GTA
All Springer/NP/PCP Air Gun Discussion General => Air Gun Gate => Topic started by: UlteriorModem on November 07, 2018, 08:39:25 PM
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Before I get started I was not really sure what sub forum to put this in. Sorry.
Now, I have read a lot about how folks have had their guns 'tuned' or tuned them themselves, and how they were overjoyed with the results.
I have a vague notion of what goes into tuning but not really a full understanding. For instance I know that for springers they coat the spring with some kind of grease that deadens sound and dampens vibrations. But what about gas pistons?
What brings me to this is I am going to knock down my Benji Titan and have a look inside. "dang" thing is just so inconsistent I cant stand it. Tried different scopes, ammo, etc. It just wont shoot a good group. Yes I checked the screws, yes I use an artillery hold. I can get good groups out of my Mayhem but not with the Titan.
So what is involved? Smoothing and deburring? Changing ports? etc etc
Also I saw it mentioned somewhere to line the compression tube with some sort of grease? I thought you used silicone lubricant for Gas Piston?
Thanks in advance :D
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Tuning is just the natural progression of being an airgun enthusiast. You are going to tinker. Airguns fill 2 roles for us:
1. Serious tool, like a firearm, but fills a nich
2. Tinker toy!
You really don't know what you're missing! The troublesome Titan is about to become your favorite thing to play with and soon the rest of your guns will fall victim, err, get upgraded as well!!
I would start with a breech seal shim of dental floss. But if it used to shoot well then I would suspect piston seal or maybe the breech lockup. Piston seals are cheap, from Crosman or aftermarket upgrades from ARH or Vortek. Might as well debur and lube with moly while you're in there, and try to get you an aftermarket drop in trigger. Also brass washers for the breech.
This is the gateway to the real addiction. You can turn one of these rifles into a really great shooter with a few simple tricks and it really feels good to do it yourself and maximize the gun's potential.
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Eliminate sharp edges - especially the cocking slot. Clean all old lube from the compression tube - I suggest brake cleaner or similar solvent. Get a new piston seal from Air Rifle Headquarters, not Crosman. Ensure it is the correct size - two or three pounds of pressure to move piston and seal through the compression tube. If you lube the compression tube with moly lube wipe it out before reassembly, leaving just a film. I prefer to burnish molybdenum disulfide powder into the tube. Put a film of moly lube or Krytox onto the piston seal. If there is any slop side to side with the barrel fabricate some bronze pivot washers. Purchase and install a replacement trigger from charliedatuna.com. You'll have a different gun.
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How is the crown looking on that Benji Titan ?
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Already put a CDT trigger in the gun, I could not stand the stock trigger.
How is the crown looking on that Benji Titan ?
Forgive my ignorance but "Crown" ?
Oh yea also I have heard about the brass pivot washers, I need to look into that as well. Is there any good how to out there?
Eliminate sharp edges - especially the cocking slot
How do you do that? Just run some sandpaper or something down the slot?
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The crown is the edge of the bore where the rifling exits the muzzle.
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I'm all for tuning but must ask, does your Titan have open sights and if so, have you tried shooting groups on paper at ten yards with the open sights instead of a scope? If your groups tighten up with open sights you can begin to narrow your problem down before opening the gun up.
I believe the Titan is based on the B19 clone (originally Gamo). If that's the case you really need to troubleshoot the barrel pivot & lockup before digging any deeper. The B19 pivot can be problematic, stray shots, bad groups, not at all unusual with those guns. Can be difficult to correct too, depends, gun to gun.
If you have open sights mounted, do yourself a big favor and do some target shooting on paper first.
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Already put a CDT trigger in the gun, I could not stand the stock trigger.
How is the crown looking on that Benji Titan ?
Forgive my ignorance but "Crown" ?
Oh yea also I have heard about the brass pivot washers, I need to look into that as well. Is there any good how to out there?
Eliminate sharp edges - especially the cocking slot
How do you do that? Just run some sandpaper or something down the slot?
