It's official, I'm getting all wrapped around the axle about OAL. I'm loading .45 ACP.
First: For 230g RLN what should the OAL be? I'm finding conflicting info in my manual/on-line

Second: When reloading, do all weights/nose design need a diferent OAL?
i.e. What would I use for .45 200g SWC?

And while I'm at it, does the brand of primer change the load?
Thank you, thank you, thank you...

The easy answer is; load to the longest OAL that your mag & chamber allow.
Yes, diff bullet profiles will have diff OAL. Diff. pistols will accepet one style @ one length & in th enext pistol it will be too short, jambing into the rifling. Keep the longest OAL in mind & it will keep you out of trouble. Make several dummy rounds & try them in your magazine & chamber.
FWIW, most LRN will load between 1.230" & 1.265". I run at 1.250" for most of my 45s.

I load all mine at 1.250

Okay, first of all, that icon of your dog is hilarious.

A couple of things might help explain OAL. First is that every manufacturer who tests loads is doing it with a different bullet, etc. Even with the same bullet, some will test at a longer or shorter length, just because that's how they loaded it. The reason they give the OAL is because the same bullet loaded shorter or longer will potentially create higher or lower pressure. But what you're seeing is (semi) random choices by the tester as to what to load. And it's true, primer brand will change the pressure and other characteristics of the load. Whether it's noticeable or not is only told by starting with a low charge and working up.

Here's another perspective on OAL. The official specified maximum legnth is 1.275 for the 45 acp. It's based in part on some notion (alleged mil spec) of how long the chamber is supposed to be and where the rifling begins. If you looked at a side view cut away of a cartridge in the chamber, you'd see the front lip of the case pressed against a small ledge in the chamber. That ledge prevents the case/cartridge from going any further deeper into the barrel. The bullet itself, being narrower in diameter than the case, extends further.... which is where the real action is with OAL: Since the bullet diameter is slightly larger than diameter of the lands in the barrel, if the bullet curve is not very sharp, then the bullet can extend far enough that it jams into the lands. You don't want that for several reasons.

1. It can force the bullet back deeper into the case which reduces volume and increases pressure.

2. Jammed into the lands, the bullet has no "free space" (my words) to start it's forward movement. Generally it's called free bore, but the point is, the bullet needs a fraction of an inch to jump start before it hits resistance in order for pressures to stay reasonable.

3. If you decide not to fire, the bullet jammed into the lands may stay in the bore and the case pull out... spilling powder, etc. The lands act like a bullet puller.

As you can see, theoretically you could have a longer bullet if the nose didn't jam into the rifling and if you didn't have to worry about the bullet fitting in the magazine. Think of an aardvark or anteater shaped bullet. That nose could go all the way out the barrel without jamming into anything and weigh a whole lot! But if it had the flat face of an orangutang, the same weight bullet would be jamming into the lands immediately.

Now, one other aspect of OAL. On the other end of the bullet, the base, the critical thing is how much space is remaining in the cartridge case. For any specific bullet weight / profile (aardvark vs. orangatang) changing the OAL means pushing the bullet deeper or shallower into the case. The more case volume consumed by the bullet, generally the higher the pressure will be. 9mm Luger is very sensitive to this. 45 acp is too, but not as much.

All this adds up to this: What Fred said. Seat as long as you can (up to 1.275) IF and ONLY IF you test that exact bullet and OAL combination in each gun barrel and magazine combination you will shoot it in. You want to make sure the cartridge drops freely into the chamber without the bullet touching the rifling, and you want to make sure it fits in the magazine.

My two experiences were 1) with Berry's 200 grain flat points - they'd fit the chamber but not the magazine even though they were loaded at 1.275. 2) Berry's 9mm flat points would fit fine in a standard Sig 9mm barrel, but NOT in Bar Sto after market chamber. That chamber was shorter and the shoulder of the bullet would jam the rifling.

Longer OAL generally feeds better and generally keeps pressures lower - if you dont' go so far as to jam the rifling. Footnote - This is true in 45 acp. It's not always true in rifle cartridges. There are true weird combos of low powder and large volume cases which can have wierd high pressure spikes. But not a concern in 45 acp.

Very informative post.

Thanks,

A.T.

rcjohnson: Thanks for all the information, it really helps! That's what this forum should/can be all about-each of us helping others.
Doggie licks to you (but not from me)

rcjohnson..sir, you did a beautiful job explaining that. Some where in there you mentioned the shelf in the chamber. This being the place where most auto pistol rounds seat to establish head space. Thought I'd mention that. Excellent post rc.