Models 150, 250, 255, 270 and 275,
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NOTES:<br>BARREL, RECEIVER,  HEADSPACE, and LOCKING PLATES:  All 200 Series barrels are pressed into the receiver and then secured with a threaded collar that must be staked in position. To remove barrels – remove all forearm parts, unscrew the barrel collar and use a block of hard wood against the face of the receiver while driving the barrel and receiver apart. To install a barrel or receiver, clamp the barrel in a padded vise and use a “V” shaped aluminum block or scrap stock against the receiver while driving the barrel and receiver together.
NOTE:  Use a “T” square or straight edge to align the barrel with the receiver as they are forced together. This should be followed by driving the barrel collar up tight and staking a bit of barrel metal into one of the slots on the underside.
A loose barrel will create headspace and/or burst cartridge heads/ In the case of a loose barrel, always back off the barrel collar before driving the barrel back into the receiver, then re-stake the collar as above. 
<b>Special note on locking plates.</b> When fitting a locking plate to this gun, locking plates usually come long, so you will have to grind the rear of locking plate at a 10° angle. Take a few thousands off and then try it in the rifle using the above headspace testing. If you fail to do this properly, it can ruin the receiver and could cause severe personal injury.
The 200 series 22 rifles all use a “Cone” shaped cartridge rim seat in the barrel and require headspace gauges with a full radius to the rim. Or an extra chamber on the front of the gauge rim. 
Headspace should be checked with the action upside down, minus the trigger guard assembly. On the Model 290 or Model 290 autoloaders, use two  ½” wide strips of typing paper between the shoulders of the breech bolt and barrel head with minimum (“GO”) headspace gauge in the chamber, or use a no go gauge. If headspace is correct, the bolt should grip the paper strips, otherwise headspace is too tight and the gun would crush fire on closing. A new breech bolt or barrel would be required to correct the problem. 
On lever and slide action 200 Series rifles, also place the action upside down minus the guard assembly. Then with a minimum (“GO”) gauge in the chamber, slide the bolt and locking plate forward. If the headspace is correct, the locking plate just will drop into the receiver locking recess. To confirm this fact, the same locking plate should not drop into the receiver recess when tried with a maximum (“NO GO”) gauge in the chamber. 
After you have completed the above work, put a GO gauge in gun and close the action and safety should go on with ease. If there is any resistance the headspace is short, and needed to be reset.