Any one ever heard of the Dynamic PCP air rifle?

[nervoustrigger]

Good point, one of the first things I did was remove the shroud to check the baffles.  I found one barely perceptible marking on one.  Rather than drill them out, I wrapped each one with a couple turns of tape until they were a slip fit to the shroud.  But after reassembly, the wandering POI was still there.

I hope the barrel band fixes your Stormrider.  My FD-PCP was behaving similarly and a 2nd band out near the end of the air tube totally transformed it.  Won’t always be the case of course but it’s a good thing to try.

[Wolverineshooter]

I saw on a youtube video the extra barrel band was installed right at the front of the stock and the owner claim much improved accuracy (he has a drooping barrel issue). I installed at the end of the air tube. I will try a few different positions to test.

I wonder with unregulated air rifles, if the barrel harmonics changes with different air pressure. Regulated air rifles are more likely to have the same harmonics due to the same pressure driving the movements.

[Wayne52]

Jason I think my favorite mold is probably the 217-24-RF mainly because most of my guns are .22, I also really like the .22 BBT's as well as the .25 Magnum hunters as well, those magnum hunters in .25 are really accurate at 40 yards from my DAR25.  NOE makes some really quality molds for sure.  Jason what type of material do you recommend for a probe o ring cause my SPAM16 needs another one already(the harbor freight ones don't last long at all), I'm sure the best would be something durable yet flexible.  I also want to get a stronger hammer spring for it because the original got stressed and lost it's tensile strength, I need one that I'll have more adjustment with rather than cranking it all the way.  That SPAM16 really shoots the .22 BBT 30 grainers very nice at 42fpe and very accurate too.  The Prod actually likes them as well.

[nervoustrigger]

Wayne, polyurethane is the best for bolt O-rings because of its tear- and abrasion-resistant properties.  However EPDM and Buna-N are both good materials as well so I wouldn’t sweat it if polyurethane isn’t convenient to get.  Just keep in mind a harder material doesn’t abrade as quickly so use 90 durometer when possible.
 
FWIW, usually if I encounter a bolt O-ring that doesn’t last long, it’s usually because the bolt and barrel are slightly misaligned.  The DAR bolt, for example, allows a little lateral movement so it can find center and slip into the O-ring without undue abrasion.  Some may interpret it as sloppy tolerances but in my opinion it’s a good design.  Barrels often have a slightly off-center bore and sometimes the bolt itself is slightly off.
 
Regardless, an O-ring in the barrel that seals against the bolt (mag fed) has a harder life than one that’s on the bolt itself (single shot).  Every time it’s cycled, the O-ring has to pass 3 bumps—the head, the skirt, and the bolt—so yeah it really pays to get it right.
 
 
 

[nervoustrigger]

I was chasing a wandering POI...was trying different things with the barrel band and stock to see if I could remedy it.  Still need to test some more, particularly after it has been stored overnight.  That’s why I was procrastinating about taking it down to address the slow leak.  The POI was stable but after reassembly, it wasn’t.

Okay guys, about this wandering POI after reassembly...

The issue stunk of vibration/harmonics or barrel movement so I tried a few different iterations of isolating/coupling the air tube to the stock, and playing with different fitments of the barrel band to the air tube and barrel.  Unfortunately nothing seemed to hold POI for more than a few shots.  Meanwhile I also noticed my first shot after being idle for a while was at a reduced velocity, indicating some prominent regulator creep.

So I decided to go back into the regulator to check things out.  A couple of the things I wanted to look at were the condition of the valve seat surfaces and the O-ring that seals the shaft of the regulator spool.  The valve seat looked fine under a loupe.  To be clear, the seat is where the narrow end of the regulator spool meets the plastic piece embedded into the brass thumbscrew.  Nevertheless, I went ahead and dressed them with 400->600->2000 grit against a glass plate while I was in there. 

Then I removed the little brass ring and inspected the O-ring and it looked fine.  Likewise I went ahead and replaced it anyway given the track record of the factory O-rings.  That's when I noticed the spool was slightly scarred where it passes through the brass ring.  Turns out they were mating with a slight interference fit so I wrapped a piece of 320 grit around a dowel and carefully relieved the opening until the parts moved with a slip fit.  A slip fit because I don't want the spool to have any lateral play, I want it to be guided to the same spot on the plastic seat so it cycles with as stable a setpoint as possible.

I think that fixed it up.  I shot it a good bit this evening.  The POI has remained stable, and the first shot of the day (after ~20 hours idle) was dead on.  So was another first shot after 3 hours.

Let's just say I have my fingers crossed.

[Wolverineshooter]

Again Jason, fantastic job . Hope the fix sticks.

[Wayne52]

Thanks again for some very good info there Jason.  I think it's time I put the -12 o ring in my .177 because it's definitely got a very slow leak and I'd be willing to be it's more than likely the internal reg o ring.  I'm tempted to do it right now but for today I'm going to be using the DAR25 if I manage to get out and that all depends on the rain situation, I'll be keeping a lookout on the radar before I leave though.  Later today I'll be doing some tinkering with my DAR22 because the parts I ordered for possibly fixing the safety should be in the mail today.

