VV-N133 + 70gr Varmageddon

[notagrendel]

notagrendel... do you have any factory ammo & if so, does your rifle cycle with it? It could be your gas system doesn't work well with either of those powders. This is where an adjustable gas block come in handy.

Since I haven't tried IMR4198, & I'm just guessing, it looks like you could have started with a bit more powder. I haven't seen any 6mm ARC loads anywhere with IMR4198 so, like you, I'd have to use the 6PPC as a starting point. Since the case body of the 6mm ARC is 0.027" longer than the 6mm ARC I would probably start at 23grs & work up to 25grs in .2gr increments with the ARC. Not saying you should do that. It's what I would do. I would be keeping an eye out for pressure signs & stop shooting if I see any before reaching 25grs.

I noticed in the Hodgdon manual that for the 6 PPC they only have a one or two grain differences between starting & max loads using IMR4198 with any bullet, 55 to 80grs. That's a pretty narrow load range. Since it's a fast burning powder, I guess it can reach max pressures pretty quick. I used to use IMR4198 shooting cast bullets in my 45-70 Rolling Block. The load range is narrow for that cartridge as well.

I'm not familiar with MP405 powder. Is it Vihtavuori over-run N133 re-labeled as Midwest Powder? I did a little digging & found a site that says to use Vihtavouri data minus 10% for starters with MP405.

Aren't doing load work-ups fun? I think so! :-)

The gas setting is set up with 108gr Match (6 clicks with an SA AGB while running a can). I verified it running a few rounds after the test.

I based my starting points using the Lyman 50th. I found H4198 in Hornady's 10th, but not IMR 4198. After had been running 4198 in 40gr 223 Rem. I should have known that I can push it pretty good past book data, at least I have been able to push it without pressure signs in the past. Also, the 6PPC data in Lyman 50th sat their bullet 0.075" shorter than what I did.

MP 405 is overrun N133. It didn't do well in any of my 223 loads from 40gr to 60gr. In this first round of tests, velocity spreads were pretty bad, but they shrunk as the charge got higher.

I hate being a guinea pig, but someone might as well do it.