When loading for the .40 Cooper (10mm), is it better to make the C.O.L on the minimum side of the American National Standards? Wouldn't this assure that the rounds would function in guns of unknown barrels? Wouldn't this afford you the opportunity to decrease powder loads while still creating high barrels pressures and hence reported muzzle velocities? Less powder used means more savings in the manufactures pocket.
Why am I asking this question? Because I found that an ammunition manufacture that appears to be doing just that. I use as my reference the Hornady reloading manual. Hornady states that the C.O.L for their 155 gr XTP at 1.260" (max). The American National Standards (ANSI/SAMMI Z299.3-1993) shows a min. C.O.L of 1.24" and a max C.O.L of 1.26". I have always strived 1.26" for in my loads, just as the Hornady manual recommends for maximum. I use Starline brass, WLP primers, XTP bullets and Blue Dot powder.
I recently purchased Grizzly 155 JHP ammunition which is rated at 1400 ft/sec. The Grizzly ammunition uses Starline brass and bullets that resemble the XTP. I measured the C.O.L and found an average of 1.24".
I have a box of Remmington 180 gr MC (metal case) ammunition. I measured the C.O.L and found that the average was 1.254". Should I use 1.25" as my target C.O.L? When do you change the C.O.L versus the powder charge?

I keep my 10MM Magnum cartridges under the SAAMI max COAL of 1.555" and my 10MM Auto cartridges to under the SAAMI max COAL of 1.26"

These work fine in all of my firearms that are so chambered.

What is the nominal C.O.L for the 10mm Auto? How did you derive that C.O.L?

I do not believe I understand what you are asking

Max COAL is a published specification, there is nothing to derive

The max C.O.L is published as 1.26". Is the nominal value of your 10mm auto 1.26" or a value less than 1.26" but more than 1.24"? If it's something less than 1.26", what is it and what made you choose that C.O.L? Did it chamber better in your barrel for example. How did you adjust the powder charge for that C.O.L? By chrono maybe? Do you load using the min. C.O.L understanding that it will function in any pistol barrel?

Trying to extrapolate anything based on the OAL and appearance of factory loads is asking for trouble.

You have no idea what powder is in use in the factory load, nor it's charge weight. Unless the bullet is specified, you have no idea of what bullet is in use or it's resistance to the rifling and any effect that may have on pressure. All you do know is that the factory (hopefully) found the pressures acceptable with that bullet/powder/OAL combination.

You do know that Hornaday (or any other manual publisher) found pressures acceptable for the load data published with that particular bullet and specified OAL.

BTW, take velocity claims of any ammo maker with a grain of salt-unless personally verified with your guns & a quality chronograph. I am personally leery of claims of high velocities and acceptable pressures by boutique ammo makers.

I'm a bit confused. I've been reloading for 45 years and load for several different calibers.. I even enjoy reading about where and when cartridges were developed.
Like the 375 H&H Magnum was developed in 1912 by Holland & Holland.
The 44 Remington Magnum was 1955 by Remington along with S&W & Elmer Keith ..

But I'm not familar with a .40 Cooper.

( edit) Sorry , from the other text , it appears you are talking about the 10mm Auto. Never mind..

Sorry for the confusion. I decided to honor Mr. Jeff Cooper, developer of the 10mm, by refering to the cartridge as the ".40 Cooper". Similar to how the .357 Sig is referred.

Understood. However, the MAXIMUM C.O.L published by SAMMI and Hornady is 1.26". That does not mean it has to be exactly at 1.26". It can be less but more than 1.24". If your loads are less than 1.26", how did you achieve that C.O.L.?

The Max COL is a standard set by SAAMI. In theory that length should fit any firearm chambered for that caliber.

Look up any caliber say 9mm, None of my ammo is loaded to the Max COL most any caliber is under that which is determined by the barrel and the plunk test.

Different types (shapes) of projectiles will also have different COL A FN HP will certainly be a different length than a RN FMJ

You may need to adjust a few thousands to have it fir the barrel.chamber and mag.

If you have the exact bullet (say a XTP) then use what Hornady tested at. Or a Gold Dot use Speer. If it is a off brand find the closest weight and shape.

It also depends on where you look for the Max CL. SAAMI is 1.250, CIP is 1.260 The min is 1.240 so you have that room to play with. With a FN bullet

http://www.saami.org/pubresources/cc...0Automatic.pdf

10mm Auto - Wikipedia, the free encyclopedia


Bottom line is do not go below the min and as always start powder charges low and work up

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Still Running Against the Wind

This thread has spent more time worrying about "Nominal COAL" than I have in 25 years of loading the 10MM Auto cartridge.

Projectiles with cannelures are loaded to the cannelure

Projectiles without cannelure are loaded to fit 1911 magazines

I almost never measure COAL

Never do I try and adjust powder charge to match anything or compensate for anything

First of all, I don't know if you think you're being cute or unique by calling the 10mm Auto the .40 Cooper but you're not. Also, Jeff Cooper did not help develop the 10mm round although the was involved with the .40 G&A project. That round is closely related to the .40 S&W and the prototype gun was a Browning HP which is not large enough to accommodate the .10mm Auto cartridge.

