Wal Randy stock fit on a shotgun is a mighty personal thing. What's right for one ain't necessarily so for another. I can't say if it's too long or too short or too whatever sitting here not looking at you with it and shooting it. No one can really.
To the best of my knowledge all of the Rem870 receivers should be close enough that which one you use shouldn't matter. Stocks too haven't changed much if any in dimensions from old to newer. IF the stock now on it is a factory stock with factory butt plate or pad it should be the same pull length as any other pretty much. As I recall on an 870 the pull length should be 14" from center of butt to trigger in a straight line. Drop at comb I believe is about 1.5" and at the heel 2.5". You might check and see if yours has these dimensions. If so you're gonna hafta look elsewhere for a reason you and it don't hit.
Can be lots of such reasons. Barrels are NOT always straight. Choke tubes are not always installed correctly. Either of these can make the point of impact POI of the shot charge go wide left or right or high or low of your intended point of aim POA. Might be you're using a tighter choke now than in the past and that's the reason for the lower scores. Might just be your rusty in your shooting and not doing as well. All are possbilities.
I'm not much of one to use a pattern board. Partly because I shoot off my right shoulder with both eyes open but have a left master eye. Thru years of practice and many tens and hundreds of thousands of rounds I have learned to do this pretty well. At least on my good days.
But I can't shoot that way at a stationary target like a pattern board for squat. I have to close the left eye and use the right to hit any stationary object. This isn't the way I shoot moving targets so to me a pattern board is useless in determining where my POI is in relation to my POA. BUT for you a pattern board might tell you where you're hitting in relation to where you're aiming. If so then you at least will know what needs fixing.
Trouble is what are you gonna do once you know? Getting someone to bent a stock or straighten a barrel isn't cheap. You might first try a different barrel if you know someone who will let you borrow one to rule it out as a problem. Then if you have a friend who will agree you might even try changing stocks with him for a shooting session. Or you can just do as I do when I buy a shotgun that me and it don't geehaw. I trade it off and try another. When you find one that fits and you hit well with don't do a stupid thing like I always seem to and trade that one off. Oh how I wish I could get back some I've let go of.
GB
