Climbing velocities

14 August 2002, 17:04

<Metrix>

Climbing velocities

Gentlemen, your thoughts on this problem will be most appreciated.
I loaded an 8x57JS with 200gr Nosler Partitions, WLRM primers, W-W cases, and 51grs of Re-15. A total of 8 rounds were loaded and fired, with approximatly 3 minutes between firings. The temperature on that day was about 18 degrees C, with overcast. The velocities given by my Chrony were, in order-2488, 2519, 2524, 2531,2540, 2653, 2694, 2758fps. Yes, I realize that as soon as I hit 2653, I should have stopped and pulled the rest for components, but curiosity got the best of me and I had to see what the remaining rounds would do. You would expect vertical stringing, but I got horizontal stringing instead! This load shot 4 into an even 2" at 100m. I have previously used 50grs of Re-15 in this load for an average of 2510fps. Why the climbing velocities, could it be copper fouling? I just about had to mine the copper out of that bore, but that's normal for any Nosler bullet (200gr Partitions, 180gr B.T.) in my rifle. The rifle is a Husqvarna on a commercial 98 action.

15 August 2002, 02:03

Hot Core

quote:
Originally posted by Metrix:
Why the climbing velocities, could it be copper fouling? I just about had to mine the copper out of that bore...

Hey Metrix, I think your assumption is probably correct. As the copper builds up in the bore, the resistance to the passage of the bullets increases, which increases the Pressure, which increases your Velocity.

I've had a rifle where the 7th bullet in a string began to open the group - considerably. The last time this happened to me, I was trying to make some non-moly coated BarnesX bullets work. But, the first 6 shot fine.

Just clean the barrel while at the Range. Here is where using JB Compound and a good Brass Bore Brush may prove to be the best cleaning combination. A side benefit is that it tends to help smooth out tool marks which may be the "root cause".

Good luck to you!

15 August 2002, 08:29

Bill Leeper

I have experienced the same sort of thing in one rifle when using a certain type of powder but not with others so powder fouling may well play a part as well. After about 6 shots the velocity levels off and is subsequently quite uniform. I'm experimenting with different primers to see if it makes a difference. Also testing this powder in some other rifles. (VV165) Regards, Bill.