Will the tightness of the screw holding the stock to the rifle have an effect on accuracy?
Screw torque
- Thread starter Skip-in-WV
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Tends to be more of a factor with spring piston guns than PCPs, but it depends on the nature of how parts interact with each other.
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It depends on the design and construction of the rifle. With most PCP air rifles, I believe the answer is no, it's not critical. With many metallic cartridge rifles, especially sporters, the stock attachment torque is very important. This is largely due to the fact that, with most PCP rifles, the barrel is well removed from any influence of the stock attachment, and there is not enough recoil to influence movement of the action within the stock. Just my opinion, and I'm often wrong.
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I admit I haven't tested it but I do not think so. I recently made wood stocks for all three of my P35s. The POI shifted slightly - like less than 1/8th inch at 30 yards - but it doesn't seem to have affected accuracy at all. If changing the stock material doesn't affect accuracy it's hard for me to see where screw tightness will. I probably can try different torques but I'll have to get a little creative on torquing the rear screw because the stock is in the way. I can probably use my torque wrench screwdriver on the front screw and a regular 1/4 inch drive torque wrench on the rear if I can rig up something short enough to fit into the cutout of the stock. The rear screw goes into a piece attached to the block where the action is and the front goes into the trigger guard which is attached through clamps to the air tube. So neither directly affects the barrel, it is a level above. But still the POI did shift slightly. But it takes very little change in the barrel support to shift POI. Accuracy is a lot more complicated.
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The torque on the action to the stock will definitely effect the accuracy....when I was building rimfire benchrest rifles, in my opinion one of the most important parts of getting the most accuracy from a rifle was having it properly pillar bedded in the stock. It took me a long time to learn how to properly pillar bed a rifle. With an air rifle, unless it's in a conventional stock, there's no way to properly pillar bed one. The way to check a rifle to see if it's been properly bedded is to put it in a cradle and set up an indicator on the barrel near the end of the barrel then loosen the front stock screw, if the indicator moves at all when loosening the screw then that means the barrel has stress on it and has not been properly bedded....Here's a couple pics of a rimfire benchrest rifle I built and pillar bedded it.....
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One can't assume that for all guns this applies or doesn't, really depends on the construction and layout of parts, in most cases a screw somewhere will effect accuracy.
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I tighten the stock screws on my hw/r9 as i shoot . I set a card up at like 10m with a level vertical line and aim point using irons set center and low take a shot the trigger screws affect high/low the forend can pull left / right. I guess its like tuning or zeroing the stock to the receiver.. lol. Anyway no guns the same but works out or not its just a thing i do.
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I understand bedding for powder burners and have bedded my PBs. There are, of course, conflicting camps with some saying a little upward pressure at the end of the stock on the barrel is best. Others want only the action and maybe the first inch of barrel touching to stock. Some believe neutral bedding is best.
But the big thing different for most airguns is the barrel is not close to the stock. On a bullpup, the action separates the barrel from the stock and probably the air supply too. With a more conventional arrangement the air supply still may be between the barrel and the stock. The barrel is often shrouded and sometimes the shroud may touch the stock. But rarely the barrel. Without contact between the barrel and the stock any impact of the screw tension has to be transmitted through the pieces separating the two. Certainly possible but not close to the arrangement of most PBs.
But the big thing different for most airguns is the barrel is not close to the stock. On a bullpup, the action separates the barrel from the stock and probably the air supply too. With a more conventional arrangement the air supply still may be between the barrel and the stock. The barrel is often shrouded and sometimes the shroud may touch the stock. But rarely the barrel. Without contact between the barrel and the stock any impact of the screw tension has to be transmitted through the pieces separating the two. Certainly possible but not close to the arrangement of most PBs.
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Yes and no. If the screw is loose then Obviously that’s no boeno. Assuming the gun has free floating barrel the tightness of the connection between the action to stock has affect on harmonic up to a degree. Key is consistent tightness so try to tighten the screw with torque wrench to the same torque value every time if you really want best accuracy for bench rest or other super high precision shooting. Differences will be small and most in most situations won’t notice it.
This is assuming the action and stock interface is tight and even, if not then bedding of the stock might be necessary.
This is assuming the action and stock interface is tight and even, if not then bedding of the stock might be necessary.
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I decided to do a little test today using my P35-177 and some pellets it sort of likes - not its favorite. I likes H&N Baracuda Match in the 4.52 head size best but shoots these 4.50 head size pretty well and it also shoots Baracuda Power pretty well. The Power have the largest heads according to my gauge. The rifle is in a mahogany stock I made for it. I used a torque screwdriver to apply 10, 12.5, 15, 17.5 and 20 inch pounds. 20 is about as much as I would want to apply with an allen key pushing against the short end, for and idea of these torques. I applied the same torque to both of the action screws. I include pictures of the target and the gun.
I measured the center to center spread of each 5 shot group (at 30 yards) and the center to center for the best four. Biggest variable was my shooting, of course. The five shot spread was typically 1/4 to 1/2 inch and the best four were more consistently about 5/16 inch. Theory for the best four was to throw out my flier. I don't think these results prove anything. There was no magic torque that made the group get obviously smaller. I left the gun at 15 inch lbs. It seems like it might have grouped a little better at that torque and it seems like a reasonable torque to apply to these 5 mm screws.
I measured the center to center spread of each 5 shot group (at 30 yards) and the center to center for the best four. Biggest variable was my shooting, of course. The five shot spread was typically 1/4 to 1/2 inch and the best four were more consistently about 5/16 inch. Theory for the best four was to throw out my flier. I don't think these results prove anything. There was no magic torque that made the group get obviously smaller. I left the gun at 15 inch lbs. It seems like it might have grouped a little better at that torque and it seems like a reasonable torque to apply to these 5 mm screws.
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