OAL Question

[ah141nj]

Hi Guys,
I know all manuals usually list the min. OAL & the maximum OAL for a 9mm is 1.169.
Always load so the finished cartridge fits into the chamber & magazine.
I know that decreasing OAL creates higher pressures.
So what is the "rule of thumb"?
Shorter or longer OALs. Which is better to strive for?

I have just started loading for my 19 using WIN 231 with WIN 115 gr FMJ

Did some test cartridges last night using 4.3 gr - 4.8 gr of 231 with the same OAL of 1.155. Should I also adjust the OAL's with the different charges?

[Shoney]

I go through threee steps to get my AOL for semi-auto pistol, for each bullet weight and shape. You have named the first two.

1. cartridge fits in the magazime without ever hanging up;
2. cartridge fits into the chamber correctly;
3. cartridges feed reliably during live fire.

I have had some AOLs meet 1 & 2 but not 3. In the large majority of these, I had to shorten the OAL. If you need to lengthen, usually they will not do 1 &/or 2. In that event, either ramp work was needed, or the magazine needed to be modified. And in a very few cases the charge weight had to be modified.

Good Shooting!

[fourrobert13]

What does your manual say? I try to stay at or above what is published in the manual. I have a few manuals, but most are all right about the same. How did your test loads do? Did you like the results? I usually load to what the manual says. If after firing the rounds I don't like the results, I'll start to tinker. First with the powder charge, either decrease or increase. Then if that doesn't work, I'll play with the OAL. I never go below the listed minimum in the manual, but I will go longer. If I still don't get what I am looking for, I try a different powder.

[Unclenick]

In general, long COL's tend to produce the best accuracy with lead bullets in pistols, but jacketed don't seem as particular. Longer COL means lower pressure, so if you shorten it, like any change in your loads, you should work the load up again. The longest COL that fits the magazine and feeds is what I aim for (I shoot mostly lead). The only exception is a very light bullet with so little bearing surface that the bullet is not secure in the case if I seat it out too far. If, during shooting a bullet occasionally (or more) jams such that the bullet is visibly tipped up in the mouth of the case, you need to seat deeper.

If you use jacketed bullets with crimp cannelures or cast bullets with crimp grooves, set the seating to use that groove unless it gives bad accuracy or leading. The manufacturer will often have load data on his own bullets. Check that first.

[Shoney]

After reading fourrobert13 post, it dawned on me that I didn't mention the caveats of shortening pistol loads. Loading manuals give a range of either minimum to maximum loads, or just listing the max load with directions to start at 10% below the max charge. It is never a good practice to start at the max, then do adjustments in OAL or do the next lower powder charge.

Whenever shortening a cartridge length, you must be aware that this will increase pressure. It can be dangerous to shorten loads that are at max! With some powders, a very slight decrease in OAL when at max produces a very high spike in pressure.