Sandpaper works to debur the cocking slot. I prefer a chainsaw file. A lot of people like to use a dremel.
I used to really try to smooth the out. All you really need to do is break the edge. The cocking slot is stamped and it can leave a nasty bur that will cut you like a razor. Piston seal doesn't stand a chance, almost always gets nicked when installed at the factory.
Edit- also wanna break the edge on the holes for the retaining pins. Pretty much any holes or slots in the tube. Much easier to protect the new piston seal from damage.
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The crown is the edge of the bore where the rifling exits the muzzle.
I had a look at it and frankly it is hard to see. It is slightly recessed into the muzzle break. But for the most part it seemed okay if not a little rough round the edges. But nothing mis shapen or flash type defects were obvious.
If you have open sights mounted, do yourself a big favor and do some target shooting on paper first.
The gun does not have open rear sights. At least from the factory. I have tried two different scopes on it with basigally the same results. At first I thought I had a bad scope, swapped it out for a known 'good' scope and not much changed.
you really need to troubleshoot the barrel pivot & lockup before digging any deeper.
These seem to be fine, however I will take a closer look. But there is no side to side wobble and the lockup seems tight and consistant.
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I'm guessing the Titan's power relative to its light weight isn't going to make for easy groups (advertised 1200 fps & 6.75 lbs).
Checking your crown (if you can get to it):
-If your muzzle brake is non-removable your out of luck or grab a hacksaw and get to cutting.
-First try twirling a loosened up cotton swab where the rifling meets the crown. If it leaves some cotton behind when withdrawing the swab you have a burr that needs removing. The burr will throw a pellet off.
-A bad crown may not snag cotton, it may not be concentric (round) or it may be restricted.
-Push a pellet through from the breech. If the pellet stops hard at the end of the push and the pellet head is at the absolute end of the barrel (almost protruding out), you have a constricted crown that needs massaging with some polishing compound to open it up barely.
-A constricted crown is not the same thing as a "choke". A choke will cause slight resistance as the pellet approaches the crown, maybe 1/2-1 1/2" before the end of the barrel. Don't mess with that, it could be a good thing.
-A non-concentric crown (out of round) requires recrowning. Do a search here in the forum on how to.
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Thanks for all the help so far.
I had a chance to put a few more rounds through it today and it is still all over the place.
I went and got the Mayhem and it shot nice and true so something is up with the gun.
I did check the pivot pin and noted some slight movement so I will look into that this evening first.
Yes I cannot really get to or inspect the crown due to the muzzle break. I can see any practical way of removing it (the brake) no set screws or any such thing.
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Well what do you know. I 'think' I may have found the problem.
But first I did manage to get the muzzle break off. For anyone in the future that wants to get that off of their Benjamin Titan NP you just have to twist it … really hard to twist at first. One of those rubber jar lid grippy things helps a lot! It is just kind of slip fit on there. Oh and the crown looks fine.
Now to the 'problem' as it turns out the pivot pin, which is just a bolt with a slot head in it was loose, very loose! In fact I think the only thing that was keeping it in there was that it was rubbing against the stock! The slot head of the bolt actually had some wood shavings in it from rubbing against the stock. The stock even has a slight divot in it where that bolt had been rubbing!
So I got it apart and also found one of the pivot washers had a small 'thread' of material hanging from it. One of the pivot pin holes had some burring around it, quite sharp and had been digging into the pivot washer all this time. I fixed that with some sandpaper.
Now I am ready to put it back together with some locktite on the bolt, but had a question. What would be the best grease to use there?
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Keep your eyes on the pivot bolt to see if it backs off (unscrews) after several cycles. That's the Achilles heel of the b19 type air rifles. There is no nut on the other side of the breech block opposite to keep the pivot bolt from twisting. Not absolutely necessary in all cases (Norica's are the same but better built) but it is good insurance never the less.
Use the screwdriver slot on the bolt head as a visual index. Ensure it does not walk counter clockwise after several cocking cycles.
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Thanks I put some blue locktite on it and going to let it dry overnight. Will keep an eye on it. Using the slot as an index is a great idea.
