GTA
Airguns by Make and Model => Benjamin Airguns => Topic started by: Psipumper on April 18, 2021, 05:15:17 PM
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I just finished building two 392s pumpers. Giving these to family members.
Really turned out nice .
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Sighting in at 27 yards. The center group is my wood 392pa.
HN FTT 5.55 pellets. I have found these to be the most accurate for me.
I checked the bore at .2197”. Seems the 392 may be a true .22 English bore.
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Ok, you said building two 392s... what were the mods besides the ldc’s?
Looks like they’re shooters. :D
I’ve been trying to convince myself to pick up one of the 392 synthetics, although I already have a 392 p and pa model.
Sure would make a nice weather proof hunter.
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Ok, you said building two 392s... what were the mods besides the ldc’s?
Looks like they’re shooters. :D
I’ve been trying to convince myself to pick up one of the 392 synthetics, although I already have a 392 p and pa model.
Sure would make a nice weather proof hunter.
I was sure glad to see good groups with the time I have invested in them.
These were built leaning towards durability over power .
With the 14.3 CPHP , 8 pumps is 800fps, 10 pumps is 870fps.
Mac1 parts: billet lever, end plug and adjustable piston.
Maurauder poppet and many Valve mods.
The transfer port is .170” square.
The valve is 4.5 cc . 1350 psi @8 pumps. 1680 @ 10 pumps.
10 pumps is the max on these.
They are somewhat easier to pump since the pump handle is two inches longer than the wood version. I adjusted the piston length for an easier cam over as well.
Scopes are cheap 4x16x44 sitting on Air Venturi intermounts. Good clear view.
Had to bend the bolt handle for clearance issues as usual. A 50 mm scope would work with the rear sight removed.
I made a few refinements to my designs and these overperform in power.
I think I can apply the changes to my older 392PA and get 850 fps on 8 pumps.
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870 on 10 pumps? Good grief!! That’s serious pumper power plus the durability of the Mac1 parts. :D
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Charles,
850 at 8 pumps with your 392pa and 14.3 gr. pellets would be super pump efficient.
My steroid takes 14 pumps to hit 860 with the same pellet.
What kind of longevity do you get from the mods you do.... I know you said some of them were new mods you came up with.
Very impressive work for sure! 8)
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I think your family members will be very happy with you !
What scope mount you are using ? And do they stay on target with these big scopes ?
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Charles,
850 at 8 pumps with your 392pa and 14.3 gr. pellets would be super pump efficient.
My steroid takes 14 pumps to hit 860 with the same pellet.
What kind of longevity do you get from the mods you do.... I know you said some of them were new mods you came up with.
Very impressive work for sure! 8)
Buddy,
They should last a long time. No need to cock before pumping. No retained air. 11 pumps wouldn’t be a problem .
I could have built them with more power but they only needed enough to push the HN pellets at 800 or so was the goal.
The scope rings are Hammers low . The 392 has very little recoil so scope movement should not be a problem. Takes a pretty long scope to get back to eyebox area. The scopes are CV Life brand .
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Charles,
850 at 8 pumps with your 392pa and 14.3 gr. pellets would be super pump efficient.
My steroid takes 14 pumps to hit 860 with the same pellet.
What kind of longevity do you get from the mods you do.... I know you said some of them were new mods you came up with.
Very impressive work for sure! 8)
Buddy,
They should last a long time. No need to cock before pumping. No retained air. 11 pumps wouldn’t be a problem .
I could have built them with more power but they only needed enough to push the HN pellets at 800 or so was the goal.
The scope rings are Hammers low . The 392 has very little recoil so scope movement should not be a problem. Takes a pretty long scope to get back to eyebox area. The scopes are CV Life brand .
Pumpers are my favorite airguns and I do a ton of shooting with them... one or the other, or all of them get shot pretty much daily.
Naturally, I follow your threads with a lot of interest... just wish I had the knowledge and equipment to do some of this on my own!
You make me want to go back to school for shop class! :o ;)
What was the reason for using the marauder poppet stem in your mods?
I’ve noticed when I have to do a reseal on my 39x guns, the seal on the stock poppet stem is always shredded.
I always just replace all the seals to be sure the problem is fixed while I have them torn down, but that poppet seal is the primary suspect each time.
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Buying the Maurauder poppet is just easier than making one from scratch.
Being an overmolded delrin piece, it should be less likely to fail by pushing the stem through it with hammer strike than any homemade part.
The stem is smaller @ .125 so the valve hole has to be sleeved. The valve seat has to be machined to be wider also.
I think it is good to have an available service part if needed.
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Something new I am going to try on the valve retention.
The factory stud that holds the valve is undercut where it comes up to the shoulder. I welded it up to turn it to the size of the hole in the brass tube. I have a 12/36 NS die on order in case I need more threads.
This should take care of elongation of hole in the pump tube as the valve is pushed rearwards under pump pressure.
Since the radius is different where the stud touches , the contact patch between the tube and stud is small. As a 392PA breaks in the hole is elongated some until the brass tube matches the stud radius and then the elongation slows. Since the new welded area diameter will be larger it will take more pressure to plow/elongate the hole .
The washers in the photo have the tube radius machined on them and keep the stud from digging into the tube when tightened.
