Disco loud cracks have me puzzled.

[JTank70]

I took it that aack meant the transfer port seal. 
At least if that is the seal below the tiny nipple/coupling that goes from the air tube to the hole in the barrel into the breech. 
I recall giving it a good look when I did my change to .22 cal and being careful to get the nipple back on right side up.
The seal looked good then. 
I used Gary's write up on the swap over and it was a good guide to follow.  Thanks Gary!

I am just going to tear the gun down as far as I went when I did the barrel/bolt & oring swap.
I just want to be sure things look and seem fine and Since I have a spare bolt o-ring I might just change that too.
After I am satisfied that things seem well, I am going to shoot the gun being extra attentive to details such as how a pellet feels going into the breech (loose/tight).

[sawtoothscream]

hmm never had that happen with my disco.    let us know what it is if you figure it out

[shadowr1]

I emailed Mike at TKO.
He promptly emailed me back with an invite to call him on the phone.
He was a great guy and I could tell he is a very smart man.
The pellet residue on the end of the barrel is normal and the "bare metal" look on the inside of the brake is also just pellet dust collecting there as well and also normal.  
He offered to look the brake over a put it throught a few tests.  
Oh, and get this, he also offered to pay the shipping both ways and replace my brake with a new one even if he finds nothing wrong with mine just to give me peace of mind I guess.
After talking to Mike I have confidence that the brake is probably fine but I may mail it to him since he said he would like to check it over too just to be sure all is well.
Great service, great guy, thanks Mike.

I think sometime in the next day or two I will disassemble the gun to give it a good look over then do some shooting with it and see how it goes.

Thanks for listening
JT  

That right there is A+++++ customer service. I have a TKO break and like it just fine.

[JTank70]

hmm never had that happen with my disco.    let us know what it is if you figure it out

I will let you know.

Part of me hopes to find something on the teardown to explain it.
Part of me hopes to find nothing and not have it ever happen again.

Thanks
JT

[JTank70]

That right there is A+++++ customer service. I have a TKO break and like it just fine.

Agreed

[JTank70]

Just an update,

Here was the original plan:

1. 30 shots as is with muzzle brake NOT installed
2. 30 shots as is with muzzle brake installed
3. Unassemble/inspect/reassemble gun
4. 30 shots with muzzle brake NOT installed
5. 30 shots as is with muzzle brake installed
If the Banging shot re-occurs at any time, adjust plan accordingly.

Here is where I am at so far:
The only thing I have done to the gun is remove the muzzle brake, loosen and re-snug the barrel bands screws and dry patch the barrel.

1. Fired 30 shots the brake not installed. 
Shots 1-5 and 25-30 were plinking.
Shots 6 thru 25 were at a target with 4 bulls (5 each bull). 
The shots were grouping low and large but grouping non the less.

2. 30 more shots with the brake installed.  No other adjustments or changes to the gun or scope.
Shots 1-5 and 25-30 were plinking.
Shots 6 thru 25 were at a target with 4 bulls (5 each bull). 
The shots were grouping low still but seemed maybe just a bit tighter.
The targets looked nearly identical.  Minor differences I am sure were me and not the gun.

3. 30 more shots.  Brake still on.  This time with intent of sighting in.
Used 3 targets 10 shots each target.
Getting a bit windy out and it is shifting direction and speed often.
Managed to get close to zeroed in with quarter size 10 shot group at 35 yards (shots 21-30).

Here's a Few observations:
1. The POI shift throughout the 30 shots was much much less than I had grown used to over the previous 400 rounds (barrel bands??)

2.  I  noticed that some pellets "felt" different when pushing the bolt forward.  Some as if there was not even a pellet there and others just "snug" , and still others "tight" feeling.

3.My brother and shooting partner has a Beeman RS2 Break barrel. 
He was paying close attention to how his pellets were loading. 
Of course his pellets are pushed into position by hand so he has a better opportunity to "feel" how the pellet loads.
He saved out 3 pellets for me to try loading once we were done shooting.

Pellet number one actually fell into the loading position and did not even have to be pushed in at all.
It also fell out when he turned the gun over and gave it a slight shake.

Pellet two had to be almost forced into place.  I mean tight. No way that pellet was going to budge without firing the gun or a push rod.

Pellet three went in snug, did not feel too tight or too loose and felt "right".

All three pellets came from the same tin  of his, and we both got our .22 cal Crosman Premier Hollow Points from the local Wal-Mart.

So,  That's where I am at so far.

No more loud cracking shots yet.  At least out of 90 so far today.

At the moment I am also leaning toward the "pea wee" pellets or just &^^& pellets from Wally's as the cause of the issue.
I suppose a couple of pellets in the tin could have had oil on the from the factory too. ??
I just have a feeling the gun itself is fine though.
I plan to finish zeroing later on today with 30 more shots.  We'll see how that goes then I'll decide wether or not to move forward with a teardown.

I had already ordered a chrony that should be here Wednesday and the other day ordered some JSB Exacts and Crosman domed's.
It'll be fun to see what different pellets and a chrony can tell me about the Discovery.
I also have one of Art Bradens power adjusters.  I just don't want to put it on and try it out until I know the gun is good to go.

