GTA
Airguns by Make and Model => Crosman Airguns => Topic started by: Sdparks on August 04, 2012, 06:56:50 PM
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Hello everyone! This is my first post on the GTA forums. I've already gleaned a great deal of info by reading many of the posts here.
I bought a Rem Vantage 1200 (springer) a year or two ago to keep back in TN when I visited family so I could plink in the backyard. It is my first airgun with any serious power, and was fun but the trigger was terrible, so I started looking into how to improve it. So, me being me, that turned into taking the entire gun apart to see what I could do with it. I'm sure I'm not the only person that has happened to, right?
As I was tearing the gun down, I jotted down several notebook pages of "findings" -- apparently making a $100-ish gun requires cutting a lot of corners. Burrs everywhere, rust, rough surfaces, metal particles embedded in the seal, you name it. Surprising that the gun worked at all.
I am looking to improve the shooting experience with this gun. I don't care too much about fps, as this gun is plenty powerful for my needs, and a little speed this way or that won't matter. I'd like the gun to be smoother to operate, and quieter would be nice, and of course accuracy is important. I've already worked the trigger, and converted it to a two-stage pull which I think is going to be very nice when I get the gun back together. I've deburred every burr I could find, and that sort of thing. I'm keeping a list of things I've done, and will share some of the more interesting ones in later posts.
Right now I have a few topics I'd like to get the group's input on:
1) Honing - I see this is recommended in CDT's tuning guide. I used a borescope inside the compression tube, and there is NO cross-hatching where the seal travels. None. Just a nasty hot-rolled steel finish with lots of pits. Yuck. There's an obvious need for some honing here, but I am concerned about getting taper in the end of the bore, where it is hard to hone out as much material as in the middle of the bore. I'm thinking that the right way to think about this is to try to just add some cross-hatching without cutting enough material to change the base diameter. Does this sound right? 400-grit stones are diffcult to find for the 3-stone brake cylinder hones, so I am considering just a brief and light treatment with the 240-grit stones and then some additional passes with 400-grit paper glued to the stones. Any thoughts?
2) I'm trying to keep the cost of the tune down to $50. No real reason, just a self-imposed challenge to not go over 50% of the purchase price of the gun. It will challenge me to figure out how to do improvements on my own, and keep me from buying stuff of questionable value. It seems like the best place to spend money is on the seal, spring and lube. Looks like I can get all of these from one place from JM. My compression tube ID is .985" (at least before honing), does anyone know which seal I should use? On the spring, I know which one has been recommended for the Quest-type guns, but it is harder to tell what the value of an aftermarket spring will be. Longer life? Better fit? Power change? On lubes, it sounds like it would be silly not to use the moly paste and tar.
3) Transfer port - The transfer port is really nasty on this gun. It is over .125" in diameter, and has a really nasty finish on the inside. It also had a burr on the inside end that was so bad I couldn't force a 1/8" rod through it. I got the burr off and rounded the entrance end of the port with a dremel with a rubber abrasive bit (think about how to set that up...) Anyway, the finish in the inside is still bad, should I try to ream it out just enough to clean up the surface, or just leave it alone?
Well, that's enough questions for now. Your replies are much appreciated! I'll keep everyone updated on my progress, and I hope I can contribute as much to this forum as I have already received.
-Stephen
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Let's see if I can attach some pics here... One of the compression tube finish (where the piston has been rubbing), and one of the transfer port inlet after polishing (what were they ramming into the end there?)
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I hone with 800 grit wrapped around paper towels, that are wrapped around a woodend dowel.
Seems to always have worked for me. The key is not doing too much I think.
IF it is Quest in different clothes, then it should have a b-19 trigger group. If it does, then a Tuna trigger should fit it, I would think.
The group is a little tedious to get apart and back together, but should be attempted to at least polish the stamp marks from the surfaces.
Button the piston, and make a custom spring guide. The spring should almost have to twisted on. IF you dont have the tooling for turning a guide....then shrink wrap the existing one. I am a real backwoods redneck, so I use this all the time. I also punch my buttons out of abs plastic or drink bottle plastic with a hole punch. Search buttoning the piston.
I use 1500 grit paper on the spring ends after I shape them nice and round where theyve been cut. THEN I use fiber optic polishing paper, which is measured in microns. REALLY puts a shine on the ends almost like a mirror.
I use moly paste on the ends of the spring, coupled with plastic washers cut out and inserted into piston/on guides. I put heavy tar on the spring, and tend to go heavier with my application than most would. This cuts velocity a little, but makes shot cycle a little quieter, at least for awhile.
