Nice shooting. If you can get them, try Sierra 77 gr TMK and/or 80 gr SMK over Varget.

Second range session with the gun.
This time I loaded some good rounds.

Lapua brass
CCI 400
Varget
69 SMK

25.6 Gr of Varget is the winner. It shot in the 0.2s at 100Y for two consecutive 5 shot groups.

I'm pretty impressed by the accuracy of this rifle.

I can see why.

That'll work.

Nice shooting, were you using your Harris bipod when you shot those groups?

Thanks.
Yes, I was shooting with the Harris bipod and a rear sand bag. Yesterday was pretty windy, so who knows....maybe it can do better than that with the 25.6 gr load.

For the next range session I'll load some more of the same 25.6 gr load with the 69 SMK as well as some 77 gr Midway factory second bullets (looks like 77 SMK).

The rifle is obviously very accurate. But I do have a reliability issue. On all my 3 mags (1 MDT, one accurate mag with the front polymer sanded to take longer rounds, one new accurate mag), I'm having some sort of nosedive issue.
I was shooting the new accurate mag during the last session and the 8th round would nosedive into the mag most of the time.

I think the recoil is moving the rounds forward into the mag, causing a nosedive. I'll just have to experiment a little more.

BTW I was having a similar issue before the barrel swap.

I have a similar issue with a .257 Roberts on a long action. If I don’t pay attention to how I load them they nose dive. Maybe tap the Mag to back before inserting it, I’ve saw it done but never tried it myself. It seems though if you had to work to get clearance there wouldn’t be enough walk available to cause a problem. 10 round mags = weak springs with only a couple left.

Tapping the mag doesn't do it.
I think I've found the issue.
2 of my mags (MDT and the new accurate mag) seem to have an issue.
I'm able to manually do a nosedive.

On my other accurate mag (front polymer sanded), I simply can't push the front of the round down to have nosedive. When I push the front of the round down, I can't push it forward at the same time (which I can do on the MDT and the new accurate mag). This has nothing to do with the front polymer being sanded, but everything to do with the geometry of the mag (probably the lips are tighter?)Now that I think about it, I don't recall having a nosedive issue with this mag. I didn't have this mag with me last time. I'll confirm next time. But if even by manually forcing I can't cause a nosedive, I'm pretty sure this mag will work fine.

Another outing with the gun.
I loaded a few rounds of what I though the gun likes (69 SMK, 25.6gr Varget).
It did not shoot as well as the last time. Not sure what's going on.

The gun was reliable with my other accurate mag. The nosedive is a mag issue.

I replaced the AR scope mount with low rings. It's much more comfortable to shoot and now I don't need a cheek riser.
Today I shot the gun with the same load (25.6 Varget, 69 gr SMK).

What is remarkable is my first 5 shots , from a squeaky clean barrel and with the new scope rings (that was not re-zeroed)was an impressive 0.352" right in the middle with POI=POA

The average for the first 3 five shot groups was 0.356"
For some reason the last group opened up bringing the overall average to 0.419".

The other notable thing is that I got a couple of pierced primers. I don't know if it's because today was a little warmer or the barrel has speed up, but going forward I'll drop the charge by 0.3 grains.

I’m pretty sure the pierced primers was because of too much resizing. I say that because last time I got a couple of pierced primers even with the lower 25.3 gr load.
This time I only neck sized the brass. With 25.3 gr I had no issues and no signs of pressure. Next time I’ll bump up the load to 25.6 gr which is what I think the gun likes. But even 25.3gr seems to work pretty well.
With 25.3gr I got an average of 0.374” for 3 consecutive 5 shot groups.
I tried lighter loads (24 and 24.3 gr) and the gun didn’t shoot them that well.
I also shot a 5 shot group (0.548”) of factory ammo (77 smk Norma Match)

The gun was100% reliable.

Quit messing with powder charge and buy some headspace gauges.

Set the sizing die to bump the shoulders .002" and move on.

You're chasing your tail with too many factors. Clean vs fouled, variable powder charges, you are making this difficult for no reason.

Glad you fixed the reliability issue. Your 69 SMK/25.3 Varget load looks good, Are you using CCI 400 primers? I've had them pierce when running higher pressure loads. Cups are thinner than some other primers.

When I resize, I usually turn the die by 1/8 turn until I can easily close the bolt on the empty case.
I was going through my reloading stuff and noticed that I also have a 223 Wilson case gage that I rarely use.

Yes I'm using CCI 400. But initially I went up to 25.9 Gr with no pierced primers.

Why this way instead of measuring the fired case and sizing a thou or 2 down?

JG, are you suggesting that he should use a Go-Gauge to set his sizing die? I have not thought of doing that.

No, not at all. He is suggesting headspace comparator gauge or something like that. The names seem to vary but the following is the most common one by hornady.

https://www.hornady.com/headspace-bushings#!/

Many others out there. This way one is measuring to the point on the shoulder that makes measuring how much the brass is sized MUCH more consistent.

Edit: some others
https://www.sinclairintl.com/reload...t-style-bullet-comparator-prod34014.aspx
https://www.shortactioncustoms.com/modular-headspace-comparator-body

Thanks for clarifying KR