Cold weather Chronograph results.

[Greyfox]

I think confirming the change with actual drops, tested at long range is a good idea. 100 fps will definitely be noticable. Having experienced so much variation with chronographs due to lighting etc. I am usually suspect, not so much with the precision of the outputs, but the absolute velocity readings. I have found Retumbo in my 6.5-284 to be very temperature insensitive, less than 20fps, with drops tested at 700-1000 yards between 0and 85 degrees. This is the temperature range I can experience during hunting season(Wyoming in early October tp Alberta in late November). IMR 4350 has given me the worst in my 270WSM with +50 FPS changes by chronograph with corresponding changes, of +7" in drops when tested at 500 yards. In my 308, Varget gives less thaen a 20 FPS difference in velocity between 30 and 85 degrees.

 

[Cold Trigger Finger]

I see that Lee now has the Factory Crimp Die for the 6.5Creed .
What's the opinion on a good crimp. Does it help reduce shot to shot variation? ?
I use them in all my revolver and larger caliber rifles, but haven't tried one in the smaller calibers ..
I am talking about using them on cannalured bullets. Probably giving a thin jacketed target bullet the squash wouldn't help accuracy I imagine.

 

[Lefty7mmstw]

I see that Lee now has the Factory Crimp Die for the 6.5Creed .
What's the opinion on a good crimp. Does it help reduce shot to shot variation? ?
I use them in all my revolver and larger caliber rifles, but haven't tried one in the smaller calibers ..
I am talking about using them on cannalured bullets. Probably giving a thin jacketed target bullet the squash wouldn't help accuracy I imagine.

I don't like crimps and rarely use them unless recoil or feeding issues demand it. It's simply an unnessary variable unless it is really needed.

 

[FEENIX]

Just like the powder/load testing, the chronograph is also affected by the extreme temperature. What is the (recommended) operating temperature range of your chronograph? I.e., RCBS AmmoMaster has an operating temperature range: 20 – 120º F. Having said that, I'd expect reading variations/inaccuracies outside the said parameter.

-40–120º F test load vs 20 – 120º F chronograph's capabilities.

Just saying! Good luck on your testing and keep us posted.

 

[Cold Trigger Finger]

Ya the chrony I keep inside the cabin by the wood stove. I shoot in my back yard. Its 60-100 miles to anyone living behind me.

I've found that if I do a 3 shot sstring the recordings are accurate. Any more than that and it shows an error. Then the LCD freezes and its brain freezes. So. I heat the unit up to about 80° and it works great for 3 shots

 

[Cold Trigger Finger]

My RCBS 6.5 Cm dies have the standard roll crimp and I use it just enough to help the round get into the chamber. It used to be that a crimp helped even out velocity.
The most consistantly low variation I have found in a cartridge is the 416 Remington. Shooting RL 15 or IMR 4064. The 375 H+H with RL 15 has produced some amazingly low variation for me also. I'm hopeing I will find a temp stable powder that has a consistent. Recorded velocity that has a low variation.

 

[Cold Trigger Finger]

Well I just did some more speed testing.
6.5 Creedmoor, Ruger m77 MKII Hawkeye Stainless 26" factory barrel.
temp. 40 below F.
Hornady Superformance 129 gr SST
Rifle an ammo were outside for 2 hours before speed test. Ammo was stood upright and seperated from each other.
1, 2893
2, 2933
3, 2932. Feet per second

The vel listed on the box is 2960 f.p.s.
It felt when chambering each round prior to firing that the chamber was tighter or the ammo was fatter. Doesn't steel contract when it gets cold. Anyway the brass was tougher to extract. But it did extract. There was a dark colored ring around the brass about midway up the case. Also a buffed ring around the brass . The primere are a little flatter than when this ammo is fired in this rifle at +60°F. But they were fine.
There is a gas ring around the necks approximately 1/8 " down the necks.