Do you know of a resource that explains how to set up this scope properly?

No, unfortunately, I don't.  Belding & Mull were very good about documentation, however.  Therefore, you can hope to find a copy of the user's guide that came with the scope.  Ebay, for example, has several dealers in gun-related ephemera and paperwork that might be able to help.  Another possibility is the Belding and Mull Handbook.  That relatively common booklet was updated regularly and more or less covers all of B&M's products at the time.  My guess is that the scope was made between 1935 and 1950, or maybe a little later.  But before you buy one, it would be wise to ask if that particular copy has the information you need.

Lastly, if when you tested the rifle it seemed at least reasonable accurate, unless you wish to shoot at other considerable different distances, I'd say leave the scope as is.  The close-ups of the gun's breech indicates to me that the 'smith who built that outfit knew what he was doing and how to do it well.  Therefore, I'd wager you can safely assume that he mounted the scope properly too.

In short, just always shoot reasonable loads and enjoy your rifle.  And when you decide to sell it, give me, MrTipUp, first shot (bad pun intended).

Bill Lawrence

I'd neck-size using the full-length sizing die.  In setting the dies in the press, simply set them so there is about 1/8" (3mm) of space between the sizing die and the shellholder when the press is at full stroke.  To verify, darken the neck and shoulder area of case with a Magic Marker, and run it through the press. Part of the neck the ink will be rubbed-off where the case made contact with the die.  There will be a clear ring above the shoulder where no contact was made.  This is good.  The unsized portion will hold the case centered in the chamber, improving accuracy.  The sized portion will grip your bullet.  This assumes you will be shooting jacketed bullets. Cast bullets need one more step, which is to open the neck back up a wee bit so the bullet doesn't get distorted by the force needed to seat it. You are probably already doing this for your 45-70.  Tiny .22 bullets are much more sensitive about this.  

uscra112 wrote on Nov 8^th, 2020 at 11:39am:


Thanks, really appreciate the specificity of your description.

Roger

Welcome to the world of precision reloading.  A worthy obsession that will gratify the mind and deflate the bank account.  How are you fixed for reading material? Lots of good books and web sites to occupy your every waking hour.  Especially if you fall down the casting rabbit-hole.  If you don't have the Lyman handbook, get it now.  Also Lee, Hornady, and McPherson. First and foremost, study up on tools and techniques.  The "recipe list" handbooks can come later.   

Considering the thoughtful way he modified the firing pin set up, I also wondered if the barrel was now a "screw job".  Not that the owner shouldn't still shoot only light Hornet loads.

Bill Lawrence

Over the last week pulled bullets on about 40 .22 Hornet cartridges - dumped out the powder and replaced with 2g of Trail Boss re-inserted the bullets with a very light crimp.

I also got out the screwdrivers and set the front and rear mounts for the scope as low as they would go and used my digital micrometer to center the scope in the front and rear rings.

Last night I took it to my local indoor range.

Of the (40) rounds I had, 5 got stuck in the barrel. Those that fired initially were about 3" high and 3" left at 7m and 5" high and 5" left at 9m. I took (2) full turns of the elevation screw for the front mount which put me right on line with the bullseye but still 3" to the left at 7m. At this point I opted to call it a night.

Conclusion I should probably stick with 3g or higher for the Trail Boss, although I have to admit the problem could have been with the primers as the bullets I dismantled were a donation and of indeterminate age. Right now I am waiting on a couple of press parts and and some cast lead bullets so I can build some from scratch using the fire-formed brass I now have. Looking forward to getting back out there with this rifle.

B & M scopes discussed in detail ... (You need to Login or Register to view media files and links)