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Today we have the guest blog from reader Hank, who goes by the handle Vana2. He shows us the building of that gorgeous curly maple stock for my new Benjamin 397. I hadn’t planned on publishing this so soon, but the stock is so beautiful that I just couldn’t resist.

If you’d like to write a guest post for this blog, please email me at [email protected].

Take it away, Hank.

Benjamin 397 – A Tale of Two Stocks

This report covers:

  • The curly maple stock
  • Varnish drying jig
  • The laminated birch stock
  • Summary

397 maple finished
The Benjamin 392 in curly maple.


392 birch finished
The Benjamin 392 in laminated birch.

A Slavia 618 break-barrel was the airgun I learned to shoot with but it was my Crosman 101 that really got me into shooting and hunting. Being a .22 caliber “pumper,” it has some serious power — plenty for small game hunting! 

Since I like multi-pump pneumatics, it’s not surprising that I took a special interest in this Benjamin 397 series. But I never anticipated how interesting it would become. 

It started innocently enough — we were discussing the issue with the synthetic stock comb being too high for iron sights and RidgeRunner suggested that he might be interested in a wood stock for the Benjamin. Teasing, I suggested that if he would buy me a Benjamin 392 I would make us both a wood stock. Well, RidgeRunner knew I was pulling his leg and declined — what I didn’t expect was an email from B.B. saying that he would like to take me up on that offer. Long story short, two weeks later a Benjamin 392 (.22 caliber) was delivered and I got down to making some stocks.

Initially, I was going to make a pair of firewood-style stocks but in looking things over it was not a practical approach. With the way the trigger-block and the pump-arm are designed I felt that the stresses would be higher than the thin sections of cross-grain wood would be able to handle. So the options were for a standard construction stock or a laminated stock.

In checking my materials I found a curly maple blank and some odds and sods pieces of birch plywood in the wood bin – which worked out perfectly, since I needed to make two stocks.

392 close up
Here are some close-ups of the stocks to show a bit more detail.

Both the curly maple and the laminated birch stocks are very difficult to show off in a still photograph, you really need a video to appreciate how the highlights move in the wood as they follow the light.

The Curly Maple Stock

392 maple construction/product/benjamin-variable-pump-air-rifle-black?m=4869&swcfpc=1
The top image shows the maple blank with the cardboard template and the Benjamin 392 with the factory synthetic stock. The bottom images show details of the inletting for the receiver. 

The curly maple stock was made in the traditional way — start with a hunk of wood and carve away all the wood that doesn’t look like a stock. This “subtractive” approach is sometimes referred to as “hogging it out of a solid”.

The stock construction is straightforward. Do a layout on cardboard to review all the important features and cut it out to use as a template; transfer the outline to the material and cut out the stock profile; inlet the stock for the pump-tube and trigger-block; shape the stock to its final dimensions then sand and finish to suit. The images above show the first couple of steps in the construction, the ones below show the rough stock fitted to the action and the shaped stock ready for final sanding and finishing.

392 maple unfinished
Here is the action mounted in the rough stock (top) ready for shaping and the finished stock (bottom) ready for final sanding.

392 varnish drying jig
Varnish drying jig.

Varnish drying jig

This is one of those kind of projects that always gets put off and when you finally get around to making one you wish that you had done so years ago. I thought that I would show-off my fancy drying jig. The best way to avoid runs and drips is to (constantly) rotate the stock while the finish sets up. I made my jig from some scraps of wood, a piece of threaded rod that turns in bearings, some hardware and a BBQ rotisserie motor. It took about an hour to put together.

To continue with the finishing, the sanded stock was “stained” with Aqua-Fortis [ED: nitric acid] and coated with high gloss polyurethane. Aqua-Fortis is a reagent that works particularly well with curly maple — it interacts with the sugars in the wood and really makes the grain “pop”! Basically, the Aqua-Fortis is applied to the wood, allowed to soak in and then “blushed” with the application of heat. When the desired finish is achieved, the Aqua-Fortis is neutralized and the stock washed before it is left to dry thoroughly.

The next thing is to apply a protective finish. Before applying the polyurethane the stock is sanded lightly to remove and raised “whiskers” of wood grain then cleaned with alcohol or naphtha. Several coats of thinned polyurethane are applied followed by several “build coats” of regular viscosity polyurethane with sanding and cleaning done between each coat. The instructions say that you can re-coat after several hours but I prefer let the polyurethane dry for (at least) 24 hours between coats to avoid trapping solvents between the layers.

Note: I stippled the pump-arm and hand grip just before applying the final coat of polyurethane. That way the stippling would be sealed but not filled.

I typically use gloss polyurethane and buff the surface with pumice (AKA rotten stone) to a satin sheen but on this stock for the Benjamin 397 I left it at full gloss to show off the grain. The glow in the curly maple shifts and shimmers all over as the light plays over the surface, didn’t want to lose any of that. I figure it is a plinking rifle so shiny is okay.

The laminated birch stock

392 birch construction
These images show the roughed out birch plywood stock (top) and the pieces (bottom) prepared for making up the blank.

The birch stock blank was assembled by gluing various thickness of plywood together to create the bulk to carve the stock from. Using an additive process to build a stock allows you to add wood only where it is needed saving a lot of rasping later on. The cavity for the trigger-block was created by adjusting the core layer to leave a space in that area. If you look closely, you can see the pinning holes used to align the sides and the core for gluing.

Once the glue is set the rest of the stock construction follows the usual pattern. Transfer the outline to the material and cut out the stock profile. Inlet the stock for the pump-tube. Shape the stock to its final dimensions then sand and finish to suit.

Birch plywood is readily available and makes a nice stock but there are a couple of things to be aware of.

You should test a scrap sample before trying to stain a plywood stock. The laminations in a sheet of plywood alternate, running horizontally and vertically through the material. These changes in grain direction affects stain absorption resulting in very high contrasting stripes in the stock which may or may not be to your liking. I tried several stains and didn’t like the results.

The inner layers of the plywood frequently have “flaws” like knots and such that may be exposed during shaping. I don’t mind these “surprises” as they add a little character to the wood.

Also, because of the thin laminations and the (relative) softness of the wood the surface of the birch plywood does not take checkering or stippling the way a solid wood stock will. It just kind of splinters and falls apart.

All that considered; the birch plywood sands very smooth and shows deep highlights that dance and shimmer under the polyurethane. I don’t usually care for light colored, glossy stocks but I’m quite pleased how this one turned out.

Summary

It seems that the Benjamin 300-series multi-pump rifles have been around since the 1940’s. My friend bought a Model 347 in the late 60’s. The current (version 3) .177 Model 397 and the .22 caliber Model 392 have been available since 1997. Goes to show that they are a good thing!

I am glad to have a Benjamin 392. Iron sights and hand pumping are way different than scopes and PCPs. I’m enjoying the change of pace, smacking tin cans and getting some exercise at the same time… been away from that for too long.

Thanks Tom, hope you enjoy your new stock!

Hank

[Editor’s note: I put this guest blog in today because Hank sent it to me and I was still jazzed about the curly maple stock he made. I’m not trying to ram a Benjamin multi-pump down your throats, but I do want you to see what one does when the stock is shaped more normally.]