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Discussion Starter · #1 ·
Gday,
I was doing some measurements on a number of blank slides, and comparing them to guns in my inventory. Well so what you may say, but wait theres more....

It appears both my Kimber Target II Stainless 1911 one in 9mm and one in 38 Super, actually run a 40 cal Breach face.

This, to me is poor.

So, for those who wanted to know, yep, its true Kimber use 40 cal breach face for 9mm and 38 Super.

Makes my decision on their fate a whole lot easier...

Cheers,

Aussie D

:(
 

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Discussion Starter · #4 ·
Trevor,
yes, there is that ability to go the path of .357SIG if you want.

Fildugn,
Im a accuracy nut, hence I beleive that the rear of the cartridge being guide by a surrounding breach face increases the chances of the cartridge case being more centralised in the chamber from the moment of ignition and hence corresponding accuracy.

Secondly, from a reliability perspective, the round upond feeding slides under the extractor claw, with a larger breach face there is a higher chance that the cartridge may move sideways, and hence not feed correctly.

Thirdly, from a reliability perspective, the round upon extraction, may also slip sideways due to not being held firm on the breach face, and hence a higher chance of extraction/ejection malfunction.

So, I put it to you this may, you walk into a Bar, order a Millers Geniune Draught, but get a Budweiser instead. Now there both Beer, but its not what you wanted for whatever reason you have chosen. While both will taste of beer, and both will get you drunk, its just not the same.

Now before I get a tirade of MGD v Bud abuse, it was just for the comparison...

Cheers,

Aussie D
:)
 

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Aussie D, there's nothing wrong with your theories, but my reality is that my 9mm Pro Carry II is one of the most accurate pistols that I own. The reliability has not been 100%, but that's not because of extraction issues. I believe it's because the pistol is oversprung. For the record, I'm not comparing it to other 9mm 1911's, but rather other pistols in general.
 

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Aussie D,
This has been known for a while but doesn't seem to cause "that many" issues.

Your first theory of accuracy simply isn't correct. Once the round is fully in the chamber, the breech has nothing to do with adding to or detracting from accuracy and has nothing to do with lockup time.

Your second theory is correct and has been experienced by some Kimber 9mm owners. A properly tensioned extractor usually prevents it but there is some "extra" room there.

Your third one won't happen with a properly tensioned extractor but it does cause a little more sensitivity to extractor tension.
 

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Discussion Starter · #7 ·
Bret,
For combat accuracy, the Kimber is fine, for competition accuracy it lacks.

Kruzr,
The Extractor pushing on the rim of the case, in a generally larger sized chamber (probably still within specifications), will push the cartridge to the left away from the extractor. The depth of a Kimber chamber seems to be a bit large (probably within specifications) which will allow it to minutely pivot using the extractor as the pivot point, thus having the crtridge ever so slightly off axis to the centre of the barrel. The projectile will then exit the case hitting the lead of the rifling slightly off centre with a corresponding twist down the barrel and out of the muzzle possibly inducing a little bit of yaw.

Ok, its not going to be much, but when accuracy really counts, its just another thing that adds up...

I have inspected fired cases and there is pronounced scorche/powder mark on the case on one side, which happens to be the opposite side to the small mark left by the extractor. This adds to my theory.

Cheers,

Aussie D
 

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Accuracy comes from the chamber, barrel and lock up, not the position of the cartrige on the breech face. I repeat, what's the problem? The only possible problem I see is that if the cartrige is far enough off then firing pin would strike the primer off center. I don't think that .02" variation would cause a problem. Maybe they're using a 38 & 9 breechface for the .40 caliber?
 

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Kruzr,
The Extractor pushing on the rim of the case, in a generally larger sized chamber (probably still within specifications), will push the cartridge to the left away from the extractor. The depth of a Kimber chamber seems to be a bit large (probably within specifications) which will allow it to minutely pivot using the extractor as the pivot point, thus having the crtridge ever so slightly off axis to the centre of the barrel. The projectile will then exit the case hitting the lead of the rifling slightly off centre with a corresponding twist down the barrel and out of the muzzle possibly inducing a little bit of yaw.
There isn't enough slop in the chamber to allow the bullet to enter the barrel crooked. The round headspaces on the case mouth and if there were that much tolerance (which is hard to believe) in the chamber, that is what would determine the round's orientation in the chamber.

You are correct on feeding issues and with a weak extractor, the ejection issues..... but accuracy is not involved here.
 

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Discussion Starter · #10 ·
Kruzr,
I have attached some pictures to explain my issues, which, potentially, will be exaggerated by a 40 cal breach face.

