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Old November 20, 2009, 10:15 PM   #1
Lilswede1
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Join Date: September 8, 2008
Location: NW Wash State
Posts: 216
Measuring freebore, where to begin

Only my second year of reloading and am always amazed at how much I dont know, but then, that is why I come here.
Just got the Hornady Lok-N-Load Bullet Comparator gage.
Also have the Hornady OAL gage and the RBS Precison Mic Gage.
Trying to determine bullet length for my CZ Bolt Action .223.
It was also suggested in here to take a fireformed prepped case, use a small Dremel to cut a slot in the neck so a bullet would slide in and out of it.
Took 10 measurements with the RCBS plastic bullet gage. Measurements varied .002" - .004" but average was 1.944" using the Comparator gage mounted on calipers.
Took 10 measurements with the Dummy Case (split neck) using actual bullet to be loaded. They varied only .001" - average was 1.960".
I trust the Dummy Case with actual bullet. (50 gr. Sierra Blitzking)
This would mean the total OAL of my rifle using the Sierra Blitzking would be
2.358". If I set the bullet back .020" for freebore I would have to load finished rounds to 2.338"
This is quite a bit longer then factory ammo.
I need advice.
Do I have a rifle with a extemely long chamber?
How abnormal is that?
Am I doing something wrong?
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Old November 20, 2009, 10:21 PM   #2
GeauxTide
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Join Date: April 20, 2009
Location: Helena, AL
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Don't complicate the obvious

Load some with listed COAL and shoot it. If it groups to your satisfaction, which in a short sporter barrel is 1 MOA, then you're done.
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Old November 20, 2009, 11:18 PM   #3
Lilswede1
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Join Date: September 8, 2008
Location: NW Wash State
Posts: 216
Looking for a little better than that.

Im trying to get down to a 1/4" moa. or better. At 1/2" moa now but would like to get it a bit tighter.
Want more consistent clean kills at the 250 - 300 yd. range.
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Old November 20, 2009, 11:58 PM   #4
Rusty W
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Join Date: January 27, 2009
Location: Oklahoma
Posts: 84
Here's what I do to find COAL for a certain bullet. I take a bullet, slide it in the chamber so it engages the rifleing. Take an empty case and slide in behind the bullet. Slide the bolt forward enough to hold the case & bullet in place. Take a brass cleaning rod and slide down the muzzle end untill it touches the bullet. Make a mark on the rod at the muzzle. I just twist the rod and the rifleing marks it for me. Then take the empty brass and bullet out. Close the bolt. Slide the rod back down the muzzle to the bolt face and make a mark. Again I just twist the rod and the rifleing makes the mark for me. Measure the distance between the two marks and you know that is what oal is too the rifleing. You coud seat the bullet there or .010, .020 or .030 from the lands. Depending on what your magazine will allow too. With a 50gr bullet it may not be an issue. I like to seat the bullet so the base is flush where the neck and taper meet. I've not tried the Sierra bullet. I've had great accuracy with the Hornady Vmax and the Noslet BT in .223. I have a Savage 12FV and the Nosler has a slight advantage in it. I think it's because the Noslet is a boat tail and the Hornady isn't.
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Old November 21, 2009, 06:54 AM   #5
hodaka
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Join Date: April 23, 2006
Location: South Texas
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The method Rusty has described is exactly what I do, except I use a magic marker on a stainless rod. Each bullet type will differ slightly in how it hits the lands. I believe I first read this in an old Nosler manual.
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