What load data to use .308?

[Manhusky]

This is probably a noob question, as I have been reloading for about 5 minutes.

I am reloading .308 with 175gn Sierra HPBT and seeing significant max load recommendations between different sites. I currently have 2 types of powder IMR-4320 and VihtaVuori N550

N550
Berger reloading book 46.6gn - VihtaVuori site 45.8gn

IMR-4320
Berger reloading book 43.4 gn - Hodgdon site 45.7gn

I don't plan to reload to max anytime soon, but as a noob I am hoping to see some consistencies so I can be comfortable that I am doing things correctly.
These seem like pretty significant variations, so please let me know if I am missing something, or what information is best to trust.
Thanks in advance for your help.

 

[clcustom1911]

You can trust both. Pick one and go with it. Read all the "Hand Loading for Long Range" sticky threads on this sub-forum. There is an absolute TON of info in there which will answer many of your questions you may have.

also, Fun fact: the Sierra book doesn't even list N550 or IMR4320 in their reloading manual.

 

[Austinjunks]

The closest weight hornady lists is 168gr bullets, imr4320 max load at 42.2. Hornady does not list 175gr just 168 and 178, no 4320 weight for 178gr.

 

[Doom]

IMR 4320 should be the better powder. It’s close to 4064 in burn rate. N550 is going to be too slow. During the last powder shortage several people tested 4320 and found it a good substitute for 4064 in 308 with 168 and 175 gr bullets. Stay away from max charges in hot weather as this powder is temperature sensitive and can result in high pressure loads.

The 308 will usually find best accuracy in midrange charges so going to max loads is seldom required.

You need to be aware when loading 308 that brass capacity varies significantly and affects max loads. In particular, Winchester brass has about 2 to 3 grains of water increased capacity over Federal, LC, RP. Keep that in mind when reviewing load data. I don’t see brass type listed on the Berger data.

 

[Manhusky]

IMR 4320 should be the better powder. It’s close to 4064 in burn rate. N550 is going to be too slow. During the last powder shortage several people tested 4320 and found it a good substitute for 4064 in 308 with 168 and 175 gr bullets. Stay away from max charges in hot weather as this powder is temperature sensitive and can result in high pressure loads.

The 308 will usually find best accuracy in midrange charges so going to max loads is seldom required.

You need to be aware when loading 308 that brass capacity varies significantly and affects max loads. In particular, Winchester brass has about 2 to 3 grains of water increased capacity over Federal, LC, RP. Keep that in mind when reviewing load data. I don’t see brass type listed on the Berger data.

Ok. The brass capacity is something I hadn't thought about. Currently using LC brass.

Does this explain the variations published in the above mentioned areas?

Or is the conservative approach just to use the loads where both publications overlap?

As for the N550, I hope I can find a combination that works for my gun as I have a bunch of the powder.

 

[JTinMO]

Will second what Doom said. You will likely find a good node in a mid-weight charge, and not have to push it real far.

 

[FCS]

Ok. The brass capacity is something I hadn't thought about. Currently using LC brass.

Does this explain the variations published in the above mentioned areas?

Or is the conservative approach just to use the loads where both publications overlap?

As for the N550, I hope I can find a combination that works for my gun as I have a bunch of the powder.

Case capacity is a variable that will cause charge weight differences.
Viht data is usually with Lapua brass, LC (depending on what year, type LC) is about 0.5 gr LESS capacity than Lapua.

Factory rifle with SAAMI chamber or a custom rifle w/shorter freebore chamber?

 

[Doom]

I would use the Berger data. [The Hodgdon is for a JLK bullet and the velocity given is outside the normal 175 velocities. The quoted Berger velocity is close to the typical 175 velocities.] As a general rule I tend to favor the bullet manufacturers data over the powder manufacturers unless the bullets are the same.

Be aware, the minimums should be safe in any rifle, but a listed max may be excessive in any given rifle, especially if it has a custom chamber.

Note: The Berger data is probably tested to SAMMI while the Lapua is probably tested to CIP which are different so that may explain part of the difference. Also, the maximum load listed may not correspond to a maximum limit per a Standard, only that it does not exceed the maximum pressure.

EDIT: the JLK reference above is wrong. IGNORE!

 

[Manhusky]

Well I ran some tests today to see how the loads developed with N550 the higher end didn't match published data. Both say max is around 2630 FPS.
Fired with Savage Model 10 (factory), suppressed, indoor range, 5 shot groups, magneto chronograph.
LC Brass, 175gn sierra HPBT, Winchester primers.

I am not sure I have conclusive data as to which load to develop in the future, the 45.0 was a good group, but the others weren't too bad.

In general is the higher velocity better as long as the groups aren't getting too wild?

Approx Formula: FPS=GN x 89.067-1244.18

GN	AVE FPS
42.0	2477.6
42.5	2557.6
43.0	2591.2
43.5	2640.3
44.0	2688.0
44.5	2712.2
45.0	2744.8

 

[FCS]

Group size?
ES?
SD?

Personally, I’d test @ 2 or 300 to make a decision.

 

[Mr Tibbs]

This is probably a noob question, as I have been reloading for about 5 minutes.

I am reloading .308 with 175gn Sierra HPBT and seeing significant max load recommendations between different sites. I currently have 2 types of powder IMR-4320 and VihtaVuori N550

N550
Berger reloading book 46.6gn - VihtaVuori site 45.8gn

IMR-4320
Berger reloading book 43.4 gn - Hodgdon site 45.7gn

I don't plan to reload to max anytime soon, but as a noob I am hoping to see some consistencies so I can be comfortable that I am doing things correctly.
These seem like pretty significant variations, so please let me know if I am missing something, or what information is best to trust.
Thanks in advance for your help.

Sierra‘s data for both of those powders are used with their 180 gr-2.77 % = 175.0
Imr-4320 42.5 2500 FPS + 2.77 % = 2569 FPS
VN550 45.5 2600 FPS + 2.77 % = 2672 FPS
these are MAX loads from a 26 inch barrel, IMR-4320 seems a little fast burning for a 175 Gr BTHP

 

[Deleted member 10043]

Noob, this is the Internet. Stay within the published data for now with what you have and fuck people wanting to recommend their pet loads. You're in the learning phase and will be for a while.

 

[Deleted member 10043]

Published Sierra 308 reloading data

http://www.6mmbr.citymaker.com/f/Sierra308Win.pdf

 

[FCS]

OP,
Factory or custom barrel?
If custom barrel, button or cut rifled barrel?
OAL to touch lands with 175 SMK?
What brass are you using?
Narrow up the variables a little bit.