The Pump-Assist Benjamin 392 – Part 4

by B.B. Pelletier

Part 1
Part 2
Part 3

 

The new pump-assist Benjamin 392/397 with Air Venturi intermount attached is revised and more powerful.
Pyramyd Air is now stocking the pump-assist modified Benjamin 392 and 397 rifles. It complements their new Air Venturi intermount perfectly, by making it easy (for the first time) to pump the rifle with a scope mounted on it. So, I’m returning to this modification for more testing and this time I’ll have a scope! Before we get to that, I want to give you some news about the gun, itself.

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.

More power!
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.

35 thoughts on “The Pump-Assist Benjamin 392 – Part 4

  1. $325? At that price are they going to do the simple things to improve the gun such as a trigger job to lighten and shorten the pull on that horrible stock trigger, or remove the over sprayed paint from inside the barrel?

    Do they fix these simple things or are they going to sell them still with a heavy sloppy trigger and paint in the barrel still for $325?


  2. Adam,

    The price is just for the conversion. This isn’t a job for someone who wants a tuned gun. It’s for scope users and people with disabilities.

    It is expensive and if you don’t need it, you probably don’t want it, but there are plenty of shooters who want to mount conventional scopes or who need a little help when it comes to pumping the gun. This is for them.

    B.B.


  3. Just seems a shame to put such a nice pump lever linkage on the gun and not bother with cleaning paint out of the barrel and doing some simple work on the trigger somebody has lost focus. I mean airguns are about accuracy and yet to spend all the time and money to make it easier to pump and not a minute on removing paint or improving the trigger is the typical current mentality of airgun maker….Gimmicks! So it is easier to pump that is nice. Now how about getting them to spend 5 minutes cleaning up the paint in the barrel? A gun that sells for $325 and has paint in the barrel is a pass for me, really does not matter how easy it is to pump…it is not acceptable.


  4. BB,
    I bought the intermount for my 392. I used a very short scope so I could still hold it normally. i noticed there was some side to side movement on the mount. it wasnt that bad but i was wondering if yours did the same thing.

    Okay now i have a random question. Are there any restrictions on blank guns? Im refering to the full auto and such. I was wondering if anyone made blank rifles or SMGs. If anyone made a full auto blank MP5 i would buy it.

    Nate in Mass


  5. BB, I’ve got a TF89 (.22) on order, hopefully Compasseco will get it out today. With any luck, it won’t be a major disappointment like the other 2 “TF” guns I’d gotten in the past. However, I now know a little about the AR1000 series, so I’m fairly confident that I’ll be happy with it unless I get an oinker.

    BTW – looking at the lower grade “Contender” series, I’m guessing that the TF59 (almost certainly a QB23) is a derivative of the old TF(QB)25. That rifle combined Norica-type construction now used in the AR1000 (ball bearing lockup, similar piston/seal arrangement) with what looked to be a Gamo-type trigger. It wouldn’t have been a bad rifle if the spring didn’t keep taking a shorter and shorter set from just sitting uncocked. Every time I picked that rifle up, it shot weaker than before.


  6. Nate,

    I will finish the report of the intermount on Friday.

    Regarding blank guns, they cannot be bored through the barrel.

    Blank guns have never been big sellers in the U.S., so I don’t know if there are SMGs, but if the market expands, no doubt there will be.

    B.B.


  7. Vince, When I tested the TF 89 Contender, mine was a peach. Every bit as good as an R1. I hope you get a good one.

    Chinese springs are one of the remaining weak points in the guns. Fortunately they are easy to change.

    B.B.



  8. B.B.,
    im trying to determine whether to get a webley longbow or a webley tomahawk, i can’t make up my mind so i thought i would ask you which you would prefer. i read your feature article about the tomahawk and the venom style stock with the trigger. but at the same time the longbow has a lothar walther barrel and weighs about a pound less. all in all which would you choose?

    thanks, scopestop



  9. Scopestop,

    I see that the Longbow is out of stock. Let’s see if the Turkish-made Longbow still has a Lother Walther barrel when it arrives.

    As the specs read now the Longbow seems like the better deal, but let’s wait and see.

