Lately I've been reading about the importance of using a caliper to measure OAL when reloading. So, I received mine today from Cabela's, and I have a question or two.

First, my loading data lists "Minimal Overal Length"; so how do you determine what the Maximum Overall length is, since oversizing a case can lead to high pressures also?

Secondly, what do you do when your particular shape/weight bullet isn't listed in your load data so you have no OAL figures?

There are 2 main reasons to check OAL: 1. pressure goes up if you seat them deeper, and 2. too long can cause magazine/feeding/chambering problems.

There are SAAMI standards for each cartridge on max OAL in many different reloading manuals, but for specific guns, some cartridges can be loaded long.

When you have no data for a bullet, be sure it does not go deeper than one you have data for, and start low on the charge to be safe.

If you have a question on a specific cartridge, I can look it up for you.

OKFC05:

Thanks for the reply. Specifically, I am loading a round nosed 155 Gr. Lead bullet in 40 S&W cal. Fired in a Sig-239. My last load was 5.7 Gr. of WSF powder, and it shot very accurately, but, my primers (Federal + known to be soft) appeared pretty flattened.
On paper, it was not a heavy load. But, my bullet was seated out so that the driving band was out about 2 1/2 mm. I was thinking that maybe they were seated out too far.

SAAMI max OAL for .40 S&W is 1.135 in.
You did not state your OAL, so I can't comment on that. To get OAL, measure from base of case to tip of bullet.

All that you will get from trying to judge pressure from looking at the primers on a .40S&W is eyestrain. WSF is not my favorite powder for light lead bullets, but I see no reason to believe the pressure is excessive. Straight-walled pistol cases are difficult to judge by eye. TIP: Be sure the barrel is completely free of copper fouling before shooting lead bullets; lead can accumulate quickly in a fouled barrel.

I suggest you pick up a copy of the Hodgdon reloading manual, which has loads for Alliant, Hodgdon, IMR, and Win powders, and excellent sections on basic reloading theory and practice.

You don't measure "Minimal Overal Length". It is a value that your measured OAL mut be greater than for a particulat bullet. This value is determined from test results so the volume of the case for the powder, with the load specified, will not result in an over-pressure condition.
What do you mean by "oversizing a case" ? I've not heard that before.

I guess I wasn't very clear when I said "oversizing the case". What I meant was that the OAL of the cartridge was too long: turned out it was 1.048. I only realized that now since I got my caliper, and checked a cartridge that I loaded at the same depth as the one in question.

I found a second problem that is snafooing me in my 9mm loads. Here's the problem. Checking Lee's figures, they list the OAL of a 9mm 115 gr.FMJ bullet, using WSF powder @ 1.095 whereas, according to the Hodgedon site, given all else the same, the OAL is: 1.169 .........that's a huge spread in bullet depth!
~~~So, which do I follow?~~~

quote:

I found a second problem that is snafooing me in my 9mm loads. Here's the problem. Checking Lee's figures, they list the OAL of a 9mm 115 gr.FMJ bullet, using WSF powder @ 1.095 whereas, according to the Hodgedon site, given all else the same, the OAL is: 1.169 .........that's a huge spread in bullet depth!
~~~So, which do I follow?~~~

Either one, or anything in between.
They are just telling you what the OAL was on the load they tested.
The SAAMI max OAL for 9mm Luger is 1.169 in.
Lee says their load is OK at 1.095 in.

No offense, but it seems you don't "get it" about what OAL is all about. If you were told to keep your car tires inflated to between 30 and 35 pounds, would that freak you out? Same idea on OAL: there are safe ranges, and within that range makes little difference in safety.

What you have to watch is shortening a load that is already at pressure limits, because that changes the expansion ratio and increases the pressure.