[Wayne52]

Good point, one of the first things I did was remove the shroud to check the baffles.  I found one barely perceptible marking on one.  Rather than drill them out, I wrapped each one with a couple turns of tape until they were a slip fit to the shroud.  But after reassembly, the wandering POI was still there.

I hope the barrel band fixes your Stormrider.  My FD-PCP was behaving similarly and a 2nd band out near the end of the air tube totally transformed it.  Won’t always be the case of course but it’s a good thing to try.

The aluminum baffles in the shrouds of all three of my DAR's seem to be one thing they got right with these guns because I haven't had any clipping from any of them.

[Bob Pratl]

Thanks again for some very good info there Jason.  I think it's time I put the -12 o ring in my .177 because it's definitely got a very slow leak and I'd be willing to be it's more than likely the internal reg o ring.  I'm tempted to do it right now but for today I'm going to be using the DAR25 if I manage to get out and that all depends on the rain situation, I'll be keeping a lookout on the radar before I leave though.  Later today I'll be doing some tinkering with my DAR22 because the parts I ordered for possibly fixing the safety should be in the mail today.

I'm curious to see now the 1911 detent fits your DAR safety. Good thinking.

[Lastdog]

Got a replacement 25 the other day. Like a kid on Christmas. So glad to have one back. Of course o-rings failed after a couple of days shooting. Looking on different thread for the o- ring list and now getting eye strain for scrolling. Still have not found it. Anybody know where it is?

[Rat Sniper (AKA: PaulT58)]

James, the o-rings for the regulator and both ends of the air tube are -117 duro90. 

My .25 let go yesterday, all the air went right out the barrel.  I tore it down and all the o-rings looked good, so I suspect it was the valve poppet.  I swapped the cone shaped spring to the valve I previously removed from it, put it back together and all is good!

As for the baffles, I'd still like to try some of Rocker1's baffles in it to see if that will quiet it down any.  I did receive an adapter and put a Rocker1 LDC on it and that made a significant difference!  I'd still like it quieter though...

[nervoustrigger]

James, I put up a miniature O-ring manifesto here https://www.gatewaytoairguns.org/GTA/index.php?topic=146178.msg1521409#msg1521409

Also, Ron (Gertrude) had posted a photo of a packing list with O-ring sizes...you could probably find it fairly quickly with the forum search.  Put him as the author, ring as the search term, in the last 0-60 days.

[Wayne52]

I use -117 70duro on both ends of the airtube, -117 90duro on the outside of the regulator and -012 90duro on the inside of the reg.  Jason also replaced another internal o ring as well on the regulator which I haven't replaced on any of mine.

[BigMike1]

I received my new DAR today.. It had around 1800psi in it so I  Scoped it up and cut one off at the bullet trap.  Immediately started leaking from bleed hole Arr   reg orings.. Ohwell put the good ones in and move on.

[nervoustrigger]

Mike, just a thought reading that description.  Firing would not expose the O-rings on the reg body to any stress, but it does to the reg’s internal O-rings, particularly the -012 size on the top of the brass spool.  Just saying I would not chance only replacing the -117 O-rings on the body.

[BigMike1]

Agreed !  I am going to replace all of them..

[Lastdog]

Thanks guys, had the 117-90s from before. Thought I would get an order together and do them all cause I know the others will be failing soon.
Thanks Jason your list shows what I will was looking for.

[Wayne52]

Thanks again for some very good info there Jason.  I think it's time I put the -12 o ring in my .177 because it's definitely got a very slow leak and I'd be willing to be it's more than likely the internal reg o ring.  I'm tempted to do it right now but for today I'm going to be using the DAR25 if I manage to get out and that all depends on the rain situation, I'll be keeping a lookout on the radar before I leave though.  Later today I'll be doing some tinkering with my DAR22 because the parts I ordered for possibly fixing the safety should be in the mail today.

I'm curious to see now the 1911 detent fits your DAR safety. Good thinking.

Here's that detent/spring assembly that I got in the mail today, I'm thinking I can get something to work here

[Lastdog]

New dar problem for me?
Put the 177-90 Duros I had laying around on the reg and both ends of air tube. Adjusted the regulator some. Loaded up a mag and shoot ten 50 fpe shoots and had a big smile on my face. I was happy to have a dar 25 back in my possession. Put a scope on made a target and tried to zero it in.
Smile faded. Shooting very low and no matter how much I turned the elevation knob could not get it zeroed . Maxxed out the knob. Maybe the scope? Tried two others off other guns and same thing. I’m stumped.
So went in side to the ac and now thinking about. I did have to shim the rings but I did that last time and no problems. Same scope and rings as I had on the one I sent back and worked great.
Even though I could not get the scopes dialed in the gun was shooting great groups,just to low and a little bit left. Never had this problem on any gun before.  Any ideas from you guy will be appreciated.

[nervoustrigger]

The barrel band takes the barrel anywhere the air tube goes so check to see if the air tube pulls down when you install the stock screw.

The other starting question would be, does it group?  It’s low but do 5 pellets land close to each other if you keep a single point of aim?