400 grit why not 1500 grit wouldn't that be better for wearing and sealing property or am I thinking about it wrong
Upvote 0
Tuning FX Impact Mk2/M3 - slower first shot - no reg creep - quasi-scientific analysis
- Thread starter Seeker
- Start date
Gun back together and set back to old tune. Will shoot it over the chronograph in the morning. I used a Viton75. After initial assembly the gun sat for quite a few hours in an untuned state because I had to go shoot my archery league. When I came home I shot it over the chronograph to see if my starting velocities had changed before I start backing the gun down. The good news is my first 5 shots were all fairly tight for a gun that was shooting wide open. No slow first shot. I also buffed the valve rod where the oring sits. In the right light I could see where my PUR oring had been rubbing on the rod so I just polished that area. Everything in there is lubed with Superlube.
Upvote 0
If you have a mirror like finish then there is no way for the lube to stick to it. You can think about it as cylinders in your engine. They dont't have mirror finish. They have honing scratches for the oil to stick.
Upvote 0
Tested after 24 hours my RAW. 1st shot spot on in fps.
Following shots also very close.
Used NBR 90 in my RAW.
Following shots also very close.
Used NBR 90 in my RAW.
Upvote 0
After sitting 24 hours: 938, 946, 942, 943, dup, 942fps. This is a major improvement and unless there is some side effect that shows up down the road, I’m happy with the peek/Viton mod. One will go in my M3 the next time I have the gun disassembled. Glad I got involved with this topic. Hats off to Seeker for pressing to resolve this issue and everyone else who productively contributed. The only gun in my safe that was a shot dumper is healed. My M3 is showing symptoms but the PUR in the gun is still fresh. I will monitor it from time to time to see if it gets worse.
Upvote 0
Hi guys.
I can 100% confirm PUR90 does not work when we want to have a cold bore shot which is 100% consistent. My first shot was 25FPS slower after sitting for more than 24 hours. Anti-extrusion backup peek washer and grit 400 polished rod covered with WS2 did not help. Stiction increase is too significant with PUR90. This issue affects every Impact user who uses PUR90 oring.
My final decision is I go with Viton80. I am worried about its poor abrasion resistance. If it does not last long enough I will replace it with NBR90 which still should be better than PUR90 stiction wise. Viton80 is very, very good stiction wise but its downside is poor abrasion resistance.
It seems that Impact - a hallmark of FX - is improved after being available for many years and owned by thousands of users. How cool is that?
I am going to write a full summary in the first post of this thread with the investigation completed.
I can 100% confirm PUR90 does not work when we want to have a cold bore shot which is 100% consistent. My first shot was 25FPS slower after sitting for more than 24 hours. Anti-extrusion backup peek washer and grit 400 polished rod covered with WS2 did not help. Stiction increase is too significant with PUR90. This issue affects every Impact user who uses PUR90 oring.
My final decision is I go with Viton80. I am worried about its poor abrasion resistance. If it does not last long enough I will replace it with NBR90 which still should be better than PUR90 stiction wise. Viton80 is very, very good stiction wise but its downside is poor abrasion resistance.
It seems that Impact - a hallmark of FX - is improved after being available for many years and owned by thousands of users. How cool is that?
I am going to write a full summary in the first post of this thread with the investigation completed.
Upvote 0
All credit goes to you.
I am making a video containing pros & cones of M3 and this matter is also discussed in the video with your name.
I hope you will be able to watch it soon.
Bhaur
Upvote 0
Well, other members were also involved. I am especially impressed by Bob Sterne's analysis on oring extrusion in balance valves. I claimed that Impact's valve is not a balanced one. However, after double thinking I guess it can be classified as a special case of a balanced valve.
mubhaur, I guess you are still waiting for the first shot with NBR90.
mubhaur, I guess you are still waiting for the first shot with NBR90.
Upvote 0
I watched your video. Very nice presentation based upon facts, not myths. Thanks for mentioning my nickname. Once I prepare the final description of the solution of the issue I will enlist all members which I felt contributed.
Upvote 0
It is important to understand that I use a peek valve poppet and the results I got are with that poppet. I am not sure how it is going to behave with a delrin poppet.
Upvote 0
I understand that O ring sticking issue has no relationship with peek or delrin valve.
However delrin has itself a bit of tendency of sticking on valve seat and getting compressed as compared to peek.
But that seems to be immaterial.
What is your experience switching from delrin valve to peek valve in your Impact?
Bhaur
Upvote 0
My gun has the stock poppet. To rehash my findings, they went like this. While Seeker was testing Viton, I built the peek disc and tested the PUR. The PUR still caused an unacceptable low first shot even with the peek tapered disc. When I installed Viton, I got the same results as Seeker and I believe he got the same results as me when he tried the PUR. Right now my gun is doing the long sit. I just want to see if I can provoke a low first shot if I leave the gun sit for longer than 24 hours. I will shoot it tonight for the 48 hour test. It might be difficult to pinpoint if there is a difference between Seekers peek poppet and my stock Delrin because I’m positive we have different hammer spring settings. He would have to test both at his settings to determine just how beneficial the peek poppet is for cracking the valve after a long sit.
Upvote 0
Are folks that run peek poppets machining those or can those peek poppers be purchased aftermarket?
ever since I got into PCP’s I’ve heard of folks upgrading to peek poppets on all sorts of pcp platforms. If it is a superior material over delrin why hasn’t the manufactures of Airguns incorporated this peek into their valve systems? Curious
ever since I got into PCP’s I’ve heard of folks upgrading to peek poppets on all sorts of pcp platforms. If it is a superior material over delrin why hasn’t the manufactures of Airguns incorporated this peek into their valve systems? Curious
Upvote 0
First shot problem was still there.
@Bigragu, PEEK is VERY expensive if you compare it to delrin.
Upvote 0