Well, I think I am onto something.

My old Winchester 1892 .32-20 was keyholing with bullets with .312" which is what the barrel slugs out at, and (115 grain Lyman bullets). So while I wait for .313" bullets to get here, I decided to try paper patching the .312" bullets. I used rice paper which is almost water soluble as delicate as it is. If it's wet and not in place when you want to wrap it, it will tear it is so delicate. I got the bullets with the rice paper sized out to .315" and I used Lee Liquid Alox bullet lube over the paper when it dried.
I took the gun out this morning with a light charge of 2400 and I actually got the gun to shoot accurately. I didn't mess with sighting it in as I wanted to see if the gun would group.

There's no keyholing anymore and while it's not match grade accuracy, it's a definite improvement.

Here's the .312" bullets at 25 yards, notice the start of the keyholing and what is a 4 or 5 inch group.



Here's with the paper patch bullets at 25 yards.

__________________
Vaya con Dios

Nicely done! While common only with "rifle looneys" now days, there was a time when many reloaders/shooters paper patched to get to top accuracy out of their rifles. We complain about "Quality Control" on modern guns. But do a bore slug on most anything made before 1900 or so and what the book says it should be and what it is, sometimes isn't even close.

When you slug any barrel, the finished slug is the diameter of the tightest spot in the entire length of the barrel. The muzzle are often larger from cleaning rods wearing on it and hot smokeless powders used to be erosive/corrosive for a few inches in front of the chamber. Certain papers act as a squeezable gasket that help forgive a thousandth or two of over sized bore adaptation! Don't try typing or copy paper! (Very hard and abrasive!) I used to use the lightest grade of artists parchment, In a micrometer you could see it was "springy" on thickness, but was thick by patching standards. I never thought of Rice paper. Very good call Dave!

Ivan

P.S. Now you'll never sell me that 92!

I had a 1943 Remington 03-A3 with worn two groove barrel.

The throat was .312, mid bore was .309 and the muzzle was .311.

And the most accurate jacketed bullets in this rifle were Hornady 170 grain flat point 30-30 bullets. I always assumed the softer lead core in these bullets when kick in the seat of the pants expanded more to fill the bore and grip the rifling.