Lead ring?

[borg]

How the heck do you stop the ring from forming in the throat?
The first two shots are darn near touching, then the ring happens.
After that, I'm lucky to keep them on paper until I run brush through the barrel.
Can something be done to the chamber to put a bevel on the throat?
Any help?
Thought about using some JB paste and just working on just the throat, but thought I'd ask here if there are any better corrections.

[Hickok]

Give us some info on the gun, load, cartridge, etc.

[GhostHawk]

First off some information is required. Rifle? Pistol? Model?

It does make a big difference. Cartridge/caliber bore and groove size, what the throat looks like could all have an effect.

[mdi]

Yep, need to know whut gun and caliburr yer askin' 'bout...

[Mal Paso]

Lead is stuck to the chamber? Try a larger bullet.

Lead shavings is what you should get if a sharp edge was the problem.

[borg]

Sorry, I know better.
300 Blk, 8" twist Wilson Barrel, AR upper.
Load doesn't seem to matter, they all did it, mold is Lyman 200 gr 299, with and without super lite crimp.
BBT in HF red, sized .309, bore is .308, brass is cut RP and expanded to .307 neck, annealed, shoulder pushed back .002.
These were all single loaded from mag.
Can't think of anything else except that these are shavings left by the sharp shoulder at the end of the chamber.

[Maximumbob54]

You are using an expander on the case mouth before seating the bullets, right?

[borg]

Neck expanded to .307 with a Lyman M die.
On about the 9th round, a round wouldn't chamber.
When I got it out, it had a ring of lead on the bullet from the previous rounds.

[Cherokee]

Sounds like a sharp shoulder on the chamber throat shaving lead.

[243winxb]

The 2nd step on the M die should open the case mouth more than to .307" But it depends on how your taking the measurements?? I would not crimp, but if i did, taper crimp in a separate operation after seating.

[popper]

Sounds like soft alloy and large freebore in barrel. Also mic some loaded to make sure they are really 309 after seating. Mine takes 3085 but not 3089, boolits stick good. Can you trim longer and still chamber a case?

[Yodogsandman]

Your problem is that you're not expanding the case mouth enough with the Lyman "M" die. The Lyman "M" die has two steps, the first is to expand the neck for the proper tension, the second step is to "bell" the case mouth so the boolit will enter without shaving any lead (or ring of lead). This will leave a shelf or step for the boolit to set on while awaiting seating. The "bell should be enough so that when a gas checked boolit is inserted, the gas check enters the neck at least 3/4 of the thickness of the gas check. I like to have the full gas check thickness in the neck before seating. The "bell" can be reduced or removed when seating and crimping. Some like to leave a little of the "bell" to help the case neck fit the chamber better, mostly in bolt action rifles for increased accuracy..

[MBTcustom]

You've got the bullet shaving as it enters the throat. I've had this happen when I shoot a bullet that is too big for the throat. Like on the 30XCB rifles, I designed the throat entrance to be .310 exactly. In other words, the neck diameter is .337 and it joins the .310 diameter throat entrance via a 45 degree angle. That 45 degree corner is sharp enough to shave a ring of lead from the bullet diameter and it did if anybody tried .311 diameter bullets.

Getting back to your situation, I figure your chamber is either made wrong (throat entrance on a typical match grade 30 caliber barrel is .309) or, (more likely) your bullets are doing something weird.
Now you say you sized your bullets to .309, and that may just be too darn close for comfort, assuming your bullets are not bumping up when you kick them. Try sizing .3085 instead.
However, I would suspect that 300blk being what it is, you are likely getting your bullets expanding in diameter a little bit as they are being pushed from behind, and this issue exacerbates the problem even worse because your bullets are already throat diameter (I do hope you actually measured those bullets before stuffing them in the cases? Just because the die says ".309" on the side doesn't make it so with your alloy. Oh, use a micrometer, not a set of calipers). This bumping up can be a good thing, but only if you get the sucker in the throat before it happens.

