ACCURIZING THE
STOCK BEDDING RESULTS
Images
courtesy of Bernd Kaercher
Bernd emailed me some time ago with a
specific problem with his No4 Mk2. It appeared that his rifle was grouping
nicely for the first several rounds and then it began drifting high. Bernd
believed the problem must be stock bedding. So together, over a couple of
emails we decided that it was most likely an issue of the original wood heating
during firing. This was causing the wood to expand and push on the barrel, thus
changing its shooting characteristics.
Bernd decided to try not only the action bedding method that I described on the
Stock Bedding Page but also use the center bedding instructions as well. Below
are the results of these bedding methods, described by Bernd himself.
As the pictures show, our theory was correct, that the cause of his original
problem was the wood expanding and effecting overall accuracy.
I'm quite glad to report that my
Let me tell you what I did:
The results are shown in the enclosed pictures. All testing was done with a
Leupold BR36 scope fixed by a SK-Mount. All cartridges were composed of Norma
cases with CCI BR2 primers. Group 1 was loaded with 17grs Viht N110; the rest
was loaded with 15grs Viht N350. All bullets were moly coated Sierra 180gr
Pro-Hunters. Seating depth is so that the bullet is just touching the lands.
Group1 (10 Shots)
Shows the starting point with 17grs Viht
N110. The action was Epoxy bedded like you explain it on your Stock Bedding
Page.
Group2 (10 Shots)
Shows the results after adding the center
bearing with 10-lbs. upward pressure at 5 inches from the action.
Group 3 (10 shots)
Group 4 (10 shots)
Shows the results after I had removed as
much wood as possible between the center bearing and the action screw. This was
replaced by Brownell's Acra Glas (red). So I tried to make the forestock
stronger and more temperature insensitive. As you can see, the rifle was now
very accurate but "double grouping" - no longer drifting! Group 3
were first 2 groups like Group 4. The last shots just landed between the
groups.
Group 5 (20 shots)
Shows the final results. I opened up the
center bearing slightly with fine sandpaper, so that the barrel is just able to
move better in the bearing.
I hope that the size of the groups is easy to estimate by the size of the
bullet holes.