Benjamin 397C: Part 3
by B.B. Pelletier
Photos and tests by Earl “Mac” McDonald
Before we begin today’s report, I’d like to give you an update on two projects. First, I’ve replaced the trigger in the RWS Diana 34 P rifle, so I’m ready to do the T06 trigger evaluation. It was the easiest trigger replacement/piston removal I’ve ever encountered! I used to think Weihrauchs were easy to work on, but now that Diana has gotten rid of the T01 trigger that had a couple small things you needed to know how to do, replacing a trigger in one of their rifles is about like putting batteries into an airsoft AEG. I did the whole job in 20 minutes, start to finish, which included set-up and clean-up time. A lot of the credit for that goes to the Air Venturi spring kit that was in the gun, because the mainspring is not under a lot of pre-compression. I’m sorry to see that product go, because it made a world of difference in the performance of the gun.
I was so pumped with the success of the trigger swap that I tackled the Slavia 631 next. It’s also easy to take apart, and you won’t believe the improvement that just lubrication has brought. A 35-lb. cocking effort is now down to just 21 lbs.! I had guessed it could drop to 28 lbs., but that was way too conservative. I also got rid of 80 percent of the vibration, but that’s something I will save for the next report. Since the rifle is now so different from the way it was, I’m going to retest the velocity for you in a special report.
There’s lots more to tell about both projects. This was just an update to let you know how things are going. And, wprejs, this week I’ll pack the harmonica rifle and send it to Vince. Now, let’s look at today’s test.
Let’s take a look at the accuracy potential for the Benjamin 397C that Mac’s been testing. There’s been a lot of interest in this little rifle since this report started, and practically nobody knew of the gun’s existence before now. Even so, it was produced so recently that there’s still a good chance of finding one in near-new condition and still in the box, so this is one of those sleeper opportunities that abound in this hobby. As I finish this report, you have to ask yourself what it is that you like about airgunning; because if it’s finding rare guns for very little money, this carbine is one to look for. And, you need some references like the Blue Book of Airguns to help you find things like this.
Because this is a multi-pump pneumatic, there are some things we need to know before we look at the targets. The number of pumps that were used for every shot. Mac shot the carbine off a rest at 25 yards, and each shot got the maximum of eight pumps.
The way this gun works, some high-pressure air will always be trapped in front of the pump piston head after the pump stroke is finished. All the air does not go into the reservoir, even on modified guns.
As the number of strokes increases, the amount of air trapped in front of the piston head increases, so naturally it’s always the greatest when using the maximum number of strokes. When that happens, the air pushes back on the piston head, forcing down the pump lever, which is the carbine’s forearm, just a little. When you shoot, the air pressure inside the reservoir drops instantly and the tiny bit of high-pressure air in front of the pump piston head pushes its way into the reservoir. That allows the forearm to return to its relaxed position, and the shooter feels this as the whole gun settling. It’s a trait very common to a multi-pump, and it allows some movement of the gun with the shot.
There’s nothing a shooter can do about this movement when it happens; when it does, the pellet is already out of the barrel. The slight movement should have no effect on the accuracy of the gun. However, I want you to remember this discussion, because it had an effect on the outcome of the test.
Mac notes that the little carbine is hardly a bench gun, and we wouldn’t expect it to be at just 4 lbs. Sometimes, light weight and overall shortness can be a detriment to accurate shooting, as these little rifles are so twitchy (sensitive to how they are held).
You’ll remember from Part 1 that there is a Williams peep sight on this gun. Mac installed the hunting aperture, which has a larger hole for more rapid target acquisition. Peep sights with large apertures are quicker to get on target than regular notch sights, but the downside is you give up some precision to get the speed. I love the way an M1 carbine gets on target in an instant, but nobody will ever confuse it with a target gun because the large aperture reduces it to a minute-of-person weapon.
The first pellet Mac tried was the 7.9-grain Crosman Premier dome that’s usually one of the most accurate pellets in these multi-pumps from Crosman, Benjamin and Sheridan. But this day there was no joy as five pellets went into a group measuring 0.93 inches.
Next, he tried RWS Hobby pellets, which he also thought would be wonderful. They disappointed as well, with a five-shot group that measured 0.77 inches at the same 25 yards.
Finally, Mac tried the pellet he likes the best for most air rifles in .177 caliber — the RWS Superdome. But try though he might, five of them grouped only 0.84 inches at 25 yards. Then, he had a thought.
Remember that forearm that moves on every shot? Mac noticed it, too, and was holding the rifle with his off hand close to the triggerguard, the way you’re supposed to hold a breakbarrel. He decided to throw caution to the wind and rest the rifle with the forearm lying on the flat of his palm. He just knew that the moving forearm would throw him off, but he tried another five RWS Superdomes and discovered the secret. That’s the perfect way to hold this little carbine! Five pellets went into 0.24 inches at the same 25 yards.
What this test tells us is that conventional wisdom isn’t always right. This reminds me of the time when I decided to hold my Beeman C1 carbine with a super-light hold to see how bad it would group and wound up discovering what I now call the artillery hold!
The bottom line for this little gun is that Mac loves it. He likes it most for its size and weight, and it’s the gun he most often hands to guests when they want to do a little shooting. Offhand, it shoots much better than these groups might suggest, and Mac doesn’t worry about the loss of velocity. As long as everyone has a good time and can hit the targets, everything is fine.