06x6spdGTO
New member
Just received 2 NIB barrels from McGowen and measured the OAL to the lands using the Hornady tool before installing them in Aero Receivers.
I am getting a COL length to the lands using the following projectiles.
Speer 39grn TNT - 2.352"
Hornady 45grn SP - 2.314"
Nosler 40grn BT - 2.36"
Both barrels are within .005" of each other.
This seems like excessive freebore considering MAX COL length on 20 TAC data shows 2.245". Anyone else jumping 20 cal bullets .060 - .100" to the lands and achieve 1" or better groups @ 100yd accuracy?
I wrote McGowen back with the measurements in which they sent me a drawing with dimensions of the Pacific Tool Reamer and the following comments:
"The throat reamer will not tell you what distance from ogive is to the lands. And even looking at the SAAMI spec it will give you the minimum. The best way to check is using a dummy round or you can also get one of the chamber gauges that is made from the same piece of material and using the same chambering reamer."
I am getting a COL length to the lands using the following projectiles.
Speer 39grn TNT - 2.352"
Hornady 45grn SP - 2.314"
Nosler 40grn BT - 2.36"
Both barrels are within .005" of each other.
This seems like excessive freebore considering MAX COL length on 20 TAC data shows 2.245". Anyone else jumping 20 cal bullets .060 - .100" to the lands and achieve 1" or better groups @ 100yd accuracy?
I wrote McGowen back with the measurements in which they sent me a drawing with dimensions of the Pacific Tool Reamer and the following comments:
"The throat reamer will not tell you what distance from ogive is to the lands. And even looking at the SAAMI spec it will give you the minimum. The best way to check is using a dummy round or you can also get one of the chamber gauges that is made from the same piece of material and using the same chambering reamer."
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