K-20 Sporter & Pro Sporter Extra barrels
In addition to 20 gauge barrels, the K-20, in both rib configurations, can be fit with extra, interchangeable small bore barrels in 28 gauge and .410.

Complete List of Interchangeable K-20 Barrels
| Gauge/Chamber | Length | Chokes | Rib | Ounces | Pounds | |
|---|---|---|---|---|---|---|
| O/U | 20ga/3" | 30" | Choke Tubes (5) | Tapered flat rib, 10-6mm | 541/2 | 3lbs 6oz |
| 20ga/3" | 32" | Choke Tubes (5) | Tapered flat rib, 10-6mm | 55 | 3lbs 7oz | |
| O/U | 28ga/3" | 30" | Choke Tubes (5) | Tapered flat rib, 10-6mm | 521/2 | 3lbs 5oz |
| 28ga/3" | 32" | Choke Tubes (5) | Tapered flat rib, 10-6mm | 541/4 | 3lbs 6oz | |
| O/U | .410ga/3" | 30" | Choke Tubes (5) | Tapered flat rib, 9-5mm | 543/4 | 3lbs 7oz |
| .410ga/3" | 32" | Choke Tubes (5) | Tapered flat rib, 9-5mm | 56 | 3lbs 8oz |
K-20 Stocks and forearm
| #7 Schnabel forearm 1-4/5" x 1-3/4" x 10" |
#3 Sporting stock Length of Pull 14-3/8" 1-1/2" x 2-1/8" x 2-5/8" |
#9 Skeet/Field stock Length of Pull 14-1/4" 1-5/16" x 2" |