I will check things out tomorrow.
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What is tuning?
Years ago I asked the same question. Was told it was like getting out of your old Datsun (look it up) and buying a brand new Nissan of similar size and quality. The doors close with a a soft smooch instead of a bang. Brakes are crisp and don't grab. Acceleration is smooth and consistent.
How to tune is different. But asking what is a tune is kinda like asking 'what is hip?' (tell me tell me if you think you know!). You'll just know.
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From the conversation thus far I'll surmise this is specifically for a Benjamin Titan NP. I've attached instructions for brass or bronze pivot washer construction for any Crosman - NP series gun. They work on the NP2 series as well.
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Thanks for this thread! I have a Titan as well and it needs some help. I accidentally broke the stock but have an optimus stock coming from Crosman. I have filed all the edges smooth and don't feel any burrs. I did notice the piston has some wear near the seal the black paint in worn down to bare metal. Should I be concerned over that? I am going to clean out the compression tube and order a new seal from ARH. The stock seal pretty much just slides right into the compression tube with no force needed, no where near 2-3 pounds of force.
I tried to remove the barrel but it isn't coming off, I think the pivot bushing slide to one side. What do you guys use to push a pellet through the barrel? I ran a qtip around at the end of the barrel/breach and no cotton got snagged should I still do the pellet push test?
Edit: So I just went ARH but am not sure what seal will fit the titan as they don't list it or any crosman guns for that matter. How would I determine which seal is needed?
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Thanks for all of the help and suggestions. I will probably do the brass washer thing and have a closer look at dressing the crown, once I get the spring compressor, seal, and lubricants all together for a knock down tuning.
In the mean time I can report that after tightening the pivot pin and the thread lock it is shooting much batter. Can stay in a 1.5" circle for the most part at 20 yards, still the frequent flyer rewards though :(
Still does not like CPD's at all, it shot H&N FTT's and JSB jumbo pretty well. Seems to like the bigger heads eg the CPD's check out right at and sometimes under 5.50, the JSB's check out at around 5.52, and the H&N check in at 5.55 average.
I got 5 dozen rounds through it before the rain was coming and the pivot pin did not move at all. Guess the blue lock tight worked. For now.
I will probably have all the parts and tools by next week sometime so stay tuned :)
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Glad it's coming together for you Tom. After the pivot pin fix (and others you do in the future) the pellet it likes will often change. Be sure to try them all after you're done working on it. Hopefully it still likes the cheapies!
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I found the seal at Vortek but it says no lube required http://vortekproducts.com/ourstore/Airgun_piston_breech-seals/Crosman_Benjiman_Airgun_piston_seal (http://vortekproducts.com/ourstore/Airgun_piston_breech-seals/Crosman_Benjiman_Airgun_piston_seal) should you still use some sort of lube on it and the inside of the compression tube?
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I was able to find a Crossman seal at Pyramid air. Other types have been suggested but I will see how it is when it arrives.
Quick question … what size screw for recrowning a .22 cal? Or is it not all that critical?
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The critical part is getting a brass one with a ROUND head. I think a number six or number eight should do nicely. It simply needs to be large enough not to fit into the bore. You want to polish the perimeter of the bore where the pellet exits, not the bore itself.
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Thanks for the input everyone. Still waiting on the tools and parts for the full tear down and 'tune'.
But I did the breech thing this morning. It was easy.
The results? At first I was cursing shooting about 2 dozen JSB's they were all over the place "Nothing has changed" I thought.
I switched to some H&N FTT's and things started to tighten up some. I dont know if it was the pellets or the fact that there had been a couple of dozen rounds down the pipe after the thorough cleaning I gave it after the crowning.
Lastly I switched to CPD's I was pleasently surprised to see things tighten up nicely. 3/4" group at 20 yards, and it was a little breezy. Still have a few flyers come out, way to many like 1 in 5 or 6 or so :P This gun sorta liked SPD's when I first got it before it went south. I am glad that it does once again. Hope to sort a tin tonight and try to weed out the potential flyers.
