Vastly differing load recommendations

[emp1953]

I've been loading my old Remington 700 30-06 with 47gr IMR3031 and 165gr Nosler Partitions since the mid 70's. I had an old Sierra reloading manual and got a minimum starting point and worked up from there.
In my closet I just found a 28th edition Lyman manual which suggests IMR3031 minimum at 44gr and maximum at 49gr.
I just went to IMRReloading.com and was redirected to http://www.hodgdonreloading.com/....... Does the IMR line now belong to Hodgdon?
Anyway, putting in my data above it recommends for a 165gr Hornady GMX - 41gr as the starting minimum and 44.1gr maximum.
and for a 165gr Sierra SPBT 45gr minimum and 48gr maximum. Nosler partitions are not listed.
Is this due to changes in the chemistry between the older and newer IMR3031, or the makeup of the jacket alloy of the bullets? or both.
I don't want to damage my trusty old model 700.

 

[GLTaylor]

Powder chemistry and pressure measurement has changed a lot over the years. Recommend you follow current recommendations from the manufacturers.

 

[Buster Hemlock]

The GMX is a mono bullet and the Sierra is a cup and core. Monos typically have higher engraving pressure going down the barrel because it doesn't have the soft lead core like a cup and core so that's why the difference in charges for those two bullets. IMR is owned by Hodgdon as well as Winchester powder, Accurate powder and Ramshot. Powder chemistry and allowable pressures have changed some but since you will be using a new lot of powder you should reduce your charge and work back up anyways.

 

[just_jon]

Lawyers!

 

[emp1953]

The GMX is a mono bullet and the Sierra is a cup and core. Monos typically have higher engraving pressure going down the barrel because it doesn't have the soft lead core like a cup and core so that's why the difference in charges for those two bullets. IMR is owned by Hodgdon as well as Winchester powder, Accurate powder and Ramshot. Powder chemistry and allowable pressures have changed some but since you will be using a new lot of powder you should reduce your charge and work back up anyways.

I was afraid that I was going to get recommendations to re-develop the load. It now shoots under an inch at 200yds. And now reloading components are scarce as hens teeth.

 

[Buster Hemlock]

I was afraid that I was going to get recommendations to re-develop the load. It now shoots under an inch at 200yds. And now reloading components are scarce as hens teeth.

You don't have to fully redevelope the load, just back off around 4% and load one up in .3 grain increments to your previous load looking for pressure signs and checking velocity. 4% off your 47 grain load is 45.1 and working up in .3 grain increments will take 7 rounds. Solid insurance to make sure you don't overpressure and hurt the gun or yourself

 

[emp1953]

You don't have to fully redevelope the load, just back off around 4% and load one up in .3 grain increments to your previous load looking for pressure signs and checking velocity. 4% off your 47 grain load is 45.1 and working up in .3 grain increments will take 7 rounds. Solid insurance to make sure you don't overpressure and hurt the gun or yourself

Understood, thanks