300gr SMK & VV N570

6MT

Sergeant of the Hide
Full Member
Minuteman
Sep 1, 2014
161
239
ITU Zone 2
I’m looking for some load info for my newly rebarreled .338LM. I used to use Retumbo, but that’s not been available up in Canada for over 2 years In the quantity I desire (or the prices). So, I’ve chosen VV N570. I see on their site that the max charge weight for the 300gr SMK is 91.3gr. I consulted locally with a fellow shooter of the same bullet and N570, and he tells me that he has found a node with his 26“ barrel with 93.0-93.5gr. I talked with another fellow shooter, and he has found a node with his 30” barrel at 94.2gr.

Is the consensus to load beyond VV’s maximum posted weight? Or is that just the lawyers advice? My goal is around 2900fps with my new 31” barrel. My former 26” pipe got a velocity average of 2880fps with 93.6gr of Retumbo. Yes… a stout load. Bolt lift was moderate, and I always got ejector marks on the case head. The reason I continued with this very accurate load was that it worked very well to a mile and all the way out to 1900 metres. Brass life didn’t seem to suffer either. I annealed every firing and got an average of 14 cycles before case separation occurred.

I‘m about to roll up some rounds for load tests this weekend. Here’s what I’m thinking: 90.0, 90.5, 91.0, 91.5, and 92.0 for my first outing. For those of you (I know there are a lot using N570) loading a 300gr class bullet, am I going in the right direction? I will using my LabRadar to check speeds.

I guess the most pressing thing on my mind is the fact that shooters are loading over VV’s maximums (and in some cases by a lot). I guess I will pay close attention to bolt lift and other signs. But I’m curious to what everyone thinks.

Andy 6MT
 
Last edited:

Allthewatts

Private
Minuteman
Feb 8, 2020
76
43
I'm interested in the same answer. I have a 30" barrel. Have shot 300gr Sierras from 86.00 to 92.00 grains. Velocity under predicted by 50fps by GRT, but slope was near perfect.

loading (gr)Velocity (fps)
862578
872617
882666
892681
902699
912732
922762

No pressure signs, I think there is much room to go. Mind you I have a long throated barrel, so a bit more volume.
 

disky1

Private
Minuteman
Jul 24, 2013
14
18
The only thing I remember about the n570 was that it is horribly dirty.

I had great results with imr 4350. Its in the sierra manual as the accuracy load.
Inside an inch at 400m. Through my AI Ax338. 27in.

Dont have the speed numbers anymore.
Best of luck!