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Filling transfer port with epoxy?

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UCChris

UCChris

Member
Mar 12, 2017
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Chicago, IL, United States
I'm working on tuning my wife's Bandit carbine without a regulator. I currently have it to where the bell curve is over the pressure range that I want, but the max velocity is a bit higher than I want. The bell curve is also sharper than I'm wanting, though I understand there are limitations with such a small air tube. It's doing 20 shots in an 8% spread, with a peak power of a bit over 12 fpe. I'd like to flatten that to a string of 24 shots with a peak of 10-11 fpe, so I'm thinking a smaller transfer port is the correct next step. Has anyone used 5 minute epoxy to fill a transfer port for drilling out? Or do I need to use some sort of JB weld metal putty? The transfer port is brass and is .146" in diameter.

Any advice would be appreciated.
 
I have never used 5 minute epoxy, but I have used JB weld to close up transfer ports on numerous occasions. I have done it to repurpose barrel, a few times when I messed up the port and it was too wide for pellets, etc. You just need to be careful and pay attention to how you are going to prevent it from migrating to other areas. I typically will plug the chamber with a tight fitting slug. Put some shoe polish, etc on the slug so the JB doesn't still to the slug.

While this isn't the way a pro would normally handle a paying customer, for your own stuff I see no problem with it. If you ever sold it, I would make sure to disclose this detail.

Being a DIY hack I have never sold any guns that I carved on.
 
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JbWeld should work. If you plug one side with modeling clay (I bought a pack of multiple colors from Walmart for about $2) then you can fill it without it running out and glueing it to your work bench. You could contact Wes at Airgun Archery Fun and see if he has a transfer port he has taken out of a Canada legal Bandit. They are a 2mm hole that can be drilled out to what you need. A stock Bandit port should be 3.5mm. I’ve never tried it but the port being brass you could also try filling the hole with solder.
 
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marquette said:
JbWeld should work. If you plug one side with modeling clay (I bought a pack of multiple colors from Walmart for about $2) then you can fill it without it running out and glueing it to your work bench. You could contact Wes at Airgun Archery Fun and see if he has a transfer port he has taken out of a Canada legal Bandit. They are a 2mm hole that can be drilled out to what you need. A stock Bandit port should be 3.5mm. I’ve never tried it but the port being brass you could also try filling the hole with solder.
Click to expand...
Beat me to it lol seen the small one that you can drill out(been eyeballing it)🥴😅
 
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@UCChris,

Is there enough meat on that port to tap it for an 8-32 grub screw? I use those to tap crosman ports all the time and then just drill inside the socket head.

The solder idea is a good one too, I wouldn't trust an epoxy or filler to not eventually dislodge and possibly get stuck in the barrel. Drilling it out could weaken its grip to the bushing walls.
 
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Boostcreep said:
@UCChris,

Is there enough meat on that port to tap it for an 8-32 grub screw? I use those to tap crosman ports all the time and then just drill inside the socket head.

The solder idea is a good one too, I wouldn't trust an epoxy or filler to not eventually dislodge and possibly get stuck in the barrel. Drilling it out could weaken its grip to the bushing walls.
Click to expand...

I measured the port at .147" back in 2019 when I bought it. So it looks like 8-32 would require just a tap ran through it
 
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I won't use JB weld on anything, and if you use it in this application you are taking the chance of getting it into places it really should not be.

I agree with Bostcreep. Drill, Tap and drill a grub screw to the desired size. But again, be careful about metal filings and chips. Those could translate into a bad situation.
 
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Nylon has worked for me, yes, though I opt for something closer to 75% thread engagement when dealing with soft materials. The Bandit's transfer port, at 0.146" per your measurement, will yield slightly less than 50% thread engagement at #8-32 but I expect it will hold up if the transfer port is as tall as other SPA transfer ports I'm familiar with (a t-shape with an O-ring on each side).
 
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Vetmx said:
I made some transfer ports for a guy over on GTA to help him flatten his curve on his Bandit. He was messing with springs and stuff and I knew he was just running up hill. If you could find that topic you could see what sizes I made him and the results. His name was Aviator or Avatar or something like that.
Click to expand...

CP2 gets a big upgrade. - Airguns & Guns Forum

CP2 gets a big upgrade., Air guns, Airgun Forum
www.gatewaytoairguns.org

I think I found it, but not the same username. If, by chance, you would turn another in exchange for monies, let me know. Regardless, thank you for the heads up, lots of good info in that thread!
 
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Many different methods have been listed, each having their merits. It really depends on what the OP is capable/comfortable doing.

I am not familiar with this particular gun, but if it indeed has a brass transfer port, soldering the portŕ closed and drilling to size would be near the top of my list. But not everyone keeps a mini torch, flux, and solder in their toolbox...

Every method listed here is capable of working and lasting, it just boils down to which is the best fit for the OP's tools/skills.
 
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All I did with the crosman ports is run the tap through them. Have ports from 1/16"-3/32" that will still unscrew with the hex bit, and let me use a full port. One I drilled to 7/64" and it took off the hex sides so it's a permanent.

I chucked the t port into a vise with wood, and tapped just shy of all the way through. Screwed in the 8-32 grub screw and drilled each out til the 7/64 one got stuck. The stock crosman port is .140" so very close to the one you have.

It really leveled out my strings for that mini safepac carbine I built. Gives me 4 different tunes from 12 fpe for 14 shots, 15 fpe/10 shots, 18 fpe/8 shots, or 22 fpe/6 shots.
 
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Boostcreep said:
All I did with the crosman ports is run the tap through them. Have ports from 1/16"-3/32" that will still unscrew with the hex bit, and let me use a full port. One I drilled to 7/64" and it took off the hex sides so it's a permanent.

I chucked the t port into a vise with wood, and tapped just shy of all the way through. Screwed in the 8-32 grub screw and drilled each out til the 7/64 one got stuck. The stock crosman port is .140" so very close to the one you have.

It really leveled out my strings for that mini safepac carbine I built. Gives me 4 different tunes from 12 fpe for 14 shots, 15 fpe/10 shots, 18 fpe/8 shots, or 22 fpe/6 shots.
Click to expand...

Thank you so much for the info. I will pick up a tap and some set screws.
 
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Drilling and/or tapping round thin walled items such as transfer ports....

For tapping a thin walled round item, such as a transfer port. One can carefully chuck the transfer port in a drill chuck as a method of securing the port while tapping.

Often when the need arises to increase the diameter of a hole in thin walled round items, such as transfer ports, I will chuck the part in my drill and clamp the bit, stationary, in my vise or vise grips...

These operations may or may not be a good fit, but are options to consider.
 
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