I would call stuff like this durability .
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The stud screw mod makes a lot of sense. I would definitely say that would add to the longevity of a “ powered up” 39x rifle.
You definitely put a lot of thought into your builds.
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I found the regular seals on my 392 to fail too soon after installing the Billet Pump Linkage from Mac1 for strength at more than 8 pumps. I ordered some poppets from Crosman that are for the AS392 CO2 guns. They are a harder seal material to stand up to CO2. Same poppet as the 392 only the seal is different. No more problems now after 5 years of use. I don't know if Crosman still has them in stock though as the CO2 gun was discontinued.
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Charles,
850 at 8 pumps with your 392pa and 14.3 gr. pellets would be super pump efficient.
My steroid takes 14 pumps to hit 860 with the same pellet.
Goes 830 now. I sighted it in with 6 pumps @ 750 fps. Not the most powerful though. During testing, I have seen 1117 fps with my old original 392 “K1”.
These two synthetics have about the same valve size as the steroid and make about the same power. I think the pressures in the steroid would be close to the same @1680-1750 psi. A little bit higher than previous estimates.
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Wow, K1 was smoking! 8) That’s amazing!
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Nice builds,,OP...U got skilz....just a FYI...I used a baker mount on my 392S ,high rings and regular length variable tasco...plenty of relief.....I have wood...but really like the Syn...except for cheek fitment.....good luck
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Nice builds,,OP...U got skilz....just a FYI...I used a baker mount on my 392S ,high rings and regular length variable tasco...plenty of relief.....I have wood...but really like the Syn...except for cheek fitment.....good luck
The Baker mount is a good solution. Does it make it harder to load a pellet because of the extra width at the loading port ?
The Air Venturi mounts I used on these do not have as much vertical clearance due to the rail sitting over the loading port.
I have some custom mounts that work well on the wood version. May be a little low for the synthetic stock. Only problem is they aren’t versatile, need a longer scope like the 6x24x42 Tasco.
If I could cut the saddles off of some generic mounts and bolt them to the Air Venturi mounts in place of the rail ? May try it.
I bought another 392 synthetic for myself . I am going to build it along with my buddy’s wood 392PA. Will probably be the last time building the 392’s for me.
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I just got my 392S to go along with my other two wood stocked Benji 392's and my Sheridan hold down safety model in perfect shape.
I must say I do like my "S" model, it feels good and not cheap at all. The high comb is an issue with iron sights, but nice when using a scope.
I'm excited to see how this gun shoots, as the rest of my Benji 392's I'll lay odds it shoots well.
I made up another small round tin that holds the oil, salt if I get dehydrated along with a few compressed towels - about the diameter of a nickle and 1/4" thick --- a great addition to the pack !
Are you going to add butt packs or adapt a sling or keep them clean.
Later,
wll
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I redid the scope mounts by cutting a slot in some generic rings to match the Air Venturi lower mounts. Scope is fairly low and has better clearance to load pellets.
The rings were for a 30mm tube but came with spacers to use a 1 inch tube as well. A 30 tube scope would be 2.5 mm lower than this scope.
I had already bent the bolt handle previously and has plenty of clearance.
When I machined the slots , I made the front ring 1 mm taller and angled to keep the saddles parallel. The height difference is to keep the scope more optically centered.
Not the lowest scope out there but a good setup. This 392s has got to be one of the best ,at least for now.
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I'm interested in how you were able to attach LDCs to the 392s with only a nub of a barrel sticking out past the front sight band. That's my only 'complaint' on my 392PA, the noise. Most if not all of my shooting is in the suburbs and while (so far) my dad's neighbors are good about our shooting in his back yard, *I* would like to quiet down my rifle. Not necessarily to the point of "just hearing the mechanicals click" but at least to a more 'neighbor friendly' level. I'm just not sure of how to do it.
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I'm interested in how you were able to attach LDCs to the 392s with only a nub of a barrel sticking out past the front sight band. That's my only 'complaint' on my 392PA, the noise. Most if not all of my shooting is in the suburbs and while (so far) my dad's neighbors are good about our shooting in his back yard, *I* would like to quiet down my rifle. Not necessarily to the point of "just hearing the mechanicals click" but at least to a more 'neighbor friendly' level. I'm just not sure of how to do it.
A 392 makes some noise for sure especially modified ones. I have all custom made parts to mount the LDC.
Not much available as an easy option. I saw one on eBay sold by “froggy239” that may work pretty well.
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I'm interested in how you were able to attach LDCs to the 392s with only a nub of a barrel sticking out past the front sight band. That's my only 'complaint' on my 392PA, the noise. Most if not all of my shooting is in the suburbs and while (so far) my dad's neighbors are good about our shooting in his back yard, *I* would like to quiet down my rifle. Not necessarily to the point of "just hearing the mechanicals click" but at least to a more 'neighbor friendly' level. I'm just not sure of how to do it.
A 392 makes some noise for sure especially modified ones. I have all custom made parts to mount the LDC.
Not much available as an easy option. I saw one on eBay sold by “froggy239” that may work pretty well.
If you were interested in doing so, how much would the parts (minus the LDC) run to mount the LDC to the rifle?