Just purchased a 9mm EZ, shot a few boxes of Herters ammo thru it and started reloading the brass. There is a half circle under the firing pin on the bolt face and the primers are forming to it when shot. I literally have to sand down the bump on the primer to just be able to get the shell to slide into the shell holder. Was curious if anyone else was experiencing the same issue, and if so what are some options to fix it. Thanks in advance.

Sounds like a primer issue with that ammo.
Lee makes a hammer powered decapper that you drive the primer out with before sizing. You can use the decapping stem if you don't get to heavy handed.

Ivan

By the way; Welcome to the greatest gun forum on earth!

Ivan

Thanks for the info. Gonna hit the range in a couple days with some different ammo. I was thinking it could be the primers on the Herter ammo are to soft. Thanks for the welcome.

Wouldn't the imperfection on the bolt face be the problem & need attention?

The area of the bolt face that contacts the primer should be smooth, right?

.

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Waiting for the break of day

we need a pic of a case and one of the bolt face....

What brand of shell holder are you using in your press? I've had issues with the Lee shell holders in some calibers and one for 38 special didn't allow cases with slightly thicker rims to fit. The solution was to purchase RCBS shell holders because they have enough clearance to allow for a variety of rims thicknesses and conditions such as "high" primers.

The bolt face of your gun may be the problem It should be smooth with no protrusions or indention's (other than the firing pin hole).

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H Richard
SWCA1967 SWHF244

Can you take a photo of the primer area of one of the spent shell casings and post it here?

A couple of possible explanations.....this might be caused by primer drag. Primer drag, or damage to the primer cup can occur when the end of the striker is still engaged with the primer at detonation, the slide begins it's opening cycle, and the barrel cams down, making a drag mark in the primer cup.

There can also be an artifact or raised area in the primer cup caused by the cutaway at the bottom of the firing pin hole in the breechface. That is, if there is a cutaway. Some pistol breechfaces don't have them.
This "raised area" or bump appears in the expended primer just below the impact site of the striker, and is caused by pressure exerted on the primer cup forcing the cup into the cutaway in the breechface. (as you stated in your OP)

Both of these things are considered normal, unless you are experiencing primer failure or "blowouts", which can allow gasses to be expelled from the primer cup.


Cutaway (arrow) under striker hole in breechface:




Typical drag marks:

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Ret. LE, FA Instr, S&W Armorer

I pick up and buy a lot of once fired 9mm Luger brass and have noticed this "primer protrusion " on several cases ... the protrusion will keep the case from going into a shell holder . The primer has tried to flow back into the fireing pin hole , I see it often on +P Cases ... that primer protrusion is the problem .
It could be hot loaded ammo , soft primers or sloppy firing pin fit / weak fireing pin spring .
First try another brand / loading of ammo . Standard velocity / standard pressure ammo ... If it still does it ... it might be the pistol ... call S&W .

When I discovered why the fired cases wouldn't fit into the shell holder I started keeping a file handy and would knock the pesky protruding part off so the case would enter the shell holder .
I reload my 9mm's with mid level velocity/pressure loads and CCI primers and don't have this problem with them .
Gary

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Certified Cajun
NRA Member

9mm M&P EZ Breech Face and Primer Strike Issue

Same here with photos. .

I shot 3 more Brands of ammo today. Federals had the same issue. My reloads that are 1100 fps with CCI primers had the same issue. I shot Winchester ammo also and had no issues. The pictures above are exactly what I'm seeing. I don't know how to post pictures or I would. None of the ammo I'm shooting is plus P. I shoot a ton of this same ammo and plus P thru my G19X and have zero issues. I don't understand what the half moon under the firing pin is for, but it's exactly what is being formed into the primer. Love the 9 ez, but I'll be damned if I'm gonna file every shell before I can reload it.

The cutaway in the breechface under the firing pin hole is provided to minimize the possibility that small pieces of brass could be sheared off of the casing or "protruding" primer cup by the edge of the firing pin/striker hole during cycling. (as the barrel cams down during firing)

Apparently, these small pieces of metal have the potential to contribute to stoppages (misfires) as they interfere with the free motion of the firing pin/striker.

