The Pump-Assist Benjamin 392 – Part 4
by B.B. Pelletier
When I say the gun, I’m referring to both calibers .177 and .22, which are the 397 and 392 models, respectively. Other than the calibers, the guns are identical in all ways.
Testing the new unmodified guns
Bob Moss, the inventor who designed and builds the pump-assist modification, has done some additional testing and improved several features of the gun. For starters, he’s boosted the velocity. He purchased 10 new guns and measured the average velocity for both .177s and .22s. The .177s averaged 719 f.p.s. with Crosman 7.9-grain Premier pellets, and the .22s averaged 605 f.p.s. with 14.3-grain Premiers. That was for the recommended 8 pumps maximum for both guns, and it’s the average of four 397s and six 392s.
Moss then set about to increase the power in his modified rifles, one of which he kindly supplied to me for testing. On 8 pumps, the modified 392 averages 613 f.p.s. with Crosman Premiers. You may recall that the first rifle I tested averaged 589 f.p.s. with the same .22 caliber Premiers, so the power has definitely been increased. Moss says all guns will go out at this new power level.
Even more power!
As with the initial test, I pumped this test rifle more times than the factory-recommended 8, just to see what would happen. Neither Moss nor Pyramyd Air recommend doing this with your own rifle as it can stress the pump mechanism beyond its design limits. With 9 pumps, the gun averages 632 f.p.s. with Premiers, and no air remains after firing. With 10 pumps, the average climbs to 651 f.p.s., and, once again, no air remains after firing. On 11 pumps, the average velocity for Premiers is 667 f.p.s., but the spread from highest to lowest velocity opens up beyond 10 f.p.s. and there is air remaining in the gun after the shot. So, 11 pumps are clearly too many for the valve in the test gun. Again, I don’t recommend pumping more than 8 times, but I did it to illustrate how the gun works.
A LOT easier!
Remember in the earlier reports I revised my pump efforts for the standard rifle downward after talking with the inventor? Well, he tested this new batch of guns and found them to be much harder to pump in their final strokes. The eighth stroke took an average of 40 pounds of effort and one rifle in the batch of ten was off the scale, at over 50 pounds! That is what is being reduced to between 12 and 14 pounds! The linkage was also revised to stop the pump arm from rising as the stroke count increases.
Let’s test it!
Now that we have an easy-pumping 392, the Air Venturi intermount that positions the scope above the receiver makes sense. I’ll mount what I think is the perfect scope for this rifle and give it a test. We can compare it to the results of the first rifle and see if this modification is worth the expense. That will come on Friday. Tomorrow, though, I have a surprise.
What did you get?
Tomorrow, I’ll share what I got for Christmas with you, and then I want you to tell me what you got. I know all of us don’t celebrate Christmas, but I also know that this season brings out the buyer in all of us. So, consider this your opportunity to tell all of us about your favorite new airgun or accessory.