Throat erosion

[Barlow]

I just measured the coal on my 6 Dasher to the lands and after 500 rounds it has gone from new 2.815 to 3.023 with a hard jam. 33 gr RL15, 105 Amax and 450's. Is this normal or average? The comparator nut is in the measurement. Barlow

 

[brxbrad]

You might want to check that again. That is .208 or 3/14 inch. If that's correct, your bullet is about to fall out of the case neck.........right?

 

[ridgeway]

Something is definitely being measured wrong. That works out to be almost 1/4".

 

[savagedasher]

What bullets are you using Berger you can get that much difference between two types and the same grain weight Good Shooting
Larry

 

[Barlow]

I'm using the 105 Amax, and it would not stay in the case at this length. I will measure again this morning. Barlolw

 

[Barlow]

Whew! I thought about this all night. I have a modified Lapua case fired in my chamber that was drilled and threaded by our local smith, no problem there. I tried to chamber that case this morning and it would not chamber. I resized it and it chambered fine. I could not get a slip fit, so some dumb a$$ (yours truly) pressed a .257 diam bullet into the neck and of course bulged the case and it would not chamber. I resized it again, and found a proper drill, and drilled out the case to get a slip fit. It worked fine, and my coal is 2.819. I feel pretty stupid, but am happy it worked out. Barlow

 

[lpreddick]

put me on the list...i did the same with a fired case my gunsmith threaded so i could use it with the hornady device. once sized the measurements made sense. i now follow throat erosion by chambering a sized empty case with the bullet seated a little long and observe the lands engraving...seat bullet .005 deeper and rechamber. continue this until no engravings seen. this measurement is usually the same or close to the one obtained with the hornady device, but i go by the actual lands engraving measurement since it's what i'll have with loaded rounds. i suspect short freebore chambers erode lands quicker than ones longer and need to be checked more often?