Make sure your breech seal is in good shape, and while its apart, you might consider some brass washers in the pivot area.
Most of the supplies you can get from ARH, but you can easily substitute the stock spring seal replacements. They work fine. The piston seal and springs from ARH tend to improve performance a little.
God bless and good luck,
Farmer
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Farmer, thanks for your reply. Ohhhh, the piston. What a mess. The piston is neither round nor straight. In fact, I found that it would get a little tight mid-stroke when sliding it back and forth in the compression tube. I put it in my little lathe and turned off the high spots. This was a little abusive for my micro-lathe due to the interrupted cut caused by the cocking slot. Heck, just figuring out how to hold the warped thing was hard enough. After I had taken off just a few thousandths, I cut a groove near the back end between the cocking slot and the sear slot and made a Delrin bushing to go in there and centralize the back end of the piston. I haven't completely convinced myself that this was a good idea, but the piston now moves very smoothly and quietly in the compression tube, and doesn't get tight mid-stroke, so so far it seems to be an improvement.
The trigger group PN is B18‐05‐00, and a GRT-III will fit it. The GRT-III looks great, but I wanted to see if I could conquer it myself, and I think I've done that. But yeah, without improving the trigger, it wouldn't matter what else you did to the gun. If you can't concentrate on your aim while pulling the trigger, forget it. The stock trigger pull was that bad.
And the breach seal - I should probably get one of those to be on the safe side. The breach faces on this gun are nasty. Lots of dings, some of them on the sealing surface. I haven't determined yet if they are bad enough to cause problems.
-Stephen
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Hey Stephen, I just recently took my Remington Summit 22 apart, just yesterday. Ive been in the very same boat as you! I read and read, got as much info as possiable. My Summit actually looked really good everywhere, except i thought it had very little lube any where inside, which really surprised me. Im going to take some pics of what everything looks like out of the Rifle and post it in a couple of days. The Transfer Port is a good question, out of all the things i read on this Forum and othe Airsmiths Sites, i still havent found anything on maybe Cleaning and Polishing the Port??
Ive messed with Hot Rods in the past and Porting and Polishing the Heads in the Combustion Chamber highly improved airflow and Gas Flow which turns into big Horse Power Gains. So me personally im going to try to just clean and Polish the Port on my Summit and hope for better,quicker,smoother airflow for the Rifle. Im also stuck on a after market spring and seals,but ive seen alot,and i keep running back to James Maccari Site, and probly just get something from him,but it will be a month or 2 i think. Im going to do the Charlie Tuna B19 Super Tune on mine and get some lubes from James M and put mine back together and see how she shoots after that. Pics are coming. Later Good Luck
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Photo of the piston rear bushing I made. The bushing is Delrin, the groove holding it is .030" deep. I'd be interested to know your thoughts on this vs. buttoning.
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Interesting.....
Doesnt interfere with cocking or release does it?
Might create a little more drag, as it has much more surface area than buttons would. Be interested to see if it affects velocity much....if not, leave it till it stops working/fails. If so, remove it, and add buttons.
69GT, I am of the same mind as you are with polishing, smoother port, smoother airflow. Cant hurt.
Just be careful not to remove too much.
Good stuff..
God bless,
Farmer
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No, no interference with operation.
For the transfer port, I turned a piece of drill rod with a very slight taper on it, hardened it, and then rotated that back and forth in the transfer port with some diamond lapping compound on it to clean up the worst of it. There are still some scratches and a few gouges that are way to deep to take out, but it is much improved overall. This process opened up the diameter by about .005". Below is a picture after cleanup.
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The transfer port before lapping.
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The buttoning setup there can work and have seen it done before and as long as the piston is fitted with the compression tube without drag should be good. Transfer port's can be tricky and even a slight enlargment can drop the fps. Several GTA members and myself played with and tested the idea of transfer port diameters a long while back. We were testing the China B3 airgun and after testing found that there is a slight gain with a slight inlargment of the port it wasn't enough to warrant going through the proccess. We slowly increased the port size and the fps dropped like a stone. The airgun designers have found the magic diameter and the best that we could do was squeeze a couple more fps out before the bottom fell out of it so to speak. Polishing it up without removing material would optimize air flow I imagine. Ed
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Thanks for your reply, shadow. Yes, there's always a risk of screwing something up if one gets over-ambitious with good intentions. Hopefully I haven't messed things up too badly.
