Increasing oal

dajowi · February 12, 2012, 03:48 PM

I'm currently loading a 147 Gr. FP hard cast bullet in 9mm. The reload data suggests a OAL of 1.058". I've been shooting a 115 Gr. FMJ with a maximum OAL of 1.104". Both of these functioned in the gun.

Would anything untoward happen if I increased the OAL of the 147 Gr. cartridges to an OAL of 1.104? Does this effect the pressure?

PA-Joe · February 12, 2012, 03:56 PM

The FPs will contact the lands if you use the RN bullet data. Yes, this will increase the pressure and they may not feed correctly in the first place.

OEF-Vet · February 12, 2012, 04:00 PM

Increasing the OAL does affect pressure in fact it lowers it, so as long as the bullet is seated properly and the round feeds properly it should be a non-issue. However any velocity and energy calculations will also be reduced a minuscule amount.

89blazin · February 12, 2012, 04:02 PM

If the FPs do not make contact with the lands when chambered, the pressure will be reduced. Make a test FP bullet at the longer OAL w/ no powder or primer and see if it chambers as normal.

OEF-Vet · February 12, 2012, 04:06 PM

I second 89blazin's approach of a dummy round. I didn't factor the bullet reaching the lands in less the 5/1000 of an inch in my previous post but it is possible.

February 12, 2012, 03:48 PM	#1
dajowi Senior Member Join Date: November 2, 2005 Posts: 1,196	Increasing oal I'm currently loading a 147 Gr. FP hard cast bullet in 9mm. The reload data suggests a OAL of 1.058". I've been shooting a 115 Gr. FMJ with a maximum OAL of 1.104". Both of these functioned in the gun. Would anything untoward happen if I increased the OAL of the 147 Gr. cartridges to an OAL of 1.104? Does this effect the pressure?

February 12, 2012, 04:00 PM	#3
OEF-Vet Senior Member Join Date: October 23, 2011 Location: Backwoods, PA Posts: 284	Increasing the OAL does affect pressure in fact it lowers it, so as long as the bullet is seated properly and the round feeds properly it should be a non-issue. However any velocity and energy calculations will also be reduced a minuscule amount. __________________ Jim "If a man does his best, what else is there?" - General George S. Patton Jr

February 12, 2012, 04:02 PM	#4
89blazin Senior Member Join Date: March 13, 2009 Posts: 107	oal If the FPs do not make contact with the lands when chambered, the pressure will be reduced. Make a test FP bullet at the longer OAL w/ no powder or primer and see if it chambers as normal.

February 12, 2012, 04:06 PM	#5
OEF-Vet Senior Member Join Date: October 23, 2011 Location: Backwoods, PA Posts: 284	I second 89blazin's approach of a dummy round. I didn't factor the bullet reaching the lands in less the 5/1000 of an inch in my previous post but it is possible. __________________ Jim "If a man does his best, what else is there?" - General George S. Patton Jr

February 12, 2012, 03:56 PM	#2
PA-Joe Senior Member Join Date: June 9, 2010 Location: NEPA Posts: 909	The FPs will contact the lands if you use the RN bullet data. Yes, this will increase the pressure and they may not feed correctly in the first place.