GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Topic started by: eeler1 on April 19, 2024, 12:21:52 PM
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Got a project, replacing a barrel (PRod). Original barrel has an internal oring, and I’d rather not fool around cutting an internal groove in the new barrel. So my preference is for an oring on the bolt instead. Seems like many, maybe most, pcp guns use the internal oring. Any reason to go internal v bolt, other than ease of machining for me.
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I wonder myself which is better ???
Have both styles: PROD and 17xx.
What barrel are you going to replace it with?
I use a 20” or 21” LW MROD barrel on my PROD.
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So you did something similar to your PRod? Caliber? How'd it turn out?
I got turned on to 20 cal for pcp guns by Scott S (Motorhead), who has had good results with similar conversions. I did a 20 cal conversion on a MRod using a Weirauch barrel a while back, and it turned out really well, lots of shots and super accurate. Don't know why more people don't try 20 cal, I guess the bigger pellets have everyone under spell.
I tried Krale for a 20 cal LW barrel, but it would have been a long wait for an expensive barrel, like 200Euros. The Air Force barrels were too short for what I wanted, and still pricey. So I went to Air Venturi and got a barrel by Beeman (actually made by Weirauch according to pyramid air). 22 inches choked. Although I had to cut about 3 inches of a larger diameter off at the breech end in order to fit the receiver, so it's 18-19 inches long now.
Still kinda pricey at a little over $200, but I couldn't find any other 20 cal barrel available. Plus this one comes with a shroud that has essentially the same OD as the original PRod shroud. Turns out the Weirauch shroud is threaded at 18mm-1.0mm, while the PRod shroud is 11/16-24, which by chance are compatible with each other.
Right now I'm at the decision point for the barrel v bolt oring.
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It’s almost a drop-in ‘cuz all you have to do is increase the “acreage” on the 2 flat spots for the breech screws, aka file it.
Very accurate 👍
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.22 caliber.
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A .177 MROD barrel would also work if you pair it with a .177 Fortitude bolt and probe assembly.
It’ll be a single-shot though; use a MROD SST, file the base a bit, then voila 👍
My PROD uses .22 MROD/UMAREX Gauntlet SST, but I had to sand the bottom a bit (1 mm or so).
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Got a project, replacing a barrel (PRod). Original barrel has an internal oring, and I’d rather not fool around cutting an internal groove in the new barrel. So my preference is for an oring on the bolt instead. Seems like many, maybe most, pcp guns use the internal oring. Any reason to go internal v bolt, other than ease of machining for me.
If the bolt travels through a magazine, it’s generally best to have the oring in barrel to save wear/tear on the oring. Single shot doesn’t matter so going with ease of manufacture is ok.
Dave
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Got a project, replacing a barrel (PRod). Original barrel has an internal oring, and I’d rather not fool around cutting an internal groove in the new barrel. So my preference is for an oring on the bolt instead. Seems like many, maybe most, pcp guns use the internal oring. Any reason to go internal v bolt, other than ease of machining for me.
If the bolt travels through a magazine, it’s generally best to have the oring in barrel to save wear/tear on the oring. Single shot doesn’t matter so going with ease of manufacture is ok.
Dave
That makes a lot of sense 👍
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A .177 MROD barrel would also work if you pair it with a .177 Fortitude bolt and probe assembly.
It’ll be a single-shot though; use a MROD SST, file the base a bit, then voila 👍
My PROD uses .22 MROD/UMAREX Gauntlet SST, but I had to sand the bottom a bit (1 mm or so).
To clarify, I’ve never tried the PROD-.177 MROD barrel-Fortitude bolt and probe combo, but it’s here somewhere.
It was thread by Mr. John/FuzzyGrub that also included (I think) the Fortitude tube mods, which only requires 2 forward-location additional breech holes to fit the PROD breech.
