Thread: "Extreme Velocity Spread"!

I was working up a load for my Remington 5R .300 Win Mag with 26" barrel and went to the range and fired several 3 shot groups with some groups appearing promising. So, with that in mind, I set out to duplicate that load as close as I could.


This load consisted of a .30 cal.180gr. Hornady SST bullet pushed by 72.5 grains of IMR 4350 powder. Primers are Federal 215 Large Rifle Magnum. Cases are Nosler Custom Brass (already fireformed in this rifle) with clean, clear flash holes. Dies are Redding Competition with a .331 sizing bush, which I think sizes them about .003" undersize!


I uniformed the primer pockets and seated all the primers consistently to the correct depth. I then deliberately set my Lyman DPS3 digital Dispenser Scales to 72.4 grains, so that I could top the load up accurately on the RCBS 1010 balance beam scales to 72.5 grains.


I seated the bullets and, using Hornady's LNL bullet comparator and 30 cal bushing, they came out like this:


1/ COAL = 2.903" Bullet Runout = .001"

2/ COAL = 2.9035" Bullet Runout = .0005"

3/ COAL = 2.903" Bullet Runout = .001"

4/ COAL = 2.904" Bullet Runout = .001"

5/ COAL = 2.9035" Bullet Runout = .002"


I was aiming for 2.903" for COAL and of course .000" Bullet Runout!


Right, now off to the range I went with these perfectly uniform "Blue Printed" rounds!


The velocities were as follows:


1/ 3225.41 fps

2/ 2965.45 fps

3/ 3084.07 fps

4/ 3090.37 fps

5/ 3160.56 fps

Extreme Spread was 259.96 fps

I personally would've thought somewhere along the line of #3 and #4 velocities for that amount of powder! Granted, I was trying to load as close to the lands as possible, however, as you can see #1 (which gave the highest velocity) boasts one of the "Shortest" COAL!

I haven't exactly been leaving my powder and primers laying out in the rain or anything and it's certainly not a double or over charge!!

Has anyone any idea of why such an extreme velocity spread, when all these rounds are supposed to be loaded meticulously the same?