Redding S neck die made a marginally better difference. Did not solve the velocity spread. I'll keep looking, the groups were better with the Redding die. :-)

It is possible to have a load that yields inconsistent velocity yet groups well, but what you may find is that if you extend the range you're testing these loads at then more vertical spread will show. It could be that Varget just isn't going to yield consistent velocity and you might try something like Re15, H4895, or something else.

What can happen is that you hit a node where the bullet is exiting as the muzzle is approaching the top of its excursion. The theory is that if the bullet is moving just a tad slow it will exit a little later with the muzzle pointed just a tiny bit further upward which makes up for the increase in drop, due to increased flight time, due in turn to the lower velocity. This phenomenon can work for you to make up for velocity variations, but it will only work well within a limited range of distances.

Testing at 200 or 300 yards might dissuade you from thinking the accuracy really IS good, which in turn can make the decision to switch powders a little easier.

Get a balance beam and check you weights, The 270 is a larger case and slight variations in powder do not have the impact on charge like the smaller cased 223. Do your modified ladder test again at 200/300 on a calm day. Possibly change powder. The 80 grain smk's like R-15. How many rounds fired, think anneal.

Have you verified your chronograph is giving you accurate data.

Thanks for the responses. It may be the chronograph, and admittedly the 270 small SD number was a 5 shot sample. I had a SD=8 for the first 5 rounds of my last 223 string.

I think a new powder is next. and I'll dispense and balance beam weigh each load. I do let the Chargemaster warm up, out of drafts...etc. If the elementary math I did is on track, I would need a several tenths swing in charge weights to cause the velocity spread I'm seeing. I have the tools to check and I will.

It would seem to me that during testing, velocities should be consistent for each load, no matter downrange results. So if true, it shouldn't take many rounds to find a more consistent powder. Any experience otherwise? I do have some RL-15, 4064, 4198, BLC(2) and TAC on the shelf.

I didn't read quite all of this, but most. Something I didn't see anyone mention was clean barrel or fouled. I would assume that could cause a large range in the first few shots on a clean barel as opposed to a fouled one.

Could be the chonograph. May want to shoot through a friend's to see how it reads.
Could shoot a known good sd batch through your's, say Fed GMM 168's or something.

Ooops not 308, but get some match ammo and check the sd with your chrono.

I was using 25.4 gr of varget over SGK 65's in 223 and getting good sd, not spectacular,
+- less than 15fps so about 30.