Blackened cases

CamoWildcat · Mar 28, 2006

Went out to the range today intending on grouping some loads in 3 rifles. Raining, (yeah, in Arizona) so I decided to sight in the 3 rifles (because I switched some scope mounts around and added lock-tite) and call it a day. After firing 4 rounds in my 223 WSSM, I noticed the brass cases had quite a bit of black powder burn all the way back to the base. I'm shooting 44 grains of Varget pushing a 50 grain moly coated bullet between 3800 and 4000 FPS. Thats another puzzling thing - my 4 shot averages vary between 3800 and 4000 FPS with the 44 grains of powder. The only variable is bullet seating depth which ranges from .010 to .060 off the lands. I would say air temp has varied from 60 to 80 degrees.
Any ideas or suggestions? My best guess is the brass is a little under sized and it isn't expanding enough to fill the chamber. I didn't notice this problem shooting reloaded factory nickle cases. And I've got no idea why my velocities vary so much.

JD338 · Mar 29, 2006

CW,

Is your powder charge a starting load? I am wondering if you are not getting enoough pressure to seal the chamber. The 200 fps spread could be a result of not filling up enough of the case capacity.

You might want to look at increasing the charge weight (if you are on the low end) or try a different powder.

JD338

Eagleye · Mar 29, 2006

Smoked outsides of cases indicate very low pressures. The case has failed to seal the chamber at the throat since insufficient pressure is ther to push the case out tight to seal the rest of the chamber. Work up till this stops and then graph it. You will see a lot better consistency once you are not losing some of those gases back through the action. Regards, Eagleye.

CamoWildcat · Mar 29, 2006

Thanks 'JD338' and 'Eagleeye',
Actually Hodgdon states 44 grains for a max Varget load. And Nosler states 42.5 grains. The Lyman 48th edition states "On average, moly coated bullets resulted in a three percent reduction in chamber pressure and a one to two percent reduction in velocity compared to uncoated bullets". Applying logic to that statement would indicate I should be able to increase Hodgdon's max load to 45.3 grains. Since I'm not seeing any pressure signs, I think I will increase in .5 grain increments to 45 grains and see what happens.
Thanks again, Gentlemen.

rick smith · Mar 29, 2006

excess oil in the chamber will also cause blackened cases.Rick.

clearwater · Mar 29, 2006

poorly annealed brass or work hardened brass can contribute to the problem by
preventing good exansion for a seal.

R Flowers · Mar 30, 2006

Well, the problem is basically due to the very thick brass that Winchester uses in the .223 WSSM. The one I had would smoke cases all the time with 40 grain bullets even when loading max and getting 4600 fps on the chronograph.

If you will look at or measure the case necks you will find they are VERY thick. I always got blackened cases with any loads using 40 grain bullets and with 50 grain bullets till I got close to maximum.

The other guys are right, smoked cases usually means low pressures. I get smoked cases all the time shooting cast bullets in my 7-08. However, in this case the pressures are probably right up there, it is just that those necks do not make a good seal.

Why you are getting so much velocity variation is more puzzling to me than the smoked cases, however.

CamoWildcat · Mar 30, 2006

Thanks Gentlemen,
Yes, I am very puzzled about the large variation in velocity. After cleaning, I squirt a shot of RemOil up into the chamber area. So a combination of that and thick necks on the brass cases could be causing the black. The black doesn't coat the cases uniformly, so it could be oil getting burned.
I'm heading out of town to Cleveland to televise boxing on Showtime, but when I get back, I will be trying a half grain increase in powder and some loads using H4895. I will also clean the receiver area of any excess oil and see if the black persists.
Thanks again, Guys.

Hegland · Jun 1, 2006

Had the same problem from my 243. I bumped up from a 55 to 58 grain bullet and it quit. But, I did have to back off the powder a grain or two to keep the groups.

clearwater · Jun 2, 2006

Oil in the chamber is a no-no. It increases back pressure on the bolt and could be
part of the sealing problem too. Wipe that chamber clean before you shoot.