I'm encountering a fine "lead mist" on case necks for
my .308 Win. Does anyone have any experience with this?

I'm using Lymans 311334 out of WW weighing 205 gr with lube & gas check. Velocities are right at 2000 fps. Powder is 50.5 gr of WC860 with a WW LR Mag Primer.

The bullet fit to the throat of my rifle is about as tight as I can get it without having a sizing/swageing die made using a chambering reamer etc. I have done a throat casting on this rifle by upsetting a pure lead bullet into it. Prior to this I'd assumed that .309 was the size I needed but now I know and I'm sizing the bullets to .3105. The ogive of the bullet is well marked by the lands and the forward driving band of the bullet is also well marked by the forceing cone completely around it's circumferance.

The lube I'm using is FWFL from the batch that Felix made up and mailed out a while back. I probably need to adjust the lube for higher velocity but can't find the adjustment directions Felix posted some time back. I think I need a bit more castor oil but not sure.

Accuracy with this load is very good. I'm getting sub minute of angle groups at 100 yards. After about 10 to 15 rounds I have to swab the bore with a tight patch as I am getting leading at the muzzle. After one fouling shot the accuracy comes back right away. No real effective way of adding more lube to bullet other than adding liquid alox. I prefer not to have exposed lube if possible.

The "impact" throat / chamber casting shows that the chamber would accept a case of up to 2.065 length. My brass is trimmed to 2.015 or under so that leaves a gap of at least .050. I sized some military 30-06 brass to .308 and trimmed to 2.050 but with a bullet mounted I had scrape marks on the case neck after chambering a round and decided not to fire them. I'll try some commercial 30-06 brass which hopefully will be a bit thinner at the neck.

If this gap is allowing/causing "lead mist" to collect around the neck of the case I can only assume that "lead mist" is also being blown forward ahead of the bullet and is the cause of the leading near the muzzle.

I have not annealed the necks of my brass.

It appears several things could be at play here.

1. Lube is failing and needs to be adjusted for higher velocity. (I want to do this anyway as my desired velocity is actually up around 2250 - 2300 fps.) I don't see anything more I can do to improve the fit of this bullet to the throat

2. Un-Annealed case necks are allowing blow back /blow by in conjunction with the long neck of the chamber. If I anneal the case necks it may allow quicker / tighter obturation and preclude some of the gas cutting.

3. "Short" case necks are allowing gas blow by causing the "Lead mist". "Longer" case necks may help this. It would be necessary to closely monitor case length if this is done.

4. Plastic wads under bullet might be useful.

I've probably missed something simple.

Any information on this matter is greatly apprecitated.

Thanks, Have Fun, JCherry

Maybe your alloy is a little too soft. It takes a hard bullet to go 2000+ fps without leading.

Junior1942,

I failed to mention my bullets are oven tempered WW to a SAECO hardness of about 9.5 / BHN of 18-20.

You may have a valid point. I'll try some bullets of a different metal with a bit more hardness.

Thanks, JCherry

"so that leaves a gap of at least .050"

Your bullet is obturating into this recess and lead is being sheared off the bullet. Then the hot gases distribute it were ever they go..

Then the amount of lube given the ball powder could be another mitigating factor.

It appears everybody is correct. The extra viscosity in the lube sent out was to help cover revolters which are out of time. Cutting the viscosity a tad COULD correct some of the buildup problem by allowing some slivers to rid themselves out the muzzle before the next shot. Avoid castor oil for this go around, because that could degrade your accuracy if you get too much. Try cutting an ounce of that same lube with a half-tea-spoon of baby oil and wipe on some boolits by hand and see if that works. If not, I'll help you with some castor oil. Castor oil works when you have a complete seal, but we have to make sure of this first. If you get castor oil down there, your boolit could loose some important grip at startup should you go to a faster powder. ... felix

Several ounces, not one ounce. Cut thickness by about 20 percent at most. ... felix

I made a post but for some reason it didn't show up so will try it again.

