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Old October 9, 2012, 11:04 PM   #1
Colorado Redneck
Senior Member
Join Date: January 6, 2008
Location: Northeast Colorado
Posts: 1,497
Effects of long freebore

I have a CZ in 222 Rem. The barrel length is 22 inches. To determin OAL of handloads, the method of using a spent case that is modified by cutting 3 length wise slots into the case mouth and seating whatever bullet to be loaded, then inserting the case into the chamber and closing the bolt. Then to double check, placing the bullet into the barrel throat and tapping it in lightly, and using a wooden dowel to determine the distance from the bolt face to the bullet tip (more complicate than this, but no need to explain more).

The freebore seems to be fairly long. To seat 0.03 off the lands with Nosler 40 BT, the COL is .050 longer than specified in the SAAMI spec. So all of this is well and good. The issue is, velocities are significantly less than the load data indicates for everything I have put through this gun. 100 fps less is perfectly acceptable, but 250-300 fps seems a bit out of whack to me. I had a 22 Hornet that did nearly as well as this 222 Rem. I have used Barnes load data, Nosler, Hornady, IMR, Alliant.

The chrony has been fairly close with factory ammo specs, and most load data in various calibers.

Questions: Could excess freebore be a major contributor to this?
Are there other factors that might be involved?
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