PM9 Scorched Casings (pic)

[redbeardmcg]

During my last few range session with the PM9 I noticed that the casings were quite scorched on one side. I don't notice this (at least not to this degree) with any other gun that I own nor do I recall my spent casings looking like this with the PM9 in the past.

Is this a warning sign? I'm not sure what could be causing it. Below is a picture of the casings, I turned a few to show the other side of the casing (still looks clean).

[wyntrout]

I would mark a few cases with a Sharpie from rim to bullet and load them with the mark on the extractor side. My guess would be that the opposite side is getting scorched by residual blast from the chamber as the case rotates out to the right. This is probably going to change as the recoil springs weaken a bit more.

In my flash stills from firing video there is a lot of flash coming from the ejection port and sometimes inexplicable places aft of the ejection port. Timing changes as the spring takes a set and varies with the burn rate of the powder.

Wynn

[redbeardmcg]

Thanks Wynn. It sounds like it is about time for a new recoil spring.

[wyntrout]

Not necessarily. If the case is being ejected with a lot of combustion still going on with a longer burning powder, it will be ejected sooner with a stronger spring. I don't know how old your recoil springs are, or how high a round count, so it's hard to say. Then again, the case might get out of the "combustion" area sooner.

I'm no expert and just "guessing".

JMHO

Wynn

[dzldust]

I just got an older PM9,is there a time/sign of when to change the recoil spring?

[jocko]

are

During my last few range session with the PM9 I noticed that the casings were quite scorched on one side. I don't notice this (at least not to this degree) with any other gun that I own nor do I recall my spent casings looking like this with the PM9 in the past.

Is this a warning sign? I'm not sure what could be causing it. Below is a picture of the casings, I turned a few to show the other side of the casing (still looks clean).

those nickel or aluminum casings. It cold be they just show the gasses more than a brass casemight. It has to be some escaping gases, which I can see no harm being done. It is normal??/Hell I neverlook at my casings. If thegun goes bang every time, I have no complaints. Ur chamber might not be as tight either, whichy for some they like it that way. IMO: just shoot it like u stoleit.

[redbeardmcg]

Those are brass casings, just 115gr Federal FMJs. My gold dots (nickel plated) do the same thing though. As I was cleaning up my brass the last time out the burnt casings caught my eye, so it's definitely a new development. My concern is that it's indicative of a bigger problem that will keep getting worse.

I ordered a new recoil assy. from Kahr (also wanted a few backup mags and a kydex mag pouch anyway so I figured what the hell) I'll post back once I get the new part in to see if this goes away.

Thanks,

-Ryan

[jocko]

send kahr the photos by email attn: Jay and ask for his opiion and advice. I am wondering what the indication of a bigger problem would be. I doubt if a new recoil spring will take care of that. but saying that I have no proof either and indeed new springs seems to cure alit of little ills.

[Gliderguy]

A nick in the chamber throat? Do all the scorch marks end in that fairly clean line about 1/8 inch up from the extractor groove?

Look at the smear mark on the primer, when the round was in the gun the smear mark is up from the main firing pin impact point. If the scorch marks all center on the same clock position with the primer smear marks all aligned I would expect maybe the chamber is a bit loose or has a small flaw letting gas through and around the casing.

[Gliderguy]

also stop half way through a fired magazine, eject the unfired round in the chamber manually and see if it is already scorched. that would tell if it is getting blasted while still in the mag and not while actually being fired.

[Gliderguy]

Thurd thought for the day (yea, spelled it that way intentionally): looks like the heat scorching stops right where the head of the brass casing gets thick and does a better job of wicking the heat away. Makes me think that the scorched part of the case is not touching the chamber when the round goes off, has nowhere to dump all that heat energy from the gunpowder, and gets discolored. Is there any lube or residual hard burnt powder in the chamber that could be acting as an insulator? That could be making that part of the case run hot. Especially if it is a newly developing problem and you cannot see any cracks or other signs of distress in the barrel indicating it is bulging at the chamber.

[redbeardmcg]

@Gliderguy -- good observation, it seems pretty clear the casing is still in the chamber when this happens and not being ejected. I sent an email to Kahr support, but will do a thorough chamber cleaning as well. I will say though that I clean this gun every time I shoot it so I find it unlikely that the chamber is fouled up.

[CJB]

I'm glad someone picked up on the abrupt end to the scorch mark.

Question is - did it end there due to .... heads being a little bigger than the casemouth?
Or was that where the ramp began? Or?... Dunno.

Possible causes -
a. over crimp with a tapered crimp, right from the factory.
b. chamber pressure low (I've seen this LOTS on revolver loads, cant remember on autoloaders)
c. slightly out of round chamber (probably not the situation here)


My best guess at "most likely" is a combination of things. Lets say Federal squeezed those cases, bullets inside 'em, and over crimped them with a taper crimp. Now we have small cases, small bullets too. If they were ordinary standard loads, those are actually on the low power side of things. So combine an overcrimp, now low chamber pressure due to undersize projectile, and lower power which would cause a slight delay in case expansion... could be the explanation.

[TucsonMTB]

Is the scorching really a problem?

We have several 1911's that do that from time to time, seemingly depending on the ammo fired. This particular batch of ammo is 185 grain Federal Classic JHP. I have several different manufacturing lots of this same ammo mostly purchased over several month's time about three years ago when it was relatively inexpensive. In the same gun, some lots of this ammo produce the black marked cases, some do not. I guess I thought it was "normal".

I probably should add that this ammo seems very accurate, feeds and ejects well, etc.

Oh, and here is what it looks like before shooting. Note: The plastic carriers pictured are from another brand ammo.

[DKD]

I agree with CJB. You must be a reloader. I have experienced the very same thing with low to moderate pressure reloads in my 45 colt rifle loads in a lever action winchester 73. It does seem like blow by due to low pressure and crimp that isn't sealing off the chamber, thus causing hot gasses to escape and down the side of the casings. It is hard to get the balance right when we are dealing with short barreled pistols with large powder charge weights. Some loading will require a heavier crimp, while others not so much...eacj piostol is an individual.