c.o.l.

Deadboyreloads · April 7, 2013, 09:31 AM

I am loading 270 win with Speer 130 gr sp using Imr 4064. All data i find was tested with a c.o.l. of 3.24 but my Tikka will only hold 3.14 without it touching the lands. the starting load is 43 and max is 47. What adjustments should i make for the .1"?

dmazur · April 7, 2013, 10:17 AM

The way I understand this is that published COL's are for the test barrels the mfgr used when developing the data.

For bottleneck cartridges, the change in volume for a 0.100" difference in seating depth isn't as significant as when working with pistol cartridges. IMO, you should worry more about not jamming the bullet into the lands than about the slight increase in pressure the increased seating depth will cause.

I would seat for 0.010" off the lands and proceed with working up a load from minimum.

**Unclenick** · April 7, 2013, 10:54 AM

Deadboyreloads,

Welcome to the forum.

As you have discovered all bullets do not have the same ogive shape. If you look at Hodgdon's online for the .270, they have a 130 grain Barnes seated at 3.23" and a 130 grain Hornady seated at 3.18".

That said, since Speer's own data for their particular bullet uses 3.24", I am concerned that your chamber is not made to standard specifications. I've read of at least one rifle with such an error, a roughing reamer rather than a finish reamer apparently having been used to complete setting headspace, thus leaving no proper throat. I would have the rifle checked by a gunsmith or a make a chamber casting. Something is amiss here.

PA-Joe · April 7, 2013, 11:10 AM

Use your 3.14 and start with 43 grains of 4064. Then work up to where you get the smallest groups.

April 7, 2013, 09:31 AM	#1
Deadboyreloads Junior Member Join Date: March 31, 2013 Posts: 4	c.o.l. I am loading 270 win with Speer 130 gr sp using Imr 4064. All data i find was tested with a c.o.l. of 3.24 but my Tikka will only hold 3.14 without it touching the lands. the starting load is 43 and max is 47. What adjustments should i make for the .1"?

April 7, 2013, 10:17 AM	#2
dmazur Senior Member Join Date: July 5, 2007 Location: Pacific NW Posts: 1,310	The way I understand this is that published COL's are for the test barrels the mfgr used when developing the data. For bottleneck cartridges, the change in volume for a 0.100" difference in seating depth isn't as significant as when working with pistol cartridges. IMO, you should worry more about not jamming the bullet into the lands than about the slight increase in pressure the increased seating depth will cause. I would seat for 0.010" off the lands and proceed with working up a load from minimum. __________________ .30-06 Springfield: 100 yrs + and still going strong

April 7, 2013, 10:54 AM	#3
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,060	Deadboyreloads, Welcome to the forum. As you have discovered all bullets do not have the same ogive shape. If you look at Hodgdon's online for the .270, they have a 130 grain Barnes seated at 3.23" and a 130 grain Hornady seated at 3.18". That said, since Speer's own data for their particular bullet uses 3.24", I am concerned that your chamber is not made to standard specifications. I've read of at least one rifle with such an error, a roughing reamer rather than a finish reamer apparently having been used to complete setting headspace, thus leaving no proper throat. I would have the rifle checked by a gunsmith or a make a chamber casting. Something is amiss here. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

April 7, 2013, 11:10 AM	#4
PA-Joe Senior Member Join Date: June 9, 2010 Location: NEPA Posts: 909	Use your 3.14 and start with 43 grains of 4064. Then work up to where you get the smallest groups.