On my SMR the ramrod channel was drilled just about into the lock inlet (one of the early kits), when I did the final inletting for the mainspring I broke into the ramrod channel quite a bit. I opened up the hole in the lock inlet and made a scraper I could use from inside he lock inlet to turn the hole more toward the opposite side which corrected the problem. I didn't want to taper the 5/16" ramrod to make it fit because I feared going any smaller would make it too fragile so I chose to enlarge the hole instead.
I sanded the oversized ramrod some but not enough, in a brief senior moment I pushed it a little too hard into the hole opening trying to make it go in the forestock and cracked the wood at the entry pipe, superglue to the rescue.
A little more ramrod sanding at I had a perfect fit.
On my latest build had a bow in the ramrod groove that I didn't notice until after I inletted the pipes, this put the groove and the drilled hole on the forestock at a bad angle and the ramrod wasn't going in.
This time I peened a burr on the square end of a 5/16 ramrod drill and filed to be razer sharp and used this burr as a scraper to take out the bad angle in my ramrod hole. It took a surprisingly small amount of scraping to remove the obstruction for an easy ramrod fit.
I posted these pictures on another poor ramrod fit thread. I think you would need a 1/4" rod to make a scraper for a 5/16" hole in a SMR, seems like a 5/16" rod would get stuck. I am scraping out a 3/8" hole in the pictures.
My scraper;
Shimming the entry hole with leather to to put pressure on the scraper to make it hit the area that needed wood removal.