Effect of OAL on FPS

I wasn't sure how to title this.

45acp 230 FMJ
5.6 of W231
WLP
crimp .469

If I increase the OAL from 1.21 to 1.265 what would be the impact to FPS? Faster Slower Same??

- Dave

Slower but just a little.

Dave C.

Anytime you alter the inside case area it alters FPS and case pressure, its simple,(as long as its exactly the same, case, charge, bullet and crimp) more OAL = less pressure less speed. Less OAL= more pressure more speed but 1.265 Probably wont feed reliably, 1.250 is about the place you should be.

The reason I asked is I ran across some old Hardball loading specs and they were suggesting
Spec:
OAL: 1.265" Nominal to 1.270"
Crimp: .470" Typical (.469 works well)
Primer: WLP (hottest ignition)

I'm currently running a little on the short side (1.21) and was thinking about moving to 1.25 or 1.26.

At the same time I'm looking to change my short line loads to something around 4.6gr. I've always loaded short and long line the same (5.6grs W231).

Doing some chrono and ransom rest work tomorrow.

- Dave

The discussion here applies to pistol.  However, it is often not the case for rifle. Read this, especially the last line.

A change of COL within the safe range has almost no effect on velocity. The whole COL concern was brought about when one of the companies showed the effect of the bullet being pushed into the case by more the 0.2".
I am more concerned with the COL that is totally reliable and produces the best accuracy (generally, the bullet "kissing" the lede/rifling).

I have found that 1.251 is the perfect length. I know that is a bold statement but I can explain. I load my 200 gr L-SWC to a COL of 1.246. I have found that if I don't mess with my bullet seating die I get a COL of 1.251 with the 230 gr bullets. OK, so I'm lazy. But it sure saves me a lot of grief when switching bullets. When you load both loads with the same powder ( 4.2 BE ) you can really put out some bullets.

Len   Old and Lazy