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PostPosted: Sun Jul 29, 2018 12:49 pm 
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Location: Bowmanville, Ontario
The gun appears to be happier with its butt planted into something...

Bad one is bench rest, all forms of hold, (artillery, firm, sandbag positioned front-mid-rear)

Then better is resting on the ground with the bag and hand on front, butt in the ground/shoulder.

Jesus. Finicky gun...

Any suggestions? The guns obviously really torquing/jumping around.


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PostPosted: Sun Jul 29, 2018 1:45 pm 
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Breech screw came a bit loose. Barrel had some wiggle to it. (brash washers) tightened.
It's still kind of all over. Trying 21 grain barracudas now...

On the bright side, the gamo .177 under cock and xisico .22 undercock seem fine. The game is dead nuts with a 10.6 grain. The xisico being 450 fps and under can't handle the heavy pellets.

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PostPosted: Sun Jul 29, 2018 2:30 pm 
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Well.... I have no idea.
It has good times, then it has terrible times. I'm trying every conceivable hold and position, I get some good then immediately it's bad again. It's almost like it sneezes and throws everything out of wack. For a bit it seemed the barracudas were holding well, then all of a sudden they weren't. The breech screw was loose, but it's almost the same as the last time I found the breach screw loose. As soon as I tighten it, it's terrible again. I made brass washers that are smooth and tight fitting. The barrel cocks smooth. when I tighten I cannot determine if there is wiggle, can't see or feel it. But it's almost like the gun wants to wiggle.

Each time I think I've figured something out everything changes again.
Next time I get some time I'm going to try the scope from the gamo. That gun has a ridiculous amount of recoil, but it holds dead center every time.

I've put a lot of work into this Benjamin and I'd love it to work, but I'm running out of ideas and might be back to the idea that it needs to be slowed down a bit. However, with the heavier, better pellets I cannot see any more instability or spiraling. It just shoots all over the place...

I will accept any and all ideas, please.


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PostPosted: Sun Jul 29, 2018 4:07 pm 
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I wish I had a slow motion camera to see what's happening.

What if I try a shorter barrel? The torque of the piston is moving the gun around while the pellet is still in the barrel, what if I shorten the time in the barrel?
Has anyone out there ever done the math, or computer graphics, of where the pellet would be by the time the piston hits the breach?

What's bothering me so much about this is how the pellets are all over the place. The recoil should be the same each time from the same distance, right? How could the impact zone be so large and random?

I used several of chevotas methods to help the smooth the piston and spring, buttons, spring shroud, washers to reduce the twist from the spring, etc.

What about using buttons/shims aft of the breech screw? Eliminate any possibility of the barrel from moving side to side when firing.






Yes, this is bothering me THAT much... If I just cease this battle and buy either a fixed barrel or co2/PCP I'll feel like I gave up on this gun after so much work and time... I'm not good at that.

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PostPosted: Sun Jul 29, 2018 5:32 pm 
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I think we should bring out a paper and list all the potential reasons for the strange result and cross then out one by one when we did... They just affects each other and you will never get an answer from them....

As OP mentioned the gun works better with open sight. We can remove the scope first, then find out a best pellet for the gun first....

Something like that, we can do it one by one....

Just my 0.02~

Good luck ~

Sent from my LG cellphone

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PostPosted: Sun Jul 29, 2018 6:03 pm 
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I don't suggest shortening the barrel unless it's just a little bit to remove defects/damage at the muzzle end. If 177 you'll lose power, and whatever cal it'll make it harder to cock. You can try weight on the barrel, like clamping whatever to it as a test, and if that works they sell a steel brake that weighs ~4.5oz. Should be ~$4.40CA if they're still available; # B19-7-00-100.
There's a link in my guide to a high speed vid of a barrel doing its thing, and this flopping ~ is why they're such a pita to shoot. If all the flaws are fixed it isn't all that bad b/c imo the barrel whips ~ less and it does it the same way each shot so the pellet exits at the same moment and you're good. Imo it's no doubt possible that the pellet will exit mid-whip, meaning if the pellet exits a micro-sec early or late then it'll hurt poi much more than if it's at some other point in the barrels movement. This is imo why small changes sometimes make a big diff in accuracy, or why one pellet is horrible and another of the same wt is great. It's also likely why a gun is so hold sensitive, or super sensitive with certain pellets. Fixing the air leaks and bumping compression with a seal mod will boost power and dampen the piston impact that causes the barrel to whip. A heavier scope will alter how the gun moves, getting it to move fore-aft rather than also flipping the barrel up and down. You could also buy a shrouded barrel assy, or just the shroud if you can thread your barrel. It should act like a brace to some degree, but since you can't have the suppressor function you would have the option to put rubber inside. Like really fat O-rings or fill it w/ silicone or whatever. I've never tried it but I can't see how it would not help. If filling with silicone then I guess no need to thread it since the silly will hold it together. The shroud assy is 3-pieces and each pc should be ~$2.30CA.

