For sometime now I've been trying to figure out why I'm still seeing higher spreads than I think I should be getting. For example, over the last few days my spreads have been anywhere from 80 fps to 123 fps where i'm typically seeing 50 fps to 70 fps - and I think the latter range is higher than it should be.

So my PRS buddy that I shoot with so much, devised an interesting test. He would give me 26 sized, primed, cases to load and he would load another 26 and we would see what happens when he shoots them in his custom bolt gun.

The gun is a 24" heavy barrel chambered for 223 - not 556. Most of my guns are chambered for 556 and I've been suspicious for a while now that the 556 chamber is part of the problem with the higher spreads. Well today was test day. We chrono'd and recorded each round. He alternated between my loads and his loads. One shot from one and then one from the other until all 52 were shot.

Each set of 26 was shot at one target, i.e. his loads would be on the left dot; my loads on the right dot. So what happened? Let's start with the accuracy. Here are two of my recent targets shot with my Mossberg MVP LC bolt gun with a similar load using similar components, specifically, Sierra 77 gr MKs, Lapua cases, Federal 205M primers and 23.5 gr of H4895. The groups of interest are on the left in both pics. The groups on the right were with a different load - and I will add - what a difference a bullet made!



Then a follow up the next day with the same load,



As you can see, the groups are quite similar and the bulk, i.e. about 85% of the hits were within or better than 1 MOA. Then today, the custom bolt rifle produced these groups. The group on the left is the ones my buddy loaded and the ones on the right (middle dot, top row) are the ones I loaded.



These groups are essentially the same as the groups in the first two pics although they look a little smaller because the pic is larger, making the target and groups look smaller, but the left group is right at 1 MOA and the right is about 1.2 MOA not counting the outliers.

Then the numbers, and I'll keep this short and sweet, his loads produced an ES/SD of 48/11.6 fps and mine was 38/10.4 fps. So his loads had the edge in accuracy and mine had the better numbers.

Both his numbers and especially my numbers were better than what we had been seeing from similar loads in my guns. I think what is responsible for the improvement is the more accurate chamber in his custom bolt gun. Another thing that I've been suspicious of for sometime now is the caliber itself. Because I shoot so much with my PRS buddy, I get to see what more hmmm, "robust" calibers can do, primarily the 6mm BRA and 6 mm Dasher. The groups are about 1/2 MOA consistently, and the numbers are about half what we got today.

I don't see anything else that would make enough difference to be significant. And I would remind us that one shot was fired from one group and then one from the other. So, shooter fatigue, barrel heat, etc. is pretty well even for both groups.

I don't know what it is about the 223/556 caliber that would make it perform at a lower level than larger calibers, but there's something going on. I know for example, 223 Lapua brass is not nearly as consistent in weight, neck concentricity, and neck thickness uniformity as some of their other calibers. I believe this is because most of the manufacturers' efforts go into the long range calibers and much less care is taken with the 223 cases.

So, it looks like, and this is based on many months and many rounds of testing, about the best we'll get from 223/556 in bolt guns or semi-autos are spreads in the range of about 50 - 70 fps with, of course, a few occasional exceptions.