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Old 05-08-2019, 02:03 PM
JSH JSH is offline
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Default Finding length on zero freebore

This is a brand new barrel so no fired brass.
I started off using dykem on a bullet 25 grain vmax. Kept seating until just the faintest hint of contact, so I called that my “touch” length to ogive.

If I were to take a case and seat a flat base bullet backwards, would that give me a dead length? I know there was discussion on such using slugs, but I could not find the thread.

I ask because this is my first zero free bore. I am more used to just trying to find the throat.

As now there is some ogive beyond the case mouth. Yet it is seated deeply, or rather a fair bit deeper than normal. Bullet base looks to be just below the neck according to my math, not that I am concerned with that. My load is not close to compressed.

Jeff
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  #2  
Old 05-08-2019, 02:24 PM
coyotespotter coyotespotter is offline
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Bolt gun or semi, a bolt gun I would strip the bolt(using a dummy round) and start long and seat bullet .001 deeper until bolt closes with no pressure. Remember no heavy bolt pressure you do not want to stick or distort the bullet as you check each seating change.
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Old 05-08-2019, 03:11 PM
JSH JSH is offline
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That is the way I went at it, bolt gun.

I have some seated 10 deeper to see how they shoot and get a zero on my scope.
This is a 17 Remington 1/8 Shilen select. Plans are to run 25’s exclusively and save the 20’s for the 17FB.

I get these Savages up and running I have a couple of Howa minis for donor actions for projects. The four CZ’s will be looking for a new home. I knew I would be dangerous when I started playing with the lathe.

Jeff

Last edited by JSH; 05-08-2019 at 03:14 PM.
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  #4  
Old 05-08-2019, 03:28 PM
Oso Polaris Oso Polaris is offline
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Jeff,

I dealt with this exactly 1 month ago. Go find my thread "17-222" on April 8th. Starting on page 2 of the thread you will see beginning of discussion of the Sinclair Case Length Gauge and then my experience set-up, usage, and missteps.

Quote:
Originally Posted by JSH View Post
This is a brand new barrel so no fired brass.
I started off using dykem on a bullet 25 grain vmax. Kept seating until just the faintest hint of contact, so I called that my “touch” length to ogive.

If I were to take a case and seat a flat base bullet backwards, would that give me a dead length? I know there was discussion on such using slugs, but I could not find the thread.

I ask because this is my first zero free bore. I am more used to just trying to find the throat.

As now there is some ogive beyond the case mouth. Yet it is seated deeply, or rather a fair bit deeper than normal. Bullet base looks to be just below the neck according to my math, not that I am concerned with that. My load is not close to compressed.

Jeff
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  #5  
Old 05-08-2019, 03:48 PM
Ackman Ackman is offline
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You're making it more difficult than it is. Use a split neck case, it's not difficult. Necksize a new case and give it a good inside chamfer. Then with a dremel cutoff wheel, slit the neck lengthwise and just slightly into the shoulder. Barely seat a bullet and chamber the round. Carefully unchamber it and you'll see exactly where the ogive contact point is. This is a stupid easy way to find the right seating depth. *** If you don't have a dremel tool, you should. Get one.

Last edited by Ackman; 05-08-2019 at 03:52 PM.
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  #6  
Old 05-08-2019, 05:38 PM
JSH JSH is offline
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I have slit cases in the past pretty much the way you describe. I got to the point of putting dykem on the bullet. There were several times the bullet would pull when extracting.
Then getting a good measurement on the ogive without moving it could be a trick at times. I may revisit it just to compare to previous measurements.
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  #7  
Old 05-08-2019, 07:48 PM
Ackman Ackman is offline
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Quote:
Originally Posted by JSH View Post
I have slit cases in the past pretty much the way you describe. I got to the point of putting dykem on the bullet. There were several times the bullet would pull when extracting.
Then getting a good measurement on the ogive without moving it could be a trick at times. I may revisit it just to compare to previous measurements.
After you've done it awhile you develop a touch for how much neck tension to use on the case. Do several with the same chamber and get the feel of it to where you're confident it's accurate. Every now and then there'll be a chamber throat that doesn't want to let go of the bullet, or a particular bullet. Then neck tension is trickier, you have to back way off and find the right combination. Unchambering can be tricky with Remington style extractor, espcially if the ejector spring is full strength. Mine are all shortened and I stlll push in on case until it clears the port. It's all a matter of just learning and then it works beautifully. I've been doing it this way since the 80's.
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  #8  
Old 05-08-2019, 09:42 PM
TinMan TinMan is offline
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I usually do it five times and average, with different bullets, to get a good feel for the measurement.
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  #9  
Old 05-09-2019, 02:13 AM
trotterlg trotterlg is offline
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If you run your reamer into a die blank when you get your barrel done you will have a seating die that perfectly puts the bullet exactly at the lands.
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