OAL - how does it affect firing

[JimG]

I don’t get it (yet).

If I load one .40 Winchester case, Remington primer, 5.2gr 231 and star 180 JHP to an OAL of 1.125 and second .40 Winchester case, Remington primer, 5.2gr 231 and Star 180 JHP to an OAL of 1.185 are there any differences in the way the 2 loads fire?

tia,

[Ron Ankeny]

As a general rule of thumb, the deeper you seat the bullet the higher the pressure. Of course, if you seat the bullet out far enough to ram it into the rifling pressure can also go up.

I have seen instances where the bullet strikes the feed ramp and seats the bullet deep enough to blow primers when the round is fired. It would be interesting to chronograph the loads that you mention to see if the difference in depth means diddly.

[Shooter Grrl]

Jim,

Most of the people I have talked to adjust their OAL for FEEDING reasons.  The longer bullets tend to be more reliable in the S_I guns.

[John Heiter]

I can't speak for 231 but I can give you one example.  I had a major load for IPSC competition of 185gr. Precision over 4.6gr. of N320 to an OAL of 1.200.  I solved some feeding problems I was having by going shorter (not typical but it worked for me) so now I'm loading the same 185gr. Precision to 1.160 but it's only taking me 4.4gr. of N320 to make major now.  In my case, shaving 4 hundreths of an inch on my OAL meant dropping 2 tenths of a grain per case to get the same velocity.