Observation about R17 today

[minute of elk]

Not quite sure how to fit this into my head at the moment, but shot quite a few 208's through the 308 today, with my standard 48.5 grains of R17 & the dope didn't vary more than .5 mils out to 1205- and it was in the -15 to -20 temp range by then. I've seen more variation than that on a breezy summer day...

I expected to use more turret to hit the long steel, based on everything I've read.

 

[royinidaho]

Is what you are saying is that RL17 isn't temp sensitive?

That may be so. I have experience with 22 & 25 which are.

 

[flashhole]

High BC bullet, really low density air ... seems like the powder temperature sensitivity would have a bigger influence at those temps.

 

[royinidaho]

The colder the temp the more dense the air, wouldn't ya think?

That's why airplanes use more runway in the afternoon.

 

[minute of elk]

It had me scratchin my bundled up head more than once. During the 6 minutes & 23 seconds that the iPhone was functional at -15, it claimed a 62% humidity, 4300 ft elevation, and -17F. Shooter app told me to run the standard dope, & it worked. I fully expected to be putting an extra mil on it past 1k, but ended up running right on most of the day, and putting maybe an extra .3-.5 on for the last stage's 1075 & 1205 targets (made hits on em!) The sun was down by then & we had .7 mils of wind. My trigger finger was beyond numb by then, too, so I could have been jerking things.

I've seen R17 heat up a primer or two at 100F, and definitely do buy into "warm" temp sensitivity, but so far despite a couple conversations with montanamarine about it, I haven't seen much to support a downward track on muzzle velocity in the cold.

I think I should go shoot tomorrow to gather more data before our nice cold snap goes away....

 

[blksno]

Fire a group at a range your comfortable with in the sub zero temps and document the drop.

Keep the same number of rounds inside your clothes next to your body, so you can estimate a solid 90 degree powder temp and fire at the same range.

You should be able to calculate the velocity difference based on your drop...and see what it corresponds to in MV Loss per degree of temp drop.
If I remember correctly...I have less than 1 entered into Shooter.

It's been my experience that it's an exceptionally stable powder...maybe not THE MOST, but it's not as bad as people assume.

In my testing so far, 33 seems to be on about the same level with 17, which would make sense since they are made in the same facility.

 

[Mikecr]

.5mil is 22" at 1205yds, or 1.7moa off from expected POI.
I would call that significant in that you couldn't hit with any precision without it.

If it really seems insignificant to you, try hitting what you're aiming at with single shots.

 

[royinidaho]

I think I got mixed up with the mil/moa thing. . . again.

1 Mil = 3.6" @ 100 --- 1 MOA ~= 1" @ 100. Have to say/type that to resync my thinkin'

0.5 Mil @ any distance is significant.

 

[Outlaw6.0]

.5 mil is significant BUT, where did it come from? From what i'm seeing (unless I missed something), that half-mil could have come from plummeting temps increasing density or in my case, shaking like a crackhead looking for a fix due to the frigid weather.

Granted a chronograph would have been nice, they probably don't work any better than I do in those temps...

Not just the powder at work here....


t

 

[minute of elk]

As a "control group check"- during summer temps, my dope will quite often go from 10.2 mils at 1k at first light down to 9.2 mils (or even less) if it tickles the 90's.

During our "frostbite classic", I only saw half that- and I'm starting to suspect that we had a downdraft on that last stage where I had to add .5 mils, as the wind was quartering to us down the hill. It was the only stage that my dope was low. My trigger hand was mostly numb during the stage- but that had become common by then! My core temp was comfy at the time, but the breeze was enough to give us all ice cream headaches. Maybe my brain was locking up & I was hallucinating...

A few of you have shot with me, so I won't make any claims to having any extra badassery behind the trigger. I'll just say that I think I'm good enough to make the comments I'm making >>

Alas, my window of opportunity to enjoy shooting at 20 below is slipping away. We got above zero today. Maybe I'll get motivated during the next cold snap

 

[GrdHogr]

The alliant website claims consistancy even in extreme weather, Has anyone worked this up in 280
Rem. I am thinking with a 4350 burn rate but with more vel. should be a winner,