Easy Gap Fix On Standing Breech.
When I noticed a loss in accuracy in my 257Roberts Handi, I found a 0.003" gap in the standing breech I was not pleased. The rifle was never subjected to max pressure loads. But the seat was very poorly machined, MAYBY accounting for the gap? When a Handi develops a gap in the breech it will also at the same time the loose forearm contact with the action. This contact is as important as a tight breech, because it creates unwanted vibrations.
Of course we all know about the several available fixes. Like gluing in a shim or building up the hinge pin seat with weld. I found the glue in shim is very unsatisfactory. Build up with weld works well but is very involved.
When you look at the hinge pin from the rear you will see two shiny marks one each side with no bearing in the 0.312"wide hole in the underlug. The unsupported center gap became more foods for thought. The hole reduces the bearing surface of 0.361 sq/in by the considerable amount of 26%.
The open end in the underlug is a manufacturing short cut. Instead of a solid steel bock for the hinge pin seat and a stop for the ejector spring a simple split pin is installed for the stop. This pin is not needed to remove the spring also it can be. Installation of the spring and ejector is much easier from the breech end.
The fix I came up with kills to birds with one stone, one it eliminates the gap and two, improves the hinge pin-bearing surface by 26%.
Remove the ejector and the spring from the breech end. Make a stick of wood .300x.240 to fit the hole 4" long. Don't remove the spring stop pin. Clean the hole in the hinge pin seat with sand paper or a needle file and dimple the sides with a sharp punch up to the ejector stop pin and dimple the radiused seat. This will make small craters for a mechanical bond of the Steel Putty. Wash and wipe the hole and the hinge seat with acetone.
With a Q-tip thinly prime the hole with 51CURE or West System 5-1 epoxy. Wax the wood stick and have it in place against the spring pin to prevent epoxy to get into the spring race, fill the hole with Devcon Steel Putty and finish flush with the seat radius. Tap the wood stick to flush the Steel putty in place and avoid overfilling the hole. Let this set up solid.
Once solid apply primer to the hinge seat and apply a thin layer of Devcon Steel Putty and apply thin coat of STP or paste wax for release to the hinge pin. Carefully install the barrel and compress the Devcon Steel Putty. Tap action in place until the latch will lock solid. I would think that this should take care of a gap up to six thousands or more?
The back thrust against the standing breech for cartridge like a 243 or 25-06 is about 7500psi on a 0.173sq/in case head. The effective thrust area is 0.1246 sq/in. The above load is transferred to the hinge pin , which has more than twice the aria at 0.361 sq/in when the hole is filled in. Always use a good grease to lube the hinge pin and seat after the Devcon Epoxy steel is cured. Allow one week to cure, for sure.
One problem with a gap is, the loose barrel will add impact to the hinge pin each time the rifle is fired. To demonstrate take a 50lbs hammer and lay it on a 3/8 pin nothing will happen. Take the same hammer and drop it a foot and you will have a dint in the pin. The more gap the more impact. My Handi action developed a 0.003" after about 160 rounds.
Of course a gap will also place the latch in various places on the latch seat. This causes vertical stringing. The Devcon Steel Putty may in time compress but can be fixed easy by another thin layer of Devcon Steel Putty. Devcon Steel Putty has a 8400psi compressive strength more than enough to keep things tight. I have done my 257 Roberts in a trial fashion as above. The action now locks up tight as a vault with no gap and 20 warm loads with 100 gr bullets have shown no signs of compression. Which is very encouraging because the rifles good accuracy was restored.
You could make you own putty using West System 5:1 epoxy and atomized steel or Tungsten from Brownell. Devcon Putty is also available form Brownell page 253 cat # 57.
How long will it stay tight, I don't know, more shooting will tell. From what I have seen it will stay a while. The Steel Putty is very hard and compression at the above rate would be very minimal.
Devcon Steel Putty is also available from industrial suppliers. Do not use 1:1 Devcon Epoxy Steel.
Fred M.
