cartridge oal question

[jay]

Hello, I have been reloading on and off for many years and never really took the OAL very seriously. As long as it was within sammi specs it was ignored for my revolvers. With the automatics, i have read listings of max oal in the reload manuals and most of the time they are too long for the magazines close to specs.
So i change the oal to the maximum that will cycle in the kimber 45 acp and 380 auto magazines and pistols. Is this proper procedure or am i increasing the pressure too much if i make a .025 oal length change to the smaller side.
the casings after being fired show no excessive pressure signs.
thanks john

[versifier]

Welcome to The Guide.

With the .45ACP and the .380 it is not really a big deal, as long as you don't go overboard and are not redlining your loads already. That is one good reason when you are shooting jacketed bullets to have a copy of the bullet manufacturer's loading manual as they will have workable and safe OAL's for their specific bullets. With higher pressure rounds like the 9mm, .40S&W, and 10mm, though, you really have to be careful.

Because handgun cartridges (even the hotter ones - and I don't mean single shots chambered for rifle cartridges) generally operate at lower pressures than do rifle cartridges, they do not always show any pressure signs even when beyond the red line, so just watching your primers is never a pratical way to gage their actual pressure. Even some rifles don't show obvious pressure signs on the primers and for that reason the method is not always as reliable as many would believe. When present, pay attention to them, but when absent, never assume and don't go above MAX. With rifle cases, you can mic the heads before and after for reliable proof that you're over, but I do not believe it will work effectively with lower pressure handgun rounds. For them you need a test barrel with a strain gage to know what's going on, so you have to trust your manuals (of which you should have a minimum of three current editions).

[Tom W.]

Remember that when you reduce the size of the combustion chamber, in this case the volume inside the brass, you will increase pressure.
That said I seat my bullets for my Colt so that they are seated out as far as possible, but will also reliably feed. And I cycle every one through my Colt before I'll accept it.