Went to the range today, Wind 30-35 MPH the temp was in the high 30's. All of the loads I shot in the summer are going 50-75 f/s slower at this temp. I thought Varget was an extreme powder! The group size was much bigger by 50%. Some of that may have been due to watering eyes and very cold hands. The rifle is shooting 2" low and about 2"left. I still need to do some more load development. The good news is I shot 25 rounds and my right shoulder is doing just fine. I did use a pussy pad. But I was shooting in just a sweat shirt. The Chronograph was messing up again so the data was very inconsistant.

Leonard, glad you are going strong.

Varget Extreme will probably have a velocity change of about 0.5 fps for each degree F change.

Since you are comparing data that is about 70 degrees F difference, that is not too far out of line. Do I recall some 107 degree F temperatures?

It depends on the cartridge too, but it could have been worse:

In my experience this approximation works pretty well:

H4350 and Varget Extreme: 0.5 fps/degree F
RL-15: 1.0 fps/degree F
IMR-4350: 2.0 fps/degree F

You said your chrono data was suspect too, and I have noted that chrono's can be unreliable due to near freezing temperatures alone.

So there is no use working up the tropical load for this rifle until later. Also the rifle will be going to Tanzania this August and need it to be spot on for that trip. I also have the double rifle that with two different calibers to sort out before then. Too much to do, too little time. RIP, will you be going to Dallas?? Sue and I would like to get together for dinner if we can.

LB,
My wife and I made a quick trip down to Dallas last year, but this year the family has something else planned that I have to go along with. Catch y'all later hopefully.

Look forward to seeing you in the spring.

Leonard,
At the ranges you'll be shooting with that 500 you'll be spot on!

I sure hope so. That beast wants to kill at both ends!

What was your point of impact on the warm days?
Timan

Timan,
Until Leonard gets back, I can show you a group I shot with his rifle in 107 degree F OK summer heat, humidity was not too bad except in my shirt



This was initial load development and sight checking. I think he has made progress in getting the sights and load adjusted since then, but this sure speaks of an accurate rifle, since I put three shots into one hole at 50 yards with the small gold bead. The big moon bead spreads things a bit, and lowered the POI as I was using a fine bead hold at top center of bead.

A combat hold on the center of the bead would also raise the POI.

A lower velocity would increase barrel time and raise the POI with recoil, just like with a double rifle, but without the complication of twin tube crossing and lateral recoil movement.

And I was shooting from the bench and may have been holding the rifle down too firmly to be comparable to an offhand shot as from a standing rest, and so on and so on ...

Leonard will be the final authority on the current POI versus POA with the final load, and I am sure it will be from the sticks/standing rest/offhand, since he is going after DG with this rifle, which is a very accurate one.

LB glad your sholder is doing better
Maybe we can get out to the range soon and shoot some! I have a load worked out for my 375 rum with tsx now need to move to the banded solids.
Im in FL now and I give ya a shout when I get back.

How much closer to center wiil the lower velocity ammo hit?
Stuart

I am doing a center hold and the groups, all four of them were two inches low and two to three inches left. It needs to come up at least 4-5" and over 2-3". This is a lower velocity round with 5 grains of filler. I get much better consistancy with the filler and more fps per grain with the dacron also.

Leonard,
You need a slightly lesser height to center of front bead, and the rear sight drifted to the right, eh? What is the sight radius on your rifle?

Yea, what rip said.
Timan