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Ret. LE, FA Instr, S&W Armorer

Thanks for the info. I just looked at my shells again, it's definitely not firing pin drag. It's actually forming the half moon into the primer. Is it possible that the gun is creating too much pressure? ( IE lands issues or depth seating issues?)

Perhaps, if it's occurring with several different types of ammunition. Have you had any other problems, other than the "bump" in the primer causing the interference during reloading?

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Ret. LE, FA Instr, S&W Armorer

Those "smeared" firing pin indention's could be the sign of the gun unlocking too soon and jumping back out of battery before the firing pin has rebounded. A consistent problem with most Glocks.

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H Richard
SWCA1967 SWHF244

Google primer drag and look at the videos. There are many video links that show the problem.

I cant speak specifically to the 9mm EZ, as I don't own one, but primer drag marks are common on a lot of semi-auto 9mm pistols. It is more common on compacts, as they tend to have higher slide velocity, and unlock a little sooner than full size guns. A heavier slide spring might alleviate the issue, but make for a harder to rack slide. If they are raised to the point they interfere with the shell holder you are using, the recommendation to try another brand of shell hold (RCBS) is a good one.

If it is actually being caused by the small, teardrop machined into the breach face below the firing pin hole, the end cure for your issue is still trying another brand of shell holder.

Larry

I have had no other issues with the 9ez. I have tried both my Lee and RCBS shell holders with no luck. I've eliminated the pin drag issue, a couple of my Glocks have the pin drag markings after firing but they do not interfere with the reloading process. I've been a fairly avid pistol shooter for over 20 years and I'm completely stumped here. I'm gonna reload some more shells this week using small rifle magnum primers and see if that helps due to the primers being pressed from a thicker alloy.

Get out the famous Dremel tool and deepen the small grove in the shell holder so the primer will easily slide into the shell holder. I have RCBS, Hornady, and Lyman shell holders that all have the 'factory relief' machined in them. I just had to make it 0.015 deeper for offending 38 spl or 9 mm range brass.

EDIT: I reload at the local indoor range on a Dillon 650. You cannot see the primer entering the primer station, and some primer pockets are crimped in non-rifle brass. Recovery of mis-loaded rounds became my "other" job when bad ammo accumulated. I pulled the bullets on a RCBS Rock Chucker press with a shell holder extension with the correct shell holder.

After a reloading nitemare with European primers, the solution was to grind the "primer relief" in a 38 Spl, 9 MM, and 40 S&W shell holders so bullets could be pulled, powder dumped, and bad primers removed. The Dillon shell plate has much greater clearance than a conventional shell holder.

Defective primers are found by loading plastic ammo boxes primer up and then dumping good ammo into zip lock bags.

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S&WHF 366

I went to measure the clearance between the case base and the primer inlet on several shell holders and was surprised to find how much they vary.

Even ones from the same manufacturer appear to vary.

Using a simple dial caliper I measured one Lyman that was just 20 thousandths clearance. The rest of mine averaged 30 thousandths with 34 being the extreme.

Those must be some more kinda high protrusions.

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GOA
USA Shooting Supporter

I was just going to post this very same thing. I would also give this a swing.

Having loaded a vast variety of head stamped 9 mm, the problem is most likely the shell holder having overly tight tolerances. I've no idea why, but 9 mm seems to have a wide variance in case rim dimensions. I've also noted some cases seem to pick up slight burrs on the rim. This is easily solved by using either a Lyman 9 mm shell holder or one for .38 Super. (Lyman does a 9 mm/.38 Super shell holder)

I need to note that while it would seem that the top of ram to shell plate bearing surface should be the same on all shell holders, it generally isn't. You may have to very slightly reset your dies when going to the shell holder with more generous case rim dimensions.

I made this discovery some years back after buying a new set of RCBS dies and a RCBS shell holder to go with them. Didn't take too long to realize with RCBS, the .38 Super shell holder was the way to go. A 0.005 in shim eliminated resetting the dies.

Mr. Dremel tool it is. I appreciate all the feedback and help with this issue. Thanks to all.