Bore Diameter of a Cartridge?

Here is something for you all to ponder from the CMP Rule book.

Please educate me if I am not reading this correctly, but the words are: 

4.2.3 a) U. S. Government or Colt M1911 Service Pistols or commercial versions of the same type (M1911). These pistols may be chambered for any cartridge with a bore diameter not less than 9mm and not greater than .45” and have a barrel length not greater than 5.100”. 

I've never seen a "bore diameter" listed for any cartridge.  Bore diameter is typically a barrel measurement from my understanding.  

If they are talking about "bullet diameter" then it looks like you can shoot a .38 Special or even .380 Auto, along with all the various "Supers and 9's" in a 1911.  

If they are talking about "bore diameter" of the barrel, then you can't shoot a 9mm because the actual bore diameter of a 9mm barrel is less than that.

If they did not mean either, then why not just say 9mm cartridge or other calibers like the Service Pistol list?

CR10X wrote:Here is something for you all to ponder from the CMP Rule book.

Please educate me if I am not reading this correctly, but the words are: 

4.2.3 a) U. S. Government or Colt M1911 Service Pistols or commercial versions of the same type (M1911). These pistols may be chambered for any cartridge with a bore diameter not less than 9mm and not greater than .45” and have a barrel length not greater than 5.100”. 

I've never seen a "bore diameter" listed for any cartridge.  Bore diameter is typically a barrel measurement from my understanding.  

If they are talking about "bullet diameter" then it looks like you can shoot a .38 Special or even .380 Auto, along with all the various "Supers and 9's" in a 1911.  

If they are talking about "bore diameter" of the barrel, then you can't shoot a 9mm because the actual bore diameter of a 9mm barrel is less than that.

If they did not mean either, then why not just say 9mm cartridge or other calibers like the Service Pistol list?

Yeah I think they mean bullet diameter. So looks like 9mm pistol is illegal

Hi CR,

I may be misunderstanding your concern, but if I restate it as:

                    0.35"  (more than) bore diameter (less than)   0.45"

(odd, it doesn't accept the math equivalency signs)

then any cartridge that can squeeze a bullet down the pipe in that range is allowed.

Now the scientific side of my brain hurts due to the mix of units and lack of appropriate significant figures, but that's my guess at an interpretation.

Am I way off?

(Edit yet again:)

Of course bore diameter is smaller than groove diameter, but perhaps these values are close enough for government work, where 2+2=5 for sufficiently large values of 2.

well if you are going to interpret 9mm being .3543 and 45 being  .4500 then we'd all have an issue.. I sort of  doubt that's what they mean.

.355 is typical of a 9mm    45acp is typically .4515

I'd suspect that anything between and including those those would be fine.. haven't had them slug any of my barrels yet

if you want to use the 380 then tell them it's a 9mm KutZ



poorly worded rule..

Wiley Clapp in American Rifleman wrote:https://www.americanrifleman.org/articles/2011/3/15/terminology-bore-diametergroove-diameter/

Here's the definition, right out of the NRA Firearms Sourcebook. It is “...the minor interior diameter of a barrel that is the diameter of a circle formed by the tops of the lands.” That is the bore diameter, but groove diameter is “...the diameter of a circle circumscribed by the bottom of the grooves...”

just wanted to add to the confusion. its' my nature...

Probably no need to over think it.  9x19 should be fine.  If someone really wants to go through the hassle with no real advantage, arguably 9x17 would be okay too...but why would anyone bother going through the extra expense and effort?  If you want .380 recoil, just download 9mm...the extra 2mm of case capacity isn't going to make a difference.

Cecil, I didn't think it got cold enough in Carolina to get cabin fever in the wintertime. Do you need me to send you a can or two of WD-40?

Maybe cabin fever, maybe not.  Maybe just good Bourbon.  

A 9 mm barrel bore is given as 0.346 +0.004/-0.000 and the bore diameter of a .38 / .357 barrel is generally about .350 - .352" so neither one makes the actual wording if it means the barrel bore.

But, if they mean "groove diameter" or "bullet diameter" then the 9 mm and .38 special makes the cut being equal to or greater than 9mm. 
 
So, maybe having some fun showing up at EIC match with a .38 Special wadcutter 1911.     Either the .38 special would get to shoot, or the 9mm 1911's would not get to shoot. 
 
CR

I have some 38 Short Colt brass and I’m going to try developing loads for some plated wadcutters.  We’ll see what they do in my old Colt 38 Mid Range.

CR10X wrote:Maybe cabin fever, maybe not.  Maybe just good Bourbon.  

A 9 mm barrel bore is given as 0.346 +0.004/-0.000 and the bore diameter of a .38 / .357 barrel is generally about .350 - .352" so neither one makes the actual wording if it means the barrel bore.

But, if they mean "groove diameter" or "bullet diameter" then the 9 mm and .38 special makes the cut being equal to or greater than 9mm. 
 
So, maybe having some fun showing up at EIC match with a .38 Special wadcutter 1911.     Either the .38 special would get to shoot, or the 9mm 1911's would not get to shoot. 
 
