What causes lead on the outside of a case mouth?

[FNGC]

I'm new to cast bullet shooting but am fascinated with it.
I bought a box of Chey-Cast 30 cal. 165 gr. FN (.309) to load in my Marlin 336 (not making my own YET) and so far am getting pretty good accuracy with a mild plinking load of 8.5 grains of Trail Boss. I'm getting 1226 fps with no leading in the barrel as far as I can see with a 9" bore scope. What's got me baffled is that I'm getting lead on the outside of the case mouth. What causes this?
The second picture is how the load groups at 50 yards.
Thanks!

[gray wolf]

It could be a few things but my first guess would be your load is not strong enough to open the case mouths enough. Does a new bullet enter the case mouth of a fired round ? how hard of a crimp are you using ?
Nice shooting.

[popper]

I've heard others say it is too much crimp. Personally I've never had it. Using a ROLL crimp? I just FCD or taper crimp enough to remove any bell you put at the mouth.

[Muskyhunter1]

Do you have any pics of loaded rounds?

If you are not flaring your case mouth maybe you are shaving off a bit of lead that stays on the outside of the case neck. During firing it gets flattened and is squeezed backward. Just a theory.............

[swheeler]

I think it has to do with the chamber of the 30/30, the neck on the chamber is longer than the neck on your brass. I had similar results with K31 Swiss and 284 Win brass and 8x56R using 7.62x54r brass. In your case try dusting the bullets in motor mica before loading, may help?

edit- if TB is not your only option you could try a slower powder and see if it helps

[chsparkman]

Make sure you,be deburred the inside of the case mouth. One of my first mistakes in loading cast.

[tward]

When I don't bell my 38 specials enough I get a nice ring of lead on the case mouth just like yours, just a guess. Tim

[bbqncigars]

I think it is vaporized lead that gets deposited on the case necks. I had the same thing happen with TB under some boolits in my .50BMG rifle. Those are NOT crimped and no lead shaving when seated.

[FNGC]

Thanks for the replies, guys.

gray wolf,
Out of 20 cases tested, 7 were too tight to insert a bullet. How hard a crimp? That's pretty relative, but look at the photo below, I think I need more.

popper,
I'm using RCBS dies, so whatever style of crimp that is.

Musky hunter1 & chsparkman,
I don't have a flaring die yet, but I am chamfering the mouth with a VLD reamer. I'm not getting any lead shavings.

swheeler,
I hadn't heard of using motor mica, I'll take a look around. Also, I'll compare burn rate charts with what powder I have on hand.

After reading everyone's comments, advice & taking another look at my loaded cartridge, I think the first place to start is a better crimp. I'm hoping that will give me a little more pressure to blow the case out more for a better seal.

[David2011]

Frankfort Arsenal Midway mica: http://www.midwayusa.com/product/2124290522/frankford-arsenal-fine-powdered-mica

1/10 oz: $4.10
4 oz: $9.99 (!)

David

[Hogdaddy]

FNGC- Great shooting. when you get it woorked out, those groups should shrink even more ; )
H/D

[popper]

I'd say from your pics you need to use needle nose pliers or something to actually flare the mouth. Then just touch the neck with the crimp (seater) die to remove any bell. Your pic shows (can't enlarge so I'm using bi focals) some lead? in the crimp groove. Probably from the commercial hard cast boolits, the lead seems to chip & ball up during seating, some even embedded in the lube. That stuff will get smashed on the necks, as pointed out. It won't really hurt accuracy, just a pain. Shaving WILL hurt accuracy.

[atr]

Im going along with GreyWolf,,,I think the load is to light to seal the case in the chamber

[swheeler]

Thanks for the replies, guys.

gray wolf,
Out of 20 cases tested, 7 were too tight to insert a bullet. How hard a crimp? That's pretty relative, but look at the photo below, I think I need more.

popper,
I'm using RCBS dies, so whatever style of crimp that is.

Musky hunter1 & chsparkman,
I don't have a flaring die yet, but I am chamfering the mouth with a VLD reamer. I'm not getting any lead shavings.

swheeler,
I hadn't heard of using motor mica, I'll take a look around. Also, I'll compare burn rate charts with what powder I have on hand.

After reading everyone's comments, advice & taking another look at my loaded cartridge, I think the first place to start is a better crimp. I'm hoping that will give me a little more pressure to blow the case out more for a better seal.

I hadn't either but when I posted about the same problem I got a PM from a member here(banned) thought BS but what the heck and tried it(I had it for neck lube), lead on necks disappeared, try it and let us know;)

[John Boy]

I think the first place to start is a better crimp
FNGC - look at the depth of the crimp groove on the new Chey Cast bullet and compare to the picture of your loaded round. You have basically no crimp which is allowing ignition gases to escape into the chamber leade! Crimp the cases INTO the crimp groove
Also:
* What is the neck tension on your reloaded bullets?
* If you have smeared lead on the fired case mouth - you also have lead in the leade (throat) of your chamber
* Dirty cases will not allow for a tight chamber seal on ignition - might want to shoot clean cases

[Horace]

Got the same results using plain base cast in a 303 savage pushing it to hard,

Horace

[44man]

Gas pressure erosion from a too fast powder and instant pressure rise. The boolit is still in the lead to the rifling when peak gets there.

[FNGC]

I made up another 10 rounds of the 8.5 gr. TB load, but with a better crimp. I want to see how that acts. Others have posted milder loads with Trail Boss, but haven't mentioned the case leading.
I'm also trying to figure out a couple more loads to try with slower powders that I have on hand. It's pretty depressing to go thru the load chart in the Lyman Cast Bullet guide & know that MOST of the recommended powders are impossible to get .

[Whiskeylima]

I actually had the same problem with the same caliber. I am using a 170 gr Laser Cast RNFP. I started at 8 grains of TB with a fairly robust roll crimp. I have better results with 10 grains and a light crimp with a Lee FCD. Velocity is around 1200 out of a Marlin 336Y. A little light for Rams at 200 but otherwise my kid rolls with it.

[popper]

That's a roll crimp & probably WAY more than needed. Just crimp for a shiny ring on the mouth. Crimp is ONLY to prevent setback in the tube mag. That said, some loads MAY shoot better with a hard crimp. 2400 powder may help. I noticed the same problem with the lasercast, but just got a few specks on the necks. I also don't use tin in my cast so don't get alloy flash on the neck - Pb & Sb don't solder well.

[44man]

Try 3031 and 4895, super accurate in my Marlin. 26 gr of 3031 and 25 of 4895 with my 187 gr boolit. Adjust for your boolit. Recoil is almost nothing and the gun and brass is clean.
Varget is good too.

[w30wcf]

Gas pressure erosion from a too fast powder and instant pressure rise. The boolit is still in the lead to the rifling when peak gets there.

+1 TB has the fastest pressure rise of any smokeless powder.....even faster than black. Loaded under a too hard plain based bullet, that combination Is very likely the problem. I use TB with good results with softer bullets.

You could try backing off the powder charge to 6 grs and then going up a bit at a time from there.
Slower powders like 2400, 4227,in 12 gr doses or 4198 in 15 gr doses would be a better combination with hard plain based bullets.

The crimp, in my opinion, is not the issue.

w30wcf