Lane's Weekly Stupid Question
 

These discussions have been incredibly helpful and enlightening for me. But, I've always been curious, and enjoy learning as much as I can about any given topic (sometimes obsessively).

Anyway - my question now is around OAL. Obviously, internal pressure can be greatly impacted by seating the bullet too deep. Every load sheet I've seen will list a Minimum OAL, which makes sense. But, why would the OAL ever vary? Specs I've seen show the OAL of a .45ACP cartridge to be 1.275. Should I be cranking out every round right at 1.275, or is there a reason to vary from this?

Inquiring minds (or, in my case mindless) need to know...

Lane

No Stupid Questions on here besides the ones Not Asked...........
IMHO because no Bullet or casing is Perfect, that is why every time I shoot a reload I measure every case and OAL after I am done, if you don't won't sit right in the mag or feed properly, and cause major problems...........



Clyde

Lane, 1.275" is the longest OAL that should fit in a good chamber with the headspace cut to the highside(.910). The longer you seat the bullet out the better it will feed to a point. Now, I only run 230 grain bullets and seat them at 1.265"( Same size as WWB and, incidentally, all Milsurp 230grain FMJ). Never have any feed-problems. Depending on what type of feedlips your mags have(Wadcutter, Hybrid, or Standard), your best OAL will vary a little but, by and large, if you stay within ten-thousandths of max( On the low-side) for the bullet-weight you'll be fine.

Lane, to my understanding... the .45acp feeds on the case, not on the OAL. OAL ( or COAL for Cartridge Overall Length) is dependent upon the bullet used. The traditional FMJ 230 gr. round nose would have an overall length of 1.260. If you were loading a JHP in 230 gr.... my manuals look for a tested COAL of 1.20 (because the top of the bullet is flattened out) Same for the 200 gr. Flat point. A deeper set bullet will increase the internal pressures, but OAL is based on the physical length of the bullet, as well as the depth set.

So.... if you were to set a 230 gr. FMJ round nose to a COAL of 1.20, I would guess you would be exposing yourself to a abnormally high internal pressure (read: Possible Kaboom!!)

Once again, I say: The loading manuals are there for a reason. Do not deviate from the mins and max's..... and watch your COAL.

DaFadda

and a +1 to what Dave says above my post.
DaFadda

This started as more of an academic question - I'm currenly loading at 1.265".

This is actually a follow on to the detonation topic. One of the theories I read was that a small amount of powder in a case would cause the powder to lay along the length of the case, allowing the primer to flash over all of it causing detonation rather than burning. Pondering this, I looked at the load charts in my Lee Handbook (BTW - this book has the most complete load data I've ever found in one spot) and noticed that the min OAL varies from 1.190" to 1.270" for .45ACP (across the various bullet sizes and powders). This got my tiny little brain thinking "are they taking some of this into account?"

Now - back to the dungeon! I've got a holster to sew...

Lane

Oh, sure. Ride Dave's coattails...

:D

Of course...now go sew my holster!

OAL can also vary due to bullet design, some longer and some shorter even for the same weight. Speer Gold Dots are shorter than many others. Many load data sources list the COL for specific recipes for specific bullets, some based on powder manufacturing test data, some by bullet manufacturer test data.