by Wyliecoyote » 04 Apr 2022, 5:48 pm
I have done extensive work to a number of these in recent times. The single biggest issue is setting correct headspace and very few if any smiths understand how to go about this on these rifles beyond google that states using the barrel shims. Those shims are actually for setting correct toggle lock up.
To correctly set headspace is a whole different process. The standard factory bolt is machined as if it were a 10/22 semi auto where the recess for the rim is deeper than it needs be and as if it was for the prevention of slam fires. Not applicable in these rifles and destroys accuracy. What the barrel shimming removal a lot of smiths do actually does is bring the bolt face into firmer contact with the barrel tennon, causing excess stress on the toggle lock up and leads to the bearing or retaining screw failing which exasperates the headspace issue even further. There should never be contact with bolt face and barrel tenon and absolutely no pressure in toggle lock up to the point where the action half cocked and dry fired should lock the action fully. If you invert the rifle with the magazine removed you can physically see the bolf face and tenon contact and even measure the distance of cartridge rim to the recess with a feeler gauge. Some gaps i have measured have been in excess of 10 thou yet the toggle is locked tight. Never shoot consistent in a million years.
So the first thing done is the bolt face is machined to have the rim recess sit around 35 thou deep so the face locked on any current cartridge can never contact the tenon. From there the shims are binned and barrel shoulder machined back to set correct headspace to no more than 43 thou, no less than 41 thou. If you run Eley Match etc only, that can be as tight as 39 thou.
With regard to fitting a barrel, i have fitted stainless aftermarket barrels, but not with the factory dovetail where there are numerous reasons why not to use that set up. The best improvement in this area is done by setting the action to screw cut the tennon bore to 3/4" x 16 TPI. That existing bore you have right now is exactly the right dimension to cut that thread size, smaller is not possible, larger and you run out of shoulder to tension the barrel with enough surface area.
There are after market kits to fit a rear action screw in 10/22s and these can be adapted to these Summit actions and i do strongly advise getting that done where it does cut down on that errant vertical flier.
One of my conversions is down in Brisvegas where if you pm me i can get you his details to have a chat with. It has a Lilja barrel fitted and all the work done as described including the trigger set to around 4 ounces.
Done correctly with a good custom barrel these rifles are the fastest action around and easily attain sub quarter inch groups at 50 meters with premium ammo. I do suggest a full steel barrel as the carbon sleeved factory barrels are far too light for any off hand disciplines like silhouette.
PS There are major issues with the extractor on some of these where the factory cut a recess too small to act properly and in such a way that it prohibits the correct toggle closure, extraction and ejection. Hence the VQ fix.