Load Manual OAL vs Push Test Results

[daved20319]

The Moderators are splitting this topic out as a sub-topic of particular and specific interest to this Forum. Original thread content is here....
https://czfirearms.us/index.php?topic=108240.0


One other question.  What is your actual OAL and how does that compare to published data for the bullet in question?  Most (all?) loading manuals include tested OAL for the load data they publish, granted, it's conservative, but it's generally a safe starting point, especially if you're on the inexperienced side.  Good luck!

[painter]

One other question.  What is your actual OAL and how does that compare to published data for the bullet in question?  Most (all?) loading manuals include tested OAL for the load data they publish, granted, it's conservative, but it's generally a safe starting point, especially if you're on the inexperienced side.  Good luck!

I'd have to disagree with this, particularly when discussing CZ, XD, and Sig, pistols.

That's why to do a push test.

[Dan_69GTX]

One other question.  What is your actual OAL and how does that compare to published data for the bullet in question?  Most (all?) loading manuals include tested OAL for the load data they publish, granted, it's conservative, but it's generally a safe starting point, especially if you're on the inexperienced side.  Good luck!

I agree with Painter.  There are several published loads I can NOT use the OAL in on my CZ.  It would work fine in the S&W or Walther, but NOT the CZ.  No idea on Sig since I don't have one.

[daved20319]

One other question.  What is your actual OAL and how does that compare to published data for the bullet in question?  Most (all?) loading manuals include tested OAL for the load data they publish, granted, it's conservative, but it's generally a safe starting point, especially if you're on the inexperienced side.  Good luck!

I'd have to disagree with this, particularly when discussing CZ, XD, and Sig, pistols.

That's why to do a push test.

Then we're going to have to agree to disagree, I load for 2 CZ's and a SIG, I've never had an issue using published OAL, provided I'm using the exact same bullet, and not something similar in weight/shape.  I do a plunk test as well, just to be sure, and I always plunk test if I'm using a bullet I don't have specific data for.  If I happen to be using a bullet that's also available in factory loaded ammo, and it's ammo that works in my guns, I'll use the same OAL as factory.

Just as an aside, my SIG is touchier about bullet shape and OAL than my 97 BD, it doesn't like truncated cone bullets.  Later.

[Dan_69GTX]

Then we're going to have to agree to disagree, I load for 2 CZ's and a SIG, I've never had an issue using published OAL, provided I'm using the exact same bullet, and not something similar in weight/shape.  I do a plunk test as well, just to be sure, and I always plunk test if I'm using a bullet I don't have specific data for.  If I happen to be using a bullet that's also available in factory loaded ammo, and it's ammo that works in my guns, I'll use the same OAL as factory.

Just as an aside, my SIG is touchier about bullet shape and OAL than my 97 BD, it doesn't like truncated cone bullets.  Later.

Ahh - you just added a LOT more info than your initial post.  You initially failed to mention that "I do a plunk test as well, just to be sure... which must be done!

At shooting competitions I have seen guns get damaged and they were using reloaded ammo.  I've never seen a gun get damaged when using factory ammo.  So, ANYTHING that can be done mitigate safety problems is something that should be done.

Each gun is unique and it could be suicide to blindly follow a specific recommended load assuming it will be just fine.

[painter]

One other question.  What is your actual OAL and how does that compare to published data for the bullet in question?  Most (all?) loading manuals include tested OAL for the load data they publish, granted, it's conservative, but it's generally a safe starting point, especially if you're on the inexperienced side.  Good luck!

I'd have to disagree with this, particularly when discussing CZ, XD, and Sig, pistols.

That's why to do a push test.

Then we're going to have to agree to disagree, I load for 2 CZ's and a SIG, I've never had an issue using published OAL, provided I'm using the exact same bullet, and not something similar in weight/shape.  I do a plunk test as well, just to be sure, and I always plunk test if I'm using a bullet I don't have specific data for.  If I happen to be using a bullet that's also available in factory loaded ammo, and it's ammo that works in my guns, I'll use the same OAL as factory.

Just as an aside, my SIG is touchier about bullet shape and OAL than my 97 BD, it doesn't like truncated cone bullets.  Later.

That's fine. I have no problem with disagreement. I haven't had the same experience. I can't use published OAL for Hornady XTP, or HAP in 9mm. Also, the barrels that loads are tested in bear no resemblance to a pistol. The data presented is simply a report, and in no way a recommendation.

