.17 HMR 10/22

This is my first .17 HMR. It is a Ruger 10/22 Magnum action that has been fitted with a Green Mountain 77/17 barrel. The Stock is a Boyd's Laminated Birch "Smart Stock."

I've had a lot of questions from people about this conversion. In what follows, I can hopefully clarify some things:

The main components of the conversion are a steel spacer that slides over the barrel shank and a wedged, "half-moon" shim that fits in the V-block.

This is an image of a barreled action with the spacer installed. Hold your mouse pointer over the image for a close-up.

Since the position of the extractor on the 77/22 bolt is in a different location than on a 10/22 bolt, the barrel must be rotated slightly to line up the extractor with the groove.

This image shows a wedged, half-moon shim that fits into the V-block. This shim is required because the dovetail in a 77/22 (77/17) barrel is cut closer to the breach face than on a 10/22 Mag barrel. The shim is "wedged" to help align the extractor groove in the barrel with the location of the extractor on the bolt. The "wide" end of the shim is on the same side of the rifle as the ejection port and bolt handle. The "pointed" end of the shim is on the serial number side of the rifle.

The factory V-block will not fit without some modifications. It is necessary to grind an angle into the top, front edge as shown:

If the shims are made and installed properly, and the rifle is otherwise functioning properly, the result is a very fun, accurate, flat-shooting rimfire. There was some concern early in the project about using the .17 HMR in semi-automatic actions due to case head expansion issues. Thanks to a lot of research, tinkering and ingenuity from several members of Rimfirecentral.com these issues have been all-but eliminated. These casings show the typical amount of case head expansion that can be expected, as you can see it is minimal.

DISCLAIMER: I do not make any claims as to the overall safety of this modification and do not accept any liability for any damage or injury caused by someone attempting this modification on their firearm. Modifications to your firearm can be dangerous. Whenever in doubt, consult a gunsmith before deciding on any modifications.

Here are some images of items that found themselves in the way of .17 HMR bullets:

This was a water-filled soda can sitting on top of a Quarter. When the bullet struck the can, hydraulic pressure actually left this impression in the bottom of the can.

.17HMR meets penny

Here is a picture of the pieces recovered from a .17 HMR bullet after striking a water-filled, 1-liter plastic bottle:

"Ruger, 10/22, 77/22, 10/17, 77/17 and 10/22 Magnum" are all trademarks of the Sturm, Ruger Company.

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