Wild velocity spread with ramshot big game

[Budget'06]

Last winter I started to develop some hand loads for my 30-06. 57.5 grains of ramshot big game under a 150gr fmj. At the time it chronographed 3067fps, right around what the manuals said it should be.

Today I went to sight in the rifle (I got a new arken scope a few days ago and was very excited to get it set up) and I wanted to shoot it over a chronograph to make sure the batteries in the Chrono were still working and I was hoping I'd have time to do a pressure test with some Berger 215s with IMR 4831. Anyways the 150gr load chronographed 3300 fps... Recoil felt non existent and the brass looked completely fine, primers looked a little pushed out but they were nice and round with no craters.

Absolutely nothing about the load has changed except temperature. When the load was chronographed through the winter and fall it was consistently around the 3050 mark where it should be, from temps at 20° all the way to 60°.

I then shot some loads with a 110gr bullet and 62gr of Big Game and it read out at 3600, which if I recall was almost exactly what the book said, and those seemed completely fine.

Anyways, any help on understanding what could cause this would be great. Until I find out, that ammo will stay in its box!
Thanks!

 

[Budget'06]

Photos from chronograph...

 

[Eric H]

How much was the difference in climate temperature?

 

[Budget'06]

How much was the difference in climate temperature?

since last time i shot it, about 25-30 degrees. hard to beleive that it would jump several hundred feet per second tho. i expected 3100 in the hotter weather.

 

[Eric H]

You should take that same load back out there but in a cooler with ice. Take them out one at a time to shoot and see what the speed is. This is why I try using Hodgdon extreme powders.

 

[Budget'06]

You should take that same load back out there but in a cooler with ice. Take them out one at a time to shoot and see what the speed is. This is why I try using Hodgdon extreme powders.

funny enough i did the opposite during the winter. I used a small heater and some hand warmers to keep them hot. so the cartridges during the winter were actually pretty warm. But thats not a bad idea.

 

[birddog 68]

I would pull the bullets and double check the charge weights.
Is it possible that they are loaded longer and into the rifling?
I've been using big game and have never had that big of swing in fps.

 

[Budget'06]

I would pull the bullets and double check the charge weights.
Is it possible that they are loaded longer and into the rifling?
I've been using big game and have never had that big of swing in fps.

seating depth is measured out to be exactly what was listed in the data i made when first doing the load. i measure the bullets and the ones i shot were all within .003 of an inch. ill have to pull a bullet, youd think with that much of a swing in velocity you would notice the charge being off. 200fps would probably take a couple whole grains worth at least right?

 

[birddog 68]

youd think with that much of a swing in velocity you would notice the charge being off. 200fps would probably take a couple whole grains worth at least right?

Agreed

 

[birddog 68]

I was just thinking about what I would check.
Very strange and would like to hear the cause if it's ever found.

 

[Budget'06]

I was just thinking about what I would check.
Very strange and would like to hear the cause if it's ever found.

Just pulled a bullet, lost a lot more powder than I should've when doing it BUT it weighed out at around 54.5 grains, there is no way I could've lost more than 3 grains of powder in the process.

 

[Budget'06]

Just pulled a bullet, lost a lot more powder than I should've when doing it BUT it weighed out at around 54.5 grains, there is no way I could've lost more than 3 grains of powder in the process.

double checked some load data sites and according to nosler max with a 150 is 58gr, so its not like ive accidently gone way over either

 

[birddog 68]

Maybe check with another chronograph. I have never had a 06 but I think at 3300 fps with 150 grain bullets you should be way over pressure and you had no signs.

 

[Budget'06]

Maybe check with another chronograph. I have never had a 06 but I think at 3300 fps with 150 grain bullets you should be way over pressure and you had no signs

3300fps with a 150 is 300 weatherby territory... the 3050 i was getting was about what most books said id get. I feel like it was a chronograph issue but im not sure why it would then read another load at a velocity that seemed perfect... i dont have access to another chrono, ill have to look around to see if someone has one