Anyhow I wish I had gotten better pictures, should have used my camera instead of my phone. Oh well the deed is done.
(https://farm5.staticflickr.com/4873/30875230497_965db51a20_c.jpg) (https://flic.kr/p/P3kCmi)20181110_121639 (https://flic.kr/p/P3kCmi) by Tom Whit (https://www.flickr.com/photos/152306872@N04/), on Flickr
Before, told you it was not a good picture. But there was no 'crown' per se. It was just flat off, but it was clean but what the heck I cant hurt anything right?
(https://farm5.staticflickr.com/4839/31944212818_809bf36ea9_c.jpg) (https://flic.kr/p/QENrxY)20181110_123751 (https://flic.kr/p/QENrxY) by Tom Whit (https://www.flickr.com/photos/152306872@N04/), on Flickr
After.
I wish I had a buffing pad but forgot to pick one up, I will do that later.
So thanks again and stay tuned :D
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That should help, looks better, I would put 20 or 30 through it and see hoe it holds up.
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Been having similar problems with my Titan. Just checked the barrel and I have no noticeable side to side movement but I tried up and down, what a mess. Lockup not worthy, no wonder my shots were rising and falling so badly. Any advice would be greatly appreciated as I will be tearing it down shortly to address this and doing a full tinker, oops I mean tune.
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Been having similar problems with my Titan. Just checked the barrel and I have no noticeable side to side movement but I tried up and down, what a mess. Lockup not worthy, no wonder my shots were rising and falling so badly. Any advice would be greatly appreciated as I will be tearing it down shortly to address this and doing a full tinker, oops I mean tune.
Take the stock off and check the pivot pin / screw. Bet it is loose!
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Been having similar problems with my Titan. Just checked the barrel and I have no noticeable side to side movement but I tried up and down, what a mess. Lockup not worthy, no wonder my shots were rising and falling so badly. Any advice would be greatly appreciated as I will be tearing it down shortly to address this and doing a full tinker, oops I mean tune.
Take the stock off and check the pivot pin / screw. Bet it is loose!
Bet it is
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I had to work on a Hatsan 125 that had less than snug lockup-it also showed no lateral movement but a light tap on the bottom of the gun would cause a visible change at the point where the barrel block met the receiver i.e. barrel tilting down. I removed the barrel and removed the lockup pin. The hole was full of shavings/debris and the pin itself was rough. Cleaned it all out, polished the surfaces of the pin, and shimmed the spring before reassembly (if you do this make sure that the pin will still compress fully into the hole). Improved lockup on that rifle dramatically.
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Well after the Titan sat around a day or two I took it out this afternoon and was quite pleased at it's performance. Maybe it just needed a nap after all the putzing around with it :D
(https://farm2.staticflickr.com/1969/45802320442_31abe77225_b.jpg) (https://flic.kr/p/2cMoS93)20181112_172901 (https://flic.kr/p/2cMoS93) by Tom Whit (https://www.flickr.com/photos/152306872@N04/), on Flickr
From 25 yards with Crossman CPD's and H&N FTT's it was a little breezy and a few flyers Those are roughly 2" targets.
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Well after the Titan sat around a day or two I took it out this afternoon and was quite pleased at it's performance. Maybe it just needed a nap after all the putzing around with it :D
(https://farm2.staticflickr.com/1969/45802320442_31abe77225_b.jpg) (https://flic.kr/p/2cMoS93)20181112_172901 (https://flic.kr/p/2cMoS93) by Tom Whit (https://www.flickr.com/photos/152306872@N04/), on Flickr
From 25 yards with Crossman CPD's and H&N FTT's it was a little breezy and a few flyers Those are roughly 2" targets.
Very respectable. I'd take it for $100.
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Heh that image is on its side. But I got a kick out of the top middle in that orientation... I had it surrounded :D
Speaking of 100 bucks, that's about what I paid for it, a pyramid air one day sale with some bullseye bucks!
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Tom, that's respectable shooting for a $100 gun with only a few different types of pellets.
