You MUST MEASURE!!! Years ago I bought a pretty generic Ball type choke gauge suitable for measuring 12 and 16 gauge only, and a Galazan brass chamber insert gauge to check the 10-28 gauge spectrum. Both cost less than $200 total at the time (c. 1980). As I began to purchase more and expensive smallbore guns, I blew it out and bought Jon Hosford's Barrel Wall Thickness Gauge and his combo choke gauge, which ran into the upper 600s of dollars.
I did some interesting comparisons between the ball-type gauge and Hosford's dial gauge; readings varied along the true bore diameter readings and the choke run at the end of the muzzle readings per each instrument, but the measurements determining the degree of choke were always congruent in the final readings. Was the investment in the higher end instruments worth it? Based on the mistakes I avoided over the years by investing in good measuring tools, there can be no question.
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