Thread: Load data - 270 win IMR 4831

Originally Posted by Floundering Around

@grandpamac,

Since I posted this I concluded that there really wasn't much point in using OCW anymore as I have easy access to a chronograph (labradar) and I have become pretty good at load development over the past two years using that method. I can see how for new handloaders without access to a chrony the OCW method Dan developed would be pretty good. I also always use 4-5 shot strings. More data the better in my opinion and beforehand with optical chronographs I found that more shots gave more data which gave better averages.

On another note, what charge weight point do you tend to start with. I usually go right through from minimum to above maximum if I can, but that is proving to take too long and is a lot of shooting in a single day. Is it ok to start at midpoint charge weight if I am trying to chase velocity and accuracy for flat shooting over 300m?

Greetings,
It really depends on the cartridge and what prior experience I have had with it and the powder involved. Some not so common cartridges don't have much data and there is not much data so I will start low. This can be followed with a head scratching session to see how my results fit and where to go next. The .270 is not one of these. There are truckloads of data and it all agrees with each other to a great extent. Starting with a mid point load and chronographing that is what I would normally do for it. Before you start it is worth deciding the velocity range that you want to be in and work up to the lower edge of that range without wasting too much ammo. Do your testing from there. Most of my old and current data seems to agree on a max load of 57 grains or a little less of IMR4831 with the 130 grain and a velocity of a little over 3,000 fps and a little over 2,900 fps for 55 grains this would be my range of velocity that I would work in. These velocities are for a 24 inch barrel so need to be around 25 fps for each inch shorter you barrel is. If I had not used the components prior I would probably try one round at 53 grains just to validate the data. I think the point is not to do much testing on the light loads other than is needed to validate the velocities. In my experience most powders produce the best accuracy at close to their maximum pressure. I am sure that you will give the rifle a thorough check out before starting you load series,
Regards Grandpamac.