Question on Revised Load Data for N135

[Doom]

I have a 2015 lot of N135 that I use in 223 and 308 recently (last.year). VV revised the load data for this powder in both calibers. Back in 2018 the max load data for the 168 SMK was 42.1gn and 2697 fps. The new data for that bullet is now 40.1 gn and 2569 fps.

I questioned Capstone on this and the the response was basically it "is what it is", my words not theirs. I am looking to purchase more powder but this seems to reflect a major change in the powder. Has anyone using this powder in newer lots seen such a drastic change in burn rate?

 

[Mulligan]

Is it a change in burn rate or did the legal team have a better day at the office than the folks with calluses on their hands?
Lower powder charge, lower velocity…….
CW

 

[jelenko]

This would be an opportunity to do a 'ladder' like 1/2 grain steps.

You could also use GRT to see the predicted pressure in your rifle. You would need to measure the fired case volume and run 8-10 rounds across a chrone to calibrate GRT.

 

[Doom]

This would be an opportunity to do a 'ladder' like 1/2 grain steps.

You could also use GRT to see the predicted pressure in your rifle. You would need to measure the fired case volume and run 8-10 rounds across a chrone to calibrate GRT.

Only issues is I don't want to buy any new N135 if this is correct as I use it in 223, 308 and 30-06. I was hoping someone might have done this.

 

[painter]

I have found that a lot of the Max. charges are on the light side.

 

[jelenko]

Only issues is I don't want to buy any new N135 if this is correct as I use it in 223, 308 and 30-06. I was hoping someone might have done this

Right. I was thinking you could run the tests on the powder you have - but that wouldn't be helpful if the powder burn rate has changed.

FWIW, a google search for "vihtavuori changes burn rate" didn't return anything about the burn rate changing in the first two pages of results.

 

[Coyotefurharvester]

Could be they changed test barrels, your barrel hasn't changed. You won't know until you test.

 

[JB10]

I use 2 vv powders. I am way over there recommend max with no signs of pressure at all. I think they are light on their max. I have even contacted berger for load data and they have a recommend max higher than vv

 

[Doom]

I am not concerned with max loads per se, it is whether the burn rate has changed enough to warrant the reduction in velocity. It is indicative of a very fast burning powder. Faster will defeat the purpose for which I use the powder.

 

[maurmun]

Hello, I found the latest lots of N135 (mine is late 2024) to be with a faster burning rate than expected/declared. Few days ago I went at the “Banco Nazionale di Prova”, the official Italian government entity to certify guns and ammo, to test some “light” .308 loads for my old Spanish Mauser M1916, and even if tested on the same barrel type of 24” 1:12, with my 35.7gr load under a 168gr SMK I got 2365fp/s compared to a 2388fp/s published by Vihta for 37gr.
For a SMK 150gr with 38gr load I got 2536fp/s very near to the Vihta published 2602fp/s with 40.9 loads.
I tested also the SMK 155gr and the results are similar.
They were new Lapua brass with Fiocchi primers.
I’m not used to look at simulations (just to check for at least 80% brass fullness ) but with GRT I have similar results for the N133

 

[SeabeeKen]

I'm running a 22 ppc 1 gr under VV max N-135 and getting 200 fps under their speed from the same length barrel. No pressure signs at all

 

[Murray Brook]

I think the only way you will know for sure is to test some of the new lot against the old lot in the same rifle. Check the velocity. JMO

 

[Doom]

I'm running a 22 ppc 1 gr under VV max N-135 and getting 200 fps under their speed from the same length barrel. No pressure signs at all

What year is the lot?

 

[Doom]

I think the only way you will know for sure is to test some of the new lot against the old lot in the same rifle. Check the velocity. JMO

That is the plan. Unfortunately, there is nowhere near me that is carrying VV. That means the cost is going to be pretty high for a pound.