The finer points of load development

[thunderbolt]

I've been reloading for all of six weeks now and I have to tell you that it's been an eye opening experience. I just got back from the range where I tested my third batch of 50 reloads for my AR. This last batch was to "fine tune" the powder charge of my general purpose load. The final results surprised me and ran counter to everything I was told or thought I knew about reloading.

My first batch was a broad range of charge weights starting with 23.0gr and running about .5 gr up to 26.1 gr. The powder is Varget btw. The best charges were 24.2 gr and suprisingly the 26.1 gr. Both grouped around 1 - 1.5" @ 100 yards.

The second group was a small batch centered around the 24.2 gr. Running .1 gr increments with 10 rnds per charge value again the 24.2 grouped @ 1.69" but both the 24.3 and 24.1 charges opened up to over 2".

Now here is where it gets weird. The third batch centered around the 26.1 load was the same, with the 26.0 and the 26.2 charges grouping almost an inch larger even though it's only a .1 gr difference. On average the 26.1 gr load was the best with average groups of 1.24" @ 100yrs. None of the groups were horrible ranging around 2" but still weird.

I was under the impression that lower charges gave more accurate loads but that's not what my rifle likes apparently. So after three trials it looks like my best load is this:
55gr FMJ-BT (Berry's MFG)
26.1 gr Varget
COL = 2.256

I'm excited to try some better bullets and have two more powders I'd like to try but as of now I'm still trying to wrap my head around this and get enough
nerve to try other calibers. I haven't played with seat depth and I know I load them kinda long. Any ideas why it works like that?

[freonr22]

barrel harmonics?

[bruceflinch]

14 years of reloading & I'm not even halfway there...

You're limited to COAL by your magazine. In a bolt gun, you seat the bullet to just about touching the lands of the barrel.

[locosway]

Different guns like different things. Just because one person runs a lighter charge and is accurate, doesn't mean your rifle will like the same load. Even if you have the same brand and model of rifle, there are differences in how the rifle was manufactured.

From what I've seen, it's usually the middle loadings that seem to give the best accuracy. Working up your load is all about finding what your ONE particular gun likes, and then running with that as best you can.

As Bruce said, in a magazine fed gun you're limited on your OAL by the magazine. On a bolt you get close to the lands. From what I've read, this is because the bullet will "jump" from the cartridge to the lands and then stop until the pressure builds enough to push it down the barrel. So you're trying to find the distance that, again, your rifle likes best in regards to this.

[sonnyt650]

There's a different style of load testing which involves longer ranges -- I believe 300 yards is suggested -- and shooting a single round at each load which are spaced like 0.2 grains apart. The idea is to see which sequences (for example shot #4,5,6,7; then #12,13,14) land close together so that you "know" you've got a node which is less sensitive to change in powder charge. There are variations on this theme, but yeah to prevent getting those 0.2 grain wide nodes this would be one way to go.

Not having any ranges near me that go out that far, I haven't tried this myself in the suggested form. I have shot this way at 100 yards, but the difficulty is keeping track of where bullets land and I failed to do this well (I've read good things about using different colored Sharpies on the bullets themselves). I do notice though that when I vary the loads trying to find a good one the POI changes relative to the POA across the sets, so this seems to have some merit even if I couldn't get it to work for me.

[popeye4]

There's a different style of load testing which involves longer ranges -- I believe 300 yards is suggested -- and shooting a single round at each load which are spaced like 0.2 grains apart. The idea is to see which sequences (for example shot #4,5,6,7; then #12,13,14) land close together so that you "know" you've got a node which is less sensitive to change in powder charge. There are variations on this theme, but yeah to prevent getting those 0.2 grain wide nodes this would be one way to go.

Not having any ranges near me that go out that far, I haven't tried this myself in the suggested form. I have shot this way at 100 yards, but the difficulty is keeping track of where bullets land and I failed to do this well (I've read good things about using different colored Sharpies on the bullets themselves). I do notice though that when I vary the loads trying to find a good one the POI changes relative to the POA across the sets, so this seems to have some merit even if I couldn't get it to work for me.

