Good advice that -don't mess with the port - the most I might be tempted to do would be to remove burrs, but make sure you understand your rifles action before doing anything that can't be quickly and easily reverted back !
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Good advice that -don't mess with the port - the most I might be tempted to do would be to remove burrs, but make sure you understand your rifles action before doing anything that can't be quickly and easily reverted back !
Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.
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I've opened them to .1195" using a decimal size reamer, and it usually fetches about 15 fps more, combined with a careful chamfering of the rear of the transfer port. This represents just a .0015" increase in diameter to the port (one and a half thousandths of an inch) as the US FAC ports are 3mm (.118). Going to .125" (1/8") may be a 'bridge too far'
The chamfering or light radiusing of the rear port.... 1mm to 1.5mm around the hole is fine. Chamfering can raise a burr that constricts the hole slightly (especially if the tool is a tad dull or the 'operator' applies too much pressure) so I usually follow up the chamfering with a decimal reamer the same exact size as the t port hole to clean any possible burr away. Good luck. RB
PS: if you're running a 12 ft/lb gun and it's very close to the limit; I do NOT recommend increasing the port size!
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