Load pressure discrepancy

[ChrisBCS]

One source says a 58 gr load of H4350 under 175 gr SMKs in 30-06 is OVER SAAMI specs for the cartridge pressure.

The manufacturer, which I would have thought to be more conservative, says that one grain higher, 59 gr, is the max charge, and still under the SAAMI max at about 58,000 PSI.

My testing says OCW in the 58 gr region may be perfect, and there were no pressure signs... So... where do I go from here? Be safe and find the node at 46.2 (~3% lower)? Or is something obviously wrong here...

 

[biffj]

Pressure can vary considerably based on the freebore of your barrel, seating depth, neck tension etc. There are a lot of different things affecting pressure. What the manuals give you is what they found for their loads in their test gun. So whoever said the load was over saami spec was telling you that in their gun the load was over. If you have weatherby style freebore and you're seating bullets out further then them your pressures will be lower. This is one reason everyone tells you to start at a lower level and work up. You have to find the load that works in your rifle. Also realize that while you may see things like flat primers or sticky bolt lift that isn't necessarily a guarantee that you weren't over pressure before that. Unless you have a pressure guage setup on your rifle you will never know exactly what you're running.

Frank

 

[I Am Hero]

Try reloading for a service rifle and you'll go nuts trying to stick to different manf. recommendations on pressure and SAAMI specs. Even Hornady's reloading manual says that the max load is under what they load their factory ammo to. So I take it all with a grain of salt, find something under max with good accuracy and go from there. So what if I have to adjust 1-2 MOA more because my round is slower, I would rather be safe than sorry when it comes to pressure.

 

[ksthomas]

Chris,
you're not reading the manuals correctly. I can pretty well assure you, none of them is "wrong" and all are perfectly correct. Problem is, they're correct for the particular combination of components, lot numbers, and firearm that they used in developing that data. You're not using any of the same components, even if you're using the "same" bullets, powder, primer and cases. Yours will be from different lots, and you're dealing with an entirely different chamber.

Every reloading manual should be read as nothing more than a report, basically stating that "we tried this combination, and this is what we saw. Your mileage WILL vary." Approach them from that standpoint, and you'll save a lot of frustration down the road. Just a report, not carved in stone, and yours will probably vary from what they show.

 

[918v]

Pay attention to the components used to develop the loads in the manual. There is a huge difference in case volume between different brands of brass. You have to adjust the powder charge accordingly.