CZ's in 45 ACP don't share the same short chambers as the 9 mm.  Is your SIG a 9 or 45?

[Wobbly]

In the interest of education, here's a photo sequence presented for this discussion....

This is a Hornady reloading manual #7...



This is a box of Horanday #35580 147gr XTP bullets on top of the correct page in the manual...



This is a newish CZ P10c, disassembled...



This is an over-length bullet/case combination to discover the Max OAL in a P10c barrel....



And the Max OAL for a 147gr XTP in a CZ barrel is....



The stated OAL in the book is 1.100", while the Very maximum OAL that will not start an Out Of Battery (OOB) condition is 1.111". That's the equivalent of only 3-4 human hair diameters. If your personal OAL has variations of +0.006" then over half that allowance has disappeared before you even start. If you happen to run across and a blem bullet or other hiccup, your 0.011" clearance could totally disappear, even with perfect OAL control and output.

Bottom line: I'm simply not seeing this "conservative, but generally safe" clearance that's been mentioned.

I'm thinking that the OAL mentioned in the manual has been mistakenly identified as a "recommended OAL". I have searched several manuals and the word "recommendation" is not one I'm seeing. Instead, the OAL in the manual is simply part of the powder testing report. In high pressure cartridges, OAL is just as important as the amount of powder. Both contribute to chamber pressure, which is the Number 1 concern of all reloaders. Therefore, it's self evident ANY complete load test report would need to contain OAL and amount of powder.

So while I concede that in a lot of cases the reported OAL will work, one can not be absolutely sure it will work in every case. Therefore these bullet-to-rifling clearances must be measured in every new situation if any level of safety is expected.

Hope this helps. 

[daved20319]

Well, I'm glad I posted what I did, even if it turned out to be a bit of a humbling experience  .  Based on your photo sequence, Wobbly, I'd have to say I've been lucky, even with the extra step of doing a verifying plunk test.  This is another good example of the pitfalls of ASSuming, for some reason I had it in my head that published OAL's were based on SAAMI minimum chambers, and also were to be treated as recommendations vs. simply a report of the conditions for that particular load.  So thanks for adding to my education.

Painter, my SIG is a P220R, so .45 ACP like my 97 BD.  Much as I love my 97, it's NOT a viable carry piece, at least for me, just too heavy and limited holster selection.  Just for fun, I was comparing the SIG to my primary carry piece, a PCR.  The SIG is 3/4" longer, 3/8" taller, about the same width, and weighs just one ounce more with both guns fully loaded.  Just struck me as curious, sorry about the post detour.  Later.

[M1A4ME]

My two plastic .40's (P07 and P09) can take extremely long overall length (nope, don't know them off the top of my head) but I know our Beretta 90-Two, my Tactical Sport and my CZ75B (all .40's) won't begin to chamber what the P07 and P09 will.  I had to shorten up all my .40 loads (135 grain hollow points and 140 grain LTC) to be able to shoot them in the other pistols.

The P09 9MM on the other hand is "short chambered" like the CZ75's/P01s, etc.  In fact, just a tad shorter than my CZ75 Compact.  The Compact will chamber/fire the 140 grain LSWC I loaded up for fun while the P09 hangs up and won't fully chamber.  When I was reloading them I had the Compact on me and used it to plunk test.  Then I decided to shoot the P09, too, as it has proven to be my most accurate 9MM.  Locked the P09 up so tight I had to use a cleaning rod to punch the bullet back away from the end of the chamber.  Shot that round in my Compact, no issues.

You really do need to sit down with your CZ family, do some testing to see which one has the shortest chamber, and load for that one so it fits everything else - unless you want to try to segregate ammo between pistols.

I confess to looking at the reloading manual overall lengths, but then I plunk test and write my overall length in my reloading logbook and don't look at that data in the reloading manual again.  That was for the pistol they used, not for my CZs.

[SoCal]

I confess to looking at the reloading manual overall lengths, but then I plunk test and write my overall length in my reloading logbook and don't look at that data in the reloading manual again.  That was for the pistol they used, not for my CZs.

And I will sometimes use COL to adjust my load, If it is shorter by a .01 or more I will adjust my starting and max load down.