JC attests that his load is in the 2000 fps bracket. According to the NRA Cast Bullet book that puts it in the medium power loading. Here are a few things they have to say about it: The usual requirement of linotype metal and high-grade bullet lubrication apply. A fiber filler is benefical even with slow burning propellant. Medium power cast loads in the short-necked .308 Win tend to leave lead on the case mouth and neck. This does not result in bore leading or prevent accurate shooting in otherwise correct loads.

Joe

Yes, Joe, you are correct because the neck thickness on 308 cases are specked way too thick in the first place, especially military, and especially for cast. Annealing will work wonders, but with a very, very fine torch stream only so as not to hit the neck slope. I torch the very top of the neck with a quick manual twirl or two, and drop quickly into water. Turning/thinning case necks should only be done with a gun with too tight of a neck. ... felix

Yes, you can turn the necks if you are going to use custom dies that allow much bigger boolits to fit the throat exactly. That is a major problem with the 308 caliber; factory dies are too constrictive. Mine are custom made. ... felix

My original thread was posted on both the Accuratereloading and the Aimoo Cast Bullet Forums.

The incoming information has been well thought out and very useful. I am going to proceed to get the tin in my lead up to about 2 percent (I figure it was about half of a percent in the batch I used for these loads.) Work on my lube mix and make a up a few "long neck" .308 shells to see what the effects are. I figure it'll take a week or so to accomplish what I have in mind but will post the results.

Thanks to all,

Have Fun, JCherry

Hi JCherry! I have seen the outside of the neck look like someone tried to solder a spot of it. No thickness.... just color . ( Steel wool may remove it.) Is this what you refer to?

I have thought & thought about this....now my head hurts! (LOL) All the answers i had- someone else already stated better than I ever could.


Leading at the muzzle? Not enough lube...or bullet damage at the start of the bore...or too soft a mixture for the pressure generated..... or a gas check with bad fit/sealing.... or uneven heat treating.... or a damaged/uneven bore.

I know what you seek is possible. I have some decent groups with a mold marked 311332 ( Although the bullet weighs 200 grains! Maybe mismarked? Should be 311334?) It shoots around 3 moa ( yes,yes, many are less than that but I want to be fair.) at 2350 fps.
I would check bullet hardness, lube amounts,seating depth ( A little deeper!)and maybe powder type ( go to a slow stick powder). Try another rifle... some lead & some do not. Let us know how everything turns out. Dale

JCherry,

Hmmmm. WIth regards to leading toward the muzzle, I would go to what others have recommended.

I have this bullet in a pre 1927 Ideal mold. It has only one grease groove. The g.c. is tight up against the last driving band and there is no space for additional lube there. I have used this bullet made from both ww + 2% tin alloy heat treated and straight linotype. Using the NRA 50/50 alox beeswax formula, and allowing the lube to flow into the scraper groove to effectively give two lube grooves, I have pushed this bullet to 2200 f.p.s. from my bolt action .30-30's with nary a hint of any leading and excellent accuracy.

Somehow, gas is getting by the bullet in its transition from the case neck into the barrel. You had mentioned that your rifle's throat diameter was about .3105" so that is not the problem.

What is the outside diameter of your case necks before firing? After firing?

Possibly annealing your case necks would help if they expand too much (over .005") and are too hard.

With regards to short case necks causing the problem with lead mist on the case necks, I have used 2.030" long .30-30 cases in chambers that were 2.09" long and never had any lead mist on my case necks, even with bullet seated well below the neck. .30-30 necks are thinner than .308 necks, though, so it is possible that could make a difference as Aladin suggested.

A .06" LDPE (low density polyethylene) wad will most likely eliminate the problem if it can be seated in the case neck and still leave room for the bullet.

LDPE wads worked on my .22-250 which is my only rifle that I ever experienced leading on the case necks. In this particular instance, the reason for the leading was that the throat diameter had opened up to .230" (6,500 rounds) allowing a .003" gap around the bullet for the gas to work on it during its transition through the throat. The LDPE wads obturated to seal the base of the bullet through the oversized throat, eliminating the leading on the case necks and restored accuracy which had been pretty dismal up to that point.

Good luck in finding a solution.

w30wcf