Inletting a homemade air rifle stock

Homemade air rifle stocks are challenging to inlet since the stock screws often aren't parallel to each other and are located both on the sides and bottom of the stock. I couldn't find much help on this topic on the internet, so I hope that these tips for inletting a DIY air rifle stock are helpful and interesting.

Here's what I did for my Walther LGU. I first milled a 1.370" diameter channel using a 1.25" half-round bit. By making multiple cuts that are offset from each other, the undersized bit can produce a fairly smooth and round 1.370" diameter channel. I then transferred the stock holes from the original stock into a 1.375" hardwood dowel that was securely taped into the receiver channel of the original factory stock. The dowel is almost the perfect size, with a diameter of 1.350"-1.360" (not perfectly round), so I wrapped it with some packing tape to get the dowel to fit tightly into the original stock. I turned the stock upside down and drilled the two rear screw holes through the stock's original holes and then through the dowel using a drill press, which helped keep the holes vertical. This doesn't work for the forearm holes since the stock holes are not very deep (yellow arrow in Fig. 1e) and although they can be used to locate the position of the front holes they aren't long enough to guide the drill bit at the correct angle into the dowel. So I machined a brass drill guide (Fig. 1b, below) that fits tightly in the forearm screw counterbore and that seats against the bottom of the screw hole (where the star washer would be). The brass bushing really helped make accurate holes in the dowel, and if there's one thing that may be new/interesting about this post, this is probably it! I then used a hand drill to make the forearm holes in the dowel (see Fig. 1a). The position and angle of the forearm holes result in exit holes in the dowel that are very close to the top edges of the stock, so I ended up nicking the top left edge of the original stock (red arrow in Fig. 1e shows the area that I later repaired). Be careful here! I then removed the hardwood dowel from the original stock and taped it into the receiver channel of my new stock. I used a hand drill to transfer these holes into the new stock (Fig. 1c). Figure 1d shows the inletting transfer dowel and the new stock after the inletting holes have been drilled. The alignment and positioning of the new holes was excellent. The hardest part was cutting the counterbore on the forearm screw holes. For this, I shimmed and secured the new stock to my drill press table so that the original drill bit was well aligned with the stock hole, and then replaced the bit with a larger Forstner bit to cut the counterbore for the screw head. It was challenging to make sure the stock doesn't move in his process. A reverse counterbore bit would have made this much easier. Although this post is a lot longer than I hoped, I actually left a lot of details out, so if you have any questions or need more info, please let me know.

Here's the final result:

Now I'm thinking if it would be worth gluing aluminum pillars into these screw holes. If you have any advice/experience with pillar bedding a springer please let me know.

Thanks,

John