do you adjust your COL?

[Halo]

In the effort to find a good load for our guns we will try different variations of case, powder, primer, and bullet. But what about COL, do you include different seating depths in the mix? When starting on a new load I always run a factory round of the same bullet style into my seating die and adjust the seating plug down until it makes contact, essentially using that factory round as a template. I've had good results this way, but sometimes I wonder if a more accurate load might be eluding me only because I have the bullet seated to deep or too shallow.

Is it worthwhile to try out different seating depths? I generally like to keep them loaded closer to the maximum length to keep internal pressure lower, and to minimize bullet jump. What things do you vary in your test loads? This is in straight wall pistol cartridges, FWIW.

 

[Jayman]

For pistol rounds I've always been more concerned with function than accuracy when it comes to OAL. For rifles, esp. bolt action ones, you need to be concerned with this for both accuracy and safety. (Loading to where the bullet is actually touching the lands will create an unsafe pressure situation.) So I've never bothered with OAL in my pistol rounds to try and chase accuracy. I can usually get 2" groups at 25 yards with good JHPs, and I'm probably not going to beat that substantively by monkeying with any other variable.

Your number one variable for accuracy is going to be bullet. A good quality bullet will be more accurate than a bulk bullet. Powder type and charge will be your next variable, and primer, IMHO, would the the third. Case type (one headstamp, mixed, etc.) plays some role, as well, although I've never been able to discern a difference at the level I play at.

 

[jim147]

On my first test loads I start at the bullet manufactures recommended COL.

After I find the powder I'm going to use and the powder charge range I may start moving COL if I'm looking for max accuracy.

 

[Walkalong]

For auto pistols I find an O.A.L. that functions well.

For revolvers I crimp in the crimp groove of a lead bullet or the cannelure of a jacketed. For plated bullets that do not have a cannelure I will play with O.A.L. a bit to see if it makes a difference.

For rifles the O.A.L. can make a big difference, but you asked about pistol.

 

[Halo]

Thanks for responses everyone. I'm just going to work up the most accurate load I can with a given COL and then play with the seating depth a bit (backing off the charge if I seat deeper, of course)

 

[AZAndy]

What cartridge(s) are you asking about? I've just embarked on an OAL experiment with .45ACP, if that's of any interest to you.

 

[Halo]

9mm and 45 ACP, so yes I'd be quite interested in the results of your experiment.

 

[cpttango30]

Only change one thing at a time. I get the powder charge to shoot the most accurate. Then I go to messing with the OAL.

 

[lordgroom]

I am still sorting through this issue myself, with rifle cartridges. For rifle's firing cast bullets, many recommend seating the bullet into the rifling, not just touching, to prevent any bullet jump. For jacketed, I have heard setting the bullet back .01 from just barely touching the rifling.

For pistol, I agree with Walkalong. In an auto loader I seat to a depth that will allow me to cycle an action. Right now that is more accurate than I am. For revolver, I set to the crimp groove.

AZAndy, I would be interested in your data as well.