Loading to Min OAL or the Shown Dimensions

[Pugsbrew]

OK, just to get this solidified in my head. I'm looking at the Lee Second Edition reloading data for the 9mm.

The picture of the cartridge, with dimensions, show the maximum dimensions for the cartridge So, the max OAL for the 9mm is 1.169. From the book, "This insures it will fit any standard chamber". page 711

Now, the load data tables gives Min OAL based on bullet type and powder used.

There can be a tremendous difference in the two values, in reloading terms.

So, determining optimum OAL would have to be a trial and error event. So, asking for suggests wouldn't be out of the realm of a time saving question, would it?

Lee states that the best accuracy is usually obtained with bullets seated at the MAX OAL and Factory Crimped. pg 714

So, what length would one start at, the max or the min?

I know it depends, but something has to stay constant while trying to figure out best load. I'm am not trying to figure out the HOTEST load that I can shoot. I want accuracy over max velocity.

 

[Walkalong]

the max OAL for the 9mm is 1.169. From the book, "This insures it will fit any standard chamber". page 711

That is incorrect. See the plunk test and also search short throat CZ.

For 9MM (Auto rounds) you need to load so the round chambers freely and feeds 100%. Tweak from there to see if accuracy can improve and the rounds still fit and feed 100%.

Load 9MM RN bullets at 1.130 to 1.135 and try them out. Go from there.

 

[Pugsbrew]

"the max OAL for the 9mm is 1.169. From the book, "This insures it will fit any standard chamber". page 711"
From Walkalong "That is incorrect. See the plunk test and also search short throat CZ."

Thanks. I was just stating the information given in the reloading manual.

really trying to figure out where to start in regards to OAL, and why.

Oh, and thanks for the link to the Plunk Test.

 

[gamestalker]

Personally, I always do my powder work up after I've established the OAL I'll be using. I do it this way so I don't encounter sudden pressure spikes or reductions, should oal need to be reduced or increased more than .010".

GS

 

[noylj]

I have three CZs and they are no shorter in throat dimension than any other 9x19. I do have a 1911 barrel with a very short throat.
COL (Cartridge Overall Length) is determined by:
1) bullet geometry
2) magazine
3) feed ramp
4) chamber/throat dimensions
When you start to load a new bullet, make two inert dummy rounds to set up the dies and establish the working COL range for you gun(s).
For lead bullets, I like to have them just "kiss" the lede/rifling. For jacketed bullets, I like to be just off the rifling.
I remove the barrel. I load two inert rounds to max COL and just remove enough case mouth flare to let the case slide in the barrel.
Do the rounds fit in the magazine? If not, then I seat the bullets deeper until they fit the magazine.
Then I paint the bullet and case with black magic marker or Sharpie.
I drop the round in the barrel and give it a little rotation back-and-forth.
Remove the round and inspect.
If there are scratches on the bullet ogive, the COL is too long.
If there are scratches at the case mouth, I need a bit more crimp.
If there are scratches on the case at the base of the bullet, the bullet was seated crooked.
If there are scratches on the case above the extractor groove, there is a case bulge that was not eliminated by sizing.
Once I get the rounds right (see plunk test), I re-assemble the gun, load both INERT rounds in the magazine and hand cycle the gun.
If they feed and chamber, I have the max working COL. If not, I reduce the COL until they do feed and chamber.
I generally stop here, but you can continue and determine the minimum working COL. Some like to run midway between, as that might be the best spot for COL variations not to cause feeding problems.
This way, you have your COL before you ever start to load and your load workup is not effected by having to change the COL.
The maximum COL will chamber the industry "standard" FMJ-RN bullet in all SAAMI chambers, but that doesn't mean that the industry all produces "standard" FMJ-RN bullets--which have a very long nose and shorter bearing surface than many FMJ-RN bullets currently being sold.
You can go to SAAMI for cartridge and chamber dimensions
http://www.saami.org/specifications_and_information/publications/download/205.pdf

 

[Pugsbrew]

Noylj, outstanding, thanks.