Yes you can put buttons inside the ears to support the aft end of the breech block. Basically strips of plastic ~4mm wide and as tall as the block glued to the ears as far aft as possible. Like the brass washers it needs to be fitted, but in this case it needs to be both snug and matched to the brass washers so they're not fighting each other. I don't know if anyone other than me has a done it but I have given the info to several people. Usually the brass washers work well enough, which should include sanding the barrel pivot bolt. Other than that I'd focus on the main seal leakage and dead air space, and sanding the barrel.


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PostPosted: Sun Jul 29, 2018 7:35 pm 
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Well...I just removed my third scope I had on the Phantom....The second incarnation of this gun has polished springs...washers...tophats...sleeved piston....shims for a nice snug barrel lockup...but not too snug...as well as new seals....It shot great but then started shooting all over the place...with every brand of pellet and however I set the scope.... As soon as I went back to open sights I was back to very nice groups....No more scopes on this gun....I've set it up to shooting 630 fps with 8.18 gr h&n' wadcutters so there isn't much recoil and I STILL can't keep a scope on it....I'm betting your scope is playing with you....And on the other side of the coin...I have the same Stoeger 3 to 9x 40 AO scope on my Nitro Venom .22 for the last 5 years and it STILL working great...a $100.00 scope so I know I got lucky on THAT one....Good luck...I hope you sort it out cuz it can drive you nuts...lol.... :D

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PostPosted: Sun Jul 29, 2018 7:40 pm 
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YepYep wrote:
I think we should bring out a paper and list all the potential reasons for the strange result and cross then out one by one when we did... They just affects each other and you will never get an answer from them....

As OP mentioned the gun works better with open sight. We can remove the scope first, then find out a best pellet for the gun first....

Something like that, we can do it one by one....

Just my 0.02~

Good luck ~

Sent from my LG cellphone



Sorry, I said the xisico had open sights and fired well with it. The Benjamin did not have them... However, I could easily make a makeshift open sight for it. It doesn't even have to be adjustable, as long as it hit my 14x16" trap at a reasonable distance it would cross a huge problem off the list. If it fires fine and groups like the xisico did with open sights, then I obviously know the gun is totally fine.
I have a machine shop in my garage, some simple sights could easily be made.

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PostPosted: Sun Jul 29, 2018 10:28 pm 
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Chevota wrote:
I don't suggest shortening the barrel unless it's just a little bit to remove defects/damage at the muzzle end. If 177 you'll lose power, and whatever cal it'll make it harder to cock.


I chamfered, dressed, cleaned up, the muzzle. But I will check this area again. I will try a bucket of water test to try and see any scoring on the pellet.

Chevota wrote:
You can try weight on the barrel, like clamping whatever to it as a test, and if that works they sell a steel brake that weighs ~4.5oz. Should be ~$4.40CA if they're still available; # B19-7-00-100.
There's a link in my guide to a high speed vid of a barrel doing its thing, and this flopping ~ is why they're such a pita to shoot. If all the flaws are fixed it isn't all that bad b/c imo the barrel whips ~ less and it does it the same way each shot so the pellet exits at the same moment and you're good. Imo it's no doubt possible that the pellet will exit mid-whip, meaning if the pellet exits a micro-sec early or late then it'll hurt poi much more than if it's at some other point in the barrels movement. This is imo why small changes sometimes make a big diff in accuracy, or why one pellet is horrible and another of the same wt is great. It's also likely why a gun is so hold sensitive, or super sensitive with certain pellets.


One of the (dumb) things I did when I FIRST got the gun was drill out the breech air transfer hole to 1/8". My old polish .177 is 1/8" and I had a dual calibre Canadian tire gun that I drilled out, it made that gun quite a bit faster. I assumed it was one of the ways they detuned the guns. I'm wondering now if that was a bad idea.
If it was a poor choice I could insert a plug into the hole and drill it a small size. Help make better compression to dampen the piston?


