Odd Ejection with 9mm RMR 147 Gr. FMJ

Hi folks,

Finally got out out to the range today and tried some 9mm rounds I loaded up using RMR 147 Gr. FMJ bullets and BE-86. I'll put the load data below for additional info, but will skip straight to the "interesting" part...

My initial loads started off normally. Looks like I hit a nice accuracy node with 3.9Gr. BE-86. But the cases were still a tad bit dirtier than I'd like and I saw nothing concerning in terms of pressure so I kept going.

At 4.2 Gr I noticed a definite up-tick in recoil (more-so than with my previous increases), and accuracy headed south. Everything seemed fine pressure-wise, but I did notice that my last round didn't eject properly. Nothing jammed - no stovepipe or anything. But the spent casing just sat there, loose, inside the locked-open action.

I thought it was a bit odd, but assumed it was a one-off (I've seen this happen now and then for no apparent reason on the last round) and continued on to my final loading of 4.5 Gr, hoping accuracy returned. This load definitely kicked, and accuracy did not return. However, almost every "last" round I fired wound up staying in the open action just like that previous one. (I tend to shoot the 1st 5 rounds at each step with just a single round loaded at a time to make sure it locks the slide back reliably, so I had lots of opportunity to observe this behavior). The last 5 rounds I did load into the magazine together to shoot. All 5 cycled just fine, but darned if the last round didn't sit loose in the locked-open action again.

Because accuracy fell off a cliff I'll be heading back towards 3.9ish Gr. for future loads, but I want understand what happened here. These felt rather hot to me and I'm concerned this lack of ejection might be a sign of high pressure? I've always heard/read that ejection issues are to be expected for loads that are too light, but is there some mechanism that causes this with hot loads as well? Or is this somewhat normal when there isn't another round in the mag to push up on the shell being ejected?

I went over these cases pretty carefully and I don't see any bulging or anything. There's a touch of primer flattening, but nothing alarming for Winchester primers (I've posted far worse looking primers here and been told they look fine). The one thing I do notice is a hint of of primer swipe. Not the kind caused by the firing pin dragging, but caused by the primer rubbing across the bolt face during ejection. I only noticed because I'd colored the primers with sharpie to distinguish between loads, and the maker is "scratched away" slightly. Looking back at them not, it's hardly even noticeable honestly... I wouldn't have even noticed if I weren't scrutinizing them because of the ejection issues. Here they are just for grins... Starting loads are on the left, with the hottest all the way to the right:



So what do you think? Any explanation for why I might see ejection issues at higher pressures rather than lower? Is this a pressure sign of some sort? Even if accuracy wasn't an issue, I'm not sure I'd be comfortable loading these this hot again, but as I said I'd like to understand why.

These were all shot from my CZ-85. I bought it used so I can't speak to round count, but it's possible the recoil spring is a bit old (and I believe it is a bit easier to pull back than the slide on my father-in-law's CZ-75 compact). If anything I would think that would aid ejection though? I also shot some factory ammo through the gun after seeing this just to make sure it wasn't an issue with the ejector or extractor. Nope - Factory Federal cases all went flying across the range like they always do.

Thanks very much!!!!!!




Just to be thorough, here's the load info for the ladder I loaded up:


These were based off of Hornady's FMJ numbers from my Hornady 10th Edition. I don't have anything else to compare this specific load to, but Hornady's data generally tends to be more conservative than similar loads in my Lyman's 50th. Hornady calls for a starting charge of 3.2 Gr., and a max of 4.7Gr. for BE-86.

Hornady does call for a COAL of 1.165" which I had to reduce substantially to "plunk" into my CZ-85 barrel. But the RMR is a shorter bullet as well (by 0.025"). So the effective case volume is actually reduced by 1.165" - 1.115" - 0.025" = 0.025" I backed off my Max charge by 0.2 Gr. to account for the reduced COAL.

Yes, all the same Magazine... Didn't occur to me to try swapping that out (was keeping the mag the same while testing reloads). Now that you mention it, it was a rather new one... On the other hand, why would it behave that way for those hot loads, but be fine for all the others?

fxvr5 said:

What is your procedure for testing accuracy?

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Well I'm no crack shot, but I do the best I can to take myself out of the picture. The 1st 5 shots I load one round at a time, use a chair, and rest my wrist and the butt of the gun on a sandbag on the bench. I use a slow trigger squeeze and let the gun surprise me to ensure I'm not flinching or anticipating. It's entirely possible I'm more apt to limp-wrist the gun since I'm not supporting its weight and letting it surprise me. That may be a factor.

My 2nd 5 shots I load into a single (same) mag and shoot normally, standing, to get an idea of real-world (with me as a factor) accuracy, as well as see how they feel (recoil, etc.)

I'd be interested to hear what other people do to test accuracy?

edwardware said:

In a quasi-Browning action, where the rear of the barrel drops to unlock from the slide, it's possible for the cartridge rim to escape downward from under the extractor and thereby avoid the requisite kick it needs from the ejector to get outta there. In some geometries, this is only possible if the next round in the magazine isn't there to push upward, and the mag follower doesn't stick up as high, or spring as hard.

It's also related to slide velocity, recoil impulse, and possibly bullet profile if the profile sticks up enough to contact the ejecting brass.

Complicated little machines aren't they!

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Yes, they certainly are! Whenever you think you have them almost figured out, they have to humble you a bit

Thanks guys,

I was at the range again today (shooting mainly factory stuff this time), and noticed that gun was doing the same thing again on the last round in the mag - even with factory ammo. So it seems it's the gun, not my loads.

Thanks for the input all!

fxvr5 said:

What distance are you shooting for accuracy?

What do your group sizes measure and what is your criteria (group size measurement) for saying something has good or bad accuracy?

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Usually around 7 yards give or take. I don't get too worked up about making precise measurements - more an eyeball test. But there was an obvious, substantial increase in group size in this case. What do other people generally do?

Thanks!

longdayjake said:

In our experience CZ pistols prefer 124 grain bullets. Not sure why. I don't have a CZ 85 though so I can't really say. Ejection issues are usually either an extractor or magazine issue.

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Thanks Jake - glad to hear it, as I have an order for 2k of your 124 Gr. MPRs somewhere in that massive backlog you're working through All my 9mm's happily gobble up your 115 Gr. MPR's (I added another 1k more of those to my order too) so I'm looking forward to trying the 124's.

Thanks!