Vihtavuori N140 vs Sierra #7768 load data is different

[SPAR]

Reloading .308 with Sierra 7768 168gr Tipped Match Kings and Vihtavuori N140.

The Vihtavuori data has a max and min of 39.7 grains and 42.9, whereas the Sierra data has a range of 39.4 to 44.9.

Is anything over 42.9 going to be a “hot” load risking over-pressure? Or is the Vihtavuori data very conservative?

Vihtavuori:

Rifle reloading data | Handloading | Rifle calibers | Centerfire Rifle bullets | Reload your own ammo - Vihtavuori

Vihtavuori offers rifle reloading data for numerous calibers and bullets for match and hunting purposes. Never exceed maximum loads.

www.vihtavuori.com

Sierra (see page 7):

https://sierrabullets.com/content/load-data/rifle/308/308-winchester.pdf

 

[markyw]

2 options here (and I can't look the figures up as away currently) in the absence of a load modelling tool..
1. Start where you feel it's safest and work up a load, keeping both maximums in mind and paying specific attention to pressure signs.
2. Pick one and work with it. Still paying attention to pressure signs.

Regards

Mark

 

[kenbro]

Is not that Vhit data for a Hollow point Boat tail, not a tipped bullet?
Kb

 

[SPAR]

Is not that Vhit data for a Hollow point Boat tail, not a tipped bullet?
Kb

Viht list it for the HPBT and don’t list the Tipped Match Kings, Sierra lump all their 165 and 168gr bullets into the same table as though they’re interchangeable (base of bullet to ogive dimensions the same?). If I were using #2200 168gr HPBT the Viht data would match without having to infer, but the question about max powder grains would still be the same.

 

[kenbro]

Viht list it for the HPBT and don’t list the Tipped Match Kings, Sierra lump all their 165 and 168gr bullets into the same table as though they’re interchangeable (base of bullet to ogive dimensions the same?). If I were using #2200 168gr HPBT the Viht data would match without having to infer, but the question about max powder grains would still be the same.

Follow what markyw says.

I tend to start near or at the top of Vhits. data….not suggesting you should though.
KB.

 

[Foxyboy43]

Hmmm.
Some would arge that Viht has a reputation for being “conservative” in their reloading data but what are you really losing by starting low and working up to your ideal powder/bullet combination? You will surely find your niche load then the initial exercise and the cost of the trial combinations will be forgotten …..

 

[aris]

Try enter your data into P-max P-Max internal ballistics

The powder space section of the calculation is where you may get the nuanced variance- you need an accurate scale and an eye dropper to get the exact number of grains of water to measure the case volume. Not all cases are built the same x for instance Lapua brass is known to be thicker - hence less volume.

You should also read up on how to identify pressure signs on your brass, lots of resources out there.

 

[SPAR]

Try enter your data into P-max P-Max internal ballistics

The powder space section of the calculation is where you may get the nuanced variance- you need an accurate scale and an eye dropper to get the exact number of grains of water to measure the case volume. Not all cases are built the same x for instance Lapua brass is known to be thicker - hence less volume.

You should also read up on how to identify pressure signs on your brass, lots of resources out there.

Thanks for those - I’ll give them both a few thorough reads before making up my next loads .