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Picked up a pair of Promasters from a member here with plans to breathe new life back into them. I rebuilt my brother’s promaster and really like them. My girlfriend and I were both looking for fieldguns and figured it would be a good direction. Upon initial inspection the reg promaster looked clean and relatively unmolested, and my girlfriend claimed it. The lasoya on the other hand was used hard and put away wet. But as with most first impressions, appearances could be deceiving.
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This one needed everything, and I do mean everything. I spent the better part of a week chasing leaks through every component. Major issues included a disintegrated LPR valve seat that sent debris through the body and noid, main valve seal was gone (some one put and o-ring in there, not successfully), rammer had been disassembled and shaft badly marred, noid leaked from every location, hoses were dry rotted, etc. I put about 500 balls through it today dialing it in. Overall it’s very solid, but I am left with a few questions. My first shot upon air up experiences major shoot-down. Second shot is near field limit and then the symptom resolves. Every air up is like this, if anyone has an idea about that, please let me know. Now, on to the Lasoya.-
It's your LPR. My guess is the piston is sticking on the initial air up. Have you ported the LPR? That might help.
Also check what "o" ring you have on the piston, it should be a #015 90 durometer. Some of these LPRs want urethane, some of them want buna....they are picky. -
I did not port the lpr, but am willing to try. I did replace the piston o-ring with a buna 70. One pro master had a buna in there, the other had a urethane. Both were disintegrated. Lubed with Dow, no leaks and feels to move with out binding. Lpr does respond with adjustment, but very minor tweaks generate large differences in fps. -
I have had pistons that HAVE to use 90 urethane and I've had pistons that HAVE to use 90 Buna. There are kind of kind of iffy tolerances on that part. The only ones that seem to work correctly with 70 Buna are the shocktech pistons with two "o" rings.
PM me your address and I can stick a few of each in the mail for you.
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Awesome you are bringing them back. Sucks that the regular PM needed so much work.Last edited by Super Nova; 04-18-2026, 09:51 PM.Feedback: https://www.mcarterbrown.com/forum/b...ova-s-feedback
WTB: ICD stuff, single trigger electro frames, Gloss lime and purple parts, smoke hoppersComment
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I took both markers out on the field yesterday. Got about 6 hours of play in the rain, sleet snow with temps dropping below 35°F and the guns did not let us down! The promasters ripped all day with not one hiccupp. They do seem a litttle air hungry and of course they really eat through the paint. Both markers are sitting at about 400psi on the hpr’s. I think they’re capable of running lower but I was excited to get them going for play, I didn’t want to take any risks. More tuning will come.Comment
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90 durometer o-rings installed and tested on lpr piston. To recap, the shoot down I referenced prior was severe. To the point that the first ball wouldn’t leave the barrel. This was super annoying because if the second shot was hot, it would explode the first ball. Sometimes the second shot was soft also and would clear them both with out issue. The o-ring swap dramatically improved this symptom. There is still minor shoot down. First shot on each is around 240fps with the second being up to speed. I tested this thoroughly and am very pleased with this result. One shot at 240 upon air up is hardly an inconvenience. As you mentioned, porting may additionally improve this and I plan to make an attempt at that over the weekend. Just wanted to say thanks again for the advice.
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The Lasoya. Set up with the same accommodations as the other. Both have Inception HPRs, EZ ASAs, and Acculock barrel kits.Comment
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So, the pair of promasters has now become a trio….
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The electronics usually go down from being too rough during a battery change or from just letting old paint cook on them for 20 years. If you are gentle and keep it clean they should keep holding up.
I would definitely swap to a chaos if you get a chance, they are only $45 and let you drop the BPS cap to 10 or 11...kind of a must if your field is strick on ROF.
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Well, hope you’re both happy with yourselves. I just ordered a chaos board.Comment
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Amazing weekend. Ran the Lasoya Saturday and the newest one Sunday. Girlfriend ran hers back to back. Went through 5 cases of with zero gun malfunctions. Couldn’t be happier with these things.Last edited by SupraDan; 05-18-2026, 08:21 AM.Comment
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In their natural habitat
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New HPR gauge and Valve spring in the Lasoya. What a sweet gun. Just a hair under 250psi and she’s real happy there. Shooting 280fps.Comment
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Up and running. I think these things are reproducing….
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It will shoot as fast as you can feed it!
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