I hope this is not a stupid question but I am confused about what size groups I shoould be getting with my stock 60's vintage SP1( approx 1,000 rnds). Its equipped with a 2-7 carry handle scope (I know but it works for me with my 58 year old eyes) bench shooting from sand bags. I hear claims that these rifles are capable of 2 MOA groups with XM193. I have never gotten 2 MOA groups consistently, its more like 3-4 inch groups consistently. I am also confused about how groups are stated by some posters on this board, for instance I recently shot these groups on 2 different outings to the range:
The top one is 100 yards shooting 45 gr. Winchester WB Varmit, the second target is 100 yard, XM193. To be accurate is the first target a 7shot, 23/8" group or would some people say its a 3 shot 1/2" group? The second target, is it a 5 shot 3 " group or a 3 shot 1/4" group.
I guess my next question is are these groups "normal" for a SP1 using low cost commerical and XM193 ammo. Thanks for any help.
Typically, when someone posts their group size, it will be for 3, 5 or ten shots at a given range, usually 100 yards. The group is measured from center to center of the two shots that are farthest apart, or edge to edge minus the caliber of the bullet of the two farthest apart. Usually the groups are shot, and any fliers that can be atributed to shooter error can be tossed out. These are "called fliers" and are basically you know that you botched the shot (like a round going off next door caused a flinch). Usually when we see someone post their results on line, we like to assume that they are really shooting 3,5 or ten shot groups, that they are discounting fliers properly, and that they are averaging their groups not just using one really good group, that could statistically be wrong.
I cannot comment specifically on your gun and ammo combination, but I will throw some stuff out, as I do a lot of scope work with my AR's. I apologize if you understand all of this stuff, I mean no disrespect.
The mechanical ability of the gun/ammo combination to put all of the bullets into one hole is primarily a function of the ammo/barrel combination. This is related to the quality of the ammo, the twist of the barrel and the quality of the barrel. Next down the list is the forend. As I suspect that your gun is not free floated (factory handguards), when you shoot the gun any pressure on the handguards puts pressure directly on the barrel. If your benching the gun, it is important to keep things very consistent, with regard to the handguards. No inconsistent pressure on the barrel and handguards.
Right behind these items is the trigger. If you have a stock trigger that is "bad", you may never get the kind of groups that you want. Bad usually means heavy, lousy take-up and or lots of overtravel, or likely all three.
I am not sure whether to say the next things are on the list in any order, but all of the above assume that the scope is not problematic, and that the mounts and rings are tight.
Usually the best approach is to confirm that you have no movement in the mounts, and possibly check the scope on a gun that you know shoots well. Basically, reduce the variables to just ammo and bench technique. Once you feel confident that it is just ammo and gun, then try out some different ammo. My newer AR's have no problem keeping XM193 very close to 1-2 moa. The Winchester 45 grain varmint ammo can be very picky about barrels.
In looking at your targets, I would say that the gun can probably shoot the XM193 into your stated goal. I base this on the three shots that are touching. It is very critical to see your crosshairs right at the point of the trigger breaking so that you can call your shot. With your factory handguards, it will be very important that you keep your pressure on the grip and rear very even. If you put weight down on your grip, it could push up on the barrel and cause fliers (depending on the location of the front bag). I like to put almost no pressure on the grip, and I move my off hand to the rear of the rifle, underneath, usually squeezing the rear bag to make that finite last little bit of adjustment. Bascially, let the rifle recoil as it wants. The goal is consistent technique. The perfect situation is to touch only the face of the trigger and the reae of the grip. Kinda like Ransom Rest like testing. It is also important to understand that shooting from the bench in a target situation is different than shooting from field positions. On the bench all you are concerned about is really group size and consitent technique. Once you want to zero the gun, then you should use the techniques that you will use when shooting for real.
Again, in looking at your second group, I suspect that your shot in the nine ring was probably a flier, from the trigger or technique. Only you can answer that one, by seeing your cross hairs right at the moment of shot, or evaluating your technique. One other thing that might be useful if you have any friends that shoot AR's would be to let someone elase try shooting your gun. Just one more way to reduce the variables, of which there are many.