    B.B.


  10. BB,

    i cant wait…

    i didn’t get an airgun. I got a .375 H&H for home defense. Just kidding, its for water buffalo. That gun is not justified for anything in the USA so i’ll be doing some traveling. I understand that Rgr has a new .375 out but i prefer the original, if you want more power > move up a caliber.

    -sumo


  11. Hi BB, Thanks for the update on the lasers! Which of those carried by Pyramid do you think is the best bang for the buck for a Talon SS. The AirForce laser seems pretty pricey. It would be used to supplement a scope at closer ranges in the morning and evening.

    Thanks, Mike T.


  12. Mike,

    Any laser you use will only be good at short range, so go for an affordable one. You might thinks the pricier ones are brighter, but except for the AirForce one, that isn’t true. A $10 laser will be just as bright as a $30 laser.

    B.B.


  13. Sumo…..
    I knew a guy one time who was going to get a .458 Win mag to shoot jack rabbits with hand loads.
    Can you say “over kill” ???

    twotalon


  14. Twotalon,

    One of my second cousins used to regularly hunt Michigan Upper Peninsula deer with a .375 H&H, then his wife bought him a new deer rifle: .416 Weatherby Magnum. He quit hunting altogether because he found the recoil and muzzle blast from the ported barrel intolerable. I could only scratch my head in wonder why he didn’t simply use his “small rifle” instead, which was a Remington 700 chambered in the puny 7mm Magnum.
    ;-)


  15. 7 mag sounds about right for squirrel. Shot one from the back porch at night (rifle, not squirrel). The flash blinded me and the noise made me deaf for a few hours.

    Mostly doing airguns now. Even the talon can make my ears ring.

    2t



  16. BB, I can imagine how a 392 is to pump normally (my friend’s ancient Model C is STILL hard to pump 8X), but how hard or awkward is it to pump a normal 392 with a scope on it? Also, do you know where I can get a parts diagram and parts for my Daisy 22SG? Seals seem to have developed leaks. JP


  17. Just listened to the podcast recitation of 14.3gr 20 cal pellet being slower than 14.3gr 22 cal pellet fired in an AF rifle. Presumably the barrel lengths were identical? I must humbly disagree with your conclusion.

    I doubt this phenomenon is caused by increased friction of greater 20 cal bearing surface relative to shorter 22 cal bearing surface. Sure the longer pellet “may” have a longer bearing surface (depends on the diabolo pellet shape and how it contacts the bore). The bearing surface most certainly does depend upon caliber since Circumference=pi*caliber, and (Bearing Area)=(circumference)*(length of pellet contact to the bore). The 20cal does have less circumference and may or may not have greater bearing area because of increased contact length. In any event, I suspect these frictional forces are more or less a wash between the two calibers.

    What DOES MATTER is the force behind the pellet. The accelerant force must vastly overwhelm frictional forces, to the extent that friction can largely be ignored, assuming the gun is to ever expel the projectile in the desired fashion.

    Newtonian physics tells us that acceleration is proportional to force acting on mass. (sum_of_Force)=(mass)times(acceleration), or more to the point, acceleration=sum_of_Force/mass. Area behind the pellet defines the available accelerant force. Area of the 22cal pellet is 21% greater than area behind 20cal.

    You hold the pellet mass constant in this comparison. Since the bore area, and therefore available force, is lower with 20 cal, the velocity must be lower.

    With a PCP rifle, maximum accelerant pressure is fixed – 3000 psi. There is your cause of velocity difference.


  18. Shooter….
    I guess if you don’t really care about sportsmanship and you don’t care about the money, you can blow varmints to confetti so bad the flies can’t find anything to eat.

    Been there, done that. More fun with high precision and low power at close range. That’s sporting.

    2t


  19. guys,

    thanks for the stories.

    Don’t worry, this .375 is reserved for a 2000 pound cape buffalo. at almost 5000 foot pounds it better be.

