I have heard many times how the looseness or slop between the upper and lower receivers is irrelevant to accuracy. This is supposedly because the part that is doing the shooting is all attached to the upper receiver. The bullet will go where the sights are aimed because the sights and upper are all one piece.
But, since the shooter is hanging onto the lower, the upper can move around relative to the lower, when the shot it fired, regardless if the lower is not moving at all. Now maybe the bullet is long gone before this movement ever happens, making the movement immaterial. If so, no problem. If not, the sights may be aiming at something else, due to movement (recoil), before the bullet has left the barrel.
Would a bolt action work as well, if the barrel/action/scope were a loose fit with the stock? Not exactly an apples to apples comparison, but hopefully the point is seen.
I am NEVER just hanging on to the lower when I shoot. The upper is supported by a sand bag, bipod when bench shooting, or my left hand when I’m standing. This effectively eliminates any movement of the upper relative to the lower.
In the DI powered AR, the bullet has “left the building” long before the gun has started to recoil.
All of the HSLD types that I have come acrossed in my years of training, never once did any of them mention to me any concerns over upper and lower slop.
So I would not pay ANY attention to the fit UNLESS you can rock the upper and lower apart so far that you can fit a popsicle stick between them.
I’ve heard this as well and I don’t believe it is correct to say that it is “irrelevant” to accuracy. mostly, I just think that the movement between upper and lower only creates innaccuracy that is within the parameters of the system.
True, should have stated this differently. If shooting off a bipod for instance, the upper at the front end IS supported. The back end, at the takedown pin, can still move laterally (mine does) relative to the lower. If there is no movement there while firing, then all is good.
I guess it kind of depends on what you are doing. If you are a “fantasy power” (High Power) shooter, then having the weapon as tight as can be would be important to you.
Start with this:
I am NOT challanging. I am asking to try to help me learn more and wrap my mind around the subject. I like to ask “why?”, I like to not take blind faith, and so I am thinking about the OP’s question and I am trying to rationalize it for myself. I have read and I subscribe to the “some bit of rattle/slop is no big deal” club, but at the same time I feel that one that does not know any better (this would be me!) can still come up with some questions inside his head. So in an effort to get one step smarter…I will ask!
On to my thoughts:
I take it that this is because the gas does not begin entering the gas block until the bullet has passed correct? Also because by the time the gas begins to really interact with the bolt carrier, the projectile has already vacated the barrel?
I again ASSume that the great majority of the recoil energy is stemming from the gas impacting the heavy bolt carrier assembly and forcing it to move whole it is under pressure to not move by the lug engaugement and the resistance of the still somewhat pressurized caseing from being jerked out by the extractor. All of this I feel (I DO NOT KNOW FOR SURE!) would come together into the one large energy spike when the gas overtakes all of the opposition to movement and very aggressively causes the bolt action to perform its function.
So the initial propulsion of the projectile is insignificant due to the low mass of the projectile being manipulated by the expansion forces? Again, an ASSumption on my part is that this projectile being propelled is in reality NOT the source of recoil, or at least not nearly as much as the forces acting within the upper?
Dumb question, if you locked the BCG in place and sealed the gas block from the barrel and fired, what would the recoil feel like if you isolated the motion to just that of the bullet?
Please don’t kill me. I am just asking a question!
One feels recoil in a bolt action rifle, with no moving bolt. Forces felt are from an equal and opposite reaction to the pressure within barrel. Pushing bullet forward and driving the rifle back. - Phil
Sorry, not a hunter! I have not shot a bolt action rifle in 20-22 years. I have a 32 Winchester that I went deer hunting with when I was about 14 or 15 years old. It’s been in the closet ever since! Was my pap’s rifle.
So, diregaurding the question about the bolt being locked, am I pretty well thinking correct about why it is suggested that a loose AR is of no large concerne?
Odd thing to me is why so many guys have this large gap, I have 5 assembled AR’s. 3 of them are complete purchased AR’s, 2 are AR’s that I did as I found parts. Not one of them has any noticeable slop unless you stand there trying to wriggle the things and pay particular attention to the very slight amount of play.
