Saturday, February 20, 2010

Fitting the old Morgan Butt Pad to the QB77

Still working on the QB77.

The butt plate is serial numbered to the gun. It's not well-fitted to the stock.

Off you go.

Remember this guy? All that work and it didn't fit anything at the time.

Clearly, this was reason enough to buy the QB.

Note the gap at the top of the stock.

Seems that the original plate didn't fit so well due to the stock not being flat. The wood is rounded over all around the end as well. I was going to re-cut the end with a chop saw, but it's too much trouble to set up for a single cut.

A couple seconds on the sander...

then to the granite plate.

In just a couple minutes the end of the buttstock was truly flat.
A quick eyeball showed that the upper mounting hole on the Morgan plate was good to go, but the lower hole in the stock wasn't in the right spot. Needed to drill a new hole in the stock, but the old hole was uncomfortably close. Elected to fill the stock hole with a small wooden dowel. Didn't have one that fit, so I trimmed one to size on the Taig lathe.

Used a toothpick to get the Gorilla Glue to the bottom of the hole.

Tapped the dowel into place and set it aside for the night to dry.

The next morning, I trimmed the dowel flush with a razor knife.

Mounted the plate to the buttstock with the upper screw and used a transfer punch to spot the new hole location.

Drilled with a 1/8" bit.

And mounted the second wood screw.

Removed the plate and coated the stock side with layout fluid, then found my grandfather's scratch awl.

Scribed around the stock...

leaving a fine line.

Ground the plate to the line on the grinder. Dressed the grinder wheel to keep the aluminum from building up. An old grinding wheel works great as a dressing tool.

It's about 99% fitted. Just needs some edge finishing to remove the scratches.

Aluminum blocks in the vise to protect the aluminum plate. I used a steel block wrapped in successively finer emery cloth to sand out the scratches. The rigid steel sanding block kept the edges sharp.

After taking the sides to 400 grit, I polished it with triple-aught (000) steel wool.

Gave it a quick buff.

Sanded the gun side of the plate one last time to ensure it was flat and leave a clean edge.

Then a final polish with Mother's Mag.

Installed. Not shown: Coated the end grain of the stock with two coats of walnut colored Watco Danish Oil. It's an almost exact match to the stock. This helps seal the stock as well as help camouflage any extremely small gaps between the stock and the plate.

Something I didn't mention--The angles of the stock must carry through whenever fitting a plate or rubber buttpad . I did most of that by angling the platen on the grinder then with a file by hand after it was close.

The fit is pretty good. No gaps at the wood and the lines flow well. I know it's an inexpensive gun, but it doesn't have to look like one.

Pad installed

Gun fits me much better now. Shoulder it and the rear sight comes right to my eye. I suppose I'll have to refinish the stock now. Well, maybe not right now as it's still 24 degrees outside. But soon. Maybe I'll do a full tear down and smooth things out inside next.

Friday, February 19, 2010

Front Sight Adapter for the QB77

After getting the trigger shoe fit to the QB77, I turned my attention to the sights.

The QB77 is extremely accurate but is hampered by the open sights. I've already got a similar rifle with a scope--a Crosman 2260--so the aperture sights provide some variety. I found this vintage Crosman 411 sight in the basement and thought it needed some gun time.

The rear sight mounted right up. The Crosman 411 front sight was a no-go from the start and didn't look like it would be easy to retrofit.

I had a spare Weihrauch front sight but it requires a dovetail on the barrel to fit. An adapter is needed. Looking at the rear sight again, I found that in the middle of the elevation adjustment, the sight was about 0.710" from the top of the breech. To get the front sight to work, it's center should be close to that number.

Found a scrap of rectangular aluminum in the pile for the adapter. The piece was 0.382" x 0.510" and about 1.55" long.

The widest point of the HW front sight dovetail is about 9 mm wide and has 60 degree angles.

Mounted the block in the Taig milling attachment on the lathe. Milled the ends off square.

A dab of dykem and found the center. Worked off the center line and scratched some lines on the top that reflected the 9mm width of the dovetail.

A small 60 degree dovetail cutter and lots of Tap Magic aluminum cutting fluid. Cut just shy of the lines, then test fit the sight. Another couple thousandths and it was on the money.

Flipped the adapter over and used a ball mill to cut away excess material. If I had the correct size ball mill (14 mm), I'd be done--but that'd be too easy.

Went through the transfer punches and found a punch just smaller than the barrel diameter. Wrapped it in emery cloth and hand-sanded the contour to size.

Like so.

Another view.

Just need to drill a hole to attach the adapter to the front sight screw hole. Drilling 1.104" from the muzzle. Used the Taig as a horizontal drill press. Drilled with a #32 bit to clear the M3 x 0.5mm sight screw.

Then counter bored the hole for the head of the fastener.

Done except for some clean-up sanding and some color.

Dykem comes off easiest with their remover. Not shown: Took all the sides of the adapter to 320 grit on a granite plate. Used Birchwood Casey Aluminum Black to color.

Installed. Left the M3 screw silver. It won't show after the globe sight is installed.

More views.

Weihrauch sight installed with one of several inserts.

Sights installed. No permanent alterations. The original sights can be reinstalled in about 2 minutes should that ever be required. The QB now shoots like a laser beam.