I will randomly buy different tins of pellets since I always end up with surprises. My CZ springers likes any RWS pellet. It also likes Crosman domes, but it ain't so good with JSBs. I tried 13 different pellets before I shot groups I like in this gun. Of course I had to go through half my box of tins before I got to the RWS pellets, but then it was like, AHA!
My Hatsan 95QE gas-piston has a hankering for Polymags and AA/JSB domes in the 25-to26-grain range. I got lucky and these were only the 4th pellet I tried. The Hatsan 19.91 domes in .25 were too light for my tastes, though reasonably accurate. Still, MAJOR difference between those lighter pellets and the gob-smacking Polymags.
My first B-3 underlever was a horrid clunky twangy abortion of chinese pallet-lumber, poorly-stamped metal, and a retarded machining job for the receiver, yet after less than an hour of effort, it evolved to far away the most brutally accurate airgun considering the 10# trigger. I passed it on without a true tune (I just degreased the spring and cleaned the leade and crown) and the current owner takes a few pests a week with that thing using simple .22 Crosman domes. It impressed me so much I bought a second B-3 that was in every regard(except shooting) a much better example, and I ended up wrapping that piece of excrement around several trees. Sometimes, you just cannot win. It gave me $40 worth of tree-wrapping excitement, at least.
I had a Crosman Optimus .22. Twangy until degreased, and once recrowned, it stopped liking Crosman domes and developed a taste for JSB/AA domes. Anything over 15 grains but under 19, really. Right now, it puts meat in the fridge during Winter squirrel season for the current owner.
My point is that you tweak the stuff you can, like the leade (where you load the pellet), the lock-up, the crown, and make sure the screws are tight, but in the end, you gotta play around with a lot of pellets to find the magic combination. Some airguns, there's just no explaining why they prefer a certain pellet. For example: My 392 pumper loves Gamo Redfire... I just roll with it.
So when you tune an airgun, be sure to do one thing at a time and then do some shooting with as many pellet types as you can, because sometimes you get surprised.
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So the spring compressor showed up and a few small hitches with it but I managed to get the gas spring and piston out. The seal looks to be in pretty good shape.
Once I get the compression tube cleaned up and some sharp edges attended to it will be time to put it back together.
But I am a little confused as to which grease to apply to the actual piston.
I have some PTFE grease "Super Lube" will that be okay?
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I crowned my rifles (deep target crown) before I ran across this:
https://rifleshooter.com/2018/03/do-rifle-crowns-matter-does-a-crown-effect-accuracy/
Kinda makes me rethink some of the things I "know" about the universe.
Then again, it might just be one random crazy person with a very lucky series of shots.
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So last night I got the spring compressor and decided to tear down the Titan.
I have to admit I was not prepared for what I encountered. What a frustrating, time consuming, and mentally exhausting task it turned into. Mostly due to unfamiliarity with the mechanics, but a lot due to the spring compressor itself.
I wont go into fine details but suffice it to say it took me over 4 hours start to finish, several dropped tools, some crawling around on the hands and knees looking for C clips, stuff like that. I will probably do a separate review on the 'rail lock' spring compressor but in a nutshell, it works... sort of, and not all that well.
A couple of stumbles where I got it all put back together and it would not cock due to the trigger assembly not being installed correctly. It is frustraing to be 'all done' but not.
In the end I got it all back together and it works, however I think I may have the gas piston in backwards :P
I will look into that tonight and weather permitting (doubtfull) run a few rounds through the chrony and accuracy tests to see if all this was worth it.
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To me, the frustrating part was that mine didn't really need anything major inside.
Other than a light deburring, the main parts were pretty nice.
My trigger was where the tuning paid off. Got my sears to a mirror finish and the trigger pull is so smooth now.
I'm glad to see you making progress. I've ripped mine down 3 times now and can just about do it without any references.
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The original question has not yet been answered.
Here is an attempt.
Tuning an air rifle is the improvement of air rifle performance by the repair of production defects, the repair or replacement of substandard or defective parts, the improvement of the function of parts to the satisfaction of the user.