Flat Spot Load Development Method
I'll have to find the links I was sent and repost them, but folks I talk reloading with from other forums clued me in to this method, and it's a pretty slick concept.
The biggest "catch" is that you have to have a chronograph in order to do it. It won't work without it.
Here's my first workup----
I took my 270 Winchester, which is a pre-64 standard rifle with a 24" barrel. I had it shooting 150gr Nosler Ballistic Tips inside 1.5" at 200 yards, chrono'ing 2900-2960fps. Great load. Killed a couple bucks with it in South Carolina.
I decided I wanted to move it over to a 150gr Partition for my upcoming elk hunt. I tried just "swap the bullet and hope". It did...ok. About 25-30 rounds of work got me 2.5"-3.0" at 300 with 2800-2825fps. Useable.
Using the Flat Spot method, I expended 19 rounds and developed a load that shot 1.88" with one shot called slightly low, and that shot stretched the 3-shot group from about 3/4" to 1.88". At 200 yards. Speed was 3046fps for the 150PT. Before anyone has a stroke over that, I've measured my case capacity in my fired brass, run that through QuickLoad, and developed pretty solid data on what speeds track to pressures close to the 65k SAAMI limit. I'd have to be over 3100 by a bit, so 3040-3050 that I am getting is a good place to be....not too close to the edge, but getting what I can from the round. And 277 Partition at those speeds will work well for about any game animal I'm gonna hunt.
So here's the gist of it...
You get your load data, and load maybe 2 or 3 charges at least a couple grains under max. Shoot them to get speeds, and groups are immaterial, so shoot them into whatever.
Getting those initial speeds helps you calibrate your rifle and load data...i.e. if your data source predicts 2800fps and you get 2720fps, you know your rifle is not at the same pressure level as the data source's test rifle, and you can go higher in charge weight.
Knowing that, you develop a speed range you want to target, and make about a 2gr "range" of charge weights you'll be working with. You start at the bottom of the range and make 1 round at that weight. Go up 0.2gr, make one more round. Repeat until reaching the top of the range you selected.
Now go shoot them for speed. Groups don't matter. Shoot them in the dirt, in a target, whatever. You just need the speed. It's good to know what speed equals your "red line" that you shouldn't cross. Whether the rifle is giving sticky extraction or other pressure signs or NOT, you should know the speed you can't cross. If you find you've hit it, stop.
Record the speed for each round. What you'll more than likely find is that you'll have increments where the speeds increase 10, 20, even 30fps for just a tiny increase in powder. And then you'll find that you have increments of 0.5-1.0gr or so where the speed doesn't increase much at all as you add powder. That's your "flat spot". You may be able to find more than one, as well.
Once you've found the flat spot(s) in the speed range you want, calculate the middle point in the charge weights. Load up 4 rounds at the longest length you can in your rifle....meaning the longest that will cycle through the magazine, or if that's not a limiting factor, get to about 0.010" off the lands. Make another 4 at -0.010" from the first length. I usually do at least three lengths, but 4 wouldn't be a bad thing either. Now go shoot for groups.
More than likely, if the group you want doesn't appear, you'll see a clear trend in group size as the length varies. Work to follow that trend and the groups should tighten.
With the 270, I found my "longest I want to go in the mag well" length was 3.345" OAL. I shot 3.345, 3.335, and 3.325 OAL's with my "middle of the flat spot" charge.
3.345 shot a 6.5" group (you read that right) at 200. Wow.
3.335 shot a 4.25" group at 200.
3.325 shot a 1.88" group at 200.
Now I plan to re-run 3.325 to verify, but then to also run 3.320, 3.315, and 3.310, too, just to see if there's any refinement to be found.
The excitement for me here is that this helps take away a lot of the "try and see" blind experimenting we do in reloading. It makes it much more scientific and less "black magic" I think.
The key component is the chronograph, but a CLOSE second place is QuickLoad software. That really allows the reloader to get tuned in tight to what's going on with the rifle in question. When I give QL solid data, it consistenly predicts my chrono speeds to within +/- 15 or 20fps. This is how I find my "red line" that I know not to cross. When my speeds get close to the line, it's time to stop, whether I see any of the classic "pressure signs" or not. If I'm at those speeds, I'm at those pressures, and there's really no way around that.
Anyway, I just thought I'd share. It's a really interesting approach. I'm working with my 35 Whelen as well, and close to a good result. I'm about to start my 300WSM, and I hope next spring to take on more of my rifles and really tighten up my load work.
Last edited by tdd; 08-30-2017 at 08:32 AM.