GTA
Airguns by Make and Model => Benjamin Airguns => Topic started by: Magman116 on February 01, 2012, 09:05:41 PM
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I recently did a full tune on my Trail NP .22. I put a new piston seal on to replace the nicked up factory seal, polished and all that. I did notice when I put the piston in with the new seal, it was very difficult to get in. I had to use a cut out piece of an aluminum can to work as a guide to get it in. I had to drive it in with a hammer and a large dowel. This fit much tighter than the factory seal.
On initial testing, it was averaging 700fps with H&N FTT 5.53's. Before it was about 730fps. After putting about 200 rounds through it, it now averaged 737fps. I thought why, then I remembered how tight the piston fit in the chamber and thought it might be too tight and now as loosed up a bit.
So the question is, how tight should a piston seal be in the compression chamber? If it is too tight, can this seal be saved and ground down?
-Chris
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Many have used a bolt and nut through the seal and chucked it up on a drill press, then use a fine sand paper to fit it properly.
You are getting the velocity it started with, but with more consistency. I would say the compression tube has already sized it for you and no need to resize.
Many have different Ideas on how snug a seal should be... from very light... Where you can move the piston back to the cocked position(rifle apart of course) then put your finger over the exhaust port and it will hold the seal in place but when you remove the finger the seal starts moving down.
Some say a snug fit where the piston stays where you leave it.
The best people to ask is....Ed ( aka shadow), Gene and Bob( aka charlie da tuna) as they are and were professional tuners.
Rob
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Mine was just as tight. The gun performs very well.
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So, it will eventually wear down to a perfect fit?
I will continue to chronograph it to see if it continues to get better.
I did shoot some RWS Hobby 11.9 gr pellets across the chrono earlier and the average was 789fps.
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That is 16.4fpe you are getting with the hobbies.
If you are into hunting, I would opt for a heavier pellet and a domed one if possible. Also the predator polymags are good too.
Between 14.3 and 16 gr you should get at least 15 fpe or more and more down range energy.
But that said, sounds good for a new seal. Yes will wear in slowly.
Rob
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ok, cool. glad it isn't a big deal having it tight.
I have so many types and weights of pellets it isn't funny. I almost always go for the H&N FFT's for target and plinking, and the crow mags for hunting. I am getting and average of 648fps with the crow magnums. They are destroyers on tree rats.
I have a Hatsan Mod95 .22 coming to compare with the Trail NP .22
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the crow mags beat the hobbies at 16.9fpe.
Feel sorry for the critter on the receiving end...lights out.
Rob
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So, it will eventually wear down to a perfect fit?
I will continue to chronograph it to see if it continues to get better.
I did shoot some RWS Hobby 11.9 gr pellets across the chrono earlier and the average was 789fps.
I guess so. Mine seemed to, and is doing great after 250 rounds on it.
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I will get some time tomorrow to shoot. I will put 100 rounds through it and check the chrono again. Even if it is the best it will be I am ok with the fps and especially the smoothness it has now.
Now that I look back on everything I did to my Trail NP, I would say the biggest improvement was the CDT trigger, then the crown job I did on the barrel. The trigger made it much easier to shoot and the crown job made the biggest impact on accuracy.
Overall, the performance is still on par with the stock rifle, but now it is much smoother, easier to shoot and has better accuracy with better consistency. It is still very hold sensitive, so if there is a round that is off, chances are it is my fault not the gun's. I just wish they rifles were made with quality in mind. For the price, I feel the RWS34 is a better all around rifle than these rifles made in China.
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Today I shot about 250 rounds of H&N FTT 5.53's. I chronographed after 100 or so rounds. The average was 739fps. It was a small gain over the last check at 737fps. It is shooting real nice and smooth. At 25yrds I was getting pretty good groups of 10 in less than nickle if I took my time. Then my new Hatsan Mod 95 .22 showed up. You know I had to have a head to head comparison.
I shot the Hatsan about 11 times till it stopped dieseling. Checked 10 shots over the chrono the average was 792fps with the H&N FTT's. So I see the Hatsan has a few FPS up on the Trail NP.
I then proceeded to sight in the scope and check the accuracy from 25 yrds. This Hatsan is extremely consistent and not very hold sensitive. I was shooting <.3" groups at 25yrds consistently with the occasional flyer. I am impressed. I backed up to 35yrds and could still get nice <.5" groups.
I went back to 25yrds and shot 3 groups of 10 from the Trail NP.22 and 3 groups of 10 from the MOD95. The winner hands down was the MOD95. But, the Trail was much smoother and much quieter and the CDT trigger is a dream compared to the Quattro trigger. The MOD95 trigger is better than the stock Trail trigger, but not even in the same league as the CDT trigger. The Trail is very hold sensitive and has more recoil than the MOD95. I would love it If I could put a NP in the MOD95 that can still maintain the same FPS or better. The craftsmanship of the MOD95 puts it ahead of RWS Dianna rifles, fit and finish; it is beautiful! The MOD95 was almost impossible to close the first couple of times cocking it. The lockup is unreal. It is similar to the the Trail's breach lockup, but so much tighter.
I can't wait to do more testing once this MOD95 is broke in.