I think the rear piston bushing will be fine as long as there is no build up of lube in the tube, in which case the bushing would have to scrape the lube forward with it, whereas with buttons the lube could possibly just move aside. Don't think it will be a problem.
With the transfer port, I don't have any "before" fps numbers, and don't have a chronograph for "after" numbers. Maybe someone in Houston can volunteer (hint, hint). Do you remember the specific diameters where you reached the drop-off (not that the number would be the same for a different gun)? I would suspect that with a smoother port, the trade-off point might actually move toward a slightly smaller diameter. I can imagine sleeving the transfer port, if absolutely necessary.
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I know this is a dead thread but I am in the same spot. I either sell the gun at the local pawn shop or I replace the Vantage's nitro piston with a 500-ish fps spring. There is no middle ground.
I am impressed by the gun's consistency and accuracy. It would only improve with a milder powerplant and easy cocking. It's big and heavy and has an atrocious trigger but it works very well and is an attractive package IMHO.
I shoulda bought it .22 but it was my first breakbarrel. I was prepared for a learning experience so I enjoyed it but the cocking effort needs to go down or it's gone. Just because I will no longer shoot ut the way it is. IOW the gun itself is fine. I just think it would be better with less power.
Pointers to a lower powered kit would be appreciated.
Thank you,
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replacing with a spring may be your way to go. order a canadian model spring from crosman (airguns without firearms license are limited to 495 fps) or get a USA spring and cut several coils down. either way you will end up with a very smooth, quiet and easy to shoot springer that is good out to 25 yards. I have used a canadian model in .177 and man o man, what a pleasure it was to shoot. The gas ram you are looking for will come from a rifle with the number 5 or 6 on the model number (B5npblahblah blah...). that would be a direct replacement.
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I know this is a dead thread but I am in the same spot. I either sell the gun at the local pawn shop or I replace the Vantage's nitro piston with a 500-ish fps spring. There is no middle ground.
I am impressed by the gun's consistency and accuracy. It would only improve with a milder powerplant and easy cocking. It's big and heavy and has an atrocious trigger but it works very well and is an attractive package IMHO.
I shoulda bought it .22 but it was my first breakbarrel. I was prepared for a learning experience so I enjoyed it but the cocking effort needs to go down or it's gone. Just because I will no longer shoot ut the way it is. IOW the gun itself is fine. I just think it would be better with less power.
Pointers to a lower powered kit would be appreciated.
Thank you,
Hi, Brent. Check out crosman.com for parts diagrams (EVP) and the phone number to order parts. An older Titan parts diagram lists a 695fps ram. I put one in a new .22 Crusher along with an NP Elite trigger pack and it is a lovely shooter at about 12.5 fpe. I needed to use a spring compressor even for the low powered ram.
The ARH Merlin spring is another option, but you'll need to order a rear guide from a spring powered gun like the Quest 1000x.
Have fun!
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The Air Rifle Headquarters Merlin XL spring is an excellent soft shooting spring for the B19 but it will yield more than 500 fps without shortening it. It will also be a loose fit on the Crosman stock guide. Does a nitro piston have a guide?
An oem Crosman B19 type with spring will have the guide and steel or plastic stepped spacer. That spacer can be modified or replaced to provide less preload and reduce fps. As I recall, my Quest with the Merlin and minimal spacing was shooting 725 fps or so. Easy cocking, easy shooting. It would be less fps with a cut Merlin spring, depends on how many coils are removed..
So you know, I used wire shrink wrap on the metal guide (first sprayed with 3M adhesive to hold the wrap on). Also lined piston with a thin plastic sheet, like from a milk jug. No twang. Merlin XL is a square wire, @ .116" diameter. Sweet spring.
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...Does a nitro piston have a guide?
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It has a hollow guide that the ram fits into.
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No, no interference with operation.
For the transfer port, I turned a piece of drill rod with a very slight taper on it, hardened it, and then rotated that back and forth in the transfer port with some diamond lapping compound on it to clean up the worst of it. There are still some scratches and a few gouges that are way to deep to take out, but it is much improved overall. This process opened up the diameter by about .005". Below is a picture after cleanup.
I know this is an old thread, but I talked to a gentleman that tried chamfering his R1 transfer port for better flow like the OP pictured, but the R1 lost a ton of velocity- presumably from the extra uncompressable volume the chamfer created...
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Thank you all for your input. I just might be keeping this gun and enjoying it :D