Headspace and COL?

[jrs1911]

I recently purchased some WST to load 45 ACP. Hodgdon specs for a 230 grain flat point show 1.2 inches as a COL. I thought I would check fit the 1.2 inch rounds I had loaded in the barrel of my SA Micro Compact and my S&W 1911. I found they were very close to flush in both barrels. I then wondered how my W231 rounds that had a COL of 1.265 would check out. The 1.265 rounds were "out too far". My question is, if the round headspaces on the casemouth, how can the COL affect how deep the bullet is seated?

 

[Walkalong]

You pick an overall length for .45 ACP that will feed and will also pass the plunk test.

The headspace has nothing to do with this.

 

[gamestalker]

As far as OAL is concerned, you use the barrel to check and see if the bullets are making contact with the lands, you don't want that. the plunk test Walkalong mentioned is when you hold the barrel vertical, chamber side facing up, drop the loaded cartridge into the barrel, if it drops in with a good solid plunk sound, and when you push on it, it doesn't leave marks on the olgive of the bullet, or doesn't want to stick, your good. Once you find the OAL that clears the lands you then make sure it fits the magazine and feeds ok, making adjustments as necessary.

Head space is determined by the length of the brass only, and is completely unrelated to bullet seating depth.

Sorry, I didn't notice your link about the plunk test until just now walkalong.

GS

 

[Robert101]

Yes, just like the boys said in prior posts. Basically, the bullet is hitting the lands before the case (mouth) is seated in the chamber. Hence, the cartridge did not seat completely in the chamber.

 

[918v]

http://www.thehighroad.org/showthread.php?t=675320

Read this thread. It explains the relationship between OAL, bullet diameter, rifling, freebore, etc.

 

[Potatohead]

Pretty interesting thread 918. So which is it, some barrels dont have freebore, or all do? Forgive me if the answer was in the thread and blew by me, Its late.

 

[918v]

They all do, to some degree. It's hard to tell if you don't know what to look for. But if you look at your round and have any of the full diameter bullet shank protruding last the case mouth, and that round chambers in your gun, then you have a freebore.

 

[LiveLife]

So which is it, some barrels dont have freebore, or all do?

As 918v posted, I think all barrels have leade/freebore/throat to a lesser or greater degree. It's the space the bullet jumps from the chamber/case neck to the start of rifling and the length of this space varies based on barrel brand/model.

Glock/M&P/KKM/Lone Wolf barrels have well defined leade but my Sig 1911 and the newest Lone Wolf barrels have almost no leade - http://www.thehighroad.org/showthread.php?p=8908155#post8908155

Lone Wolf barrel on the left showing defined leade (white arrow) but Sig barrel on the right showing almost no leade

I then wondered how my W231 rounds that had a COL of 1.265 would check out. The 1.265 rounds were "out too far". My question is, if the round headspaces on the casemouth, how can the COL affect how deep the bullet is seated?

The round headspaces on the case mouth but the OAL/COL is limited by the length of the leade and the start of rifling. As Walkalong posted and illustrated by above pictures, OAL that works will depend on the pistol/barrel. With 200 gr SWC, while M&P45 and RIA 1911 will feed/chamber OAL of 1.265", my Sig 1911 (due to short leade and quick start of rifling) will not feed/chamber OAL longer than 1.245".

This Hornady webpage has a good definition of leade/freebore/throat and many other useful reference information regarding OAL/COL - http://www.hornady.com/ballistics-resource/internal