Remember I said this was a chamber probably built to the larger size of specifications, hence, as I have said, not the best for accuracy.











there will be one more picture to follow, which will show the potential for misalignment.

Cheers,

Aussie D
 

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Discussion Starter · #11 ·
Follow on from last post

Kruzr,
This last picture shows a case (factory) inserted rearwards. Now obviously never happen, but what it shows is the potential for misalignment is increased if the rear of a case is not guided by a correctly sized and fitted breachface.



So, in this case I beleive that this Factory Kimber barrel, combined with a 40 cal breachface is far from optimun in regards to accuracy.

Funny how Kimber market "Match" Chambers, a "match" to what......

Cheers,

Aussie D
 

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Nice pics but now you need to figure out how to do those tests with the breech closed, no matter how wide, on the round. I still say there is no way for a bullet to go down the barrel anyway but straight regardless of the width of the breech.

Why wouldn't you expect a rimless round to go into the chamber part way backwards and have some movement since it isn't headspaced in the chamber? I can do the same thing with a .45 and my Baer, Brown, or Wilson. Shows nothing at all.

The 9MM Kimbers I've shot never suffered from accuracy, nor for that matter has any Kimber I've ever shot. Other issues, yes, but accuracy is not one of them.
 

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Discussion Starter · #13 ·
Kruzr,
The pictures demonstrate a few things.
1. A loaded cartridge will move in the chamber, in all directions. This is proved by the photos, especially due to the fact that the case head spaces on the mouth, but note, it is below the hood, therefore, the case can be orientation in a number of directions in the chamber.

2. The case in rearwards was to illustrate, how off centre it is possible to have a concentric object in the chamber.

3. My theory is a correctly sized breachface could minimise this movement, by centreing the cartridge, in the lateral plane as a minimun.

I have no desire to take photos in the chamber while the breach is closed.

If it wasnt an issue, then why do we buy different szed breach faced slides and match them to calibre, why not get rid of it on a .45 as well, as according to you, it is irreelavant to accuracy?

Cheers,

Aussie D

PS, Like I said previously, Im an accuracy nut.
 

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If it wasnt an issue, then why do we buy different szed breach faced slides and match them to calibre, why not get rid of it on a .45 as well, as according to you, it is irreelavant to accuracy?
Believe what you want but different widths are because it is a reliability issue as we mentioned before. It is not an accuracy issue and I'm also a target shooter and place accuracy as the number one criteria in considering guns.
 

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Discussion Starter · #15 · (Edited)
Kruzr,
Thanks for the input, appreciate your knowledge and experience.

I have learnt a lot in this thread. Its why I am here to learn, ask, offer input and advice if applicable.

So, this may somewhat explain why I seem to have to adjust the Kimber extractor tension more often than other gun, due to the breach face size being an issue in reliability.

It also means, that the 40 cal slides sitting in my safe may get a new lease of life...

Cheers,

Aussie D

:)
 

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Discussion Starter · #17 ·
Kruzr,
Is Kimbers extractor MIM? Mine has tool marks on it, looks plated, possibly Nickel.

Would an "aftermarket" quality brand Stainless Steel extractor require less retensioning in your opinion?

Cheers,

Aussie D
 

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You do realize that your backward pic theory is totally full of hot air because the 9mm luger case is not straight walled, but tapered, right? Anything you see there is due to the tapering, not a misalignment.

If it headspaces on the mouth, it headspaces on the mouth. The only issue that can then remain is whether the bullet is seated concentric to the axis that is perpendicular to the case mouth. Under firing pressure, the rest of the case deforms to exactly fit the chamber. This would be an ammo quality thing, not a gun thing.
 

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Discussion Starter · #19 ·
Jtaylor,
I guess, my point is this, I undertand 9mm is a tapered chamber, so, in theory, this demonstrates how large this chamber is, with corresponding error in alignment, which is added to by the extrator tension and breech face being incorrect.

Whist the case will expand, by this time the projectile is being thrust about with forces, and if it is not snug, allowing it to be of axis, due to the cartridge alignment. This is not condusive to good accuracy.

Cheers,

Aussie D
 

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Kruzr,
Is Kimbers extractor MIM? Mine has tool marks on it, looks plated, possibly Nickel.

Would an "aftermarket" quality brand Stainless Steel extractor require less retensioning in your opinion?

Cheers,

Aussie D
No, Kimber uses a machined extractor. A different one may or may not hold tension better. I suspect it is carbon steel in the white. See if it takes cold blue, I've never tried that on a Kimber extractor.

In any event, I would stick with a carbon steel extractor since it is more malleable than a stainless one and that is probably a good property for an extractor to have.
 
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