    If you don’t wanna hear a gory story stop hear!………
    I have a .222 magnum (they don’t make them anymore) and that make confetti out of bunny. I have a pole barn with a 20 year old jeep in it (sofa on wheels) and i shot a rabbit the next to it and it splatter all over the car and all over the kayak hanging next to it.

    i got that .222 mag and 2 boxes of ammo for $400 and walked out thinking it was a bargain…. Then realized i would have to specially order the ammo! >WORTH IT! LOL

    -sumo



  20. JP,

    It is VERY difficult to pump a normal scoped rifle. I’ve see people trying to do it and they invariably hold the scope to pump. I’ve also heard from many who claim they can pump holding the rifle at the pistol grip, but I’ve never seen anyone do it. No doubt it’s possible. You just have to want it.

    B.B.


  21. Podcast listener,

    You give a very good explanation for the .20 caliber being slower. It sounds good to me.

    However, you need to know that the air pressure behind the pellet is never 3,000 psi. The valve doesn’t pass pressure that high. It’s more like 2,200 or even 2,000, which diminishes as the pellet starts moving. But that doesn’t affect your explanation.

    Thanks,

    B.B.


  22. I am interested in the performance of the intermount. I haven’t seen a good one so far that will mount on the Benji and not move. Anyone have personal experience with the mount?

    Jimp


  23. Jimp,

    I am as interested as you. Intermounts are why I do not recommend scoping multi-pumps. They make the guns too difficult to pump and they are too flimsy. We shall see about this one tomorrow.

    B.B.


  24. I just can’t figure out what is so hard about pumping a Sheridan.

    I bought mine in ’74 brand new and put a scope on it as soon as I could find the mount and scope.
    I hold it at the grip with the stock resting just above the hip on my side. No problem with 6 pumps and but the 8th does get harder.

    I am 61 and 5′ 8″ and 145 lbs and still have no problem pumping it. But then I have worked with guys 40years younger and I have to help them to lift things that I could do by myself. I think the problem is to many vidio games and “NOT” the pumping.


  25. You make a good point bob. I like to digitally shoot ‘em up once in awhile, but for the serious gamer friends I got I recently challenged ‘em to a real shoot ‘em up: field target style plinking with an old Crosman I recently got working. I’m thinking we should all get some forest time when we get the chance. Might consider starting an “air” club locally. JP


  26. twotalon,

    That’s why I gave up hunting with rifles long ago. Took up the bow instead. Nothing like getting 20 -30 yards away from your quarry without it knowing you’re there until it’s too late. I still like blowing the crap out of water jugs, boards, etc. with a lot of power though.

    /Shooter


  27. BB,
    I agree the AF valve won’t pass the full 3000psi. Thats why I said “maximum accelerant pressure”

    If the valve were tuned for optimal 20 cal air usage efficiency, then velocity with 22 cal WOULD most likely drop because of 22 cal’s increased expansion ratio. However, I think the AF valve is very inefficient with either caliber. Essentially it is vastly “over bore” for both, so the difference in expansion ratio doesn’t come into play.


  28. BB,
    Being disabled, I pump the gun with the butt on my foot and push down like a bicycle pump. This allows me to use my upper body instead of squeezing the lever to the rifle. Being right handed, I place the butt on my right foot and use my left foot to insure the butt does not “kick out” as the stroke moves from down to down and left. It is much easier for me to pump this way. Obviously for left handed shooters you would put the butt on the left foot. I never have a problem with the scope as I am holding the top of the rifle. This is normal for my Benjamin’s, Sheridans, Crosmans, Daisys and hybrid pneumatics. I agree about the 397/392 trigger. I remove the “trigger” spring, leaving the spring wire to the sear. I file or polish the mating surfaces of the trigger, sear and bolt for a nice smooth trigger. The stamping process used creates quite a rough trigger at times. It is simple to do and might be good for a mention on the blog.
    Hellrazor



  29. Hi B.B.

    I’m interested in learning in detail what Hellrazor is describing about modifying and improving the trigger performance of the Benji .392. I own one and would consider doing the work myself, but would want the info to feel confident. Pictures would be a bonus. I can provide my email address if you’d be willing to pass my request along to him, or provide the information yourself. Please let me know.

    Thanks!
    Bill



Leave a Reply

Your email address will not be published.


+ 6 = 14

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>