Is there a bullet profile that feeds best in CZ's?

[perttime]

All I've ever seen people run through CZ mm pistols is 124/125 grain round nose. Either factory rounds or factory length reloads. I believe that is 29.0 mm or 1.142 inch. At least they always seem to feed.

[IHAVEGAS]

All I've ever seen people run through CZ mm pistols is 124/125 grain round nose. Either factory rounds or factory length reloads. I believe that is 29.0 mm or 1.142 inch. At least they always seem to feed.

125 grain sns rn at 1.15 would not feed (at least 1 ftf per 10 rounds) in either of my guns, 1.125 seems to work 100% so far but I've only shot 300 rounds or so to date. With 147 sns (rnfp, completely different bullet profile) my results were opposite.

Something I want to experiment with. With the 147's, the slide will go forward on its own 100% of the time on a brisk slide lock reload, this is very handy for IDPA and occasionally handy for USPSA (usually comes into play when you throw a make up shot that was not in your stage plan), with 125's I seem to need to make more of an effort to be sure the magazine is slammed in very briskly. Not a concern for many I know. Anyone tuned their gun (modified slide stop or whatever) to make the slide going forward on its own more reliable ?

[IDescribe]

Just an update. I'm able to load Blue Bullet 147 grain round nose out to 1.150, profile made all the difference. Thanks to Rowdy and others for the advice.

How exactly did you make that determination? That bullet should hit the lands at that length in a CZ.

[Darqusoull13]

IDescribe, I shot about 200 of my load out of the CZ. I actually tested same recipe at 1.125, 1.135 and 1.150 OAL: 3.2 grains Bullseye, 147 grain Blue Bullet Round nose with a CCI primer. I experienced similar accuracy with each load and decided to keep 1.150" OAL to stay consistent with a load that shoots well in my M&P, among other reasons.

This forum has other reports of variation in maximum allowable OAL in CZ's. In my barrel with this load, I get great function. Your barrel may be different and there are ways to remedy that to allow longer loads should your needs require it. Just sharing my experience.

[IDescribe]

So you haven't done a push test, then. You need to do a push test. If you are into the lands, you are shooting at higher peak pressures than necessary. Google -- "push test" CZ -- and read to learn how to determine max OAL.

[JLeeCZ]

SNS 147gr NLG Coated flatpoint out to 1.15, no problem in my SP01 barrel. I load to 1.135 for great accuracy. Actually doesn't hit the lands until about 1.165.

With the SNS 125 NLG Coated, 1.10 is about max from the same barrel but shoots great.

[Darqusoull13]

I Describe, these were all tested in the manner you indicated during loading. This was not relevant to my issue with another bullet profile, but is always sound loading advice.

I was having feeding issues, now solved with the load listed, which you may have read about in another post.

[IHAVEGAS]

If you are into the lands, you are shooting at higher peak pressures than necessary.

Know of any measured data available for this?

[IDescribe]

If you are into the lands, you are shooting at higher peak pressures than necessary.

Know of any measured data available for this?

Aside from what I've read in reloading documents/manuals?

Here is a discussion from the Hornady manual, 9th Edition. The example discussed here is for rifle, and there are some illustrations that go with it, but they're unnecessary to get the meaning:

To illustrate the effects of of variations in bullet travel before the bullet enters the rifling, we'll compare a standard load with adjustments made only in the bullet's seating depth. In a normal load with the bullet seated to allow about 1/32nd of an inch gap between the bullet and initial contact with the rifling, pressure builds very smoothly and steadily even as the bullet takes the rifling. Pressure remains safe throughout the powder burning period, and the velocity obtained -- 3500 feet/sec -- is "normal" for this load in this rifle. Seating the bullet deeper to allow more travel before it takes the rifling permits the bullet to get a good running start. Powder gases quickly have more room in which to expand without resistance, and their pressure never reaches the "normal" level. Nor does the velocity; with the same powder charge, it only comes to 3400 feet/sec. When the bullet is seated to touch the rifling, it does not move when the pressure is low; and not having a good run at the rifling as did the other bullets, it takes greatly increased pressure to force it into the rifling. As the expanding gases now find less room than they should have at this time in the burn cycle, the pressure rise in these conditions is both rapid and excessive. Velocity is high at 3650 feet/sec, but at the expense of rather dangerous pressure.

