I have been trying to develop a load for a friend's rifle. I suggested that he use 180gr partitions on elk out of the 30-06. The ranges he will be shooting are limited to less than 200 yards.
So far the best shooting rounds were loaded with 53 grains of IMR 4350. These rounds printed .770 and .264 inch (3 shot groups) When I load up to what most books call "maximum" the gun shoots 1.6 - 1.8 inch groups.
Most books (6 out of 7) recommend a 55gr maximum load. However, the A-square manual does list a 60 gr load for 180gr bullets.
Along with the reduced loads that shot well they are also going across the chorno (competition electronics Pro Chrono) at 2500 feet per second - which is about 150 fps slower than what the books say the reduced loads should be flying at. When looking at the primers I cannot see a difference between the loads with 51gr of powder and 55gr.
The questions: Would it be considered safe to push this beyond what most books recommend to what one book out of 7 recommends as a maximum charge (one book being truthful and all the others just covering themselves)?
Does it seem likely that the same accuracy achieved with the reduced load could be had again at a higher charge weight (is there any sense in trying a hotter load to get the group smaller)?
What effect will a change in temperature/ altitude have on the accuracy of the round? I am testing at 1000' and 90°-100°. It will be used hunting at 11k' and a lot colder than we get in southern texas. I am not concerned with ballistics as much as I am will it hit the same spot here vs there, will the powder act much differently or should it be changed etc.
I think that many loading manuals are conservative because the 30-06 has been around for 100 years (1903 Springfield). Therefore, older rifles from WW1 and 2 vintage have to shoot at a lower max chamber pressure than new modern rifles (SAAMI 60,000psi).
If you are loading for a modern rifle, then you can load to 60,000psi. I did a Quickload simulation for you with IMR4350, 180gr Partitions. Max load would be at 57.2 grains, estimated 2837 fps with a 24" barrel (you didn't specify barrel length). 55grains gives a chamber pressure of ~53,000psi, probably suitable for antique rifles.
You should be able to work your load up over a chronograph to get to a fairly close velocity to what the book says. Unless your barrel is shorter than the one in the book or just a slow barrel. Your lot of powder maybe just a little different than the lot that they used in the book?
I think a lot of people are hesitant to give advice on working up a Max load... as they should be. No one should recomend going above the posted max and everyone should use caution when working up loads... with that said some of the signs to look for are printed in every reputable loading manual. These include but are not limited to flatened primers, sticky bolt, notable velocity changes.
There are so many variables that will contribute to the differences in manuals... for instance: generally speaking a boat tailed bullet will show signs of increased pressure prior to a flat based bullet, more room in the case will change the pressure, the freebore of the bullet and barrel combination will change pressure.
I will not go as far as to say that you absolutely need to find the exact combination printed in a manual in order to start testing... but you need to have the same powder, primer type, bullet weight, and similar design to use as a starting point. A round nose flat based 180 grain will act much differently from a Berger VLD 180 grain! ALWAYS START LOW!
you may want to read through the loading section dealing with excessive pressure in your loading manual agian.
I used to re-load but now I "hand-load".
-- Well, at least I try --
Right now my plans are to load 3 shots in half grain increments above 55gr to verify that the load is not above true maximum. If I am unable to get a more accurate load after trying this I will just drop the charge down to 53 (where I saw best accuracy).
I am really concerned about accuracy more than speed because he is having problems shooting. I know that my shooting skills improved after knowing that my gun could shoot well, and I am hopeing that the same will happen with him. Also based on Gary stating he has taken elk up to 300 yards with his 30-06 this would give about the same speed as the reduced load shooting at 200 yards, so this should not raise concerns about being lethal.