You said at the oputset that the fore-end is sloppy loose. Like taking your car out with loose wheel nuts and complaining to the garage that it handles like a stuck pig. Get that sorted out and fitted properly, make sure rifle is in good overall mechanical condition and THEN range test it. Absolutely no point whatsoever doing anything else before you fit the fore-end believe me.
I'm always kind of amazed at how simple zeroing becomes such a complicated discussion. I have the 1948 Rifle and Bayonet Infantry Training Pamphlet open in front of me. It's an amazing wealth of knowledge at $15 and postage for perfect reprints by the way but… I disgress.
I shoot at a 1" black paster on an 8" x 11" sheet of paper at 25 yards using a sandbag. The point of impact with a Mk.1 rear sight using the small aperture set on 200 yards is 3/4" above the point of aim, (holding six o'clock on the paster). Permissible variation, (vertical), is +/- 2". Each height of blade should increase/decrease the POI by 1/2" at 25 yards. That's it in black and whilte as written by the MoD.
The key holing is from boat tail projectiles in a barrel well shot with cordite ammo. The throat/leade in the barrel has a wear pattern that will not stabilize the projectiles. Get some flat base projectiles as BAR suggested. Your forend may only need adjustment. IMHO, restocking is the last resort if the original can be adjusted/fitted properly.
Wobbly woodwork should not cause key-holing, just ugly groups..
Keyholes on targets are a sure sign the bullet is not even remotely stabilized. In turn, this means that it is not being spun fast enough to maintain orientation whilst battling aerodynamic forces.
The standard barrel has a 1:10" twist, left hand. At proper velocities, that twist will stabilize ALL bullets as long as the old "torpedoes" and Mk7 and shorter.
If you back off the velocity, you likewise back off the spin rate.
7.62 x 39 barrels all seem to have a 1:10" twist rate (RH). Oddly enough, even Tokarev TT-33 pistols have the same twist.
Why? Probably because ALL of their barrels were made on originals or copies of the good old British and American supplied machinery imported into Russia to make the M-91 Moisin Nagant rifles, which have that same 1:10" twist.
1:10" twist is WAY over what is required to stabilize the short 124gn bullets even at the relatively low velocities in an AK. As for the short bullet fired from the 7.62 x 25 pistols and SMGs; if it works, it is not a silly idea. The practice certainly simplified a lot of tooling and gauging at manufacture.
If you throttle back loads in a given cartridge / barrel combination, you will eventually get to a point where the low muzzle velocity will not generate a spin-rate fast enough to stabilize the bullet.
The old Mk7 .303 bullet is BASE-heavy by design. Shoot them at low velocities from a standard barrel and they will wobble badly. There is ALWAYS some of this "wobbling" going on for a short distance after the bullet leaves the muzzle. How much "wobbling" and for how far, are determined by many factors: Condition of the crown, fit of the bullet to the bore and grooves, quality of the bullet, etc..
In a related note, specialist cartridges like the .300 Whisper / Blackout are designed to shoot LONG, heavy bullets at subsonic velocities. The long bullets used require a VERY fast twist to get the ROTATIONAL velocity needed to stabilize them.
A barrel that is badly flogged out at throat, bore and muzzle will not allow the attainment of sufficient velocity and thus, spin-rate, to achieve reliable stability. An oversized, uneven muzzle also contributes to uneven muzzle blast that acts rather forcefully on the tail of the bullet. Boat-tails are especially prone to dispersion caused by the extended action of this uneven blast on the conical tail of the bullet.
Picked up some Federal 150gr flat base soft points today... They seemed to shoot well out of the rifle. I didn’t zero as I still need to get it restocked and the proper front sight, butbit stablized the bullet.
If the rifle shoots well, why do you think it needs restocking?
I didn’t say it shot well, I said it stabilized the bullet. It didn’t keyhole with the flat base. This stock has an excessive amount of play in all the wood.
You know thinking of what your saying it maybe that the wood is excessively dry and has shrunk over the years as we know nought of their history for all we know about it is it could have lived in a barn in the Arizona desert or Death Valley.
So strip all of the wood off the metal give it RLO/Min Turps 50/50 till it cannot soak up another drop letting it dry between coats whilst your there you can inspect the draws and anything else you can't whilst assembled thats what I would do as the very first thing before faffing about with anything else......
Most of the guys here are registered gunsmiths and or armourers whether in service or retired they offer their advice free of charge and with integrity, like I say to my son when he becomes to smart being a smart ar$e "Don't poke the Leopard" in reference to a game warden on you-tube who did that with a long stick to try and get a Leopard out of a cage in the back of a land Rover in Africa.
Upshot of that was the Leopard jumped out bolted into the passengers side only thing is he left the window down half way cats being cats it joined him in the cab luckily it could not get its back legs in there but it caned that chap really badly, I saw the aftermath pics he was not healthy looking more like he had been through a shredder.............
Here's the clip its worth watching the whole thing so you understand what & why the cat attacked.
Always known as a Tin Hat target in British service and at Bisley today.
Having just looked at a current NRA Zero Target from the range office, it shows the distance to be shot at as a very precise 71 feet. 7" inches.
Woe betide the man who cheats and shoots this at 71 feet and 6" inches!
Measured exactly from the muzzle SB its 22.86M for 25 yards as per target supplied by this site which is what I did when zeroing my No.4s thing is the new pills fly different and given the better BC's the only way to get you POA/POI is range time noting the site settings for each range its what I did and countless others have as well but I now have one load and DOPE for all my 303's but it was a longish road thank goodness its over for the time being...........