Benjamin 310 BB gun: Part 2
by Tom Gaylord
Writing as B.B. Pelletier
A Benjamin 310 multi-pump BB gun from 1952.
This report covers:
- Smoothbore single shot
- Size and weight
- How many pumps?
- Adjust bolt for best air seal
- Walnut stock and pump handle
Today we continue our look at the Benjamin 310 BB gun.
Smoothbore single shot
I make no attempt at hiding the fact that I like single shot rifles and guns. Usually their actions are simple enough that there is flexibility to do things you can’t with a repeater. For example, I had a problem with lead balls jamming in the Benjamin 700, and there is no easy way to clear the jam. The 700 action is all buttoned up. But the 310 is a simple bolt action that will allow me to test varying sizes of lead balls. If one gets stuck all I have to do is rod it out and keep on going.
The end cap of the box says this is a BB caliber gun — none of this .177 garbage that isn’t true!
The trigger has a direct sear that holds the striker when the gun is cocked. This type of trigger was common on this range of youth-oriented airgun, but Benjamin did something extra. The blades on most direct-sear triggers wobble from side to side when wiggled. That’s why you read that so many owners have shimmed their triggers. They want to stop the wobble. Well, the 310 trigger has no wobble.
The trigger is direct sear with no adjustments. Notice the wire spring legs go between the sear and the trigger anchor. They take the place of shims.
The picture shows how they did it. The legs of the wire trigger return spring fit between the sear and the trigger anchor, shimming the dead space very well. That’s engineering in action!
The sights are pretty basic. A notch in the rear slides side to side in a dovetail for what little windage adjustment there is and the front post stands straight with no possibility of adjustment. The barrel is soldered to the pump tube, so you don’t want to put any side pressure on it. Once broken, that solder is very difficult to repair, though I have heard that Tim McMurray of Mac-1 Airguns has done it.
That said, the sights offer a clear sight picture that’s sharp. The rear notch is a V and the front blade seems rounded on top as you look at it.
Size and weight
The 310 is 34-3/4-inches long with a 19-1/4-inch barrel. The length of pull is 13-1/4-inches. The gun weighs 4 lbs. 4.5 oz. That makes it a small shoulder gun. It’s longer than a carbine, but very handy for woods walking or barn sniping. I said earlier that it was made for youth, but I know for a fact that more adults used them than kids. That was particularly true of the front-pumpers that are too hard for kids to operate, but it carried over to these underlever pumpers, as well. Maybe it was due to the higher prices (than typical BB guns of the time), or perhaps it was the perception that these were more powerful and therefore should be taken more seriously.
How many pumps?
Here is question number one for any multi-pump. How many pumps are maximum? We saw that the Benjamin 700 repeater said it could take up to 12 pumps, but 10 was where I had to stop. The 700 is a repeater that gets several (3 or 4) shots on a fill, or you can pump it 5 times initially, and then twice after each shot to maintain velocity.
The 700 is a front-pumper and front-pumpers have a longer pump stroke, so they don’t have to be pumped as many times to get the same results. At the same time the 310 was being made Benjamin modernized the 700 into the 710 BB gun that was also an underlever pumper. They recommend pumping that gun up to 20 times, where the 700 stopped at 12. So the underlever pumpers need roughly twice as many pump strokes to get the same power as the front-pumpers. But their pumping geometry makes them much easier to pump!
The manual for the 310 says to pump it 7 or 8 times, maximum. That holds for the 317 and 312 rifles, as well. Four strokes should be enough for indoor target shooting, but we’ll see in the velocity test. This is one airgun I will definitely not over-pump.
I don’t have the original manual for the airgun, but I do have a book — The St. Louis and Benjamin Air Rifle Co.’s — written by Dean Fletcher, that includes many of the early sales brochures and manuals of these early airguns. That’s where I’m getting my information.
The other day I had a call from someone with questions about early gallery airguns. He told me there was some information about them in Larry Behling’s book on BB Machine Guns, but he didn’t buy one when they were available because, to quote him, “I didn’t have a need for one at the time.” Guys — buy the books when they are available. If you are an airgunner you never know when you will need them!
Adjust bolt for best air seal
Here is something novel. The 310 bolt doesn’t have any o-rings. It seals on an angled bolt shoulder that butts up against a chamfered breech. Benjamin provided a means of tightening this joint though a cammed plate on the left side of the receiver. Loosen two screws and tap the cam plate forward with the bolt held in the right position, and when you close it the cam will be tight. All this on a $15 airgun!
The bolt face is angled (arrow) to interface with the breech in an airtight seal.
Loosen the two screws and tap the cam plate forward (left) to tighten the bolt interface.
Walnut stock and pump handle
All Benjamin airguns had stocks made from American walnut. They bought the wood in Stover, MO. American walnut is one of the fastest growing hardwoods, so it is practically a sustainable resource. It is usually very plain and straight-grained, but that gives it strength that a fast-growing wood often lacks.
Combining the walnut furniture with the shiny black nickel gave the Benjamins of this era a firearms’ look other airguns didn’t equal. Sheridan came the closest, but they used paint instead of plating on their blued rifles.
The problem is that black finish is extremely fragile. I just wipe it with a clean cloth because I don’t want any of the black to come off. I told you my gun has 80 percent of the original finish, but it’s closer to 90. I always like to rate them conservatively because nobody wants to be disappointed when they see the gun in person.
That’s the end of the description. Next time I will do the velocity test — though I have so much to test that it may take more than one report, as well.