Primer hit question

[distra]

I finished fitting the Kart 9mm NM barrel to my SA 38 super 1911 and took it to the range this morning. It shoots just as good as the super so I'm pleased with that, but I did notice a difference in how the primer strikes look between the 9mm and 38 Super. The 38 super has a nice round dent in the primer where as the 9mm (out of the Kart barrel) looks like it has been blown back. The sides around the primer dent look to have errupted to the rear of the cartridge and the scaped off during the ejection process. The inside of the breech face has some flakes of primer case as well. Any ideas as to why the primer strikes look different? I used both reloads and factory 9mm or 38 super with same results. Attached is picture of what I'm talking about. Is this really worth worrying about or am I just being type A? 9mm cases on the left 38 super on the right.

 

[nitetrane98]

It's called cratering and it's a classic sign of over pressure. The casing is forced back against the breechface with so much force that the primer tries to flow into the firing pin hole around the firing pin. I'm a little confused about which caliber is doing the cratering. In the first part you say the .38 looks fine and the 9mm is cratering but later you say you use reloads and factory in 9mm and.38 with the same results.
There might be a mechanical reason for the cratering but I don't know that much about it. My guess might be if it is only cratering with the new 9mm barrel that it is sealing much better than the barrel that you used to work up the 9mm load and now that load is too high. It might just be too damn high but cratering with fatory loads is puzzling.

 

[Jim Watson]

I got some really ugly primers in my SA Ultra Compact 9mm; factory and handload. All the problems went away when I put in a steel firing pin (Brown 826) and a Wolff firing pin spring to replace the California pattern titanium firing pin and stiff spring.
http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=1323&title=1911 AUTO FIRING PIN

 

[RogersPrecision]

This will lead to light strikes as debris will accumulate in the firing pin hole.
I'm guessing that the 9mm rds are higher pressure than the 38's.
I've experienced this quite a few times.
In each case the problem was cured by using a closely fittied firing pin with
no more than .002" diameter clearance.

 

[distra]

I'm a little confused about which caliber is doing the cratering. In the first part you say the .38 looks fine and the 9mm is cratering but later you say you use reloads and factory in 9mm and.38 with the same results.

Sorry about the confusion. I used both reloads and factory 9mm rounds and got the cratering using the newly fitted Kart 9mm NM barrel. I then switched back to the 38 super barrel and fire some reloads and factory 38 super rounds that did not crater. For 9mm, I loaded 124gr FMJ RN with 4.6gr of Bullseye chrono'ed @ 1032fps and then used Remington factory loads again 124gr FMJ RN that chrono'ed @ 1120fps. I thought these primers looked like a sign of over pressure, but the factory loads did the same darn thing and that really confused me. The 9mm barrel is a Kart EZ fit and I am assuming the chamber does not need to be reamed.

Firing pin replacement is a cheap and easy fix if it works in my case.

 

[nitetrane98]

This is kind of interesting. If we take away the mechanism to show signs of overpressure is it no longer too hot? Or was it never too hot to begin with? Kinda like, "If a man says something and there's no woman around to hear him, is he still wrong?" Maybe you could throw together a round or two dropping the charge a 1/10 gr each until you don't get any cratering. Then if you got down to , say, 4.1grs, you could say, "No way is this too hot." But then there is the individual gun factor.
Your 9mm load, while certainly healthy, doesn't look to be a grassburner. And then there's the factory ammo doing it too. The .38 Super is no slouch on pressure either. The only variable in the deal is the new barrel. How does the headspace looK? I'm wondering if the 9mm might be getting a little headstart and slamming into the breechface. I've heard of headspace problems manifesting in cratering. Maybe 1911tuner will chime in and comment.
Little known fact for the day, primer blanking is the correct term for cratering.

 

[distra]

Little known fact for the day, primer blanking is the correct term for cratering.

Learn something new everyday. The factory loads are puzzling. They slip into the chamber no problem and the base of the case is even with the top of the barrel hood. I seated my reloads so the round drops into the chamber easily. I'm going to load a few lighter loads and run them tomorrow. I'm wondering if the chamber needs to be reamed or if there is something wrong with the barrel fit. The barrel hood just touches the breechface and appears to be similar to the factory 38 super barrel.

 

[JackOfAllTradesMasterAtNone]

Is there an update to shooting the reduced loaded 9mm cartridges?

I'm no gunsmith..

But the primer hits seem to be a bit off center. Is the chamber in alignment and square with the bolt face?

The barrel hood just touches the bolt face? Is there a spec measurement for what that distance should be?

Currious, Does SA list a different firing pin and spring for .38super and 9mm?

-Steve

 

[log man]

distra, You didn't mention in what gun this happening and more specifically which slide. The reason I ask is in parallel to what Chuck said and if this is a Springfield and you are using a std. 9mm firing pin that is the problem as the SA pin is larger.

LOG

 

[tractorshaft]

You can also put an unprimed 9mm case in the chamber and look down the barrel through the case at the breech face and see how the firing pin hole "Lines Up" when in lockup, not an exacting method of measure but the ole "Eye" is pretty good at detecting discrepancies that would surprise you. Review this thread on headspace;

Chuck Rogers is THE MAN!

Here is the Ed Brown firing pin you need from Brownells;

#087-205-825

To quote:
"Mfr: ED BROWN

Sized To Correctly Fit & Eliminate Primer Flow

High-quality firing pins that are specifically sized to reduce the chances of primer flow. Proper weight for positive ignition with heavy-duty springs. Correct tip diameters in 9mm/.38 Super provide a close, firing pin hole fit for slides built to Colt or Springfield Armory dimensions.

SPECS: Tool steel, blued. #824 fits Series 70/80 Colt .45 ACP, #825 fits Series 70/80 in 9mm/.38S/ 10mm/.40 S&W. #826 Special size for 9mm/.38S, .45 ACP Springfield, Inc.

Catalog page 18"

http://www.thehighroad.org/showthread.php?t=176251

Get your 9MM Go-No-Go Headspace guages here

http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=19298