Re: M40a1 build guide
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rainier42</div><div class="ubbcode-body">10x ... it's not that I can do the above, it's just 1 less thing that I was hoping I would need a gunsmith for.</div></div>
Okeedoke. If you have a new stock from McMillan inletted for the M70 bottom metal, here's how I remember doing mine....
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Install the trigger guard (either cut or uncut) and measure from the center of the front action bolt hole in the stock to the front of the shoulder on the trigger guard where the end of the floor plate should end up. Then measure from the center of the hole in the floor plate hinge to the centerline of the floor plate and scribe a small line , where it will be cut to length. Then scribe a line across the floor plate at that line for your cut line. Make sure you have the cut line straight across, i.e. do not use a square to make the line, as the sides of the floor plate are not parallel.
Clamp the floor plate and either band saw or hack saw across the floor plate to make your cut, leaving the scribe line showing. Then, use a fine flat file to dress the cut straight across.
Install the floor plate and check for fit. It should need a bit more shortening to bring it to length. Use the file to remove a little metal at a time and adjust the angle of the cut until there is a small and even amount of clearance between the trigger guard shoulder and the end of the floor plate.
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Remove the floor plate release pin, spring and plunger from the trigger guard. Install the trigger guard in the stock with the action in place with its magazine. Scribe a cut line on the front of the trigger guard flat at a point where the rear of the magazine sits, leaving enough clearance between the two so they will not touch when completed, but leaving as much of the flange as possible for enough space to drill and countersink for your front trigger guard screw. Cut or mill the front of the trigger guard flange off at the line, and dress as needed.
Drill and countersink for your front trigger guard screw.
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Tape your receiver and bottom metal in place in the stock, leaving the action bolt hole areas free. Make sure the trigger guard is all the way to the rear, and the floor plate all the way to the front. Get a 1/4"-28 bolt about 5" long, and cut the head off. This will be your indexing bolt to index the parts at the proper angles for milling the bolt holes in the trigger guard and floor plate so the shoulders of the bolts mate properly in the countersinks.
Screw the bolt into either action bolt hole, and leave the bolt's headless shaft end sticking out through the trigger guard or floor plate hinge, whichever you are working on at the moment (The bolt <span style="font-style: italic">should</span> center in the holes if the inletting is good to go). Carefully lift the rifle and chuck the shaft in a drill press, lower the chuck and clamp the stock enough to hold it securely in place at whatever angle it ends up being. Make sure, though, that the shaft is not being flexed in any way, or the cut will not end up square to the axis of the bolt.
Loosen the chuck and raise it from the indexing bolt shaft. Remove the bolt from the receiver and chuck up a 3/8" end mill. Turn the end mill at slow speed into the bolt hole to remove the tapered countersink and cut a square shoulder to match the square bottom of the bolt head. Only cut enough as needed to provide sufficient surface for the action bolt to torque against, leaving sufficient metal for strength.
I cannot honestly remember if I hand turned the chuck, or ran the end mill under power, but slow speed and careful is key here. It helps to have the trigger guard cut and the front screw in place to help hold it during milling, so have that step done before doing this. Everything needs to be taped really well and solid so it doesn't shift during the process.
Repeat the process for the other action bolt.
The same can be done carefully with a mill under power, but I didn't have access to one at the time.
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You will need to mill or carefully file the trigger opening in the trigger guard to provide clearance for the Remington trigger and bolt release.
Measure twice and cut once. Check and recheck everything along the way. Go slow and be carefull. But, I'm sure that all goes without saying.
Do at your own risk, or send it out to have done. Good luck.