Loading 308 Winchester with 200.20x

Okay so I got an FTR gun now 30-in barrel 10 twist. I started putting together some loads for the 200.20x. I'm using Peterson Small rifle primer brass I put together an IMR 4350 load which shot nice up to about 45.5 grains but it ran out of case capacity. It capped at at 2,500 ft per second. I then put together a load with cfe223 which I've used in the past with 175 grain with no issues and I got some really weird results with the 200.20x. My velocity was all over the place. I'd have one charge that went off fine. The next it would get like a tink and it would be as much as two 300 ft per second less. The brass was really sooty on the slower velocity rounds with the odd sound and I'm assuming that it wasn't getting a proper ignition from the small rifle primer these were a book data load from Hodgdon other than coal being long. Anybody else have any thoughts on that? Also, I'm looking at testing out some VV N150 next.

Tagging in. I suspect you'll be advised to try a small rifle magnum primer with CFE223. I have a jug of this stuff for my 308's but haven't tried it yet.

FWIW, When Berger quit loading these for the 308, I asked them what powders they were using. Tech told me it either Varget or N540, depending on what they had available.

RL17 was wonderful for my 30" 308 & 200.20X.
Surprisingly N135 shot better than any other powder in cold weather.

N150 for 200.20x

I second N150. Varget is accurate but slower.

My experience and that of other UK shooters I've talked with is that 308 peterson srp brass and ball powders/double base powders not a good mix. Single base powders ignite much more consistently, showing up in really low SDs
Vhitavuouri powders 130, 133, 135, 140 and 150 suit the loads better. Favorite primers magtech srp. I have found 133 and 140 suit me best 133 probably having the edge but my marksmanship skills are limited and I'm just duplicating what the hi rollers are loading.
I feel bound to say that velocities for the 130 range are very very temperature stable, at least mine are - they won't match ball/double base powder loads velocity by 100-200 fps mv but they are good enough.
If the UK retail market is indicative of anything, 130, 133 and 135 like rocking horse crap, 140 and 150 available. Just saying my $0.02 worth, I can't say why this is but I understand that much of Vv product range is loaded into military ammo ( all the powder is blended to comply with NATO standards) and that may well be why it's in short supply as the Ukranian weather varies from well below freezing to 30 + Celsius.
FWIW, I use more cast boolits out of my Peterson srp cases with low to middling amounts of powder, currently experimenting, with some success, using Vv N120 and N110 in 308 and 30/30, though using W-W brass LRP in the 30/30.

Tagging in. I will be starting load development soon. Planning on using Varget, Lapua Palma brass (SRP) and CCI BR4's. May try VV150 if I can find.

Be curious your results.
Mine is a 8 twist 30".
At the moment shooting 185 Juggs, 450's, N150 Lapua palma brass. Settled on 2850 velocity