Jarvis Conversion Barrel .40 cal to 9mm

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JonP99

Discussion Starter · 5 mo ago (Edited)

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I converted my Gen 1 P99 .40 cal to 9mm. The barrel functioned almost flawless for 50 rounds 115 gr and 150 rounds 130 gr. Half the rounds were in the OEM spring and half were in a DPM spring system. I did have one failure to return to battery. It jammed up pretty good, but I was finally able to rack the slide and eject the live Federal American Eagle 130 gr round. Funny enough, the failure happened during the OEM spring. The DPM spring was flawless. Mind you the spring was the longest spring so I did receive some brass in the face area and on top of my hat, but flawless function none the less.

Overall, I would recommend the Jarvis barrel. The fit is very tight and the rubbing is obviously noticeable after 200 rounds. I did not send in my slide for fitting. My question to the forum here is: Will this rubbing or friction damage my original slide in any way?

If you have any questions let me know.

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JonP99

Discussion Starter · #3 · 5 mo ago

It looks slightly worn, but the original barrel is very worn in the same places too. It was my fault for not inspecting the slide better prior to firing today.

I will say the tight fit is actually better than the OEM barrel.

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JonP99

Discussion Starter · #5 · 5 mo ago

romeo_alpha01 said:
With this setup, you didn't have to swap magazines and sear assemblies?

I bought a 9mm mag, but out of 4 of the .40 cal mags I own, one can actually retain 9mm ammo. I have no idea what brand it is though. All black and zero markings. The base plate actually makes me think it’s a Beretta 92 mag.

no swap on the sear assembly. I was really surprised at well it functions. Ejects well too. Not sure exactly what cause the bind up though that one time. I assume the spring is the original factory spring from around 1999. That may have played a role in the one failure.

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JonP99

Discussion Starter · #8 · 5 mo ago

Aluus said:
I just want to know why one of your photos was flagged as "Sensitive content"...

I caught that too. Technically firearms in general are 18+. Lol.

I was just trying to show the fantastic polishing on the feed ramp. Almost superior, or at least on par, with than any barrel I have seen. Certainly better than most OEM barrels.

I was more amazed at the brilliant software that can pick up on stuff like that though. Kinda cool to squash trolls before mods can sweep them out.

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JonP99

Discussion Starter · #12 · 3 mo ago

Update:

So I took my converted P99 to the range last week. I shot a few magazines of Blazer 115 gr. I could not make it through a single magazine without FTE or FTF. I changed my factory old recoil spring for my DPM recoil spring. I still had issues. Maybe even more so. I walked away frustrated.

Tonight I had a CCW test. I bought some Fiocchi 9mm 115 gr. and placed the “shortest” of the 3 recoil springs in my DPM recoil spring. I had zero issues.

Not sure if the spring was too long and applying too much tension for the 115 gr to handle or whether it was the ammo. Either way, it was smooth tonight. I figured I would bring it up for others.

Fwiw, I am almost positive the Walther recoil spring was the original 1999 spring. For a conversion barrel AND a DPM recoil spring, I would recommend the shortest spring for the best chance of the 9mm round pushing the slide back. Last week, I felt like the casings were barely clearing the slide and landing on my wrists or in my face. Tonight, the ejection felt proper.

Ammo or spring?

My money is on the spring tension.

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