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?

did you have a nice clean oiled barrel for the first shot? That bit of residue oil from cleaning can speed up the first shot.

What crony were you using, distance from muzzle, weather conditions ?

Did it group well ?

Originally Posted by Barefoot

did you have a nice clean oiled barrel for the first shot? That bit of residue oil from cleaning can speed up the first shot.

Nah, this is on the third string! Also, what would account for the second shot being exaggeratingly low? (around 120 fps or so)

Originally Posted by Kiwi Greg

What crony were you using, distance from muzzle, weather conditions ?

Did it group well ?

Grouped like shit, 1 - 5/8" at 100m!

Originally Posted by Kiwi Greg

What crony were you using, distance from muzzle, weather conditions ?

Did it group well ?

Sorry, I didn't see your first questions!

Um, Chrony was a Chrony Gamma Master, it was (as always) 3m from the muzzle and the weather conditions were perfect!

I can only offer advice on the Chrony that the makers told me when I emailed them for virually the same reasons,speed difference and that was with an established accurate load
I was getting good grouping but large speed variance which seemed weird.
They told me I had my chrony to close to the muzzle and I should move it back to 15-17 feet.

Keep going with the load development, and please take your reloading gear and press to the range with you so you can fine tune the loads on the day.

Originally Posted by jakewire

I can only offer advice on the Chrony that the makers told me when I emailed them for virually the same reasons,speed difference and that was with an established accurate load
I was getting good grounping but large speed variance which seemed weird.
They told me I had my chrony to close to the muzzle and I should move it back to 15-17 feet.

I'd always thought that Chrony recommended 3m, that figure always stuck in my head, however, I just rechecked the instructions and it said "At least 3m from the muzzle of a High Powered Rifle"! Hey, that might not be the problem, however, maybe next time I'll set it out 4m and see if it more consistent!

Originally Posted by 7mmsaum

Keep going with the load development, and please take your reloading gear and press to the range with you so you can fine tune the loads on the day.

Yeah cobba, I'd love to, however, it's always a hassle trying to pitch a tent for the powder scales as we have no buildings here at our primitive range!

How's the 30-378 and 338-378 Weatherby shooting going... stretched any more primer pockets on them cases yet?

Originally Posted by Remington 5R .300 Win Mag

Yeah cobba, I'd love to, however, it's always a hassle trying to pitch a tent for the powder scales as we have no buildings here at our primitive range!

How's the 30-378 and 338-378 Weatherby shooting going... stretched any more primer pockets on them cases yet?

Will let you know when more fail so they can go live in your collection.

Originally Posted by 7mmsaum

Will let you know when more fail so they can go live in your collection.

Yes, only passing on what they told me, I have the middle of the chrony 15ft from the muzzle now, and seem to get better consistant readings.
I still throw the odd one or some reason,but my F1 chrony is the cheaper end.
Could well be your loads and not the chrony but worth a try if all else is equal including keeping the shades on etc,
I'd imagine a 300 would have some reasonable muzzle blast.

Try a different slower powder, say ADI 2213 or 2217.

Originally Posted by jakewire

Yes, only passing on what they told me, I have the middle of the chrony 15ft from the muzzle now, and seem to get better consistant readings.
I still throw the odd one or some reason,but my F1 chrony is the cheaper end.
Could well be your loads and not the chrony but worth a try if all else is equal including keeping the shades on etc,
I'd imagine a 300 would have some reasonable muzzle blast.

F1 Chrony is probably the same just with a few less bells and whistles, accuracy wise they're probably the same machine!

Yeah, the .300's got a bit of a blast alright, shoot long enough and you'll send the diffusers flying! I've also cracked the printer with the muzzle blast alone!