9mm @ Max Length

[GuitarmanNick]

I am but a novice compared to most here so I come seeking wisdom from the experts.

I have a Star B pistol in 9mm para that requires a very long round to feed properly.

Most factory ammo will have feeding issues since the original design was 9mm Largo which is slightly longer than 9mm para. There were some magazines that were modified to feed 9mm para but they are very rare. The only magazines I have, have no modifications to feed 9mm para and they move from front to back in the mag quite a bit while firing and cause jams.

I have been working on my loads for this gun and decided to make up a small batch @ 1.169" which is the max for this round. My 49th edition Lyman's manual has a listing for Unique powder with 125 grain jacketed HP but I am using Hornady 125 grain FMJ HAP projectiles. These feed perfectly in the pistol and make it a pleasure to shoot so now I just need to figure out the proper charge.

The OAL listed is as 1.075" and a charge starting @ 4.5 grains and a max charge of 5.0 grains.

I reasoned that because of the longer OAL on my hand loads that some additional powder may be needed to keep the velocity of the round over 1000 FPS. I did research this, but was not successful in finding a definitive answer. Deciding to be cautious and try, I made up some @ the listed 5.0 grain max, and then some @ 5.2 grains.

At the range, I fired the 5.0 grain loads first and noted no signs of over pressure on the spent brass but the primers had dents a little deeper than I normally like. I then fired those loaded @ 5.2 grains and they showed some abnormal marks on the case heads and the primers looked like little volcanoes but were not pierced. Definitely too hot.

I have only been reloading a couple of years and I am perplexed as to if my thinking initially was in error. If you make a round longer than listed, will it's velocity change from the listed value in the manual? If so, what can be done to compensate and keep the velocity near the listed value?

 

[Jdne5b]

Without a Chrono, how do you think you're close to the listed velocity? You're using a different barrel, possibly different length, different projectile, plus all the other variables in primers, brass, powder lot.

The mantra goes.. start low, work up. You started at max and went up. Your thinking probably isn't wrong, you just possibly over estimated how much extra powder or under estimated the effect your particular lot of components made vs the book.

Get a Chrono, start low, see where your at, then add powder if needed.

 

[Bill K]

You are cruising for a bruising by starting at above max on a semi-auto pistol. Use your loading manual and start with a start load and work up.
As for your brass being to short, you really should find and use the 9mm largo brass that your chamber was designed and cut for.

 

[GuitarmanNick]

Just to be clear, I had tried lower charges, 4.6 and 4.8 @ 1.160" prior to this trip and they felt weak on recoil compared to factory loads. Should have included that in my original post. Only had a few feeding issues with those, but I am searching for a reliable load that will feed every time.

Figured with the additional empty space in the case that there was no need to load the lower charges again, since they were too light in the slightly shorter length.

It would be nice to have a chrono, but being on a fixed income that is not something that is high on the priority list.

 

[GuitarmanNick]

You are cruising for a bruising by starting at above max on a semi-auto pistol. Use your loading manual and start with a start load and work up.
As for your brass being to short, you really should find and use the 9mm largo brass that your chamber was designed and cut for.

The chamber is 9mm para. The mags are 9mm Largo.

 

[Uncle Ed]

Read the link below and the posts by the Moderator Wobbly. His images are very good and this method applies to all pistols.

How to determine Max OAL for a CZ Pistol
https://czfirearms.us/index.php?topic=34225.0

 

[GuitarmanNick]

Thanks for the link, Uncle Ed.

It does confirm that my thinking is correct. One thing I did not do is check the leade length. Perhaps the bullet it too close to the rifling with the 1.169" length and driving the chamber pressure a little too high. I dropped a few into the chamber to make sure the bullet does not hit the lands, but should have gone the extra steps in Wobbly's thread, first.

Really need to keep it as long as possible to feed correctly. Back to the drawing board.

Edit: Just checked using Wobbly's method and this barrel has lots of freebore. There is well over .100 " of space between the bullet and the lands. Even with the additional length, think I'll keep them .1 grain under the listed maximum just to be cautious.

 

[AJC]

Maybe the best way to fix your issue is to get some nylon and shim some space out of the back of your mag. If your only needing a little bit then some brass shims might be better. Address the problem directly, dont work around it.

 

[Bill K]

The chamber is 9mm para. The mags are 9mm Largo.

Okay, miss read your chamber ID.

 

[GuitarmanNick]

Maybe the best way to fix your issue is to get some nylon and shim some space out of the back of your mag. If your only needing a little bit then some brass shims might be better. Address the problem directly, dont work around it.

I looked into that. The main issue is availability of magazines or parts. If you install a spacer(~1/8" thick) in the back of the magazine, the spring and follower will also need to be replaced. The problem is finding a follower that will work. A couple from other guns have been shown to work, but they too are rare. I considered modifying the existing follower, but they are unobtainium if I ruin it and right now, all three of my magazines work with the longer length hand loads.

Occasionally I find some factory loads that run it it. Speer Lawman and S&B 124 grain FMJ rounds do okay with and occasional hickup. Still haven't found any factory 115 grain rounds that will feed.

This gun would not run at all when I got it, but I could not pass up the deal. Recoil and magazine springs were very weak and were replaced thanks to Wolff Gunsprings. Then I found the magazine feed lips on two of them were way too tight(probably from being dropped). Finally got those where they need to be and once I get this load figured out, I should have a reliable and fun shooter.

Made up a couple more small batches today for the next range trip. Gonna be a week or two before I can get back out to test them.

 

[Justinmac13]

I run my 9mm 2011’s at 1.17” with 6.9gr of autocomp, I think you touched on your feeding issue when you mentioned the mag lips, most often the problem is the mag lips are not set correctly, extractor tension is too tight or extractor inlet area is not polished smooth or the feed ramp is not at the correct angle. On a factory gun the first thing I would check is the extractor inlet, then set the feed lips, then lastly add a little bot more angle to the feed ramp and smooth over the break over point on the ramp. I’ve had several have issues and after touching those 3 things they all function 99.9 percent

 

[Clark]

I have converted a couple Star Super B pistols from 9x19 to 9x23 win, and a number of Tokarev 9x19 pistols to 9x23 win.

There is no problem with the higher pressure cartridge, but there are problems with recoil. I have bored out the cowling of the slide in the Stars to accomodate a larger diameter recoil spring assembly. My preferred powder is Power Pistol and my prefered bullet is 158 gr. I still have the hardware and data, but this effort was when I was showing the load books were wrong in 2000 to 2005 that said the CZ52 was stronger than the Tokarev.

 

[ToddKS]

You may need to try a different powder if you are going to load that long. May want to try something slower burning than Unique. As mentioned above, Autocomp might be a good one to try. I have friends using that in long loaded 9mm.