I have the Fortitude tube (about $30 shipped) but have been procrastinating having it drilled :P
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Yeah, my life would be easier if I'd stayed with .22 cal and just got a longer/better barrel. I already bought a couple of PRod .20 cal magazines for it, from that guy in Croatia, per TennX in TackDriver 10's PRod thread.
https://www.gatewaytoairguns.org/GTA/index.php?topic=213130.msg156518252#msg156518252
That's another thing that got me thinking of the PRod in .20 cal.
Not what I wanted to hear about the oring, but sure makes sense. I'll have to start looking at grooves and id's and the like.
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Barrel bore I.D. groove tools are FUN to make ... Not !!!
Even more fun to use and Not break doing so.
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Barrel bore I.D. groove tools are FUN to make ... Not !!!
Even more fun to use and Not break doing so.
I can only imagine :-[
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So you did something similar to your PRod? Caliber? How'd it turn out?
I got turned on to 20 cal for pcp guns by Scott S (Motorhead), who has had good results with similar conversions. I did a 20 cal conversion on a MRod using a Weirauch barrel a while back, and it turned out really well, lots of shots and super accurate. Don't know why more people don't try 20 cal, I guess the bigger pellets have everyone under spell.
I tried Krale for a 20 cal LW barrel, but it would have been a long wait for an expensive barrel, like 200Euros. The Air Force barrels were too short for what I wanted, and still pricey. So I went to Air Venturi and got a barrel by Beeman (actually made by Weirauch according to pyramid air). 22 inches choked. Although I had to cut about 3 inches of a larger diameter off at the breech end in order to fit the receiver, so it's 18-19 inches long now.
Still kinda pricey at a little over $200, but I couldn't find any other 20 cal barrel available. Plus this one comes with a shroud that has essentially the same OD as the original PRod shroud. Turns out the Weirauch shroud is threaded at 18mm-1.0mm, while the PRod shroud is 11/16-24, which by chance are compatible with each other.
Right now I'm at the decision point for the barrel v bolt oring.
I was going to suggest Airgun Revisions, but you already have the barrel.
I wonder if the LW .20 caliber MROD he sells has the same barrel footprint as that of an OEM’s, thus making it a drop-in.
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Barrel bore I.D. groove tools are FUN to make ... Not !!!
Even more fun to use and Not break doing so.
Exactly! I did the internal barrel groove once, years ago, on a BSA S-10. Must not have enjoyed it as I’ve avoided doing it since.
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Barrel bore I.D. groove tools are FUN to make ... Not !!!
Even more fun to use and Not break doing so.
Exactly! I did the internal barrel groove once, years ago, on a BSA S-10. Must not have enjoyed it as I’ve avoided doing it since.
Can relate to that ... 1st tool I ground near 10 years ago with 5% cobalt HHS. I broke it stupidly using to put in a face o-ring groove not taking into account the radius clearance required :P
One shown I did last year using a Carbide tip tool. Much harder to grind shape, but end result it has been tough, tho always nervous setting it up & using :-\
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Another alternative is to use a flow through bolt. The o-ring is placed in the back of the barrel pocket in the breech. The barrel presses against the o-ring, sealing both the barrel and the bolt.
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Another alternative is to use a flow through bolt. The o-ring is placed in the back of the barrel pocket in the breech. The barrel presses against the o-ring, sealing both the barrel and the bolt.
x2 I did that when shortening a 2240 XL from the breach end of barrel.
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If you are using a magazine, you are pretty well stuck with the O-ring in the barrel.... It's a lot easier to put it on the bolt, IMO, and functionally no difference....
Bob
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If you are using a magazine, you are pretty well stuck with the O-ring in the barrel.... It's a lot easier to put it on the bolt, IMO, and functionally no difference....
Bob
BSA uses o-ring on the probe in their PCPs. There's a lot of those guns and you don't hear about or see any extensive o-ring wear issues due to them going through the magazines. Just put the o-ring on probe and keep it lubed. It's easier to make and when the time comes also much more easier to change that o-ring.