.30-40 Krag Auxiliary Chamber

Hi, All…I need some help on this…Scanner not yet hooked up to new computer…no photos…so here goes…I have here an auxiliary chamber…blued steel, outside shape of .30-40 Krag cartridge. Total length = 2.94". Chambered for .22 Rimfire S, L, LR, Ex L., as interior “barrel” is all one diameter and smoothbore. “Bolt” .40" long and .30" diameter fits within the rear of this adaptor. This contains a depressible spring loaded pin protruding from its exterior circumference which slides through a recess in the chamber base, and, when pushed forward, this pin “locks” into place by extending upwardly through a hole in the chamber wall. Upon the forward end of the bolt is a typical looking rectangular, raised, “firing pin”, as would be found in a .22 rimfire firearm. So, one uses a toothpick or other similar “skinny” item, pushes the pin downwardly and rearwardly, to remove the bolt, then, inserts a .22 rimfire cartridge within the chamber, whereupon the “bolt” is re-inserted in the chamber until the spring loaded pin is “locked”, aux. chamber now inserted within chamber of Krag rifle, whereupon, Krag rifle trigger is pulled, driving firing pin of same into base of “bolt”, thereupon firing the rimfire cartridge. Small, machine stamping upon “neck” of this chamber, letters EFD about .05" high and quite deep. Any ideas ?/…Hoffer-Thompson ??..Thanks Much !!..Seems like a pain to use, compared to some of the other aux chambers…Randy

Hello Randy,

The letters EFD appear on many items made by Enfield in England. Are you sure that it is .30-40 Krag calibre?


Hey, Gravel…Yes…definitely a .30-40 Krag outer shape…(not .303 Brit as neck is way too long)…Randy

But, upon closer inspection, this would most likely fit a .303 British chamber, so it may be for a .303…especiall if Gravelbelly is right about the lettering indicating manufacture by Enfield…


The position of the shoulder is not important as long as the rim dimensions and body size and taper are correct. I have seen .303"/.22RF adaptors with a “low” shoulder, I don’t know why this is. They worked 'though.



Did you do a patent search?


Jim Buchanan did an article on adapters in JOURNAL #443 and maybe he can help?

That gizmo sure sounds interesting. I can’t wait to see a scan.