Opening up the barrel/transfer port Q

[TheOtherSprocket]

Hi All,
I'm having a hard time locating a "how-to" for opening up the transfer port/barrel port.  Mostly I'm looking for info on the barrel portion of the mod - de-burring once the hole is drilled.

I have a drill press I can set up to drill the hole out and that seems pretty straight forward.  What is the process to clean out the hole once it is opened up to 5/32"?

If you can point me to a thread, I'd appreciate it.

Thanks

[Airspace]

I would find a dowel rod that fit the inside diameter of the barrel to use as a backup for the bit and try to minimize the distance you bore into the port.

[jsk68]

I saw somewhere, I think it was Baker airguns that claim over sizing the port too much actually reduces fps.
No Idea if it's true but thought you should know.

[TheOtherSprocket]

Thanks Friends - I appreciate the responses.

I was searching for pinning the valve and found this thread - actually page 3 has the barrel procedure detailed.
https://www.gatewaytoairguns.org/GTA/index.php?topic=185793.20
The thread is stacked with great info, tips and tricks - very appreciative to have it all one one place.

This will be a .177 barrel so I may build the bottom end and leave the barrel alone until I can chrony - then make a decision to open it up or not.  I do have the Boss TP seal @ .156.

[Spooner]

Yes, that was a great thread and so many people came in and shared. I learned so many things from that thread and my 1322 build thread. 

About porting the barrel and enlarged transfer ports. Wyoman explained to me that there was no benefit in doing this below .22 caliber. I do not know the reason why, but he is extremely knowledgeable, so I trust that opinion. Having said that, a aftermarket parts guy told me that there was a benefit claiming that using the larger TP but NOT porting the barrel creates a choke point that will give higher fps. My understanding has always been that the choke point is what restricts fps from being higher. As far as .177 goes, me personally... I leave the stock TP in and do not port the barrel. If I am doing  a .22 build and don't port the barrel I stick with the stock TP as well.
You will have to decide. 

[TheOtherSprocket]

Thanks Spooner - for the .177, the upper parts will remain as-is.  If I do a 22 I'll open up the barrel TP. I've got a Mellon 14" 177 and a Drifter with a 22 14" so I've got options.

I hit a snag yesterday - I tore down the rear cocker completely to see what's going on with the internals.  I realized the bolt was magnetic, meaning it shot BB's - a lot of BB's based on the smooth bore barrel - only a shadow of rifling.  Given the barrels are different on the rear cocking models, I need to decide if I want to have a barrel made, replace the hammer, etc. or just use it for parts...

[Spooner]

Thanks Spooner - for the .177, the upper parts will remain as-is.  If I do a 22 I'll open up the barrel TP. I've got a Mellon 14" 177 and a Drifter with a 22 14" so I've got options.

I hit a snag yesterday - I tore down the rear cocker completely to see what's going on with the internals.  I realized the bolt was magnetic, meaning it shot BB's - a lot of BB's based on the smooth bore barrel - only a shadow of rifling.  Given the barrels are different on the rear cocking models, I need to decide if I want to have a barrel made, replace the hammer, etc. or just use it for parts...

That's a shame with the rear cocker barrel. 

here is another thread with some awesome stuff...
https://www.gatewaytoairguns.org/GTA/index.php?topic=189013.20

[jsk68]

Thanks Spooner - for the .177, the upper parts will remain as-is.  If I do a 22 I'll open up the barrel TP. I've got a Mellon 14" 177 and a Drifter with a 22 14" so I've got options.

I hit a snag yesterday - I tore down the rear cocker completely to see what's going on with the internals.  I realized the bolt was magnetic, meaning it shot BB's - a lot of BB's based on the smooth bore barrel - only a shadow of rifling.  Given the barrels are different on the rear cocking models, I need to decide if I want to have a barrel made, replace the hammer, etc. or just use it for parts...

Mine is exactly the same, it's no longer a priority to restore it...... maybe if I get really bored.