Allowable variation in COL

[brownie]

Is there a rule of thumb for allowable variation in COL? That is, how many thousandths of an inch a cartridge can differ from the nominal length without affecting the accuracy/reliability?

Thanks,

Bill

[Woodman]

Basically you want to have an OAL that is not so deep that it causes an overpressure situation, or so long that it causes feed issues or binding in the magazine.

Each barrel is a little different. You have to watch headspace of course, but aim for an OAL that feeds reliably and has good accuracy from your gun.

[Baldy]

If I remember right a COL of 1.275" is maxim length. Most of the people I know load at and around 1.220" to 1.260". My pistols seem to work best at a COL 1.235" to 1.245". Now a word of caution, I am not loading maxim loads. I don't need full house loads to kill paper. Hope this helps you, and good luck.

[Hunter]

I try to keep to what the manual says regarding loading data. I believe they know what is going on.

[TheGerk]

Is there a rule of thumb for allowable variation in COL? That is, how many thousandths of an inch a cartridge can differ from the nominal length without affecting the accuracy/reliability?

Thanks,

Bill

It would help if you gave us an example of a load or a load you have in question.
The SAAMI max OAL is 1.275” the Minimum OAL gets a little fuzzy.
I have seen load data listing as short as 1.125”
What bullets are you using? Powder? Depending on your combination bullets seated to low can raise pressure dramatically.
Are you running a custom barrel, some of these have long or short “free-bore”
This could effect your accuracy and pressure.
My advice is to seat the bullet per the manuals recommendations and make small adjustments from there.
“Generally” you should be safe with a OAL of 1.225 to 1.260 in most cases.
Also make sure the round will cycle in your magazines, if you find you are loading on the long side run a few rounds up and down the mags you use to check for proper operation.
Good Luck

[brownie]

The load I'm working on is 4.0gr. of Clays under a 230 gr. Hornady FMJ (round nose). I'm loading it to a nominal COL of 1.230in. Measuring the actual length, most of the rounds are within +-.001, but some vary from 1.227 to 1.235. Is this amount of variance acceptable or might it cause problems in accuracy or feeding?

[Woodman]

The load I'm working on is 4.0gr. of Clays under a 230 gr. Hornady FMJ (round nose). I'm loading it to a nominal COL of 1.230in. Measuring the actual length, most of the rounds are within +-.001, but some vary from 1.227 to 1.235. Is this amount of variance acceptable or might it cause problems in accuracy or feeding?


I've been using the 230gr Hornady FMJ for awhile now and they're acceptably accurate at 1.230" over 5.3gr Winchester 231. I have some loaded at 1.260" right now, and they are all over the place. I'm dialing some of them back to 1.245" as that's what shoots best with my Ranier plated bullets (230gr ball) but I haven't tested them yet.

Load a few, 15 or 20, at 1.230" and test fire them. Do some fine tuning till you come up with something that's nice to shoot and accurate.

[Maj Tom]

The load I'm working on is 4.0gr. of Clays under a 230 gr. Hornady FMJ (round nose). I'm loading it to a nominal COL of 1.230in. Measuring the actual length, most of the rounds are within +-.001, but some vary from 1.227 to 1.235. Is this amount of variance acceptable or might it cause problems in accuracy or feeding?
The answer is it depends. In one application it may not have any impact to either function or accuracy. While in another it may impact one or both. Testing your particular setup is the only way to really determine the amount of variation you can tolerate. Sorry to be so vague, but that is the nature of the beast. I have some bullets that it doesn’t matter and others that it does. I really don’t see a variation in my loaded stuff; I experiment and see the impact of minor changes in COL. Just my penny and a half…….