To help understand the above -- smokeless powder burns faster the more pressure it's under, AND the more pressure it's under the faster it burns. It's a positive feedback loop. Anything you do at the beginning of the burn to increase pressure results in an increase in the peak pressure reached, and because it's a positive feedback loop, it's a geometric increase. A seemingly small change up front -- such as seating deeper and decreasing the initial size of the combustion chamber OR seating the bullet into the rifling -- can result in a dramatic increase in pressure at the peak.

As to seating into the rifling, imagine sitting on a bicycle in the street, pointed into a driveway, with your front tire butted into the curb. It would take a lot of force on the pedal to make that front tire go up and over the curb. You might have to stand up and put all your weight on one pedal to get it to roll forward at all, and it's possible you might not even be able to put enough force into that pedal to start the bike rolling forward. But if you back up the bike just a foot, you can roll pedal forward and travel up over the curb easily. It's the same with a bullet. If the bullet has just a little room to build momentum before entering the rifling, it passes into the rifling smoothly. But if it's already touching the rifling, it has to wait for pressure to build to a high level before the bullet is forced into the rifling, the pressure is significantly higher than what it should be at that point in the burn cycle relative to a bullet just seated off the lands, and the expanding combustion chamber will always be smaller at whatever point in the burn cycle than what it would be if the bullet had been seated just off the lands, where it can pass into the rifling with lower pressure.

To be clear, this isn't to say that someone can't develop a load seated into the rifling, and in fact many loads will produce better accuracy if seated into the rifling (though only really relevant to rifle distances), but if you're going to do that, you need to build the load up from scratch. In the case of the load in this thread. If one is into the rifling and one isn't, you're going to end up with significantly different velocities. And if it's a competition load that is appropriately loaded for the long-throated pistol, the short-throated pistol is going to be at higher velocities with higher pressures. And if this is a competition load with a fast powder and a heavy bullet, those pressures are going to climb quickly. It's something be aware of and load around.

BUT you asked for data. I actually do have a little data from a test I did to determine just how much velocity (and by association peak pressure) increases as OAL decreases. I conducted the test with a Montana Gold 124gr JHP and 3.6gr of N320, making a ladder with the same charge weight but increasing the OAL from 1.04 up to 1.14 in .02 increments. But in the HK VP9 I ran the test with, that bullet hits the rifling at 1.13, so that longest cartridge was loaded into the rifling. Velocity decreased by 15-19 feet/sec per .02 OAL increase, but when the bullet got into the rifling, velocity went back up a little. With these components, however, 3.6gr of powder was certainly under-pressured, and I suspect the results would have been more dramatic with a normal charge weight for that bullet with that powder. I am thinking of running the test again with a normal minor PF charge weight for N320, and I'll post that data here if you're interested in the results.

Edited January 28, 2016 by IDescribe

[IHAVEGAS]

Thanks. Was wondering about measurements of peak pressure, as you know a lot of folks like to build accuracy loads with rifle bullets approaching very close to or even touching the rifling, or at least it is a common practice with the few folks I know who are into precision rifle shooting. Data would tell me if they are playing with fire (no pun intended) or just making a modest pressure increase that is not something to be concerned about in their below maximum charge weight loads.

No worries. Just curious. I'm guessing that the person who provided your quote must have either had data or perhaps was looking for other signs of pressure in the primer/brass, it would be interesting to know how the conclusions were arrived at.

[vixty]

I have to load extreme 124fp at 1.035 to function in my stock 2. Even though they are really short they run just fine in both of my cz's. I load 3.7tg for a 130 pf

[himurax13]

All I've ever seen people run through CZ mm pistols is 124/125 grain round nose. Either factory rounds or factory length reloads. I believe that is 29.0 mm or 1.142 inch. At least they always seem to feed.

125 grain sns rn at 1.15 would not feed (at least 1 ftf per 10 rounds) in either of my guns, 1.125 seems to work 100% so far but I've only shot 300 rounds or so to date. With 147 sns (rnfp, completely different bullet profile) my results were opposite.

