COL question

zandor · March 12, 2013, 11:35 AM

Hello, I've just started reloading a few weeks ago and I've been following the books carefully on what I've loaded thus far.

Heres the but.

I've loaded 100 rounds of 9mm 115fmj with 4.4gr hodgdon HP-38(a little on the light side) and checking the length at appx. 1.169" as per the Lymans book.

Then I did 100 rounds 9mm 125LRN with 4.0gr hodgdon HP-38, BUT I've still been using the COL of 1.169" Now I've noticed the 1.125"COL for LRN. Do yall think the extra .044" will make a difference?

thx

Z

Brian Pfleuger · March 12, 2013, 12:00 PM

It's the space under the bullet for the powder to burn and how much of a "head start" the bullet gets before it hits the rifling that control the pressure generated.

Hodgon actually lists 1.100 as the suggested OAL for 115gr LRN.

You've made your rounds longer, which increases the space for the powder to burn (lowering pressure) but possibly moved the bullet closer to the rifling (increasing pressure).

It's a very low load and lead engraves into the rifling easily, so you're not likely to see any effect whatsoever.

However, unless you've over-crimped the bullets, you could simply adjust your seating die to push them in a bit farther.

In this instance, it doesn't matter either way as long as they fit and function in your gun.

maillemaker · March 12, 2013, 12:04 PM

I agree with what Brian said. My impression in all this that generally speaking, it's more dangerous to over-seat bullets than to under-seat them. Though, as Brian noted, if they are too long the bullet can engage the rifling during chambering, and this can increase pressures.

The real question is at the longer length do they feed and chamber properly.

Steve

zandor · March 12, 2013, 12:55 PM

Yep...they manualy cycle through all of my 9mm pistols. I've cycled them through an M&P pro and a XD tactical, then inspecter the led to see if i could notice any lan notches...none visible

March 12, 2013, 11:35 AM	#1
zandor Junior Member Join Date: July 2, 2012 Posts: 7	COL question Hello, I've just started reloading a few weeks ago and I've been following the books carefully on what I've loaded thus far. Heres the but. I've loaded 100 rounds of 9mm 115fmj with 4.4gr hodgdon HP-38(a little on the light side) and checking the length at appx. 1.169" as per the Lymans book. Then I did 100 rounds 9mm 125LRN with 4.0gr hodgdon HP-38, BUT I've still been using the COL of 1.169" Now I've noticed the 1.125"COL for LRN. Do yall think the extra .044" will make a difference? thx Z

March 12, 2013, 12:00 PM	#2
Brian Pfleuger Moderator Emeritus Join Date: June 25, 2008 Location: Austin, CO Posts: 19,578	It's the space under the bullet for the powder to burn and how much of a "head start" the bullet gets before it hits the rifling that control the pressure generated. Hodgon actually lists 1.100 as the suggested OAL for 115gr LRN. You've made your rounds longer, which increases the space for the powder to burn (lowering pressure) but possibly moved the bullet closer to the rifling (increasing pressure). It's a very low load and lead engraves into the rifling easily, so you're not likely to see any effect whatsoever. However, unless you've over-crimped the bullets, you could simply adjust your seating die to push them in a bit farther. In this instance, it doesn't matter either way as long as they fit and function in your gun. __________________ Nobody plans to screw up their lives... ...they just don't plan not to. -Andy Stanley

March 12, 2013, 12:04 PM	#3
maillemaker Senior Member Join Date: August 30, 2010 Posts: 1,635	I agree with what Brian said. My impression in all this that generally speaking, it's more dangerous to over-seat bullets than to under-seat them. Though, as Brian noted, if they are too long the bullet can engage the rifling during chambering, and this can increase pressures. The real question is at the longer length do they feed and chamber properly. Steve

March 12, 2013, 12:55 PM	#4
zandor Junior Member Join Date: July 2, 2012 Posts: 7	Yep...they manualy cycle through all of my 9mm pistols. I've cycled them through an M&P pro and a XD tactical, then inspecter the led to see if i could notice any lan notches...none visible