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Discussion Starter · #1 · (Edited)
So I purchased a P320 .357 Sig Compact x-change kit for my 9mm P320 compact. After much research, I then purchased a .40S&W compact barrel assuming it would function fine. It appears I was wrong.

I had the .40 barrel in the .357 slide and it after firing 4~5 shots, the slide jammed so hard I could not rack it. This is the second time this has happened. I believe I was using Blazzer brass this time. Previous thread (http://sigtalk.com/p250-p320-p320-x...-weird-issue-my-p320-ftf-fte-help-please.html)

After MUCH effort, I was able to rack the slide and eject the brass. (see photos) It appears the ejector somehow gets stuck on the brass.



 

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Discussion Starter · #2 ·
Time for an update. This issue is getting weird...

Took the combo back to the range. Moved the FCU and compact .357 slide to the subcompact grip and .40 barrel. Not a single issue with the setup with about 60~70 rounds.

Moved the FCU and compact .357 slide to the compact grip and .40 barrel and had several jams and failure to extract. I'm thinking it may be magazine related. Will continue to troubleshoot.

I also noticed the .40 doesn't like the Federal "American Eagle" ammo although I've never had an issue with it in other calibers on the same weapon.
 

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It may sound ridiculous, but how does the slide with .357 barrel react on both grip assemblies? How about OEM 9mm top end? Part of the problem could be the .40 barrels fit into the .357s slide, as "slight fitting may be required".

When you say jams, is it a failure to feed, or failure to eject or extract? From your first pictures, it appears the extractor has a tight hold on the cartridge's rim. The "Jamming" could come from possibly from too little headspace. The barrel has to drop down along the breech face to unlock, if headspace too tight, the expanding cartridge case may exert too much pressure. Cartridges are manufactured with a tolerance to offset chamber tolerances. If your chamber is too tight, some cartridges at the upper limits of tolerances could cause the problem. A Go/No Go headspace gauge could determine that, and again the barrel being properly fit to the slide. Try the .357 barrel,, and see if any problems. If not, check your .40 barrels "fit" and chamber tolerances.

If it is magazine related, do you have more than 1 magazine to test with of each size?
 

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Discussion Starter · #4 · (Edited)
It may sound ridiculous, but how does the slide with .357 barrel react on both grip assemblies? How about OEM 9mm top end? Part of the problem could be the .40 barrels fit into the .357s slide, as "slight fitting may be required".

When you say jams, is it a failure to feed, or failure to eject or extract? From your first pictures, it appears the extractor has a tight hold on the cartridge's rim. The "Jamming" could come from possibly from too little headspace. The barrel has to drop down along the breech face to unlock, if headspace too tight, the expanding cartridge case may exert too much pressure. Cartridges are manufactured with a tolerance to offset chamber tolerances. If your chamber is too tight, some cartridges at the upper limits of tolerances could cause the problem. A Go/No Go headspace gauge could determine that, and again the barrel being properly fit to the slide. Try the .357 barrel,, and see if any problems. If not, check your .40 barrels "fit" and chamber tolerances.

If it is magazine related, do you have more than 1 magazine to test with of each size?
I have zero issues with .357 on the same slide and no issues ever with the 9mm slide.
The jamming I referred to is the slide completely locks up requiring a lot of force to open and eject the round.

That issue didn't happen again during my last testing session, it was more like failure to extract. The weapon fires normally but it fails to eject the casing. I had to literally shake the weapon to get the brass to fall out so it sounds like it may be a headspace issue.

As far as the magazines, I have 4~5 .40 cal compact. I noticed when I tried to manually unload the magazine a few rounds seemed to catch on the front lip of the magazine. I did not notice this on the subcompact magazines.
 

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First, I would see how easy or difficult it is to manually see how the barrels chamber fits into the slide ejection port. It should literally "fall in" without any pressure. If it takes even a little pressure, that would be too much, as you must allow for heat expansion. It may just take a couple of strokes of a stone to provide the needed relief. Use of "Prussian Blue" will show where there is "premature contact". This needs to be done prior to any headspace testing. If you have to remove any metal from the rear of the barrel's hood, that will effect headspace, at the front will not

Check out the "Stickys" in the "Gunsmithing" section, on fitting barrels. Same process for the 320 as the earlier Classic models.
 
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Discussion Starter · #6 ·
First, I would see how easy or difficult it is to manually see how the barrels chamber fits into the slide ejection port. It should literally "fall in" without any pressure. If it takes even a little pressure, that would be too much, as you must allow for heat expansion. It may just take a couple of strokes of a stone to provide the needed relief. Use of "Prussian Blue" will show where there is "premature contact". This needs to be done prior to any headspace testing. If you have to remove any metal from the rear of the barrel's hood, that will effect headspace, at the front will not

Check out the "Stickys" in the "Gunsmithing" section, on fitting barrels. Same process for the 320 as the earlier Classic models.
Thanks for the ideas. Fitting it is probably something I'll leave to a "pro" but I'll look into it.
 

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First, I would see how easy or difficult it is to manually see how the barrels chamber fits into the slide ejection port. It should literally "fall in" without any pressure. If it takes even a little pressure, that would be too much, as you must allow for heat expansion. It may just take a couple of strokes of a stone to provide the needed relief. Use of "Prussian Blue" will show where there is "premature contact". This needs to be done prior to any headspace testing. If you have to remove any metal from the rear of the barrel's hood, that will effect headspace, at the front will not

Check out the "Stickys" in the "Gunsmithing" section, on fitting barrels. Same process for the 320 as the earlier Classic models.
I wonder if you could use a set of calipers to measure a known-good, proper fitting barrel to its replacement. I ordered a .40 SW caliber x-change kit along with a .357 Sig barrel. Hopefully mine works without the hassle, but you never know. Previously, I bought a factory Sig 9mm threaded barrel to use with my 9mm P320 compact pistol and it worked great from the start. I'm hoping for the same luck this week! My .357 barrel showed up, but the .40 x-change kit still hasn't shipped from Sig Sauer.
 

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I wonder if you could use a set of calipers to measure a known-good, proper fitting barrel to its replacement. I ordered a .40 SW caliber x-change kit along with a .357 Sig barrel. Hopefully mine works without the hassle, but you never know. Previously, I bought a factory Sig 9mm threaded barrel to use with my 9mm P320 compact pistol and it worked great from the start. I'm hoping for the same luck this week! My .357 barrel showed up, but the .40 x-change kit still hasn't shipped from Sig Sauer.
Realistically, you could, if you found you had problems. The problem, is that there are many factors involved, one, such as diameter of the barrel, where it moves through the port in the slide. If it is on the large side of specification, and the compound angled port through the slide (why it looks "oval"), is on the small side of specification, it could bind the barrel in being able to tilt into, and lock into the ejection port recess reliably. That is why it is important to follow the guidance in the "sticky".

It's a process you really don't want to rush, as the old adage "Haste makes Waste" can and may become reality.
 

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Discussion Starter · #9 ·
Update:

I waited awhile to post this but here's the update:

I sent the P320 back to Sig for the FCU "upgrade" in January and left the .40 barrel in the slide instead of the .357 barrel. Although Sig did not mention any barrel fitting or repairs other than the FCU update, I haven't had a single issue with the .40 in the .357 slide since then. At least 4~5 trips to the range and several hundred rounds of .40 and .357 and its back to eating any ammo I run through it.
 
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