Maximum OAL

[mi2600]

My 1970 Lyman reloading handbook says the max OAL for a .45 Auto Rim cartridge is 1.275".

When I loaded some 200gr LFN to the crimping groove, it measured 1.202". I compared the .45AR with a .45ACP and they appear to be about equal length. Why is there such a difference from the max OAL?

 

[shovelwrench]

The ACP has to fit in the mag.... ;-)

And autoloader geometry affects the length it will feed..

 

[Jim Watson]

Those LFN bullets are really made for .45 Long Colt lever action rifles where the OAL is critical and you don't want a hard roundnose leaning on the primer of the next cartridge up the magazine tube.

They usually work pretty well in .45 ACP and of course the AR doesn't care about OAL or shape.

The 1.275" book OAL for .45 ACP and .45 AR is a MAXIMUM value which can usually be done only with the elliptical roundnose GI hardball bullet in the auto. The revolver has more scope for variation.

 

[Alk8944]

What they said^^^^. Maximum means just that, do not exceed. It doesn't mean the OAL cannot be shorter than this figure. Revolvers chambered for .45 ACP/.45 AR are far more flexible that semi-automatic pistols when it comes to OAL.

What is critical in relatively short cartridges like .45 ACP and, particularly, 9mm Parabellum, is when a MINIMUM OAL is listed. This means just that, do not load shorter than this figure! This can be a very real safety consideration.

 

[fredj338]

AS noted, it's SAAMI max, not the OAL. The bullets you are lodaing are NOT the bullets Lyman put in their data. OAL is one of the hardest things for noob reloaders to wrap their heads around. Just keep in mind, OAL IS ALWAYS GUN & BULLET SPECFIC, ALWAYS. The bullet must fit your gun & magazine, REGARDLESS of what the manual says. If you load shorter than the data to get things to work, then you have to reduce your powder charge.
How much reduction? It varies w/ the powder used & caliber, but a bullet seating as little as 0.06" deeper can raise pressures quite a bit. In some calibers w/ some powders running the top end, a 0.06" deeper seating can take you into dangerous pressures. So load to the longesat OAL that works in your gun & adjust powder charges accordingly. Shorter increases pressures & longer decreases pressures.

 

[hawgleg]

The 1.275 max col is to fit all magazines. The auto rim is loaded to the same spects for conveinene. There is a million loads reciepes for the 45 acp. The 45 acp and 45 auto rim are the same internal parts just different types of brass.

I load all my 45acp at a 1.25 unless they have a crimp groove then I assume they know were the bullet needs to be seated.

 

[mi2600]

Fred, thanks for calling me a noob!!