request for load tuning stories - powder charge

[sonnyt650]

Being relatively new to reloading (a little over a year and a few thousand rounds across several firearms) the extent of my load tuning has been to figure out what my rifles like as far as bullet weight. Once that's done I haven't gone any further and so my rifles hover around the range of 1"-2" groups at 100 yards near the recommended starting loads. I'm wondering how much better those groups could be if I did ladder testing or something similar. What kinds of tightening up have y'all experienced by varying only the powder charge?

[GeoffLinder]

Not in all cases, but you can see as much as a 50% reduction in group sizes when the correct velocity node is found with ladder testing. You will also find more than one barrel node if you run the ladder far enough (min through max charge range).

It really helps to use a chronograph at the same time to establish the velocity of each node. This allows you to find that node again easily when you change powder, primer, bullet and brass batches at a later date.

Also, bullet seating depth will effect group sizes. Typically, smaller groups can be found by seating bullets long enough to get near the lands. Just don't push them into the lands without being careful of pressures.

[Fjold]

I've seen groups go from 2"-3" to 1/2"-3/4" in half of a grain of powder charge variation.

[kmca]

You'll probably see similar results with changing powders and bullet types. Working up a load for me is a measure of patience. I get the feeling I could wear out the barrel trying to find that "perfect" load.

[GeoffLinder]

I get the feeling I could wear out the barrel trying to find that "perfect" load.

LOL, many folks do just that for a hobby

[1lostinspace]

You need some sand bags and a good bipod to start off.

Then start low to high in .5 increments then after finding the sweet spot vary in .2 then .1
Also make sure you are using Match grade bullets, trim brass and make sure everything is the same every time. Then start messing with COL make it a little bigger and see what happens to your groups. I went from a 1" group at 100 yards to 1.5" group at 400.
I also like using a Lee factory crimp die. 1/2 turn.

[brando]

Ladder testing is very effective but very difficult to do - there just aren't too many places where you can shoot far enough on paper and log the impacts in a reasonable amount of time.

Load development really kind of a never ending process for some people. It can go through constant refinement from charge weights, to seating depth, neck tension and different primers. Either way, it's important to have a goal when developing a load and that will often drive your efforts in developing it. If it's just a plinking load, I tend to go for economical bullets and powder and a reasonable velocity that gives reasonable accuracy. The bottom line is for that kind of load I need to be able to make a lot of it quick and cheap and not fret over getting the most out of accuracy.

On the other hand, when developing a performance load, I tend to chose a bullet first and work from there. Often I'll do the research, both in the books, online and later through Quickload, to see what powders will give me the best combination of burn rate, pressure and velocity. From there I'll load up a range of powder charges in uniform increments, using a standard COAL. This can often be done with under a dozen rounds. Shooting these with a chronograph gives me a realistic idea of what velocities to expect - and this is important - for performance loads I often have a target velocity range I want to hit. For example, I learned one day that the 155 Scenar outperforms the 175SMK at longer ranges but only if you run it between 2800-3000 fps.

So now that I have an idea of what powder charges get me into the velocity range I want, I start loading up batches of 3 rounds in finer increments and shoot groups at 100 yards. This tends to give me an idea of where the velocity node is as some groups will tighten and others will open up. Sometimes the results aren't so obvious but they tend to rule out certain powder charges. That's when I'll refine things with more groups (sometimes 5 shots per) to hopefully nail the charge weight.

Sometimes that's all I do. I'll start using that load for its intended purpose, but sometimes I'll notice that they don't perform as well in other rifles, so I'll go back a step and refine further. Seating depth adjustments can really fine tune loads, especially when targeted for a specific rifle. Some guys like to start with the bullets jammed into the lands and work backwards. Since I tend to start this process already with a full power load, I instead start at SAAMI specs and seat towards the lands - looking for pressure spikes as well as group size.

Also keep a log of your powder lots. When I was regularly loading .408 Cheytac a couple years back, I noticed a weird swing in velocity from lot to lot of RL25. That threw my two proven loads back to the drawing board.

[sonnyt650]

Thanks all, this inspired me to give it a go and today was the day. It wasn't the best day today for shooting for groups with the winds gusting about an inch worth of error, but by the time I was done I think I found a good resonating node for my barrel. In a span of half a grain, groups shrunk from 3.5+ inches to sub 1 inch (depending on whether a flyer counts, I got a group of less than half an inch). If you're interested save the following in a text file with extension CSV, then open in Excel:
Charge Set,Order,Varget,group (e-e),group,lie,notes
1,1,22.7,1.72,1.496,4o'clock,
2,4,22.9,1.6,1.376,trapezoid,
3,7,23.1,2.16,1.936,rectangle,
4,2,23.3,1.37,1.146,3o'clock,
5,5,23.5,4.1,3.876,12o'clock,
6,8,23.7,3.6,3.376,rectangle,
7,3,23.9,1.12,0.896,2o'clock,
8,6,24.1,0.66,0.436,3/5 touching, 1 flyer to 1.60 e-e
9,9,24.3,1.29,1.066,rectangle,

Later on I'm going to finish up the prep on some .223 cases so I can load them up with the best out of the results of my ladder testing of Hornady's 68 grain BTHP 24.1 grains of Varget plus or minus 0.1 grain. Soon I probably will invest in a chrono since I only have a couple of pounds left of that can of Varget.