Thread: Understanding Group and measures

With the Howa project having fulfilled a bit of my curiosity Ive returned to an old problem child, my S&L 223. Ive shot 7 deer without a loss with it, so theres nothing wrong with it for hunting. But it does have some bad habits that were bugging me, like quite regular misfires and fliers.

So I was at the range testing various theories on its misfires (headspace being the key possibility) and I shot this group. No misfires but one round required a second go to get it away.

Heres the group Id like it to be


Not too shabby

handloads or factory rounds be a help

But here is the actual group



This group illustrates several things, firstly our tendency to try and ignore unpleasant information! It could be excused by calling the errant shot a flier (hint it wasnt pulled). It could be that it was the round requiring the second strike - it wasnt!

So how to interpret it? Well if you look at the extreme spread of the group its "blown out". However the Mean Radius tells s different story and I thank @gimp and some others for promoting its consideration as a measure.

Its a handload

And here is the next group:



Yes this rifle has issues!

There is a scope adjustment thing going on, the high shot was the first move, then I dropped it down a bit. I was a bit agast at the blow-out in it though!

Geez that looks frustrating. Maybe an argument for a return to three shot groups (joking) - you don't know what you don't know. Were you tracking velocities out of interest?

Sounds like it's buggered mate.
Give it to me and I'll takenit off you hands for cough....disposal

Scope is poked???? Mounts are loose???? Stock screws not right????

The middle group here is 27.9mm so comfortably under MOA

Have you measured case base to mid shoulder of a fired case and compared to your current "resized base to mid shoulder? The fired unresized case should be one that has had a near max charge though it to ensure it has fully expanded to fully fit grhe chamber. Another possibility is tha actual sizing die being out of spec.

Has your rifle ever shot much better than that?
What about brass consistency?
À mate of mine had issues with his 300 nm. He tossed the old brass , started with brand new ones, problem gone. Nice groups again. But on the second reload of those new brass, he had issues again with his groups. So that rifle is very uneconomical to run has it needs brand new brass to shoot well…so it seems.

Mmm interesting about the brass.
For the SL, what does it shoot like with factory loads? Maybe it's only good with factory

Originally Posted by Woody

Have you measured case base to mid shoulder of a fired case and compared to your current "resized base to mid shoulder? The fired unresized case should be one that has had a near max charge though it to ensure it has fully expanded to fully fit grhe chamber. Another possibility is tha actual sizing die being out of spec.

Yes. The measurements are relative as I don't have the correct shoulder comparator (I using a 0.308 bullet one, it's supposed to be 0.330 for true mid shoulder) but it doesn't "like" brass measuring under 1.496, most factory stuff I have here is about 1.492-1.494, and my old die set up was bumping to 1.493-1.494

Oops - cocked up the edit on the post on the fireforming groups

I think the culprit is the White River primers. They, in combination with a close to max headspace are causing inconsistent ignition. They must be a wee bit harder in the cup than some others, like the Federal 205Ms and Remington 7 1/2s I used for fireforming. In that exercise where I was using bullet jamb to "hold" headspace the WRs misfired 3-4 times in 10, the 205s 2 and the Remmys nil, and that was the best group.

The WR have been great in all my other rifles, I'm not knocking them at all, it's just them in combination with this rifle and it's kinks.