[Wobbly]

This is another good example of the pitfalls of ASSuming, for some reason I had it in my head that published OAL's were based on SAAMI minimum chambers, and also were to be treated as recommendations vs. simply a report of the conditions for that particular load.  So thanks for adding to my education.

• That's the issue right there. Although every gun barrel entering the USA has to meet SAAMI specs, the "trick" is that SAAMI doesn't fully define all the chamber dimensions. Freebore is one of those un-defined dimensions. And, Max OAL is basically the result of the length of Freebore.

That's what this chart is trying to graphically depict....




• Additionally, the fact that a lot of CZ's use a shorter-than-quoted OAL is why we do all the load testing for CZ's.


No condemnation here, Brother. It only took me a decade of stumbling around to put some of this stuff together in my head. 

[Rcher]

I'm wondering if Tanfoglio and other clones (Witness, Sarsilmaz models, Jericho) have the same free bore design as CZ.
My Sarsilmaz pistols eat any factory ammo without any problems, out of curiosity I measured OAL for Geco and S&B 124gr FMJ RN and it was 1.150, so I don't have problems with it.

[Wobbly]

I'm wondering if Tanfoglio and other clones (Witness, Sarsilmaz models, Jericho) have the same free bore design as CZ.

Tanfoglio simply licenced the "75" mechanism design from CZ. The trigger mechanism is in no way associated with how the barrel is machined. Any similarities between the 2 brands of barrels probably has more to do with the types of ammo commonly available in both Italy and Czech Republic.

My Sarsilmaz pistols eat any factory ammo without any problems, out of curiosity I measured OAL for Geco and S&B 124gr FMJ RN and it was 1.150", so I don't have problems with it.

• That all sounds way too optimistic. It would be safer to say "...so I haven't had any problems with it YET."

• I'm not following this statement... "I measured OAL for Geco and S&B 124gr FMJ RN and it was 1.150", so I don't have problems...". I presume what you measured was the cartridge OAL at 1.150". That means nothing without also measuring the barrel the cartridge fits into. What this entire thread is about is the relative fit between the cartridge and the barrel. That takes 2 separate measurements. You can't measure 1 of those and pronounce that you're OK. That's like saying my new car will fit into my old garage because I measured the car (but I didn't measure the garage).

All the best.

[M1A4ME]

And check magazine fit/feed, etc., too.

I was loading some .45 acp (230 grain LRN) for that new XD 5" Tactical .45 I bought last spring.  Pulled the barrel, adjusted/tested (plunk test) till I got what I wanted and load a box for the next range trip.

Started trying to load the ammo in the magazines and I'd get 4 or 5 of them in before they'd hang up.  Overall length just fine for the chamber - too long for the magazine.  I've never run into that problem before.

Check both.  Chamber and magazine.

[Rcher]

I'm wondering if Tanfoglio and other clones (Witness, Sarsilmaz models, Jericho) have the same free bore design as CZ.

Tanfoglio simply licenced the "75" mechanism design from CZ. The trigger mechanism is in no way associated with how the barrel is machined. Any similarities between the 2 brands of barrels probably has more to do with the types of ammo commonly available in both Italy and Czech Republic.

My Sarsilmaz pistols eat any factory ammo without any problems, out of curiosity I measured OAL for Geco and S&B 124gr FMJ RN and it was 1.150", so I don't have problems with it.

• That all sounds way too optimistic. It would be safer to say "...so I haven't had any problems with it YET."

• I'm not following this statement... "I measured OAL for Geco and S&B 124gr FMJ RN and it was 1.150", so I don't have problems...". I presume what you measured was the cartridge OAL at 1.150". That means nothing without also measuring the barrel the cartridge fits into. What this entire thread is about is the relative fit between the cartridge and the barrel. That takes 2 separate measurements. You can't measure 1 of those and pronounce that you're OK. That's like saying my new car will fit into my old garage because I measured the car (but I didn't measure the garage).

All the best.

Thank you, Wobbly! I need to educate myself before starting reloading - things are more complicated than I expected.
I know that many favor Berrys 124gr RN for reloading, but Lee manual says OAL: 1.115 for 124gr RN plated bullets, some recipes I found online for Berrys 124gr RN even say 1.116. But, from the other side - CZ barrel needs less OAL, so how it is possible to accomplish? Reducing powder charge?