I just purchased the referenced advertised as M/IC. Ithe gun is in excellent condition but I was having extreme trouble hitting anything in skeet (I can shoot) but when I hit them, it was dust. Measured the muzzle with a micrometer and they measure 0.595 and 0.575. Based on what I have found, that's full and xfull. Is that correct? A friend of mine gave me a 20g choke gauge and according to that the choke are IM/M. Just curious what is real. Thank you in advance.

A choke gage is good to have if you are going to buy a gun to see that it has choke/s. Using a small hole gauge and then using a micrometer is the best way to tell.
In order to get the right constriction (choke) you need to know the bore. A 20 gauge bore should be .615 and your reading would indicate full/xfull.

Doc Drew’s information under frequently asked questions on this forum.
Note: for some reason when I copied and pasted the columns do not line up under the choke measurements.

With the information you provided your barrels have .020 and .040 of choke.


What were the choke dimensions for L.C. Smith shotguns?

The average bore and choke dimensions (inches) were:

Gauge Bore Improved Cylinder Modified Full
12. 0.732 0.725 0.710 0.695
16 0.662 0.657 0.639 0.629
20 0.615 0.610 0.595 0.585


Starting in 1907, Hunter Arms catalogs included the following statement:
"All Smith Guns are bored full choke unless otherwise ordered. We bore all our guns according to our Multiplied Choke Bore System, which has made the Smith Gun famous the world over for long-distance, close-shooting and hard-hitting qualities. We can bore a gun as follows using the twelve-gauge gun as a standard distance, forty yards; circle, thirty-inch; shot, Tatham’s chilled No. 7 1/2, one and one-quarter ounces; American Association Measure, 345 pellets to the ounce or 431 to the load."

Full choke……………………..70 per cent or 301 for pattern.
One-half choke………………..60 per cent or 258 for pattern.
One-quarter choke…………….50 per cent or 215 for pattern.
Improved cylinder……………..45 per cent or 193 for pattern.
True cylinder…………………..35 per cent or 150 for pattern.

After about 1940, 28” and 30” barrels were choked right modified (60% pattern) and left full (70% pattern) unless otherwise specified. 26” barrels in 20, 16, and 12 gauge were choked right improved cylinder (45% pattern) and left modified.

Please note the 16g bore was .650 into the early 1930s and pre-1913 16g chokes have been measured with constriction greater than .040" .

My field grade 20ga has a serial number if FW 56064. Would it take 2 1/2” or 2 3/4” 20 gauge shells? I assume low brass modern shells would be safe? Thanks

That serial number would date your gun to the early 1920's, so it should have 2.5" chambers unless they've been lengthened after-market. Would suggest you have them measured by a gunsmith before assuming any 2.75" inch load to be safe.

Fielding: no vintage double should presumed to be safe, with any load, until it has been evaluated by a doublegun specialist. Please look over https://lcsca.clubexpress.com/content.aspx?page_id=274&club_id=43784

You should not use 2 3/4" shells in a 2 1/2" chambered 20g and I would advise against lengthening the chamber. If the chambers have been lengthened, it is critical that the end of chamber and forcing cone wall thicknesses be measured.