Load development as applied to large calibers

[done111]

I am about to work on load development of a 338LM RPR. I have done the OCW test in the past on smaller calibers and did some verification via chronograph that has produced something decent.

With this larger caliber (and I could also be reloading for a 416 Barrett in the near future) is there a better way to build an accurate load without putting lots of rounds down range.

I’m thinking of ditching my Magneto sport and getting a Labradar, but that’s a little way down the road. I was thinking if I just monitored the velocity of these larger calibers as they were being shot at whatever (not 100 yard groups), and change the grains after every 5 rounds or so, I could at least get a check on ES and SD for various powder amounts, bullet depths, etc without knowing how well they group. Maybe that’s enough?

What are you all doing to minimize the amount of firings of large calibers (waste of Barrel life and $) and still find a load your gun likes?

Don

 

[dsculley]

If you do your research you should have a good idea where to expect a node. Test in that area (working up with single shots of increasing powder to be safe) and you can limit the total number of rounds used in development. You will still need to test both sides of the expected node to verify your node. If it were me, I would test for seating depth first using a modified Berger test shooting two round of each charge to find the preferred area, then testing in finer increments. The reality of load development is that you have to use some barrel life to find your node(s) and seating depth, it is not a waste of barrel life, it is a use of barrel life. If you try to shortcut it too much then it will pretty much be a guess. You might contact Dan Newberry at his forum site (https://www.tapatalk.com/groups/practicalriflerfr/) to see if he may have a good idea where you may find a node.

 

[done111]

Dsculley, you mention using only single shots to find/verify node....are you using strictly a velocity as a criteria and not grouping? If so, how does the process work?

Don

 

[Zero333]

Audette ladder.

Nevermind velocity until you're fine tuning the load.

 

[Depart123]

I am about to work on load development of a 338LM RPR. I have done the OCW test in the past on smaller calibers and did some verification via chronograph that has produced something decent.

With this larger caliber (and I could also be reloading for a 416 Barrett in the near future) is there a better way to build an accurate load without putting lots of rounds down range.

I’m thinking of ditching my Magneto sport and getting a Labradar, but that’s a little way down the road. I was thinking if I just monitored the velocity of these larger calibers as they were being shot at whatever (not 100 yard groups), and change the grains after every 5 rounds or so, I could at least get a check on ES and SD for various powder amounts, bullet depths, etc without knowing how well they group. Maybe that’s enough?

What are you all doing to minimize the amount of firings of large calibers (waste of Barrel life and $) and still find a load your gun likes?

Don

I'll tell you how I do it for my 338 AX. I'll get pushback here, but I don't care.

Reasoning: I'm not shooting benchrest at a single distance. I am shooting out past 2000 yards on steel. I need my cartridge to perform within the maximum velocity envelope without being over pressure in the summer time.

I load three cartridges of each charge, working up to find max in 1% increments. Max being determined by indicators such as velocity, base expansion, appearance and location of powder residue on the neck, primer appearance, bolt lift etc..

For big cartridges such the 338's, I assume 1 fps per degree change in velocity per 1 degree of ambient temp. So, I also calculate from my velocity pressure testing the rate of velocity change in the last 2% per 0.1 grains.

Ex: working up load at 50 degrees, 1 fps per degree of ambient temp, 5 fps increase per 0.1 grain. I want to stay out of pressure trouble at 100 degrees. So, 100 degrees - 50 degrees = 50 fps.... 50 fps / 5 fps per 0.1 grains = 1 grain

1 grain off of my determined max is the area I want to play in. So, I have found my velocity window with very few rounds down range. From here, I play with seating depth to find the best performer at distance.

 

[dsculley]

single shots working up to the area you want to test just to make sure pressure is ok. Two rounds to test the node. Three would be better but two should give you an idea of the spread. As has been said on here by others, the third shot will not make a group any smaller.

 

[joe12180]

https://sierrabulletsblog.com/2017/06/01/long-range-load-development-2/