A moron and his uni-throater...

StumpyJohnson

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Feb 26, 2022
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Whelp a call to the folks at PTG garnered very little in terms of solutions. His suggestion was to continue increasing depth of cut while marking the reamer to see where the cutter engagement is. I think the consensus opinion is correct. I worry that I'll come to the end of the cutter and not have changed anything at the receiver end of the barrels lead angle, thus not increasing freebore at all and leaving a hollowed out section of the lead at the muzzle end. If I were to have a throater made @ 3* I would end up with a lead of multiple angles. My thought is to have them cut the shouldered portion of the cutter back to allow a longer throater, or just have them make a longer one, and risk it for the biscuit.

Oh and Yes this is a 5r barrel.
 

StumpyJohnson

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Feb 26, 2022
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20220701_084117.jpg


Ok, looks like I've achieved a freebore increase of . 010 by running the stop collars up to the point where the centering sleeve just barely covers the step in the tapered cutting surface.

In order to achieve the depth desired, I'd need to have the reamer shoulder cut back . 225 as shown.

This would give me plenty of length to keep pushing freebore forward. I can confirm that only the first 1/3 to 1/2 of the cutter is cutting.


Our theory is correct-ish I think.
 

StumpyJohnson

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If I do as described I believe I'll end up with the ability to cut the freebore I want and will have changed the lead angle to 1.5* in its entirety.
 

mulie

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Jul 31, 2009
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Colorado
I would never cut anything without a bore scope "the picture is worth" the $ 900.00 on the scope and what you spent on the rifle and what the barrel cost. PTG call is important.
 

Grumpy old man

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Dec 9, 2020
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Pennsylvania mountains Poconos
I have a modified case from hornady, I have a modified case from the chamber that I threaded myself. I have a dummy round of the desired dimensions. I have the barrel out of the action. I cleaned the carbon out, then I cleaned the copper out. I found the lands (with the uni-throater) then I marked the shaft and the double nut system, then I cut in .015 increments and clean, repeat. I've traveled the length of the desired .120 cut from where I touched the lands with the unithroater, but every bullet I jamb into this badboy has not moved from the original CBTO I measured when the barrel was new. Then I licked a window and chewed on my own shoulder. Repeat
That don't make logical sense ,pull cutter out let me see it!
 

Beluebow

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Dec 6, 2004
Messages
585
Location
USA
Did that, I'm cutting I can tell by the swarf/chips. No increase in CBTO.
I didn't read all the replys.....my guess is you are opening up the FB diameter, that's where the chips are coming from, and why the actual FB length hasn't got longer...yet...WAG on my part.
 

Terry Balding

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Dec 28, 2013
Messages
249
If a window licker grabbed himself a uni-throater, made a dummy round of his desired cbto/coal, and got medieval on his barrel and throughout the process never got to the point where his freebore has increased at all...what has occurred?

Spoiler Alert: I'm that window licker. I've checked repeatedly with the dummy round and a bullet comparator and nothing has changed. And I'm still a window licker, that didn't change either.
The Uni Throater needs to be adjusted to cut. Back off the adjustment ring and lock rung. Slide the sleeve forward. Place in chamber. The sleeve will slide back and stop. This is your Zero. Only cut a very little at a time. Maybe. 010 . The adjustment ring is marked in thousands. Turn the ring toward the sleeve. Stop when you touch. Back off .010 and make your first cut. Cover the cutting surface with a light greese. It will retain the chips with the cutter. Clean off cutter, adjust and repeat till your dummy fits. Later cuts may need to be smaller to get the fit that you want.
 

Terry Balding

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Dec 28, 2013
Messages
249
Machining to fit has been around a long time. Some things just need a be fitted. If the dummy fits as you want it to, that is what matters.
 

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