OAL accuracy? How exact do you really need to be?

[kc9aop]

I am wondering how exact others are with OAL on their reloads.

I am loading 40S&W and my target length is 1.125". I try to keep the length between 1.122 and 1.128. I guess ultimately I wonder about the significance or 3 to 5 thousandths to a cartridge. I don't ever have feeding issues and I can't see any balistic differences at the range.

I take a lot if time measuring each cartridge after I seat the bullet. I'm wondering if it is necessary to measure each cartridge.

Thoughts?

Jim

 

[PO2Hammer]

There always seems to be some variation whether you're pushing on the nose or the ogive. Anything under .010" doesn't bother me or my accuracy in handgun loads.
I only measure about 1 of every 10.
One area of concern I have is with lead bullets, lube can build up in the seater making you OAL shorter and shorter, so I'm more vigilant there.

 

[leefan]

When I was having trouble getting my 32 ACP load right, I measured the factory round I was trying to duplicate, Federal American Eagle, and found that they varied from 0.959 to 0.967 inch. Once I got properly set up it was easy to do better than that.

 

[Walkalong]

That is quite ordinary, and is definitely nothing to worry about.

 

[Edster12]

I think a good place to start is the SAMMI specs. The OAL for 40S&W according to SAMMI is 1.085 min to 1.135 max.



I have downloaded the specs and printed the cartridges that I reload. I keep it in a binder on the bench for quick reference.

 

[gahunter12]

I load on a progressive, and usually load 40s&w in lots of 1-2,000 each time. So there's no way I'm checking OAL on every load. I usually take a handful out when I'm finished, and measure. My OAL for 40s&w is 1.135". I usually get a spread of .001"+/- with the exception of my first two rounds, and last two rounds which usually measure 1.133".

 

[Walkalong]

Flat points loaded with a flat stem will give the best spread. The better the fit of the stem to the bullet, the better the spread. A .005 spread is fine. Measure some factory fodder sometime.

 

[gamestalker]

I find my target OAL, set the die up to produce that, and then check a few as I seat. And as long as they don't go beyond +/- .010" I'm good to go. More than .010" shorter can have a noticeable effect of pressures, especially with high pressure cartridges like 9mm and .40 cal..

As for accuracy issues, a few thou isn't going to make any difference unless they are getting into the lands.

GS

 

[hartcreek]

You will have a range of OAL. Pull out some bullets and measure and look at them. Bullets in the same box often have different tapers, lengths and plating/ jacket thickness differences.

 

[spitballer]

I reload for a .223 bolt action and I've found that the neck tightness has a very big effect on OAL. This is because the seating die sinks into the soft copper when it has to push into a tight (or hardened) neck. In my case I make use of the rifling to regulate start pressure (held in the case by the lands), so I can afford to ease off the neck pressure and get a very consistent OAL. I'm afraid this may not be very helpful for a handgun load, however. Obviously the key is going to be consistent start pressure, and it seems to me you have three tools to control that pressure: a crimp, neck pressure, and use of the rifling (not available in your case). A possible fourth tool might be an adhesive (glue) to hold the bullet. I know in my case I always use a bullet sealer, but just how much of an effect it has on start pressure I don't know. Hope this has been helpful.

 

[dagger dog]

I've had book spec' OAL length, and measured ogive to land length, shoot the same. As a fact in my situation the book spec shot better.

It depends on the rifle, and the person pushing the handle on the press.

 

[Bezoar]

if oal is for proper cylcing in your weapon, then you need to load it so it works through your action.
if you are loading it based on 'the manual says 1.1 inches long, i gotta get that length, then your not too far off. Why? when the articles in the hornady annual magazine talk about adjusting the seating depth on a rifle round in regards to setback from rifling, to much length is ok

 

[ddc]

I load on a progressive, and usually load 40s&w in lots of 1-2,000 each time. So there's no way I'm checking OAL on every load. I usually take a handful out when I'm finished, and measure. My OAL for 40s&w is 1.135". I usually get a spread of .001"+/- with the exception of my first two rounds, and last two rounds which usually measure 1.133".

Are you saying that out of 2000 loaded rounds (with the noted exceptions) you expect a spread of +/- 0.001"?

 

[ArchAngelCD]

I am wondering how exact others are with OAL on their reloads.

I am loading 40S&W and my target length is 1.125". I try to keep the length between 1.122 and 1.128. I guess ultimately I wonder about the significance or 3 to 5 thousandths to a cartridge. I don't ever have feeding issues and I can't see any balistic differences at the range.

I take a lot if time measuring each cartridge after I seat the bullet. I'm wondering if it is necessary to measure each cartridge.

Thoughts?

Jim

Your guess is correct, 3 to 5 thousandths is not significant. Once you set up the seating die there really is no reason to check ever single cartridge. Out of a box of 50 I check a few during loading.

That is quite ordinary, and is definitely nothing to worry about.

There you go, words of wisdom no doubt. Not to worry...