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NP2 transfer port size
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Author:  Sid66 [ Wed Jan 04, 2017 8:15 pm ]
Post subject:  Re: NP2 transfer port size

Image

Author:  Chevota [ Wed Jan 04, 2017 8:32 pm ]
Post subject:  Re: NP2 transfer port size

Excellent! Thanks for the prices too :) Did you actually buy all those parts or just checked?
The melted seal is not uncommon but a new one is always nice, especially since it was no doubt cut and they're so cheap. I'd imagine the welded hole is mostly plugged but I'd finisher off if you have it out.
Not sure if you're interested but the seal on my NPSS is just barely more than .008". I went to .008 and the piston was just kissing the end so I sanded a tad off the dovetail and called it good. But be wary about the warning in the guide and use good judgement. I'd totally push limits and would go all the way, especially with the new rubber baby buggy bumper in that piston, but entirely up to you.

As for pix you can send them to my email chevota at hotmail and I'll edit/resize them so they're both a good posting size and to the point. I can also show you how if you want. Then you can post them here instead of using some linked service which after time seems the pix usually gets lost. I always get frustrated when I find a topic for something unusual (unusual is what I'm usually into) and the thread is or may be exactly what I want but the pix link is broken.
Btw I found some old notes I had and the port was ~.155. So I'd say it's normal considering they often vary .005 depending on how harshly they drilled it.
Your breech face seems to be pretty nice, much better than the ones I put in the guide huh? And btw the pix in the guide were from my NPSS which is the gun the NP2 was based on. I would've assumed that (maybe) they used the same machine and maybe even settings but maybe not. I think the NPSS receiver tube is US made, and don't know about the NP2 but I suspect China. So could be same machine, could be totally diff country. The Xfer port of my two NPSS guns were terrible, very rough like chinese guns so really now I kinda wonder if either are US, or if Crosman is a rough with them as china is.
So anyway, good news I guess. Also please tell me what pellets and weight you're using, and if possible you think you can compare velocity to any other guns. Not via the questionable program, but by ear. It's pretty clear when shooting a gun 200fps diff, even <100 is pretty clear once you get used to it. Reason is I'm kinda wondering about the program.
Also, the spring sounds about what I'd expect, and no I can't budge my NP2 spring either.
Gotta run but will check back in a couple hours, meanwhile send those pix if you'd like and I'll do them and can even post 'em if you like....

Author:  Sid66 [ Wed Jan 04, 2017 8:57 pm ]
Post subject:  Re: NP2 transfer port size

No I never bought all the parts just the gas spring and seal. just got prices on other stuff so I knew what a mistake would cost.Will email pics to you.Not sure about the scientific value of the wood penetration test but my granddaughter's Canadian current model 760 pumpmaster only penetrates half the size of the pellet less than 1/8".Pellets used were 14.3 grain crosman hollow point for the.22 and 7.4 grain crosman destroyer for the .177 pumpmaster.

Author:  Sid66 [ Wed Jan 04, 2017 9:26 pm ]
Post subject:  Re: NP2 transfer port size

On the head space issue am I understanding this right?less head space =more power,less head space means more compression so piston stops softer because increase pressure.less head space=more power&smoother operation unless you go to far and cause metal to metal contact.Just thought about the phone app.It goes off sound so fps. readings would be at target not at muzzle correct?If so my metal target is 100 ft so my fps readings[how ever accurate they are]are for 100 ft not at muzzle.not sure how fast pellets lose speed at that distance.could be another part of my low readings

Author:  Sid66 [ Thu Jan 05, 2017 11:05 am ]
Post subject:  Re: NP2 transfer port size

The breech did not look like that.I spent 10 min with 400 paper on a flat file then another 15 with 1000.The granddaughter's 760 pumpmaster with plugged bleed hole is at least 5 times quieter than the np2.I shot a phone book from 25' with both guns.pumpmaster at 11 pumps.760,pellet 7.4 gr. stopped at 22 pages but made hole to 46 pages,.22 np2 14.3 gr hollow point went 76 pages but made a hole to page 180.This cant be any worse a test than a phone app.LOL.I sanded the melted seal,had to take .015 off to make it flat.So from my initial start of .025 I should have a .010 seal to try.At this point still about .012 over bore size.I sure jumped into this airgun thing with both feet.I have had gun since Dec 25. shot over 800 pellets so far,tore it down to individual components and sanded deburred polished everything,they tore it down 6 more times looking for power.Originally I wanted a .22 gun that would shoot 18 gr around 600-650fps.After spending many hours reading online I thought it would be a good compromise for hitting power, accuracy, and cost.Primary use of this gun is pesting 20' to 30yrd.Doing a lot of shooting right now trying to train my body how to hold the gun.I put small pieces of hockey tape the exact length of my hand on forestock so my hand goes same place every time.The thing that amased me most about the whole process was how easy it was to deform the barrel with a plastic nut by hand no wrenches or pliers.

