuy]

Why don't you test it. Drop some rounds in a baggie in a cooler full of blue ice packs, take to range, shoot over chronograph and don't fart around trying to hit the target while you're at it. Pull the round from the cooler, shoot it quickly, rinse and repeat for at least 5 shots. I do testing for my students as a matter of routine and depending on the powder, case capacity and other factors we'll see anywhere from .2fps per degF to 2fps per deg but there's often a sort of stable area, usually in the 40-80f range where things are pretty stable. If you do a hot test too (leave some ammo on the dash when it's warm out or use ThermaCare or similar hot pads to warm some up to 110-130F) then you can draw something of a slope and adjust your inputs on your ballistics calculator when appropriate.

 

[rbTanzan]

Why don't you test it. Drop some rounds in a baggie in a cooler full of blue ice packs, take to range, shoot over chronograph and don't fart around trying to hit the target while you're at it. Pull the round from the cooler, shoot it quickly, rinse and repeat for at least 5 shots. I do testing for my students as a matter of routine and depending on the powder, case capacity and other factors we'll see anywhere from .2fps per degF to 2fps per deg but there's often a sort of stable area, usually in the 40-80f range where things are pretty stable. If you do a hot test too (leave some ammo on the dash when it's warm out or use ThermaCare or similar hot pads to warm some up to 110-130F) then you can draw something of a slope and adjust your inputs on your ballistics calculator when appropriate.

This is a good approximation, and useful, but this does not change the temperature of the barrel nor will it necessarily approximate the POI change.

In other words, if there is a 100+fps velocity change you can expect a POI change as well and you will need to sight-in again during the other temperature season. But you will know the muzzle velocity, approximately, maybe +/- 25fps.

 

[Mike Matteson]

If short range it probable won't be much difference, but longer yardage yes it will change the POI. To answer your question easly look at a bullet in fight chart to see what 100fps does at longer ranges. That not the total picture, but will give you an idea as to whats going on.

 

[rbTanzan]

If short range it probable won't be much difference, but longer yardage yes it will change the POI. To answer your question easly look at a bullet in fight chart to see what 100fps does at longer ranges. That not the total picture, but will give you an idea as to whats going on.

The change is normally more than trajectory for +100fps. Velocities interact with barrel harmonics differently because they leave the muzzle at different barrel "wiggles".
Some rifles shoot loads to many different spots. I've shot rifles that spray different bullets over 10-12 inches. Such a rifle will be sensitive to different speeds as well as different weights of bullets. A person will need to see how a particular load shoots, and at different velocities even at 100 yards.

 

[jaspepp]

Checked my notes on this one. 300 wsm, 200 gr ELDX, 65 gr superformance. @70 deg, 2938 fps. @21 deg, 2909 fps

 

[CReuter]

Checked my notes on this one. 300 wsm, 200 gr ELDX, 65 gr superformance. @70 deg, 2938 fps. @21 deg, 2909 fps

Has Superformance worked well in your 300 wsm? I'm using H4350 now but thought about trying some with 178 eldx

 

[jaspepp]

Absolutely, it seems to to shoot well and isnt a super popular powder making it more available than others. Everything in my 300 wsm is way faster than the book numbers and produces pretty decent groups. Tested 178 w/ 66 - 68.5gr. Best load was 68 gr @ 3111 fps average.

 

[jaspepp]

Side note, IMO superformance seems to like heavyish bullets loaded at or close to max

 

[CReuter]

Checked my notes on this one. 300 wsm, 200 gr ELDX, 65 gr superformance. @70 deg, 2938 fps. @21 deg, 2909 fps

Has Superformance worked well in your 300 wsm? I'm using H4350 now but thought about trying some with 178 eldx

Absolutely, it seems to to shoot well and isnt a super popular powder making it more available than others. Everything in my 300 wsm is way faster than the book numbers and produces pretty decent groups. Tested 178 w/ 66 - 68.5gr. Best load was 68 gr @ 3111 fps average.

 

[CReuter]

Absolutely, it seems to to shoot well and isnt a super popular powder making it more available than others. Everything in my 300 wsm is way faster than the book numbers and produces pretty decent groups. Tested 178 w/ 66 - 68.5gr. Best load was 68 gr @ 3111 fps average.

Sweet! What length barrel are you running? I'm assuming this is a short action?