I've used this method as well, with excellent results. 100 yards is quite short to really be able to see a difference (MOA distance between rounds gets bigger the farther out you get, but the holes stay the same), but if that's all you've got... I have also seen more than one "stability node".

To the OP: your loads seem to be VERY sensitive to powder charge. It is going to be extremely difficult to reproduce loads with less than 0.1 gr. variation. How many repetitions did you fire? That is, how many groups at each powder charge did you fire? If only one, I would question the validity of your statistics. What sort of sights do you have on your rifle? Are you confident you can hold consistently enough (with clean trigger break) to attribute the variation entirely to your ammunition?

[Fjold]

The Audette ladder method is what you're describing.

The bad part of it is that it works best at longer ranges and having to mark every individual shot is very time consuming unless you have a rifle pit and someone there to mark each bullet hole in the target as they are being shot.

[thunderbolt]

To the OP: your loads seem to be VERY sensitive to powder charge. It is going to be extremely difficult to reproduce loads with less than 0.1 gr. variation. How many repetitions did you fire? That is, how many groups at each powder charge did you fire? If only one, I would question the validity of your statistics. What sort of sights do you have on your rifle? Are you confident you can hold consistently enough (with clean trigger break) to attribute the variation entirely to your ammunition?

Each powder charge loading consisted of 10 rnds with two 5 rnd groups being shot. In total I had 4 groups of most load values, a few that had just two, and the 24.2 gr and 26.1 gr loads both had 6 groups. I also threw in some commercial Fed XM193 as an added bonus.

My rifle is a SS 16" 1/8 twist barrel with a carbine gas system. It has a Burris AR332 3X red dot zeroed @ 100yrds. I don't have a full size gun vise but I shot all the groups from a table in a fully supported position. I'm not sure if the variations are from my shooting but I consider myself a decent shot with good technique. It could very well be me. I still new to reloading.

If I had a quite place to shoot I'd like to try Audette ladder but I the places I frequent are usually crowded. Thanks for the info though I'll file it away for later.

[noylj]

Just based on my experience, what you have is a trend.
I have never found a load for a rifle that could tell +/- 0.2gn. You are looking at a 0.2% difference in load and that is just too small to be real.
Before you lock yourself into a load (though it will be a good load, I am sure), load up a few more and shoot them to confirm your findings. Also, shoot them randomly so you don't know until after you have fired a set what the load was. You would not believe how much even a subconscious "liking" will let you shoot better.

[popeye4]

Each powder charge loading consisted of 10 rnds with two 5 rnd groups being shot. In total I had 4 groups of most load values, a few that had just two, and the 24.2 gr and 26.1 gr loads both had 6 groups. I also threw in some commercial Fed XM193 as an added bonus.

My rifle is a SS 16" 1/8 twist barrel with a carbine gas system. It has a Burris AR332 3X red dot zeroed @ 100yrds. I don't have a full size gun vise but I shot all the groups from a table in a fully supported position. I'm not sure if the variations are from my shooting but I consider myself a decent shot with good technique. It could very well be me. I still new to reloading.

If I had a quite place to shoot I'd like to try Audette ladder but I the places I frequent are usually crowded. Thanks for the info though I'll file it away for later.

The nice thing about the red dot sight is you only have two points to line up, but how big is the dot? Sometimes they are several MOA in diameter, making precision shooting difficult (red dots aren't meant for precision shooting). It isn't necessarily the hold, it is the ability to ensure that the dot is truly in the same place each time on the target. I haven't shot with red dot sights, I use either iron or scope, but on some days I just have a hard time reproducing the sight picture for every shot with irons.

I knew there was a name for the Audette method, I just couldn't remember it.... senior moment! It is time consuming, but if you can find a 200 yd range and can borrow a good scope, you can do it from the bench without visiting the target each time. You just have to be meticulous in your recordkeeping and not shoot so many rounds that you lose track. Hopefully, you only have to go through that pain once.