Guys,

Been reloading many years and I have a problem I cannot figure out.
Worked up some loads 2 weeks ago.
2400 14, 14.5, 15G with the 155G lee cast.
IMR 4198 18-21 grains.
All seemed to shoot fine, but the 2400 would not cycle the bolt.
I only loaded 2 or so of each so while it hit a 9 inch pie plate at 25 yards, I didn't have great or bad accuracy.
Not really enough to focus on, I was watching for pressure changes, and cycling issues.

This week-------

7.62x39 reloads in sks.
20G IMR 4198 155g lee cast sized .311 with check.
4 power scope on rifle.
Missed target at 50 yards (9 inch pie plate)
Moved up to 25 yards and got some cardboard behind it.
Almost spraying one shot 10 inches high, one 10 right, one left, one low.
(from a bench rest no less here).

So I thought scope must have come loose. Nope.
Got out some reloads of 125G jacketed.
3 shots in about a 1/2 in group.

Shot 3 more cast, and spraying. (20G 4198)

I had 3 rounds left of IMR 4198 at 20.5 grains. (loaded 2 weeks ago)
Shot those - one inch group at 25 yards.
I had 3 more of the 20G 4198 left and I shot them and back to spraying????
What the heck?

Did some more jacketed, and put some bullets in bullets.
5 shot group of an inch at 50 yards

All bullets were cast, then tumble lubed with Lee Alox, then dried, then gas check and thru lee push thru .311 sizer.
Then tumble lubed again, dried over night (or a week ) and then loaded.

Each charge was weighted.
Primers out of same 100 box.
Power out of same bottle.

What was different between 20.5 grain load that is accurate and the 20G that sucked:

20.5 grain loads, bullets didn't seem to have as much lube on them
20.5 cases were tumbled in media before loading
Bullets not wiped clean of lube of sticking out bullet after loading.

20G sucky loads -
.5 grains less powder
Didn't tumble cases, just wiped them off, since I only had 10
Wiped bullet sticking out of case

That's all I can think of.

Ideas?