XM17/XM18 Modular Handgun Passes 2018 Tests

I don't get why the MRBS and MRBF are so much worse for ball ammo. Are the pistols really oversprung and the hollow points are just hotter? That would explain the stoppages, but it wouldn't explain the failures. Is the ball ammo maybe very high pressure?

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Yes, the numbers for JHP and ball seem odd.

While my personal experience is in no way comparable to a scientific evaluation run over a sample of weapons, it concerns me that my 1935 designed pistol went 13,120 rounds without a failure. Meanwhile my 2000-era Glock 26 has had 2 stoppages, both of which occurred around 6,000 rounds. I was shooting gun show reloads and the striker indented the primer; but did not fire the cartridge. Both cartridges fired on the second go around. The 26 still hasn’t had a failure.

Maybe I’m just lucky; but 1,880 MRBS doesn’t strike me as impressive.
 
Does anyone have the original report of round count to stoppage for the Beretta M9 to compare these to?
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This isn't exactly that you're asking for, but it's close. Here's some information from the latest delivery of M9 handguns.

https://www.thefirearmblog.com/blog/2017/09/28/m17-mhs-110th-reliable-m9-beretta-claims/

Beretta U.S.A. completed the fourteenth consecutive M9 Lot Acceptance Test (LAT) this month with an average of only one malfunction every 19,090 rounds.​

Some information about the M9A3.

https://www.tactical-life.com/firearms/beretta-m9a3-9mm-pistol/

The MHS also sought to select an already-available commercial replacement and released a Request For Information calling for a pistol with 2,000 mean rounds between stoppages (MRBS), 10,000 mean rounds between failures and a 35,000-round service life. The M9 has passed five consecutive LATs (Lot Acceptance Tests) with an average MRBS of 25,000—that is 10 times the MHS requirement!​

http://www.beretta.com/en-us/fact-or-fiction/

Beretta tests, monitored by US military observers, have found that random pistols chosen from the M9 production lines for testing fire an average of 22,500 rounds without a stoppage. In one test session, under Army supervision, twelve M9 pistols were pulled randomly from the production line and fired a total of 168,000 rounds without a single malfunction.​
 
Damn on those M9 tests. That's impressive.

What are they defining as a "failure" for failure versus stoppage? If failure is parts breakage then those M17 numbers confuse me as I'd frankly expect a lot better. Also interesting that the M18 seems to significantly outperform the M17.

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What are they defining as a "failure" for failure versus stoppage?
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This might shed some light...

http://www.sadefensejournal.com/wp/?p=3044

Mean Rounds Between Stoppages (MRBS) is determined by dividing the total number of rounds fired by the total number of stoppages. “A stoppage is defined as any unplanned cessation in firing or the inability to commence or cease firing attributable to the gun.​
Apparently if it's possible to prove it's an ammo problem, it doesn't count against the gun as a stoppage.
Mean Rounds Between Failures (MRBF). MRBF is determined by dividing the total number of rounds fired by the total number of failures. “A failure is defined as any stoppage which involves part replacement or requires in excess of one minute to correct; or involves any failed or damaged part detected during scheduled preventive maintenance, the replacement of which is not authorized at the crew or organizational level of maintenance as prescribed by Source Maintenance Recoverability Code and TM-9-1005-313-23P.” ​

A parts breakage would be a failure. BUT--a stoppage could also qualify if it takes too long to clear and isn't an ammo issue.

Looks like every failure is also a stoppage but not all stoppages are failures.
 
The new XM1152 9x19mm FMJ "ball" round is very different from the NATO standard M882 9mm FMJ round with which we are all familiar and for which the M9 pistol was designed and tested with.

For one thing, instead of a round-nosed projectile it has a flat meplat and resembles a truncated cone. Secondly, instead of a 124 grain projectile, the new "ball" round has a 115 grain projectile. The XM1153 JHP cartridge uses a 147 grain projectile.

I am not all that surprised to see that a new and experimental 9 mm ball cartridge with a projectile that has a dramatically different shape might have some feed issues that require some tweaking of the magazine and pistol in order for the two to play together nicely.

And it has been my experience with a considerable variety of auto-loading pistols chambered in 9 mm Para, that reliability issues are more likely to occur with 115 grain loads than with heavier loads, and more likely to occur with pistols with shorter slides than with longer ones.
 
That would explain the stoppages but not the failures. Why would a different bullet shape cause more failures? For that matter flat nosed ammunition has been done before and isn't that radically different from hollow point ammunition, which seems to feed fine. As to the slide comment, that's the opposite of what is in the report as the shorter slide M18 seems to do better than the M17, by a noticeable margin.

Do you know where there might be pictures of the new ball rounds?

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