CR

I'm sure you are being facetious, but let's back up a minute and look at the rule book.  Full wadcutters are not legal for the EIC match, which is what you would have to shoot in your 1911 .38 Special.  I'm sure it's all in jest, but we have some newbies out there who might take it seriously.

As far as what the CMP was trying to say, let's keep it simple; 9mm is the smallest cartridge you can use, .45 ACP the largest.

As someone who runs these matches, it's hard enough determining what handguns are legal, when someone shows up with something other than an M9 or 1911.  Let's not complicate something that should be pretty easy to determine.

Hi CDRT,

CR is not being facetious, I am sure, but importantly is pointing out lack of clarity in the rules that might cause conflict.  Those coming to a match for the first time should have some clarity as to what is a legal gun and caliber, as well as those who attempt to push the limits.  Those of use who deal with these rules are best positioned to point out wording that might be confusing.  I certainly am glad that writing them is not my job, but am glad to try and help where I can.

sharkdoctor wrote:Hi CDRT,

CR is not being facetious, I am sure, but importantly is pointing out lack of clarity in the rules that might cause conflict.  Those coming to a match for the first time should have some clarity as to what is a legal gun and caliber, as well as those who attempt to push the limits.  Those of use who deal with these rules are best positioned to point out wording that might be confusing.  I certainly am glad that writing them is not my job, but am glad to try and help where I can.

I am writing the CMP today to clarify the rule.  They have listened to me in the past, maybe I'll get lucky.

I am still waiting to shoot next to somebody who is using a: 9x25 Dillon, 10mm, .45 Super, .460 Rowland...

The .38 Short Colt is amusing but would imagine the cost to build one would be outrageously high not to mention the odd ball mags. (and very little gain over say a 9mm with as .356 bore)

CRDT:

Thanks for the reminder to check the ammo rule.

4.4.2 Pistol Ammunition a) Service Pistol. Service Pistol competitors may use any safe ammunition that is loaded with metal-jacketed or metal-plated bullets. Non-jacketed, wad-cutter or lead bullets may not be used. 

However; the remaining point is that written, we cannot shoot a 9mm 1911 or any .355 / 9 mm cartridge because that is the groove diameter / bullet diameter. The bore diameter of the barrel of these cartridges is as I stated above, less than 9mm. 

So, a clarification or revision of the rule as written would be something the CMP should consider.  

CR

CR10X wrote:CRDT:
Thanks for the reminder to check the ammo rule.

4.4.2 Pistol Ammunition a) Service Pistol. Service Pistol competitors may use any safe ammunition that is loaded with metal-jacketed or metal-plated bullets. Non-jacketed, wad-cutter or lead bullets may not be used. 

However; the remaining point is that written, we cannot shoot a 9mm 1911 or any .355 / 9 mm cartridge because that is the groove diameter / bullet diameter. The bore diameter of the barrel of these cartridges is as I stated above, less than 9mm. 

So, a clarification or revision of the rule as written would be something the CMP should consider.  

CR

This is what I wrote to the CMP rules committee.  If it's not what people what, you should write to them as well:

This rule has caused some confusion among the shooters since it references bore diameter rather than bullet diameter in the 1911 pistol for EIC matches.

I would recommend you rewrite the rule to simply state that 1911's for the EIC match can be chambered for 9x19mm, 10mm, .38 Super and .45 ACP cartridges, rather than referencing bore or bullet diameters.  These are the most common chamberings for the 1911.

The rule as written has some shooters contemplating shooting a .38 Special 1911 for the EIC match.  This is problematic, since the 1911 in .38 Special requires full wadcutter bullets, which are not legal for the EIC match.

If you do not want to limit the 1911 to specific cartridges, then change the word "bore" to "bullet" in the rule and the diameter of the .45 from .45 to .452, so it reads

a) U. S. Government or Colt M1911 Service Pistols or commercial versions of the same type (M1911). These pistols may be chambered for any cartridge with a bullet diameter not less than 9mm and not greater than .452 and have a barrel length not greater than 5.100”.

.45 ACP jacketed bullets are .451 diameter, lead plated bullets are .452.

I would prefer:

a) U. S. Government or Colt M1911 Service Pistols or commercial versions of the same type (M1911). These pistols may be chambered for 9x19mm, 10 mm, .38 Super and .45 ACP only and have a barrel length not greater than 5.100”.


This would allow us to determine if the pistol is legal by the chambering, rather than bullet or bore diameter, which can vary.

As someone who runs EIC matches, it would help us to keep the rules as simple as possible.  The inclusion of the rather long pistol list has not made things simpler, but this rule change would help.

Greetings,

All this really makes me appreciate earning my Distinguished Pistol Shot Badge back when we shot the 1911 45 ACP with commercial or Military 230 grain full charge ammo.

Cheers,

Dave

a tad simpler then Dave 

fc60 wrote:Greetings,

All this really makes me appreciate earning my Distinguished Pistol Shot Badge back when we shot the 1911 45 ACP with commercial or Military 230 grain full charge ammo.
Cheers,
Dave

Me too.  But now I'm running them and while I enjoy doing it, some of it can be a headache.