Author:  Sid66 [ Thu Jan 05, 2017 5:53 pm ]
Post subject:  Re: NP2 transfer port size

i do know what you mean by not worrying about fps readings.Guns are sold by fps rating but it is ft/lbs of energy that does the job.Like car makers sell on HP but it is torque that is important.

Author:  Chevota [ Mon Jan 09, 2017 8:00 pm ]
Post subject:  Re: NP2 transfer port size

Less dead air space in the compression tube (from sanding the seal and or using a better seal if available) will net you more power, better accuracy, less risk of scope damage and be quieter. This may vary with different guns but on avg the std B18 Crosman likes it. But dry fire it once and it may break your scope right there, which is why I mention in the guide
to be careful. So I'd leave it at the 15 thou and continue to look for the real issue, then later you can go further if you want. That # will vary like so many things so you really can only push the limit with you and your gun via trial and error. Same with the transfer port; I'd call it good for now but if you wanted you could try an smaller one to see what happens.
Meaning I believe a smaller one would work better but only one way to find out. How much better would be a guess at best but I do not believe that is your problem.

Check out that link in the guide for Chairgun, which will tell you how fast speed drops based on BC.
The phone app no doubt goes by sound so it would need the exact target distance and air temp to work. Then it would give you an avg speed, not muzzle, which is why I mention Chairgun so you can plug in higher muzzle #'s to get the avg your phone is giving you to est muzzle. Pellets slow down very fast and it also depends on speed and the BC of the pellet, so kinda a pita... So a closer target would give you a better idea of muzzle velocity, but I'd imagine also higher risk of error? I spoze if could also give false readings if the shot echos off something, but I'm just assuming all the above since I've seen the app.

Btw I'd save that old nitro since (based on what you said) it's likely about as strong as a regular B18 Crosman spring but my guess is the NP2 spring will hold air longer since the shaft is smoother. So it might come in handy if you ever buy a B18, especially to convert a coil version, or simply want a lower powered/smoother shooting NP2. Considering the much cheaper price of the NP2 spring (assuming the lower powered one is cheap too) it might be worth it for someone to try it in the regular B18, either a coil conversion or to replace a dead oem nitro. I haven't tried putting one in a B18 but seems like it'll fit. I'd be interested too since I've lost several B18 nitro's and would love a cheaper and better replacement.
The regular Crosman guns can do 650 w/ 18gr if tuned, I have one doing 690 @ ~1000' elevation, so maybe 700 at 0'. Point is an NP2 should do at least 700, but maybe more like 750. That's one reason I mentioned using the lighter spring b/c maybe it'll do 650 and be sweeter all-around? Back burner but keep it in mind...
The 18gr are no doubt better on avg at longer ranges but really the 14.3 are excellent too. All depends on what you want, and I like to get speed up if I can. Like if an 18 passes thru a squirrel then a faster 14 would do more damage. Just a thought. Have you tired the the Crow Magnum pellets yet? If anything you're using is passing thru I'd give 'em a try, even if not I'd still try 'em.
Sanding the melted seal is fine as long you verify the OD is good, which you mentioned you did. Mine was barely oversize... Bizarre how they're like that, which had to have been done on purpose and the only reason I can think of is an attempt to seal up the cuts. One big neg imo was mine were off to one side due to the weight of the piston, so the piston was kissing the receiver on one side.
I don't know if I mentioned it but when I sand a seal questionably thin to bump compression I also sand the face of the dovetail smooth so it'll tell me when it hits. Most people are unwilling to take their gun apart again to check that but since you have been in there over and over I'm guessing that's no problem. It's the cork effect the pellet provides which reduces impact, so a lighter pellet, weaker skirt, deep seating etc will hit harder. Pretty easy to understand, as is what higher compression will do, changes in Xfer port volume, leakage, piston speed/weight, spring strength/rate, ambient pressure, breech to pellet stiction/friction etc. Some alternate ways to est velocity are ballistic putty or possibly duct seal. Putty comes with a chart to est speed, duct seal would likely only be a guess or to compare to a known gun. Then there's the sound barrier which is easier in a 177 but the idea is to lighten pellets 'till you get the SS crack. Of course you need a precision scale to weight down to 1/10th or less grains. Reloader type people have one, but I also scored a digital one on ebay for ~$6 (jewelers scale).
The reason I prefer ftlbs over velocity is most people say xxxfps but rarely say what pellet weight, or they may not even know so then I have no idea where there gun is. Like recently a guy posted some exceptional #'s but apparently it was b/c the pellets and the wt on the box didn't match and they were .5gr or so lighter. Generally the cheaper the pellets the less likely the weight is correct, as is the spread within the tin, tin to tin and lot to lot. So worth it to by good pellets...
Horsepower is just torque X speed so I prefer both when possible ;) I'm like you, backyard gearhead, offroader, all-around tinkerer. Not sure how much torque my Chevota makes but at least 450, maybe 500 if I'm lucky? Then I rev it so get HP too :) I tried lower rpm motors at first but it did NOT work out for me...
With pellets ideal is supposed to ~890-900fps, which is b/c pellets BC gets worse after that on up to SS where it's really bad, so what's a guy to do. I still greatly enjoy 1000+fps, especially at close range with hollow points. I also like to keep my std guns in 177 and mags in 22 so trajectory is similar.

