I have reloaded for about a year now for both my 25.06 and my .308 with great results. I recently acquired a older Model 670 chambered in .243win. One trip to the range has me questioning the reloads I made for this rifle. I loaded some Federal brass with Win large rifle primers, 105 grain Speer spitzers and 40 grains of IMR 4350.The dies were new(LEE) and I full length resized. The fired cartridges have a very distinct black smudge down the neck covering almost the entire neck. Some factory loads that came with the rifle look fine.Any Thoughts where I should be looking? The groups were about 2 inches at 100 yards.

The necks are not expanding enough to seal the chamber. If you do a Cerosafe cast of your chamber, you may find that the neck in the chamber is oversized. If that is the case, you need to rechamber. You might try anealling the case necks to see if they seal the chamber quicker, but that is only a temporary solution..

Soot on the bneck/shoulder generally indicates pressures TOO LOW to obturate the case neck against the chamber wall. Gas blows by the outside of the case neck, leaving soot on the outside of the case!! I don't know how hot your charges are FOR YOUR GUN, GIVEN THAT ALL RIFLES ARE INDIVIDUALS, but it seems you could increase them somewhat, and perhaps this will stop. Since the other loads didn't do this, it has to be that batch of ammo-somewhat underloaded! NOT YOUR CHAMBER, if it works OK for other ammo!!

Based on some interpolation I did between Quickload predictions and smoked necks and brass expansion, you can assume you are in the 50,000PSI range with that load, assuming you run standard brass with something like a .014" neck thickness.

My 223WSSM (.020" neck") shows soot nearly to 55,000 PSI, due to the very heavy brass. My PPC (.009" neck) quits sooting about 45 - 48000 PSI.

Again, this is based on interpolations and best guesses from matching Chrony speeds to Quickload predictions, but I have some confidence in them.

All that is a long way of saying: put some more powder in, and it'll go away. Assuming, of course, you aren't at max, and no pressure signs are present. FWIW, Dutch.

It's more likely to happen with slower burning powders, which have a slower rise to peak pressure and may not be high enough to obturate the neck before the bullet base has left the case mouth.

I shoot a number of loads that blacken the case neck and don't worry about it. It is possible for this phenomenon to go further, though, with gas getting down around the shoulder of the case before the neck obturates. Then when the pressure drops inside the case, gas is trapped between the chamber wall and case and collapses the case shoulder. I've only seen pictures of this in loading manuals, it's never happened to me.

I'm with Ricochet. I get soot on most of the stuff I reload, but it has not affected accuracy in the slightest.

You can try to go hotter, or check the chamber dimensions, but for now I think you're fine.

I have a 7mm Rem Mag that has always sooted the case necks and I have no intention of rechambering! I feel that it is perfectly normal! This is especially true with cases that have short necks!

in the worsd of officer bar brady..

"move along, nothing to see here"

It's the chamber pressure is FINE, just lower than what the brass requires. It wont hurt a thing, if the load is fine, keep shooting. if it's not, go with a slightly faster powder and reduex load dev

jeffe

No problem-o. After checking fired cases for proper neck/bullet clearance, toss 'em into tumbler. "Soot" marks will disappear!