Something I want to experiment with. With the 147's, the slide will go forward on its own 100% of the time on a brisk slide lock reload, this is very handy for IDPA and occasionally handy for USPSA (usually comes into play when you throw a make up shot that was not in your stage plan), with 125's I seem to need to make more of an effort to be sure the magazine is slammed in very briskly. Not a concern for many I know. Anyone tuned their gun (modified slide stop or whatever) to make the slide going forward on its own more reliable ?

I file a small 45 degree angle on the slide area that the slide stop tests on during slidelock.

So you haven't done a push test, then. You need to do a push test. If you are into the lands, you are shooting at higher peak pressures than necessary. Google -- "push test" CZ -- and read to learn how to determine max OAL.

The spin test is just as important, if not more.

Sent from my VS986 using Tapatalk

[IDescribe]

Agreed. But the OP doesn't seem terribly interested in this aspect of load development. It didn't seem necessary to go further.

My own process is to push test to get ballpark. Then load a dummy slightly longer, check to verify it's too long, then seat a little deeper, check in barrel, seat a little deeper, check in barrel, seat a little deeper, check in barrel... until it plunks and spins freely. That way I know exactly, as opposed to push test, which can be off a few thousandths.

[IHAVEGAS]

Something I want to experiment with. With the 147's, the slide will go forward on its own 100% of the time on a brisk slide lock reload, this is very handy for IDPA and occasionally handy for USPSA (usually comes into play when you throw a make up shot that was not in your stage plan), with 125's I seem to need to make more of an effort to be sure the magazine is slammed in very briskly. Not a concern for many I know. Anyone tuned their gun (modified slide stop or whatever) to make the slide going forward on its own more reliable ?

I file a small 45 degree angle on the slide area that the slide stop tests on during slide lock.

I am intrigued !

I am also a coward when it comes to removing metal from the pricey parts of a good gun.

Only if you have time and inclination, it would be real interesting to know how well this works out and anything else that you can think of that would be anti screw up information. A picture would be cool.

Sorry for the thread drift op.

[IDescribe]

It's not the bullet weight that is the difference. It's the OAL with that bullet profile. You might fix the problem with an increase or decrease in OAL by as little as a hundredth of an inch. If it's not that, it could also be your extractor being so gummed up that it can't move it's full range, and it's not giving ground the way it should as the cartridge shifts this way and that during chambering.

[GeneBray]

Round bullets.

Triangular, square, pentagonal, hexagonal, heptagonal, and octagonal don't work well, are virtually impossible to find, and brass and reloading dies are even harder to come by.

Now that I'm done being a wiseacre...

In my SP01, it feeds everything, RN, JHP, TC, TCJHP and from multiple vendors. I've shot 90, 95, 115, 124, 125, 130 & 147 grain bullets and all work flawlessly. Montana Gold, Zero, Precision Delta, and commercial JHP from Speer, Federal.

If you have a concern, then go with RN.

Edited January 30, 2016 by GeneBray

[UFO]

I've tried several different bullets and length. I have found that as long as you keep the OAL between 1.125 - 1.135 in .40, just about anything will feed. I'm currently using 200gr Xtremes @ 1.131 OAL with zero issues so far. I have tried 190gr Black and Blue @ 1.130 OAL with no issues till the barrel get a little dirty. Then they FTF. But, these are .402 diameter and I think that may be a little too large for a CZ. I have tried 200gr Bayou's with no problems, they are .401 diameter all around the 1.130 length.

Is this true while cycling them through the gun by hand? I've loaded some 180 grain round nose blue bullets with 4.2gr of wsf loaded to 1.118. I have not been able to shoot them yet, but cycling them on the bench I get about 3 ftf every mag. Wondering if a different bullet is in order? They also seem very deep in the case.

I forgot to mention it is a .40 tactical sport. All stock besides the grips.

Never really tried that, I have always just went out and shot them. That does seem a little short, I'd bring them out to at least 1.125

Update: since my last post, I tried 220gr Xtreme loaded at 1.167 O.A.L. and they cycled through the gun just fine. But, I don't think I will use them.

Edited January 30, 2016 by UFO