.243 dirty burn... powder fouling?

[the new guy]

I recently had a stainless .243 built and have been building loads for it but have had problems with H-4350 and varget. Ive put about 70 rounds through it so far so not quite broken in yet. Am loading 38 gr of 4350 with wlr primers and Hornady 100 gr BTSP; if I don't dry patch the bore every 3 shots accuracy goes from .4" to 1.2". Also, when I clean the bore I get soot... large amounts of soot... billowing soot. I've never seen this before!
I talked to some folks that claimed powder fouling. Switched to Varget with a fed 210 match primer, same story only not quite billowing, accuracy goes after 5 shots. I've had this problem to a lesser extent with the 75 gr V-Max over 40.5 gr of varget with both primers not as much fouling (I can still see it as a fine black cloud leaving the bore just ahead of the patch) but again accuracy is gone in 5 shots. Any body know the culprit? should I look for a ball powder or perhaps (hesitation) a magnum primer? I'd really like to go whack coyotes without hauling a rod and a pocket full of patches. any help would be greatly appreciated.

 

[GooseGestapo]

The H4350 is a tad on the light side (starting load according to most of my manuals). I Found best accuracy at 41.5gr, and max at 42.0.
The Varget load is bit on the heavy side.

I found with the .243 Stevens I had, best accuracy with Varget came at 38.0gr under a Sierra 80gr Soft Point. But that wouldn't explain the fouling.

With the 100gr bullet, try RL-22 @ 42.5gr, "standard" Large Rifle primer and oal at 2.625". With either the Hornady or Nosler B.T., my Stevens would shoot near 1-hole groups (5-shots at 100yds) and showed no propensity to foul or walk the groups. But, the Savage/Stevens barrels are some of the best factory barrels in the industry and are "free floated" from the factory.

I suspect that either you have a rough bore with "loose spots", or a bedding problem with the barrel thats causing it to "walk" as it heats up. If you stop and remove the bolt long enough to run a patch or two through it, you're stopping long enough for the barrel to cool which will allow the barrel to return to zero.

The loads you listed shouldn't be producing any more fouling than nominal for factory ammo. I suspect you have a problem other than the powder fouling you mentioned. If the fouling IS the problem, it's being caused by something else !!!

You didn't say what kind of barrel other than SS, so there's a lot of other possibilites.

 

[the new guy]

Gestapo:
The action is a Montana 1999, 415 stainless, with their barrel, 25" long in a light varmint contour 1 1/4" @ the chamber tapered to 3/4" @ muzzle, 416R stainless. The way I've been shooting so far is one round every 4-5 minutes, dry patch it every 5 rounds (since I noticed the problem... these are the Varget loads).
The first 15 rounds I put through it were in fact starting loads with 4350 and after the first five I patched it and could barely push it through. that's when I noticed the most soot. For the remaining rounds I patched it every 3 rounds (easier to push through but still dirty) and haven't shot that load since. I did try the same charge of 4350 with Fed 210 match primers for 5 rounds with only slightly better results.
Since I stated this whole process I have noticed less fouling... slightly, so I may just be slowly breaking the barrel in and needlessly obsessing about a problem that will sort itself out in another 50 rounds or so,after all this is the first NEW stainless barrel I've shot, and everything I've done has been at the recomendation of the builder... it's all new to me! After a while I'll load the same 4350 loads as the first 15 and see if the soot repeats.

I did load some H 450 with WLRs under the 75 gr BTs last night and they seemed fairly clean but accuracy was moderate and will take time to sort out. As far as the "walking" is concerned, the barrel is floated with a .005" gap under the chamber area and about .050" gap from there forward (another 6"...I never had much use for a long forend) and I have never had the barrel any more than warm to the touch.

I would really like to salvage the Varget load as the first 4 I can put in the same hole but that ever elusive 5th just won't join them for the party... it likes to be by itself I guess.

Thanks for the info on the RL 22, I'll pick some up next time I'm in Phx. and see what it does. Until then, I'll experiment with what I have on hand.

If you can think of anything else, let me know.
Thanks, Shawn

 

[GooseGestapo]

RE; Fifth shot...

You may have a heat treating issue with the barrel. The barrel may not have been sufficiently "stress relieved" after machining resulting in the last shot flyer.

This is an area where cyrotreating could be a significant help.

I know your frustration. I've got two rifles, one with a custom barrel, the other a factory rifle that demonstrate the same characteristic. Fortunately, both are big-game hunting rifles and it's not a big issue.

Also, this is an area where shooting the rifle actually improves the issue. Now that you have the barrel shot-in, I'd run a string of about 20rds through it to get it thoroughly heat soaked and then let it cool down. I've seen this "cure" the fifth shot or sometimes "walking" groups. Partially explains why your barrel continues to improve.

On a side note; A friend had a similar problem with a Cooper varminter he had built in .25/06. We kept experiencing the same thing with noticeable verticle stringing. He sent it back to Cooper, who pronounced the rifle "OK". (It would shoot "one-hole" on their 40yd range, but only 1-2" at 100yds. He finally in despair allowed David Sams (now located in Cartersville,VA), a former USAMU gunsmith to "Blue-Print" the action and set-back the barrel and re-threaded the barrel, re-cut the chamber, and rebedded the stock with pillar-bedding.
After being "re-worked", it'd shoot in the "high 3's" with 55.0gr of H4831SC under a 100gr Sierra MK.

You may have to consider this.............

 

[OKIE2]

My ruger 77 mk11 shoots .5 10 shot groups @ 100 yds. with 70 grain sierra smk's.
the load I use is
IMR 4064---42 grains----3540 FPS
no cleaning problem ever

 

[243winxb]

IMR 4350 is a better choice for the 243win. then H powder. The powders are NOT the same in performance or burning rate. A good all around bullet choice is Sierra gameking 85gr HPBT #1530. CCI Br-2 primer. IMR 4350 will burn cleaner as you get near the max load. If you want bench rest accuracy, look for some Berger bullets in 68gr flat base, or there 90gr HPBT match bullet (hard to find). Over all , your problem may be in the gun, not the ammo.

 

[the new guy]

So, here's the latest: the sooting problem I'm laying down to a new barrel. I just recently loaded 10 of the same rounds I started with and had no issues with them. I have shot around 170 rounds by now and I think the whole problem was a slightly rough bore ( even though Montana laps them at the factory) which by now is broken in. The fifth shot being slightly off has been a thorn of a larger sort. I shot the 20 round string (1 1/4 moa ) and then took the stock off, painted the barrel with a thin coat of zinc antisieze/oil mixture, bolted it up to see if transfered to the bedding material... it did. As I sat there gazing at 2 silver spots at 4:00 and 8:00 in the barrel channel 2" in front of the recoil lug it all became clear! After milling out the excess bedding and working up a completely new load , as the most accurate load I had was now useless (that tells me the barrel was most likely touching even when cold), I'm back down to 1/4" full 5 shot group with a warm, slightly dirty bore. I'm pretty sure I can get it a little tighter but that ain't bad. COYOTES BEWARE!!!!!

One more thing: Thanks to all for the suggestions and input!!! It helped quite a bit. I'll keep you posted on my progress...