Grand Power P40 10mm Update

spencerhut · December 03 2017 06:21:27 PM MST

So I've been putting rounds through my Grand Power P40 every week or two since the mag drop problem was resolved. I'm shooting a grab bag of PMC, Remington, Norma, Winchester, Federal in FMJ-TC & JHP from 155 to 200 grain in weight. I have a couple thousand rounds of this stuff to burn trough and at ~140 rounds (10 Mags) per session I should be through it soon enough.
I am getting 0,1 or 2 failures to return to battery per mag. Mostly get 1, sometimes 2 . . but rarely get an entire mag shot with zero failures. Pretty consistently random on which mag, does not seem to be a mag issue, or it's all of them.

Anyone else having this issue?

PCFlorida · December 03 2017 07:45:10 PM MST

I am not, my GP has been running perfectly without any malfunctions. Is there anything that seems to be the common denominator?

spencerhut · December 03 2017 10:39:57 PM MST

Maybe I'll take a break from the junk and run some of the Sig FMJ

10Tens · December 03 2017 11:33:29 PM MST

My only failures to cycle have come with cheap range ammo with 40 s&w level velocities. I'm thinking the factory spring is a bit much for the weak rounds.

SavageOne · December 04 2017 01:28:11 AM MST

Are you making sure to lube the contact surface between the barrel and the front of the feed ramp? This is an area that many forget to lube well, but is very important on the Grand Power guns, since that is the main friction point of the barrel.

Ten2six · December 04 2017 05:51:09 AM MST

Mine doesn't like low power loads either and I second that lube is critical.

Azrckcrawler · December 04 2017 09:04:34 AM MST

Quote from: spencerhut on December 03 2017 06:21:27 PM MST
So I've been putting rounds through my Grand Power P40 every week or two since the mag drop problem was resolved. I'm shooting a grab bag of PMC, Remington, Norma, Winchester, Federal in FMJ-TC & JHP from 155 to 200 grain in weight. I have a couple thousand rounds of this stuff to burn trough and at ~140 rounds (10 Mags) per session I should be through it soon enough.
I am getting 0,1 or 2 failures to return to battery per mag. Mostly get 1, sometimes 2 . . but rarely get an entire mag shot with zero failures. Pretty consistently random on which mag, does not seem to be a mag issue, or it's all of them.

Anyone else having this issue?

When it fails to return to battery is it because the slide stop locked or is a round jammed and preventing the slide from returning to battery? I picked up a new 10mm P40 last week hoping the mag drop issues had been sorted. It fails to feed the last round about 70% of the time but it is due to the slide getting locked. I am pretty sure the follower is hitting the slide lock tab with one round left in the mag so I was going to try sanding the follower.

As a data point my mag release button is super stiff. So stiff that I find I can hardly drop the mag using my right hand thumb (shooting RH). That said it does drop the mag shooting full power loads from time to time. I suspect the follower, follower spring or rounds themselves hitting the mag retainer tab due to it being centered. Was going to attach some shim stock to the back of a mag and see if reducing the play in the magwell affects the mag dropping frequency. There is hardly any mag retainer tab engagement as is so the tighter the fit the better.

PCFlorida · December 04 2017 01:26:36 PM MST

Quote from: Azrckcrawler on December 04 2017 09:04:34 AM MST
Quote from: spencerhut on December 03 2017 06:21:27 PM MST
So I've been putting rounds through my Grand Power P40 every week or two since the mag drop problem was resolved. I'm shooting a grab bag of PMC, Remington, Norma, Winchester, Federal in FMJ-TC & JHP from 155 to 200 grain in weight. I have a couple thousand rounds of this stuff to burn trough and at ~140 rounds (10 Mags) per session I should be through it soon enough.
I am getting 0,1 or 2 failures to return to battery per mag. Mostly get 1, sometimes 2 . . but rarely get an entire mag shot with zero failures. Pretty consistently random on which mag, does not seem to be a mag issue, or it's all of them.

Anyone else having this issue?

When it fails to return to battery is it because the slide stop locked or is a round jammed and preventing the slide from returning to battery? I picked up a new 10mm P40 last week hoping the mag drop issues had been sorted. It fails to feed the last round about 70% of the time but it is due to the slide getting locked. I am pretty sure the follower is hitting the slide lock tab with one round left in the mag so I was going to try sanding the follower.

As a data point my mag release button is super stiff. So stiff that I find I can hardly drop the mag using my right hand thumb (shooting RH). That said it does drop the mag shooting full power loads from time to time. I suspect the follower, follower spring or rounds themselves hitting the mag retainer tab due to it being centered. Was going to attach some shim stock to the back of a mag and see if reducing the play in the magwell affects the mag dropping frequency. There is hardly any mag retainer tab engagement as is so the tighter the fit the better.

So mine mag release came back from the gunsmith very heavy but quickly lightened up. However no more mag drops, though truthfully I never had that many to begin with. I only shoot full power loads in it.

spencerhut · December 04 2017 06:51:35 PM MST

Pretty sure it's lubed well, grease on the roller and Slip2000 everywhere else.

Low power loads could be contributing since I'm burning through some junk.

I have gotten several fails to feed on the very first round loaded with Norma JHP. I'm guessing the OAL of the Norma's is off a bit for the GP.

PCFlorida · December 05 2017 02:45:55 AM MST

What OAL are you using for the Normas?

spencerhut · December 05 2017 07:10:20 AM MST

Quote from: PCFlorida on December 05 2017 02:45:55 AM MST
What OAL are you using for the Normas?

They are factory, have not checked the OAL.

PCFlorida · December 05 2017 01:57:42 PM MST

Oh, those Normas ${$default_smiley_smiley}$

Azrckcrawler · December 09 2017 10:10:49 PM MST

100 rounds of Sig fmj thru the pistol today plus about 20 assorted hand loads with no issues.

To fix the slide locking back early I dremeled the shelf on the follower down a couple thousandths.

To fix the mag dropping I tried two things. On one mag I rtv'd a .020 thick piece of shim stock to the back of the mag. On the other mag I bent the top part of the mag catch cutout outward slightly. Both methods held the mag in without incident. Not sure what my permanent fix will be, leaning towards supergluing a shim inside the grip so I don't need to modify every mag I buy.

Intercooler · December 10 2017 02:34:58 AM MST

How hard is it to remove the magazine catch? Maybe someone could build a weld on the end to extend it making it more positive? Send it in to Grand Power for a fix?

Azrckcrawler · December 10 2017 08:38:13 PM MST

Quote from: Intercooler on December 10 2017 02:34:58 AM MST
How hard is it to remove the magazine catch? Maybe someone could build a weld on the end to extend it making it more positive? Send it in to Grand Power for a fix?

A magazine catch that engages deeper into the cutout in the mag would be great. The problem is the centered design. Any engagement deeper than the thickness of the mag body is going to result in rounds, follower and or spring to contact the frame mounted magazine catch. If it were my design I'd specify a flare on the magazine at the top of the cutout for the 10mm guns.

My Xcal doesn't have the issue but it also doesn't recoil much either so the tiny bit of mag catch to magazine engagement seems to be enough. It may also have a tighter fit between the magwell and magazine. On my P40 you can push .035" worth of shims between the magazine and rear of the magwell. I'll have to see if the Xcal has the same amount of slop.