ammo jamming?

[rwg3]

I have been working on the range and have run into a problem with my P238. It periodically fails to go into battery and the slide is open about an eighth of an inch. There is a a portion of cartridge case and the base visable when looking at the slide and it is not possible to close the slide fully, without I suppose really exerting significant pressure to do so. I haven't wanted to do that for fear of really jamming a round in the chamber and then having real issues. The ammo is from a Remmington UMC 250 pack and I have had this happen about 15 -20 times in the first 100 or so rounds out of this box. I called Sig and they said it could be a recoil spring and immeadiately sent a new spring. I cleaned the heck out of the pistol thinking it may have been fouled and replaced the spring but the next trip to the range again the random jam. At this point I am wondering if the ammo could be bad? How does one determine if the brass has expanded to a size near the base that wont allow it to chamber? Is calling Remmington the next step?
Thanks

[MoJo]

Remove the barrel and use the chamber for a gauge. With the barrel vertical drop each round into the chamber. If gravity won't seat the round fully into the chamber set it aside. If they all go into the chamber without pushing you have another problem than out of spec ammo. Compare the length of the ammo they all should be the same if you find some that are too long that can cause the problem.

Does the gun do this with other brands of ammo? Try some other quality ammo and see if this solves your problem.

[Pawpaw]

The advice to use the barrel as a chamber gauge is spot on.

I have another question... when it jams and you pull the slide back, does the extractor pull the unfired round out of the chamber?

If not, the rounds might be getting out of the magazine, ahead of the extractor. The extractor will then hit the back of the casing and stop the slide from closing.

If this is happening, the first step would be to wipe all lubrication from the inside of the magazine tube and the follower.

[rwg3]

Thank you all for the advice. Will try the tips this weekend. I only started this issue with this box of ammo and have run a few hundred rounds through the weapon without issue. The extractor does pull the jammed round but sometimes the next round in the stack poops up before the bad round comes free. I will clean the magazines thoroughly and test the rejected rounds with the gravity feed to see how if it falls in cleanly without jamming.
I do appreciate the feedback.

[MoJo]

Your gun may not like UMC bulk pack ammo. I have an XD that chokes on WWB but runs like a top on everything else I have shot in it.

[zero4o3]

Your gun may not like UMC bulk pack ammo. I have an XD that chokes on WWB but runs like a top on everything else I have shot in it.

one of my guns refuses to chamber PMC branded ammo but has never had a hicup with anything else.

where are you located?

[wgoforth]

Wife and I both have these... does it only do it first round of fresh mag? Sig will tell you do not use slide release to chamber a round, it will produce this. Pull slide back and release, as you will get another 1/4 inch of mementum to chamber a round. That is what mine was doing, and when I called SIG this was what I was told. After I began using the slingshot method, never had it happen again.