Thread: Load data - 270 win IMR 4831

Greetings,
The actual projectiles you want to use, rather than just the weight, have a big influence on maximum charges so it is best to find data for those. The solid copper types and some of the enhanced expansion types need charges reduced from the old cup and core projectiles. Online data for the actual projectile you intend to use should be your first stage. The Hodgdon data which includes IMR4831 often lists data for more than one projectile of each weight which should be your next stage.
Regards Grandpamac.
PS. Didn't read your whole post. The Hornady SST projectiles are a reasonably soft cup and core projectiles so the data from your Hornady Manual is a good place to start. Make sure that you chronograph as you go as velocity is your best indication of pressure.
GPM.

Thanks Grandpamac, valuable advice.

Originally Posted by Floundering Around

Thanks Grandpamac, valuable advice.

Greetings @Floundering Around,
I wasn't familiar with OCW so googled it and turned up a method by Dan Newberry. It is rather similar to what I used to do when I started handloading over 40 years ago. After a chronograph entered my kit 30 years ago I made a number of changes. Now a single cartridge at a start load is chronographed to validate the collection of components I am using. This can be an eye opener for some cartridges but I suspect not so much for the .270 for which there is good and consistent data. If the first shot velocity is what I was expecting then I will move up a couple of grains for some more test loads. Dan talks about looking for groups of loads that have average points of impact that are largely the same. If you are only shooting at 100 metres you may not see much difference with the .270 based on my limited experience as this type of testing is normally done at much longer range. Dan talks about watching for pressure signs without getting into too much detail but in my opinion (but not perhaps others) chronographed velocity is the best indication of pressure. Most of the load data for the .270 is reasonably stout so there is little to be gained by exceeding it. Dan also makes another point about not being seduced by one three shot group, it may just be a fluke. Very good advice. I guess the point I am trying to make is to do the bulk of your testing in the velocity zone that you will be happy with.
Regards Grandpamac.

@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?

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.

Thanks @grandpamac. I sure will. I have access to a labradar so am keen to see if I can push it a bit for speed. Thanks for taking your time to provide this detailed advise, it's really helpful

Originally Posted by Floundering Around

@grandpamac,



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?

if you KNOW what your rifle likes...EG last load developed was right on maximum from book...or was near start load...or was happiest in the middle.....I PERSONALLY BELIEVE you would be daft not to start somewhere close,if slightly below that level next time,with next load.