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View Full Version : Unusual Chamber Leading in Auto. Why?



fourarmed
09-06-2013, 01:28 PM
I was cleaning my Smith .45 M&P, and noticed a gray coating along the right side of the chamber. It was lead. I scraped it out with a knife blade, and haven't fired it enough since to see if it would recur. This was a solid wash of lead the entire length of the chamber and maybe a half-inch wide. It was not present on the top, bottom, or left side of the chamber, and it wasn't thick enough to interfere with chambering rounds. I have never encountered this before in any other auto pistol firing cast boolits. Most of the loads I am shooting are SWC with the shoulder of the bullet protruding maybe .050" out of the case, which seats the bullet pretty firmly in the throat. Firmly enough that it takes some effort to eject a loaded round. I have also fired a fair amount of LRN. All told, I have probably put 500 rounds of cast through the gun since buying it, and maybe 150 rounds of ball.

That side of the chamber does not appear to be significantly rougher than the rest of the chamber, but I can't rule that out. The gun does not lead in the bore to speak of. Any of you ever see anything like this before?

Mohavedog
09-06-2013, 01:58 PM
Wow, imo your cartridge violates one of the most important rules of reloading for semi autos. The round should drop in and out of the chamber unassisted with the commonly known "plunk" sound and no contact at all with the rifling or throat. Sooner or later enough buildup will cause ftf or possibly firing out of lockup. I'm not positive about firing out of lockup, some guns can and some cannot according to what my learning is. Minimum result is your gun won't run, maximum possibility is destroying your gun or yourself.
Be careful and do your research. Mohavedog

fourarmed
09-06-2013, 03:00 PM
Yes. Thank you for your post. I know all that. What I don't know is why the chamber leads.

Mohavedog
09-06-2013, 05:05 PM
Sometimes the answer isn't as obvious as we think. But imo the first thing I would do would be to seat the boolit deeper until it drops in and falls out of the chamber from it's own weight, and go from there if it still is leaving lead in the chamber. Mohavedog

fourarmed
09-06-2013, 05:19 PM
I agree that needs doing. And it might even contribute to the leading, if a little gas cutting occurs before the bullet is all the way out of the case. If so, I suppose it could be that the chamber is out of round or off center, with a little more clearance on the right side.

R.M.
09-06-2013, 05:27 PM
I had that happen years ago in my S&W 52. I figured it was because I was taming down already tame loads.

noylj
09-06-2013, 06:20 PM
I have never had that and ALL my .45 Auto lead rounds are loaded so the bullet just touches the lede/rifling to minimize "head space."
My first thought would be that you had some scrapped lead on a round and it was deposited in the chamber. The rest of the rounds flattened and wiped the lead along the chamber wall.

whisler
09-06-2013, 09:13 PM
If I am reading you correctly, you are getting a smear of lead even where the cartridge case sits. If so then the cartridge case would not be expanding to seal the chamber and you would still have to be blowing lead back along the case wall. My limited knowledge does not allow me to understand how this could be happening. Only other thing I can think of would be some lead being scraped during seating/crimping and then being smeared on the chamber wall during chambering. Very strange!

fourarmed
09-09-2013, 12:58 PM
I think noylj may be right about how it started, and I think whisler is correct that it would be self perpetuating. I will watch it closely and see. Thanks for all the insights.

popper
09-09-2013, 03:04 PM
Shaved lead that globs over the case mouth & gets stuck in the chamber. Extraction smears it along the chamber wall. Oversized chamber?

Horace
09-09-2013, 08:27 PM
What`s your load data on this? Was loading plain base boolits in my 303 Savage 99 got lead spray all over the neck of the case...was pushing it to fast.

Horace

fourarmed
09-10-2013, 02:13 PM
Chamber is .480". Loads are midrange or light loads of BE and 231 with a mix of home- and commercial-cast boolits sized .452. Cleaned it this morning, and there was no noticeable buildup since the last cleaning, but the last 40 rounds fired were jacketed. They leave much more fouling in the bore than the cast ones do.

bruce381
09-10-2013, 08:58 PM
I would try a deeper seating and would think that whatever dynamics the boolit is smearing a light lead film upon chambering, that gets ironed out as case is exstracted. A deper seating may reduce the boolit contact with the chamber and reduce or stop the smearing if thats what it is. FYI I seat to a OAL with a H+G 68 style at 1.250 crimped to .471-.472