So I got a box of Amrscor 9mm 124 JHP for my birthday

[Phyffe]

A buddy of mine who is also an avid shooter gave this to me. Not surprising he chose this brand because its the most readily available, considering its made here.

I've generally avoided this brand, and even posted about how many stoppages I experienced when running my first 200 rounds of non-reload JHP through my brand new P10-S (this is what conventional wisdom tells us to do with brand new guns over here).

At any rate, its a Sunday so I broke out the ole 9mm cartridge gauge and passed em through. 41 round made it.

I had time on my hands so I thought I'd give it the ole plunk test on my P10-S. Of the 9 rounds that failed, 4 passed the plunk test on the P10-S.

After cleaning the P10-S, I figured, heck, I haven't cleaned my Shadow 1 in a while, may as well plunk the 5 losers through it while I'm at it. 2 of the 5 passed the plunk test on the Shadow. At least the Shadow got cleaned and lubed.

Well, there I was with 3 "bad" rounds and time on my hands and so I figured I ought to clean my last CZ pistol (a vanilla 75B, I didn't bother with the Scorpion as I figure the big guy would happily scarf up practically anything). 

Funny enough, the 75B plunk and spun even the 3 rejects.

I didn't realize how much more forgiving a 75B is over an SP-01 Shadow.

Also this exercise at least it SLIGHTLY reaffirms my faith in my country's arms manufacturing industry who probably test their ammo on Glocks and RIAs.

[Wobbly]

If you had a caliper or micrometer you'd proabably see the difference is less than 1-2 thousandths of an inch. A dimensional difference you can't see with the naked eye. Even people that shoot regularly, generally don't comprehend the incredibly tight fit between the ammo and the chamber. Ammo fitting the chamber correctly has happened for so long now (generations, in fact), that it's all taken for granted.

It all started about 1800 with Eli Whitney and interchangeable rifle parts. Parts made to such tight tolerances that any part could be used on any rifle. What followed was a revolution in manufacturing. Not only did this lead to identical parts, but parts made so inexpensively that anyone could afford them. This went on to be applied to everything we touch today... including the computer you are reading this on, to the chair your fanny is sitting in to read it ! It's a fascinating story well worth your time to research.

So what you most proabably have is 3 chambers, cut with 3 different reamers. Maybe they all started out as the same brand and size reamers, and one had previously cut 2000 chambers, while another had cut 9500 chambers. Just the wear on the reamer is making all the difference.

Take the last of your cartridges and cover them in marker ink. Then twist them inside the various chambers. You'll proabably see them touching in 3 different places. If you measure those places, you'll proabably see incredibly small deviations.

[Phyffe]

So, Wobbly, what I'm getting from your post is that its not down to the model of the weapon (or at least not entirely to that).

I assumed my pickiest barrel would be my shortest, and then I assumed that since the 75B was designed to be a service weapon, its barrel would be reamed to be more forgiving, whereas the SP-01 Shadow, being originally designed for SF and then competition, would have been designed for finer tolerances.

But from what I got from your post, a lot of it is just luck of the draw, then?

[Wobbly]

But from what I got from your post, a lot of it is just luck of the draw, then?

Yes, but we call it "manufacturing tolerances". The guarantee is that each gun should be able to correctly and safely fire a "standard round". But that doesn't mean that the bullet can/will hit a barn from 10 feet !! The interplay of 100 parts, which each vary themselves within a set range, means that no 2 guns will behave exactly alike.

If you'll read the board posts you'll see people say they'll gladly pay more for a gun they buy in person, rather than over the net. The difference for them is in the trigger, which when they handle 2 or 3 of the same model, they can find.

My first job in the mid-60's was at a local motorcycle shop. One of the setup guys noted that a particular motorcycle was faster than the rest. It wasn't even the top-of-the-line, multi-carb, "fast" model. We ended up taking that motorcycle to the drag strip several times and beating bigger motorcycles, which going by their model name, pedigree, displacement and specs should have won. But this particular motorcycle was simply "fast" right out of the crate.

Variations abound !

[Ron IL]

I have found that any pistol that is a spin off a military gun usually has generous chambers and will shoot anything.  Customized versions usually tighter for better accuracy and stuff.  I had a 92 fs that would shoot anything that my other guns wouldn't.  My RIA 1911 and my Sig 320 the same way. 

[Wobbly]

I have found that any pistol that is a spin-off a military gun usually has generous chambers and will shoot anything. 

That's easy to understand and explain because military and some law enforcement guns have to pass "mud tests". OOW, the weapon still has to work, even if it's dropped into a mud puddle. When the Glock Gen1 hit these shores ~25 years ago, they made a big deal of this. There were ads showing the Glock shooting under water and all sorts of other environmental issues. If I remember correctly their motto was "fires every time".

Finally, Glock figured out that scuba divers didn't buy many of their guns... that it was really Action Pistol and SD shooters. And those buyers wanted their guns to hit the target. (There was a famous shootout in Atlanta about that time. In all, 57 shots were fired between several cops and several bad guys, and no one was hurt.) And so the Glock chambers and barrels have slowly gotten tighter and tighter until the newest Gen5 guns are almost as tight as the CZ !

[M1A4ME]

I have found that any pistol that is a spin-off a military gun usually has generous chambers and will shoot anything. 

That's easy to understand and explain because military and some law enforcement guns have to pass "mud tests". OOW, the weapon still has to work, even if it's dropped into a mud puddle. When the Glock Gen1 hit these shores ~25 years ago, they made a big deal of this. There were ads showing the Glock shooting under water and all sorts of other environmental issues. If I remember correctly their motto was "fires every time".

Finally, Glock figured out that scuba divers didn't buy many of their guns... that it was really Action Pistol and SD shooters. And those buyers wanted their guns to hit the target. (There was a famous shootout in Atlanta about that time. In all, 57 shots were fired between several cops and several bad guys, and no one was hurt.) And so the Glock chambers and barrels have slowly gotten tighter and tighter until the newest Gen5 guns are almost as tight as the CZ !

A Glock that shoots as good as a CZ?  I guess they're not quite there yet.  Then again, even if they figure out how to make them shoot groups they still have to change the frame to better fit my hand and add a thumb safety to it.