The Sporting Arms and Ammunition Manufacturers’ Institute (SAAMI) has accepted and published standards for the .21 Sharp and 3" 28-ga. shotshell. Both were submitted for consideration by Olin Winchester and add to the cartridges development trend American Rifleman covered earlier this year.
The 3" 28 gauge was the first of the duo endorsed by SAAMI, which has been publishing pressure and dimensional standards for the industry since 1926. Maximum average pressure is rated at 14,000 p.s.i., where it delivers a 1 1/8-oz. lead payload at a velocity of 1,200 f.p.s. With 1-oz. loads speed jumps to 1,300 f.p.s. and up to 1,350 f.p.s. with a 3/4-ozs. The latter pair of ratings are for unleaded shot.
The new rimfire is nearly identical in design to the familiar .22 LR, but the use of a non-heeled projectile opens an opportunity for manufacturers to harness improved bullet profiles and designs. Overall length (1") and average pressure (24,000 p.s.i.) for the .21 Sharp are identical to the .22 LR, as are all case dimensions. The bullet diameter, however, is 0.2105", versus the .22’s 0.2255" measurement. That means the cartridges, despite similarities, are not interchangeable. A simple barrel swap might be all that’s needed to change a favorite long rifle to the newer cartridge, although as this is being written, no complete guns or aftermarket barrels were available.
SAAMI rates the .21 Sharp as sending a 25-grain bullet out of the barrel at 1,725 fps. Winchester’s .22 LR tin hollow point load comes close in weight, allowing a rough velocity comparison. That bullet leaves the barrel at 1,659 f.p.s., according to Winchester’s website. Bear in mind, however, the test equipment at SAAMI and at any firm is rarely, if ever, identical.
Winchester currently offers polymer-tipped 25-grain rimfire loads for .17 HMR and .22 WMR. Both the new 28 gauge and .21 Sharp were not listed on the company’s website at press time.