I have the opportunity to bid for a spare barrel to suit my Gevarm E1 22RF semi-auto takedown carbine. I have always had in the back of my mind to have another barrel made up for the Hornady .17MK2 rimfire cartridge for the carbine.
The Gevarm E1 barrels have a feed ramp extension built in and by undoing a through bolt in the fore-end, the barrel with fore-end attached comes away from the action. It would be a reasonable job to mill a loading ramp on a new barrel blank (see photo) so having a spare factory barrel negates all this work.
A conversion to the .17 MK2 cartridge should be achievable using .17 calibre rifled liners that are available for a 22 RF barrels. Boring out to 5/16”, loctiting the liner in the bored out barrel, then chambering for the .17 MK2.

The one issue I see with using the Gevarm factory barrel is the loading ramp mating to the chamber would be destroyed if boring right through the barrel for a liner.
My thoughts are and question is, would it be feasible to bore out the barrel from the muzzle end stopping when reaching about halfway into the existing 22RF chamber, and then facing off the end of the bore hole in the chamber to create a flat mating surface for the liner to butt up against. The chamber reamer would then just cut the chamber in the new liner for the front half of the .17MK2 case with the rear of the case supported in the original chamber with feed ramp untouched. Would need careful measurements although headspacing is on the rim and not the shoulder of the .17 MK2 case.
Obviously there would be a join in the new chamber but if the liner was inserted with some Loctite liquid metal at the joint interface I can’t see any problems with the lower pressure that the RF cartridges operate at?

The Gevarm is a straight blow back semi auto, firing from an open breach with no hammer or firing pin, just a raised ridge on the breach bolt face. There is no extractor and the slightly extended inner lip on the magazine acts as the ejector. Very simple and robust design.
The recoil spring guide can be changed around to suit standard/subsonic and HV ammo, putting the 50gram weight guide inside the hollow breech block adds to the inertia required to blow back the heavier block for HV ammo or putting the guide at the rear of the action lightens the breech block inertia for subsonic ammo. The spring tension remains the same no matter the position of the guide.
I don’t know what difference there is between the 17MK2 and 22RF cartridges in terms of their blow back inertia but the Gevarm of all semi-autos should be able to be tweaked to get the 17cal cartridge to work.

A bit long winded but prefer to give all the info I can. What say the experts, or not so expert. Anyone converted an auto 22 RF to a 17 RF?

Gevarm E1 feed ramp/chamber


Gevarm E1 feed ramp/chamber and magazine positioning

i really enjoy the little mach 2 but getting ammo is getting more difficult and expensive thus i don't see it worth the cost and work

Ammo not hard to find in my area. Runs about 8.99 a box and plenty of it was at the last Tulsa Gun Show.

I haven't looked into ammo availability although a couple of dealers here do list some, pretty expensive. Don't know what the long term future is from the production point of view. Seems the 17 HMR is quite popular with most dealers carrying good stocks of ammo. I see plenty of empty HMR cases when at the range.

My project would be more from the point of a play around thing and the beauty of the Gevarm E1 semi-auto is that it is a simple switch barrel so I could buy in a good stock of 17 MK2 ammo and use for special occasions e.g. longer range shooting of hares in open country. The 22RF will do most other things as it has done for me for 40 odd years now.