A moron and his uni-throater...

[tobnpr]

As others have mentioned, please explain your method of measuring the comparative freebore?
Can't diagnose if we don't have the info...

If you're getting chips- you're removing metal- and that metal is coming from somewhere.
Either something is faulty with your dimensioning/technique- or that throater is removing material from somewhere other than the throat.

If the chips aren't coming from the throat, they would have to be coming from the neck area. Theoretically, you could lengthen the neck area- and that wouldn't change the original location where the bullet ogive clears the freebore. If someone, somehow grabbed an incorrect neck sizing reamer instead of a throating reamer... But you're using a unithroater, so I believe there's problem with your methodology.

 

[StumpyJohnson]

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

 

[StumpyJohnson]

What cartridge are you cutting the throat for ?
Amazon also Has Modified cases rather inexpensive if they have your cartridge. If not we can make you one for free.
Let me know if you want to sell your Uni-Throater after you are done using.
Thanks
Len & Jill

28 nosler. Preferred barrel blank, carbon fiber barrel.

 

[StumpyJohnson]

As others have mentioned, please explain your method of measuring the comparative freebore?
Can't diagnose if we don't have the info...

If you're getting chips- you're removing metal- and that metal is coming from somewhere.
Either something is faulty with your dimensioning/technique- or that throater is removing material from somewhere other than the throat.

If the chips aren't coming from the throat, they would have to be coming from the neck area. Theoretically, you could lengthen the neck area- and that wouldn't change the original location where the bullet ogive clears the freebore. If someone, somehow grabbed an incorrect neck sizing reamer instead of a throating reamer... But you're using a unithroater, so I believe there's problem with your methodology.

Fair assessment. The last sentence is likely true...but I can't find the flaw in my method. I've used the comparator technique to measure the distance to the lands and adjust seating depth during load testing on many rifle's. I'm not doing anything different.

I've also measured the cutting surface of the uni-throater. .258 just above the bushing, and .264 just below the shoulder cut. Could it be that the leade angle of the uni-throater, combined with the length of the cutting surface is not long enough to bring the point of tangency far enough down the barrel?

 

[ARlife4me]

Is the barrel free or is it on a receiver? Are you trying to check it against the bolt being closed or barrel just not fixated?

 

[StumpyJohnson]

Is the barrel free or is it on a receiver? Are you trying to check it against the bolt being closed or barrel just not fixated?

The barrel is out of the action and in a vise. You cannot use the comparator and close the bolt.

(edit): The shoulder of the modified case meets the shoulder of the chamber and the relative measurement is taken from there. The dummy case I made has a score mark that indicates .100 from desired depth of cut to serve as a benchmark.

 

[can1010]

are those measurements right .258 and .264? you said the barrel is 28 Nosler, those numbers would be for a 6.5 cal not a 284

.277 and .2845 would be for a 28 Nosler

 

[StumpyJohnson]

are those measurements right .258 and .264? you said the barrel is 28 Nosler, those numbers would be for a 6.5 cal not a 284

Sorry I missed typed, the barrel is 26 nosler. I have both. The saami chamber prints say these measurements are correct.

 

[ShtrRdy]

How about color the whole bullet with a permanent marker, let dry, then press straight into the chamber and remove straight out. Where do you see interferance?

Start with the bullet seated to where you think the bullet is just touching the lands.

 

[can1010]

Sorry I missed typed, the barrel is 26 nosler. I have both. The saami chamber prints say these measurements are correct.

you got me stumped. need to get a borescope and see what is going on

 

[StumpyJohnson]

How about color the whole bullet with a permanent marker, let dry, then press straight into the chamber and remove straight out. Where do you see interferance?

Start with the bullet seated to where you think the bullet is just touching the lands.

I'll try this.

(edit) My suspicion it that I'll see marking in the ink, but it will be from a diameter somewhere between the bore diameter and the groove diameter. My suspicion is that the lead angle of the reamer is so slight and the original freebore/point of tangency so deep relative to other cartridges that the standard 6.5 uni-throater cannot reach deep enough to affect change. Does that make sense?

 

[StumpyJohnson]

you got me stumped. need to get a borescope and see what is going on

I talk about being a moron alot, but I'm thorough in my research and consistent in my approach and this one has me baffled. That being said I've never throated a barrel before.

 

[Shooter264]

The uni throater should be 1°30 do you know what your 26 nosler reamer was? Could be 3/4° and it would definitely cut without changing seating depth but only for so long. I wouldn't expect very much before the freebore started to change

 

[can1010]

looked up the 26 Nosler it has a 3 degree angle and my uni throaters have 1.5 degree. maybe you are just changing the angle and haven't got to cutting the freebore yet, cutting .120 is barely enough to change the angle and won't be even adding length yet. really need borescope dont screw up your barrel