Accuracy testing opinions needed

[Ccctennis]

I did my first big load development test this week with my 220-swift. I used a round robin system that I read lots of reloaders use. I need help deciphering some of the results. Here are the powder charges and group size:
Powder varget. Bullet hornady a-max 40 grain. 100 yard test. .4 increments.

36.8 gr. .6 inch
37.2 gr. 1.0 inch
37.6 gr. .75 inch
38.0 gr. .9 inch
38.4 gr. 1.5 inch
38.8 gr. .5 inch
39.2 gr. 1.0 inch
39.6 gr. 1.4 inch
40.0 gr. 2.0 inch
40.4 gr. 2.0 inch
Some questions I have regarding the test.
1. What is the next step in continued testing loads?
2. What do the up and down sizes really mean? Does it mean with barrel harmonics that my rifle shoots better with lighter powder charge and a heavier one. 36.8 and 38.8?
3. Do I take the best two or three weights and shoot more or do I tinker with coal?

 

[Blue68f100]

You found 2 nodes that shoot in your gun. Now the next step is to shoot those again and see if you can duplicate it. Then work each side of the node and see if it improves or get worst. You then will have a load range , pick the middle for consistency. You can after that is play with the OAL and see if there is more improvement. Shoot longer distance will help fine tune it.

 

[spitballer]

Agree with previous post, I get two nodes also with .223 bolt action rifle and focus on the lowest node to control fouling. Also agree that longer distances are more revealing and worth a hike. I have been using 300 yards, fact I was out this morning at 300 to finish dialing in a load for a 55 grain varmint bullet. Felt kind of silly cleaning the barrel after every 5-shot target while the rest of the guys were firing away continuously, but it was worth it. Highly recommend starting each group with a clean barrel when working up a load with softer bullets; tolerances are very, very tight within the bore and copper fouling, especially, will make group comparisons worthless. FWIW I've learned that a full case of slow, dense powder is best for propelling soft varmint bullets without smearing them all over the bore, but you'll need a decent-size barrel to take advantage of it. I use H414 for my .223 and would be looking at US 869 if I had a 220 swift. Others may disagree.

 

[Sunray]

I'd be inclined to load a bunch of ammo with 38.8 and forget about the under minimum loads. Go hunting. 36 of Varget is 2 full grains under minimum for a 40 grain bullet.

 

[BigBore45]

with those groups at 100 yards, its no bench rest gun, so go with the 38.8 at .5 inches and enjoy.

 

[Ccctennis]

Load data

My book doesn't say I'm below minimum.

 

[Ccctennis]

I always use the manual from the projectile company I'm using. Sometimes I cross reference when I'm in an unusual size or oddball powder.

 

[witchhunter]

I would look at 38.8 and adjust your length to see if there is any help there. I usually start around .015 off the lands. You should see improvement either shorter or longer, try .002 at a time. I also wouldn't trust just one group. I shoot 3 of each weight and average the group sizes.

 

[gamestalker]

With many of the rifles and cartridges I load for, I often end up very close too or into the lands. Though not all have produced best accuracy when touching or jammed, this is where I've located the majority of my accuracy.

A word of caution though when working up very close to the lands, and especially when touching or jammed. I start my powder development at the OAL that will be the closest to the lands, which for me is usually touching, because that is where pressures will run the highest. It helps ensure I won't have any high pressure surprises during the process.

GS

 

[Walkalong]

See if any of those can repeat before you load a bunch.

 

[Ccctennis]

Thanks for all the good advice. I will continue to work for a larger data set and see what it looks like.