SVT40- accuracy controls

[Ridolpho]

Foul early spring weather and I still haven't been to the range since October. I have, however, added to the collection and now have '41 and '42 original snipers with good bores. Each has been equipped with an aftermarket bracket and a real scope and both are bore-sighted and ready to go (photo shows the '41). In the meantime I've been using a '41 Tula that I bought for $200.00 before Christmas to play with bedding techniques. Seems to boil down to the through stock pin being an axis and forend tip pressure being adjustable from both ends. I've made shims out of 0.012 gasket paper for the rear that also snug up the action-body fit in the stock. At the front end I've used epoxy to tighten the fit between barrel and lower handguard. This one has about 6 lbs up-pressure now which feels right- but is that how they're supposed to be set up? There is a new book out in Russian and a gentleman from the Ukraine has told me it outlines original Russian armorers techniques for shimming and that the goal was to have significant forend tip pressure.
Also monitored various websites over the winter for anecdotal info (particularly north of 49 where a lot of people are shooting these things). Unsubstantiated claims have been made that 1) removing the cleaning rod improves accuracy; 2) that free-floating the barrel improves accuracy; 3) that the gas setting affects accuracy. That last one intrigues me as on my last range trip in November a '42 Tula that had been showing potential for 2 inch groups suddenly opened up to 12-15 inches coincident with erratic cycling at the setting that had worked well in Sept. I'm now convinced that the initial downward bending of the barrel in the ultra-slow motion film is not whip but, rather, bending due to inertia of the bolt/ carrier effectively pushing out on the piston. Then, if the carrier is sluggish due to congealed grease it would potentially affect shots somewhat randomly (call it a theory).
So, my first step is going to be a range session with the test-bed gun. I'll shoot it with various forend pressures (easily adjustable with the shims) and then I'll remove all shims and swap the handguard for one without the epoxy and compare results. I'm aiming to try to use one of the snipers in RangeRovers's vintage battle rifle shoot in June so I've got to get cracking.