[Martini-Henry]

With my rifle almost being complete, I find myself with some last and final issues. My inner barrel is AEG spec ER-Hopped and I was told that EMG Atlas buckings are pretty good. After installing 3 into my gun they all gave it perfect air seal, but eventually got pushed into the barrel path. I'm not sure why it keeps doing this. I can note thst it is hard to get out of the hop-up unit compared to the standard bucking it came with, so maybe it's too large? I've had to use dish soap to actually get it inside properly. The thing is, that the standard bucking doesn't give perfect air seal... I think it being a tight fit is probably a good thing, but it doesn't explain why it keeps being pushed over out of line. Does anyone know of any other flat bucking types, or a way to fix my current bucking problem (I only have one more EMG Atlas bucking)? Thanks for any help anyone can give me! Shown below is the other 2 buckings and the current bucking in the hop-up unit.

 

[Pretzel]

Your nozzle may be ingressing too far into the bucking, when you push the hop unit onto the gearbox does the nozzle move any? You want solid squish on the lips but no movement of the nozzle itself. If the bucking is squished too hard it may be folding in from that.

Also what nozzle, tappet and cyl head combo are you using?

It looks like the nozzle is tilting upwards and eating the top of the bucking, so it may be a loose nozzle in the system which could be a wide nozzle or narrow stem. Possibly somewhat loose on the tappet plate as well, which could allow for tilting.

 

[Martini-Henry]

Your nozzle may be ingressing too far into the bucking, when you push the hop unit onto the gearbox does the nozzle move any? You want solid squish on the lips but no movement of the nozzle itself. If the bucking is squished too hard it may be folding in from that.

Also what nozzle, tappet and cyl head combo are you using?

It looks like the nozzle is tilting upwards and eating the top of the bucking, so it may be a loose nozzle in the system which could be a wide nozzle or narrow stem. Possibly somewhat loose on the tappet plate as well, which could allow for tilting.

It's a spring rifle, the ICS Tomahawk, so the nozzle is fixed to the cylinder. I can see that being the case with the black line that forms around the lips, however I wonder why it's doing that if it's fixed.

 

[Pretzel]

Oh... Ok in my defense I generally assume AEG buckings are well... In an AEG 😂

Sounds like the cylinder/hop are out of line with each other by a small amount, possibly a spacer could be a bit thicker on the cylinder or something?

I was having similar issues with my striker till I made a new cyl sleeve and REALLY centered the hopup with shims made from aluminum cans.

Have you checked for sharp edges on the nozzle tip? May be worth rounding them down with scotchbrite or something if there are any.

Still worth checking the nozzle ingress distance as well, just drop the hopup onto the nozzle with the barrel in and see how far it sits from the front of the cyl under it's own weight. If it's more than ~0.5mm you may want to try a spacer glued on the back of the hop to fill some of that void.

But it seems likely that it's mostly a misalignment issue. Unfortunately I have no experience with the Tomahawk so I'm not sure what can actually be done to fix it, as it's probably only 0.5mm off or so, but that's just enough to catch the lips...

 

[Martini-Henry]

Oh... Ok in my defense I generally assume AEG buckings are well... In an AEG 😂

Sounds like the cylinder/hop are out of line with each other by a small amount, possibly a spacer could be a bit thicker on the cylinder or something?

I was having similar issues with my striker till I made a new cyl sleeve and REALLY centered the hopup with shims made from aluminum cans.

Have you checked for sharp edges on the nozzle tip? May be worth rounding them down with scotchbrite or something if there are any.

Still worth checking the nozzle ingress distance as well, just drop the hopup onto the nozzle with the barrel in and see how far it sits from the front of the cyl under it's own weight. If it's more than ~0.5mm you may want to try a spacer glued on the back of the hop to fill some of that void.

But it seems likely that it's mostly a misalignment issue. Unfortunately I have no experience with the Tomahawk so I'm not sure what can actually be done to fix it, as it's probably only 0.5mm off or so, but that's just enough to catch the lips...

It's all good, I should have specified. I see what you're saying and will try to see what I can find, I'll make a comment on her with some pictures of what I find later. Thank you!

 

[Martini-Henry]

Oh... Ok in my defense I generally assume AEG buckings are well... In an AEG 😂

Sounds like the cylinder/hop are out of line with each other by a small amount, possibly a spacer could be a bit thicker on the cylinder or something?

I was having similar issues with my striker till I made a new cyl sleeve and REALLY centered the hopup with shims made from aluminum cans.

Have you checked for sharp edges on the nozzle tip? May be worth rounding them down with scotchbrite or something if there are any.

Still worth checking the nozzle ingress distance as well, just drop the hopup onto the nozzle with the barrel in and see how far it sits from the front of the cyl under it's own weight. If it's more than ~0.5mm you may want to try a spacer glued on the back of the hop to fill some of that void.

But it seems likely that it's mostly a misalignment issue. Unfortunately I have no experience with the Tomahawk so I'm not sure what can actually be done to fix it, as it's probably only 0.5mm off or so, but that's just enough to catch the lips...

I did some looking at found that you are probably right with what the issue is. I'm not exactly sure how I'm supposed to shim it though since it has to slide into the gun. You said you used coke can? I guess I'll try that... I posted below some pictures. Seems that on all 3 it's in the top left corner that ware begins to show, one is badly damaged, another somewhat damaged, and the last has black. I figured this shows me where I need to shim it, up and to the left. Let me know what you think... I also notice that the Atlas bucking is larger, has shorter lips, and a bit thicker than the regular one.

 

[Pretzel]

Does the hop unit itself have any play when installed?

From looking at the exploded view in the manual it doesn't seem like there's a sleeve or guide rings that could be modified unfortunately...

If either the hop or piston have appreciable wiggle that could be how it's getting damaged.

Top left makes me think it's cylinder wiggle, because when pushing the bolt forward you're probably lifting it slightly and pushing it to the left based on the handle position. May just need to return it to battery in a different manner?

 

[Martini-Henry]

The cylinder has wiggle from the left to right and the hop up unit has wiggle up and down. I took some tape and shimmed the hop up unit to the top left to hopefully counter this effect, I'm not sure how successful I was since I haven't put a thousand shots through it, but I'll let you know.

 

[Whamhammer]

The cylinder has wiggle from the left to right and the hop up unit has wiggle up and down. I took some tape and shimmed the hop up unit to the top left to hopefully counter this effect, I'm not sure how successful I was since I haven't put a thousand shots through it, but I'll let you know.

Maybe some slight polishing on the fore-half of the nozzle as well?

I know that Begadi makes multiple length bucking lipped buckings, perhaps a slightly shorter bucking lip could help as well?