As for noise you can't do a lot, but I'd imagine the 18gr pellets are pretty good. You could try Barracuda which are sweet, but too slow imo. I think 18 is as far as "I" would push it since that's awfully slow, but whatever works for you and if you're like me experimenting is half the fun. So pellet wt plus all those things mentioned earlier that affect power will affect noise too. Basically the less efficient the gun is the more mechanical noise it'll make. The lighter spring would help so one more reason it maybe try it once you get it dialed in.
If you have a syn stock then I'd fill in the hollow areas with nice rubbery open cell foam, both under the receiver and butt.
If you could make the foam so that it seals the cocking slot pretty tight but the linkage can slice thru I think that would be sweet.
The oem shroud assy no doubt reduces sound over no shroud so I'd leave it on.

Author:  Sid66 [ Tue Jan 10, 2017 12:38 pm ]
Post subject:  Re: NP2 transfer port size

Pretty slow @ work right now so I have lots of time.I like mechanical puzzles.worst case is $60 for new piston if i go too far.I don't think I will play with transfer port...yet.The only pellets locally are crosman.pointed or hollow point.my only 2 choices.So far it likes hollow points better.I did weigh every pellet in a can and sorted by weight.the best grouping ones were 14.2-14.4. higher or lower seemed to affect group size.weights ranged from 13.8 to 15.I was thinking about the heavier pellets would prob drop very quickly after about 30 yds. making it less of a chance of pellets leaving my property.Put over 1000 pellets through so far and wife is used to the noise now.LOL.I might try putting the weaker spring back in just to see.

Author:  Chevota [ Tue Jan 10, 2017 7:43 pm ]
Post subject:  Re: NP2 transfer port size

So my guess is the gun is working normally and it was the phone app that failed you... Dang newfangled gizmos... I try to keep electronics on my truck to a minimum too. I do have an electronic ignition but keep a spare points distributor with me for when it fails, which it has done several times. MSD three failures very quickly, Crane too but it lasted >10years.
I think those pointed Crosman kinda suck, or at least aren't as good by a good margin. The hollow point Premier are great other than the hollow point doesn't work so why bother imo, so just consider them round nose with a cosmetic hole.
The Crosman Destroyers do work as hollow points, and you can see why when you look at them but aren't as accurate, lower BC, and don't work as well as the Crow Mag, but as long as you're close enough to be accurate they're great.
Btw the heavier pellets will travel further and do more damage when they hit, but it also depends on their BC. That Chairgun program will give you a visual to better understand the difference, but you can also shoot different pellets at something way off in the distance and note where each hits. You need a dry dusty field or lake to see them hit but it can be a real eye opener how a something like a mid-heavy JSB round nose compares to a light wadcutter.
And let me know if you find a part # on that weaker nitro, I want to order one and try it in a regular B18 Crosman. If it works it'll be great assuming it's the same low price as the full strength. Fyi anyone reading this, I wouldn't put a full strength NP2 spring in a regular Crosman or Gamo etc b/c it's just too strong. The NP2 has a larger 29mm bore so it needs more strength to compress the air than a 25mm B18.

Author:  Sid66 [ Tue Jan 10, 2017 8:07 pm ]
Post subject:  Re: NP2 transfer port size

There were 2 #s on the weaker spring 6-NP214-012 , 201507.I tried the #s @ Gravel and said no product found.Outside dia. of gas spring is.715".

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