Thanks again for listening.

[JTank70]

Did 60 more shots this evening with no incident and have yet to tear the rifle down.
150 shots and 5 air charges today alone.
I think it is fine.
Still doing quarter size groups at 35 yards but with some work and practice I think I can tighten that to somewhere near dimes.  
I really feel as though the pellets I am using are less than consistant.

I think I am going to hold off on the teardown until next weekend unless it happens again in the mean time.

I have a chrony coming wednesday and some JSB's a day or two after that.
I will get some good stock numbers with the chrony and if everything is still good I will install the power adjuster and do the adjustable trigger two screw mod.  
When I do those two things I will check all the other screws and such.

Thanks for all of your suggestions and advice.

I'll update more as I go.

JT

[aack73]

I think you got it. probably was a small pellet. those jsb's should work well. hopefully the disco likes them.

[JTank70]

I think you got it. probably was a small pellet. those jsb's should work well. hopefully the disco likes them.

Thanks.  I hope it likes the jsb's too.
It still sort of puzzles me that I would have 2 pellets that were too small in the same tin.
You would think that if it were that common it would happen to others and we would hear about it around the forums.
I am just glad it has not happened again, no one got hurt,and it seems to have not damaged my gun.

Thanks
JT

[rsterne]

I've had tins of Crosman pellets where some were so small they fell right through the barrel.... while others were fine.... Poor quality control....

Bob

[JTank70]

I've had tins of Crosman pellets where some were so small they fell right through the barrel.... while others were fine.... Poor quality control....

Bob

Thanks Bob,


There was definately 3-4 different sizes I would have to say.

I was wondering if it was because they came from Wally's, or if I had gotten them from say Pyramyd would they still be that way?  Also if the cardboard boxes of Crosmans are any better?

So many people say their guns shoot the premiums well but I guess in some guns it could just be a flyer.

I was also wondering if it could be possible for some of whatever lube is in the hand pump to get into the air chamber?

I just lay the Disco on the carpet when I pump it up.

Like I said part of me is just happy it has not repeated itself and the other part wants to find a definite answer.

JT

[lloyd-ss]

All the pellets in Crosman box will have come from the same swaging die.  Definitely more consistent.
Lloyd

[JTank70]

Good to know lloyd, thanks.

I already have 2 tins of Premium Domes on order dang it.
I was wondering why the boxes were so much more.
I suspected they were better but did not know the difference.
I'll get those next time to try.

JT

[Tad]

I'm not clear about the discussion about oil on the pellet.  PCPs don't diesel that I'm aware of.

Dry fires can be quite loud, and I would think that a very small pellet might have the same effect.

In Chrony testing, my Disco gave the fastest fps (840 fps with CP) on the 22nd shot, shooting down from 2,000 psi.  I was surprised, as 8 shots later the fps was less than 800 and falling fast.  So, your impression that the later shots seem more powerful may be correct. 

[rsterne]

PCPs don't diesel that I'm aware of

PCPs operate at higher pressures than springers.... If there is oil anywhere in the air passage between the valve seat and the back of the pellet it could detonate when you pull the trigger.... In a 3000 psi gun, the pressure will go from 15 psi to nearly 3000 psi in about 1 millisecond....

Oil in the filling system or in the gun itself can potentially cause an explosion as well.... particularly if the filling is too rapid.... Pumps have exploded on at least two members here because they were lubricated with motor oil....

A non-regulated PCP like a Disco typically gets louder as the shot string progresses, peaking about 2/3 - 3/4 of the way through.... although even at the end of the useful string (shots 25-30 in a Disco) the gun will still be significantly louder than the first half of the string....

Bob

[JTank70]

I am going to Blame it on the small "pea wee" pellet for now I guess.
90+ more shots today and no trouble.


JT

[Tad]

Bob-It's a poor day when you don't learn something.  I was ready to argue that PCPs can't diesel, because the compression isn't done in the gun.  The pressure is released, so it's a net cooling effect.  I would buy it in a pump, since this is where the compression is done. 

But you are right, for an instant, air is compressed behind the pellet.  There have been explosions in filling the reservoir (containing oils) from a scuba tank, so it certainly is possible while firing.

[rsterne]

YUP.... the main air charge is expanding and cooling.... but the air in the transfer port is being compressed and superheated during the shot cycle.... By the time you get to the muzzle, the air is cooler than what you started with in the reservoir, and the temperature in the reservoir drops a bit as well.... but for that split second, between the valve seat and the pellet, the air is compressed and heated enough to combust any fuel present....

Bob

[aack73]

Bob, what about nitrogen. Will this make any difference? With hpa or even a springer your using air which has oxygen in it.

[rsterne]

Pure Nitrogen can't support combustion.... so even if there was some fuel present you couldn't get an explosion/dieseling.... That is how the Cardew brothers determined that springers got a fair chunk of their power from combustion.... They put a springer in a bag full of pure Nitrogen, cocked it and shot it repeatedly and the power was way down.... Took it back out of the bag and the power came right back....

Bob