You give no information on your alloy or your casting process (Water dropped? Air cooled?) but I would suggest if you are using straight COWW or range scrap that you add a little tin and water drop those puppies. If you buy a small amount of Lyman #2 and try it water dropped, and your problem goes away, you know exactly what's going on.
Check that bullet diameter before you load! Even if they were right when you sized them, and measured with a micrometer, doesn't mean they are still right a week or two later. You're so close to the max as it is, it would only take a few ten-thousandths of an inch to cause your lead ring.

[borg]

According to a pound test, the chamber is long enough to take a case that's 1.370, I trim mine to 1.358.
As per OP, the ring doesn't show up till fired, not shaved when seating boolit in case, otherwise, there'd be a ring of lead in seating die.
I can chamber a round, eject it and it doesn't show any shaving on the first band.

ETA, the alloy is 16 on the BNH scale, tested AFTER baking PC on a Cabin tree tester.
They also shoot great through my bolt 308 Win without this problem.

[swheeler]

I'd trim my brass to 1.368, that gives the lead less room to extrude into, getting rid of that .012" canyon at the end of the chamber will do wonders. Also I would water drop the bullets right quick out of your 400 deg PC oven. I ran into this problem with the K31 Swiss using reformed 284 win brass and the 8x56R using reformed 7.62x54R brass- read brass too short.

[MBTcustom]

So you did a pound cast. Excellent!
So what was the diameter of the throat enterance?
I also agree with swheeler, although I have mainly only experienced this as an issue with paper patched bullets. However the cause was the same: oversized bullets (even if the "oversized" part was made of paper). Fact is, whatever gets scraped off your bullet by the throat enterance is going to pile up in the only available gap there is, which is your case mouth to chamber end differance.
Now, my first approach to solving this problem was to make my brass exactly as long as the chamber, which should be considered a bandaid, and a way to cover up an existing problem. The correct solution is to either make your throat more cast friendly, make your bullets more throat friendly, or both. Obviously, you want to try to handle this with the bullets as they are more easily manipulated, but often you find yourself between a rock and a hard/sharp/small place, and the simple solution is to ream the throat of your barrel to something a little easier to deal with. Be careful though. Many a barrel has been ruined by somebody who didn't know how to control the depth of a throating reamer.

[dudel]

Sounds like the boolit is getting deformed as it's stripped from the mag, hits the feed ramp and moves to the chamber. I'd fire a shot, let the next round chamber, then eject it and take a look at the round.

There is some pretty violent activity going on during the feed cycle.

[popper]

Try trimming longer to get rid of the gap. It gets filled when firing that heavy boolit. I have a 40 that does that, but cases don't grow so I can't trim. H.T.ing increases BHN so it doesn't occur as much. As you did a pound cast, what is the neck diam? Mine will only take 0.333 max loaded, if yours is larger (neck/groove dia), neck may be expanding adding to the problem. I also found adding 0.3% Cu to the alloy really helped in my 'bad' 40. You didn't indicate what your load is, fps, are you using a GC on that boolit?

[borg]

The Boolit is not deformed in the least, feeding from the mag.
If my memory serves me (can't find the pound cast Boolit right now), it measured at .333.
The ring only happens when I fire the round, chambering and ejecting a live round does not leave any marks on the Boolit whatsoever.

I will have to try some longer cases to see if that will correct the problem, trouble is, everything I have is already trimmed and they don't stretch much on firing.
It didn't matter if I loaded 9.5 gr of 4227 to 14.5, they all did it. (also used some H110)

[popper]

Hodgdon shows that you are close to max load with (10.3gr) 4227 for jacketed, even with close to hardball alloy may not be hard enough - WD after cooking? I found the Cu helped a lot in my 40, add it to all my alloy now. M die doesn't stretch them at all. I tinkered with using a (proper sized) twist drill hand turned and taped to chamber size to eliminate a thousandth or so from the sharp edge. It barely took off any metal but as the 40 is HS from mouth I didn't want to do much. That would only help if the nose of your boolit is running into the edge, when fired. IIRC that mould has a step at the front band. My BO mould has a step but the band goes into the throat.