Chevota wrote:
Fixing the air leaks and bumping compression with a seal mod will boost power and dampen the piston impact that causes the barrel to whip. A heavier scope will alter how the gun moves, getting it to move fore-aft rather than also flipping the barrel up and down. You could also buy a shrouded barrel assy, or just the shroud if you can thread your barrel. It should act like a brace to some degree, but since you can't have the suppressor function you would have the option to put rubber inside. Like really fat O-rings or fill it w/ silicone or whatever. I've never tried it but I can't see how it would not help. If filling with silicone then I guess no need to thread it since the silly will hold it together. The shroud assy is 3-pieces and each pc should be ~$2.30CA.

I had a *not* shrouded suppressor on the end of the barrel since the new spring made it so much louder. It added weight, but I couldn't decide if it made accuracy better or worse on or off.

Chevota wrote:
Yes you can put buttons inside the ears to support the aft end of the breech block. Basically strips of plastic ~4mm wide and as tall as the block glued to the ears as far aft as possible. Like the brass washers it needs to be fitted, but in this case it needs to be both snug and matched to the brass washers so they're not fighting each other. I don't know if anyone other than me has a done it but I have given the info to several people. Usually the brass washers work well enough, which should include sanding the barrel pivot bolt. Other than that I'd focus on the main seal leakage and dead air space, and sanding the barrel.


I ordered a new main seal from your recommendations. Actually, that was a couple weeks ago... I wonder why that hasn't arrived yet...


Also, I did the water bucket pellet test. The rifling on the pellet looks perfect, actually. No scraping, galling, no unusual striations.


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PostPosted: Sun Jul 29, 2018 10:32 pm 
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I like the list idea.

So far I've got,

Barrel isn't catching or gouging the pellet.

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PostPosted: Mon Jul 30, 2018 5:17 am 
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Going to try to fab up some open sights today. I'll have some shop time.

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PostPosted: Mon Jul 30, 2018 11:44 am 
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Okay.... Results... 10 yards.

I cobbled together an open sight. Consisted of an aluminum ring over the barrel with a point milled into the top and a 10-24 cap screw threaded into the scope hold hole with a v filed into it.

First picture is on the bench sand bags, just resting on bags holding on the x. Consistent but wondering.

Next photo is on the ground with the butt planted into the dirt under my shoulder, this was mega awkward cause I had to get my eye soooo low to see. I only shot 4 pellets... It was obvious after 2 the gun is actually dead accurate...

Third photo is bench again, but the corner of the butt planted in the sandbag and held in place with my shoulder.
Two fliers cause I couldn't hold still. Then 4 on top of each other once I got comfortable. All holding on the x.

Soo.. ya... Not the gun... However, the gun seems to want to be held firm. Or at least the butt. It doesn't want to be allowed to push back and down,
I'm gonna try the camp's scope now. Then I should probably get some actual work done today. Lol.


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PostPosted: Mon Jul 30, 2018 12:20 pm 
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K... That's it. You're done... Go to bed.

the gamo (no name on it) scope. Mounted with centering screw, shimmed about .030", took three shots to center it. Third shot was on center. Left side is 10 yards, right side is 30 yards.
All bench rest, butt in bag and pressed by shoulder, hand grasping stock around the end of the cocking slot resting on bags, shot after shot on point. I have to imagine the only reason it's grouping above and below is just me and the trigger. But maaan, what a difference..
I gotta get to work, but this scope is obviously staying on here. Really makes me curious about the Benjamin scope. I don't think I read that they were crummy?? Hopefully I can get out here again this week and send a few more pounds of lead down and see how it holds up.

Come to think of it, even out of the box I don't remember that scope being spectacular. Certainly not like this... what to do with that Benjamin scope tho...

We will see.

I assume upgrading to a gas spring would make the gun a bit more quiet and less violent?


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PostPosted: Sat Aug 04, 2018 3:40 pm 
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I ordered and just installed the nitro piston in the Benjamin. Only fired off 3 shots in the garage into the trap. Already noticeably quieter and less recoil. Just put the scope back on and about to go give it a good test. I probably won't have any jsb's left when I'm done. That's less than desirable, but I'm happy the spring noise is gone. But now I'm very aware of the muzzle crack...

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PostPosted: Sat Aug 04, 2018 4:13 pm 
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Location: Dowling ,ontario
Dan at the forum store has the best deals on pellets . They usually ship the same day. Th link is on the home page here . Also if your shopping for a cheap replacement scope any of the Leapers true strength scopes are Springer rated . I’ve had a 3x9x40 on my Hatsan 135 for a few years now with no issue .

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