Two good loads for 5.56?

G

Grizz12

New member
I was testing a new powder for my 5.56 and decided to make test loads starting on the light side of .223 and work up to the high side of 5.56 in .5gr. increments. The results were interesting and not the first time I've seen this but this is the first time I've mentioned it online to get some feedback.

Tested at 50yrds, groups were half inch up to a little over 1". All groups were nice, no stringing in any direction, but some were better than others. Wind was steady and mostly from the rear but swirling in the shooting lanes. Cheap sand bag rest. Cheap scope set on 7 power. Brass is once fired, not matched.

The best 2 groups (5 rounds each) had three making one hole with two flyers. Eliminate the flyers and the groups were down to a 1/4" ragged hole.

Here is my question, the two best groups were the lightest load and the hottest load. Typically I see the groups getting tighter/wider as I move up and down the powder weight, how can the best groups come from total opposites?
 
If I were to guess, and purely a guess based on the little information provided I would guess a matter of Barrel Harmonics and subsequent Harmonic Nodes. You may want to just Google those terms as it can get pretty in depth. Would be nice if you had velocities? A matter of at what point on a curve the bullet exits the barrel. You also do not mention the powder, bullet used or loads not to mention rifle or barrel length and or twist so Barrel Harmonics are my best guess.

Ron
 
I used the same powder, bullets and gun in the tests and the only thing that changed was the amount of powder. How would providing that info change the reasoning behind what happened?

The rifle is SR556
powder is TAC
bullets are federal, 55gr blitzking
Loads are min .223 - max 5.56 as recommended in the TAC loading manual
I didn't chrono anything so the velocities are whatever it says in the manual
 
Grizz, how many 5 rounds groups did you fire at each powder interval? The way your post is worded it sounds like there was just one group at each interval. I would take your two best groups, load 10-15 rounds, and then have a shoot-off with groups averaged. A one off group can frequently be a fluke. It's also rare (as in never) that minimum load achieves the accuracy I seek in a rifle. That's just my experience, I understand there are exceptions to every rule.
 
I've been reloading on and off since the early 90's and like you its rare that the weakest load is the best.

This time out I only had 5rnds per load
 
50 yds won't show much dispersion for rifle rounds...I'd move it back to 100 at a minimum...200 if you can find the space. Rod
 
You must log in or register to reply here.
Back
Top