I have done quite a bit of testing with aluminum tape and aluminum sheet metal shimming the mags, magwell, and other parts and came to several conclusions. In short, all Ruger Precision rimfire polymer chassis have defective mag wells that are too long, specifically, they have too much clearance at the front of the magwell. I also think this is 90% of the problem with all Ruger Precision Rimfire accuracy and reliability issues and that Ruger must be aware of yhe issue but does not want to fix it. I will exlain in detail below.
I found that due to the way the rounds exit the 10-22 magazine, they are off center to the left and low and point up and right as they leave the mag. This requires very specific positioning fore/aft of the magazine relative to the chamber so the bullets hit the center of the chamber. Too close and the bullet tips get shaved going in at the lip of the chamber and rear face of the barrel or jam before they can enter the chamber. A little further back and the ogive gets scraped. A bit further back (fully to the rear of the magwell where function is still 100%) everything runs smooth. If it were even further to the rear, the bullet would hit wide and high and also cause problems. Ruger knows this because they have built a bazillion Ruger 10-22s that use the magzine design. For the Ruger Precision Rimfire, fully rearward where mag release function is still 100% is where the mags are intended to be placed and the factory rear of the magwell seems positioned correctly relative to the rear block, which makes sense since that block bolts to the reciever and hold the magazine release parts and the parts are made of metal which can be easilly machined to move things to correct positional issues during prototyping before manufacture.
I also found that the way the magazine locks up, it requires a very specific fore/aft mag well size. The front of the mag needs to fit in a plastic rounded notch at the front of the magwell which is part of the chasis and there needs to be adequate clearance for the rear mag release where the pin locks in to press the mag from the rear and get the front mag button to engage the front of the magwell. If the magwell is to small fore/aft the mag either wont lock in because the front button on the mag wont clear the front notch or it wont drop free easily and disengage the rear pin of the magazine. A ploymer part requires a mold change to fix tolerance issues and polymer parts are made in large batches to keep prices down. Once you make a batch of polymer chasis, you dont want to throw them away but you also have no machining to do that you can adjust to fix tolerances.
The magazines require a small enough magwell to hold the magazine body and not allow the mags to rock fore/aft, but a very tiny amount of rocking is required to get the magazines to lock in and drop free due to mag design. With too much fore/aft magwell size, the front metal button on the magazine can slip off the polymer ledge in the magwell and get stuck. Pointing the feedlups down. This causes either the bullets to jam in below the chamber which will stop your bolt travel cold, or scrapes the hell out of the bullet tips if it does manage to clear. Unfortunately, any rearward tug on the BX15 mags causes the mags to point down and the front button to slip off the ledge. It then can get stuck pointed down. On some mags and magwells, you may notice the mag freely rocks fore/aft but wont stick in either position. With other mags and magwells, you can make the magazine stick rocked forward or stick rocked rearward. In the BX15 this is obvious as you can grab the mag and rock it easily. Its a bit tougher to do with a BX1. The natural mag insertion technique of a BX15 will have you tend to insert and sort of rock back at the bottom like an AK mag. You must then be sure the mag is pushed forward at the bottom and feed lips point up to get correct positioning. The BX1 insertion tends to make you push up at the middle or front of the mag and puts the mag in the correct orientation. You can still reach up in there and pull the nose down by pulling back and down on the front edge of the magazine but it requires a deliberate attempt to do it.
The BX15 mags are also shorter than the BX1 mags. Both the length of protrusion of the metal rear pin and front button of mag as well as the thickness of the magazine polymer body are less for the BX15 than the BX1. The BX1 uses a screw to position the front button. I found it works best when the flange behind the button is flush with the mag body. This requires placing a very thin washer shim for that bolt to rest against to get the front button to protrude more. This shim requires an ID of .340" or more and OD of .435" or less thickness in the 30 to 60 thou range to get that flange flush on a current production BX1 mag. This helps keep the front button engaged on the lip of the rounded notch at the front of the magwell. Unfortunately, BX15 mags have the feed lips, front button, and rear pin as one solid metal unit that cannot be adjusted. It is also the mag that comes with the gun so the magwell should be most reliable with a BX15, but of course it is not.
My first experiment was to shim the rear of the magwell to push the mags forward so they would not rock and would catch the front notch of the magwell, since you cant add material to the front of the whole mag body without covering the front button, you cant build up the front of the magwell notch, and you cant extend the front button to catch the lip on the BX15. Pushing the mag forward resulted in 100% lock up, propper feed lip orientation and no mag rocking, and inserting mags was easy and they dropped free when relesased. Unfortunately, the magazine was too close to the chamber. It jammed and either would not function at all or mangled the bullets horribly as they were chambered.
Next, I shimmed the front of the magwell to push the magazine to the rear. This exacerbated the front magazine button falling off the ledge at the front of the magwell, but the positioning was ideal for feeding if the magzine was held to keep the feed lips pointed up. No damage what so ever. Feeding was ultra smooth.
I also did various combinations of shimming mags at the front or back to take up space. I have come across one shimming technique on the BX15 that works OK to put the magazine in a position that stops rocking, causes minimal bullet damage, holds at the front lip of the magwell, and allows easy insertion and drop free of the magazine. It involves building up a bar of material above and flush with the front button at the front of the magazine and another bar down from the rear horizontal speed bump ledge that protrudes at the rear of the BX15. I will test it more and try making a JB weld version if the aluminum tape version pans out. I still get some bullet damage but it is minimal. If I move the mag more rearward, it slips off the magwell button ledge.
All of these issues would go away if the front wall of the magazine well was just moved about 1mm or so further to the rear. I think this is the biggest reason that people get flyers, have reliability issues, etc. Its not that the chassis has flex... it is that EVERY SINGLE RPR rimfire has a magwell that is out of spec with the front wall positioned too far forward! I also think Ruger is well aware of this.
If you pull off your reciever and look at the magwell from the top, you will see the front wall intersects a circular hole that appears to not be for anything other than a witness mark to see where the magwell is located relative to that hole. The front magwall intersects toward its front edge. The front mag wall should be pushed back to where it is flush with the middle of that round hole or possibly even slightly further.
I think Ruger should do a nationwide recall and give propper spec chassis to every RPR rimfire owner. Just a bare chasis where we can swap the buttstock, action, grip, etc. Should be sent to everyone who provides a serial number. I think it is bullshit Ruger has foisted an obviously out of spec part on the American public and expects us to send in the whole rifle and hope for the best, while the 100% biggest problem with all the rifles is CLEARLY a defective polymer part spec that they dont want to spend the money to fix because it requires a complete replacement of the chasis.
Will edit and continue later....