The original Bren Ten Prototype pistol was chambered in .45 ACP and not any .40 cal. round. Jeff Cooper insisted that the gun be chambered in what he called the .40 Special for him to be involved in the project any further. Dornaus & Dixon needed his name associated with the gun and were sort of "encouraged" to comply. Another top half was fabricated for a round roughly the same length as the .45 ACP which made things a lot simpler from an engineering standpoint. Cases for the new round were fabricated from cut down .30 Remington rifle brass. Sierra provided some .41 Magnum HP's swaged down to .400". Pacific, i believe, provided a custom set of loading dies and experimentation began. When Norma agreed to provide factory ammunition, Mike Dixon provided specifications. Jeff Cooper required the now famous 200 grain FMJTC bullet at 1,000 FPS. What people seem to forget is the he instructed Dixon that this specification be target impact velocity at all practical handgun ranges (out to 50 meters in Cooper's view) and not at the muzzle. Dixon padded this spec. to 200 grains@1200 FPS at the muzzle however. He didn't believe that Norma could achieve this safely based on D&D's development work. Dixon felt however that if Norma got near those numbers, they would achieve Cooper's 200@1000 at 50 meters. Norma did, in fact, meet the 200@1,200 spec. by using a proprietary propellant they used in .357 magnum loads marketed in Europe. This actually created problems for both D&D and Norma. D&D had durability problems with the Dual Caliber MECGAR magazines. Norma had erratic pressure issues with initial lots of their ammunition.

So, while Cooper was involved with the .40 G&A to a fair extent, his involvement with the development of the 10mm Auto cartridge was minimal. As a matter of fact, he was an unpaid consultant on the Bren Ten project altogether. Dornaus & Dixon kept him in the loop because they needed to as much as anything else.

The correct OAL for the 10mm and any autoloader round for that matter is the longest OAL which will fit your magazines correctly along with feeding and chambering reliably. This number can and usually does vary from gun to gun. The number printed in the loading manual guarantees nothing. Loads are developed by trial and error regarding the OAL with lighter charges. After the sweet spot is determined, charges can be increased in order to obtain the velocity required, within safe limits of course.

Bruce

I've certainly had and continue to have different experiences with COL settings than some have stated above.

For revolver hand loads I normally use published data or the cannelure grove (if close to published data) after verification of fit.

As for my semi-autos, I adjust the COL for feeding reliability along with the powder charge if necessary... and none of my 1911s - .45 ACP, 10mm, 10mm short (40 S&W) - feed magazine length rounds.

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Dave
SWCA #2465

The .357 SIG is referred to as such because the name of the cartridge is ".357 SIG". The 10mm Auto is called "10mm Auto". It helps to be specific and unambiguous when talking about reloading. It would be like saying the SAAMI COAL should be no more than 1.26 King Thumbs as some sort of tribute to whomever came up with the inch. You probably won't get clear answers if your question isn't clear.

You can achieve a COAL of < 1.26" by adjusting your seating die to 1.26". Then adjust it some more.

With the bit about the odd cartridge name, the suggestion of impropriety on behalf of manufacturers that seat to 1.24", and the rather basic question above, it is difficult to understand what exactly you are looking for in terms of information?

How do ammunition manufactures determine the C.O.L of their ammunition that they sell to the public? The ammunition manufactures do not own all the pistols that their ammunition will be used. Why did Grizzly settle on 1.24", which is still in SAMMI 10mm specifications, for their 155 gr. 10 mm ammunition?

See the 10mm and Jeff Cooper here. Contest it if you wish.

"How do ammunition manufactures determine the C.O.L of their ammunition that they sell to the public? The ammunition manufactures do not own all the pistols that their ammunition will be used. Why did Grizzly settle on 1.24", which is still in SAMMI 10mm specifications, for their 155 gr. 10 mm ammunition?"

Here is your answer, read below.

In short, they don't, they both, ammunition and firearms manufacturer, are simply adhering to SAAMI criteria.

None of you has apparently understood what the SAAMI Cartridge and Chamber Specifications represent!

First, the SAAMI dimensions do not directly relate to handloading, they are voluntary specifications for manufacturers of firearms and ammunition. The intent, and a valid one, is if firearms makers adhere to the SAAMI Chamber specifications (Which they almost universally do!), and the ammunition makers adhere strictly to the SAAMI Cartridge specifications (Again, which they virtually universally do!), then any ammunition and firearms made to these specifications will be compatible with each other! Nothing more nor less.

gsparesa,

You are making a nearly universal error that is common to new re-loaders! You are over-thinking what is a mechanically simply process. Until you gain enough experience from actually doing for several years you will be well advised to simply use data and OAL dimensions shown in the loading manuals as-is! There is a very real safety consideration in this.

One comment you make regards seating deeper to maintain the pressure level with reduced loads! WHY??? There is absolutely nothing wrong with a cartridge developing a lower pressure level that maximum, as long as the bullet reliably clears the barrel. You will reach a point where there is insufficient recoil energy to function a semi-automatic pistol long before pressure drops this low.

Read the manuals you have. If you don't have one, BUY ONE, or, preferably, several. Read them thoroughly, several times. Every question like this will be answered in the reference material.

Gee I thought I said that, But none of us know anything

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Still Running Against the Wind

Well, you did, sort of. But then he asked the second question which I directly responded to, so it appears either OP still "didn't get it" after your post, or maybe he didn't read it!

Unfortunately getting into peripheral issues such as bullet shape, specific bullets, CIP, etc. tends to muddy the issue for the OP who is obviously a NewB.

IMO, never. I load to the longest oal that runs in my gun with a specific bullet. There isn't really much pressure/vel increase with only a 0.020" shorter oal. Use the data, load longer if you can. The only time adjusting a powder charge is required when seating deeper, is when you have worked up a max load with a given oal. If you are running below max, the 0.020" shorter means little.

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NRA Cert. Inst. IDPA CSO

In view of the fact that my information is based upon interviews my partner conducted with Col. Cooper while researching a book and yours is based upon a website with a reputation of being somewhat less than 100% accurate and most anybody can get into and edit, I'll stick with what the person in question actually said.

Bruce