Disco loud cracks have me puzzled.

[JTank70]

Hi all,

Having a great time reading and learning here while enjoying my new Discovery.

Today, however, the Disco has me a bit perplexed.  I Charged up the gun 3 times today for 30 shots each charge.
On the first charge about the15-20th shot I got a very loud cracking report from the gun.  It startled me and I noticed that the bolt was in the upward position but still forward.  My brother was with me and we both puzzled over this.

Finished up the first charge with no more cracks.
Second charge of 30 more shots no cracks.
Third charge about the third shot the POI shifted about 1.5" or so to the right from where it had been hitting (@35 yards).
I thought "Wow whats up with this?".
About the15th shot "CRACK" again.  Bolt up but all the way forward again. 
I think I felt a burst of air on my left cheek(I am right handed) but I can not be certain I did because it all happend so fast.

I am wondering if anyone may have some insight or Idea what might be going on?

Here are some specifics that may help:

The gun is about 5 weeks old.
It started out as a .177 and I converted it to .22 about a week and a half ago and 300-350 or so pellets ago.
I was slow and very careful with the conversion and it went well.
The following day I added a .22 cal TKO muzzle brake and it has been working well all along.
I am pumping to about 2100-2200# and shooting down to 1200-1000#
I am using Crosman Premier Hollow Points 14.3gr.
I have not used any oil or anything to promote dieseling.
The muzzle break looks fine too.
When I brought it in I checked all of the readily accessible screws for loosness and all were good.
Nothing stands out.

Now that I think of it, four or five evenings  ago I took a final 2-3 shots for the day after target shooting  and the gun was around 900-1000 psi and the shots seemed oddly powerful.
?

Thanks for any input or advice you can give me.

JT

[Snaab9-2]

Mine does that when the bolt isn't closed properly... has happened a few times while out in the the woods and I get a blast of air on my cheek.  I try to make sure the bolt is closed all the way before taking a shot, especially when I have been walking through a lot of brush and such.

[JTank70]

Thanks,

I am pretty sure the bolt was closed all the way.
When I saw the bolt up after the first loud crack it made me pay closer attention to the bolt location for the rest of the evening.

But, you could be right so I will continue to pay close attention and be careful that the bolt is closed properly.

After reading my own post again and Just to be a bit clearer it is a very loud crack.
My brother said "Like a firecracker" and it is.
It kicks the gun back a bit and seems almost violent.
Just seems odd with the muzzle brake and all.

Thanks
JT

[lloyd-ss]

When you push the bolt into the locked position, does it feel like it locks tight into that position?  Is the o-ring on the bolt in good condition? The pellets aren't oily, are they?
There have been some other posts about bolts loosening with age, but yours is a fairly new gun.  I had to bend my bolt just a tad to maintain a tight seal.
Lloyd

[JTank70]

Thanks loyd,

The bolt feels nice & quite snug when closed.   It takes some effort to open it (although not alot but again "snug" seems to describe the feel).

The pellets are not oily unless they came that way.  But, they do not seem oily.
In Fact they are the same tin since changing to  .22 cal.  
I have about 150-200 left in the original tin.  
So for the last 10 days I have shot nearly every day out of the same tin of pellets.  
300-350 shots in .22 cal and over 500 @ .177 before that with no issue.

The bolt oring seems fine also.  I did order a spare when I ordered the 22 barrel.  I may try changing it just in case.  But I do think the one on there is fine.

I won't have a chance to disassemble the gun until saturday maybe sunday.
I may just do that just to double check my work from the barrel swap and look for loose screw or any sign of an issue.

[rsterne]

Did you change the bolt when you changed to .22 cal?.... The nose of the bolt is slightly different and the O-ring is a different size....

EDIT: WOO HOO.... This is my 1000 th post !!!....  

Bob

[JTank70]

Thanks Bob

I did Indeed change the bolt and o-ring.

They apear to be in good condition as well.
It just seems Odd  to me that to me that out of 300-350 shots it has only happend twice, and recently with 60 or so shots between the incidents.

Happy 1000th!!!

[rsterne]

I'm guessing some oil in the base of the pellet....

Bob

[JTank70]

My bolt is nice and snug but I will give it and the o-ring another look see.

I am going to check for oil in the tin.  
They did not seem oily at all and the tin of 500 is better than half gone.  

I am also gonna dry patch the barrel a few times.

I am going to pay close attention to everything the next couple of uses.

If it happens again I am going to tear it down.
In fact I may just do that anyway.  I guess it couldn't hurt.

Is it common to get some oily pellets in a tin?  
Could it be oil from maufacturing the muzzle brake? Or, would the oil need to be somewhere on the breech end?

JT

[rsterne]

The oil would have to be on the high pressure side of the pellet.... ie in the pellet, transfer port, valve, or air reservoir.... and there shouldn't be any in a PCP, it's a VERY bad idea....

Bob

[jonnnyboy]

That "crack" makes me think something is going supersonic and you really don't want that with an airgun.  A dab of oil/lube just might be the problem.  My Disco would kick the bolt up as well and even sometimes give me a puff of air in the face but I've never heard it make a "crack"ing noise when shooting.

Something is definitely up.  Keep an eye on it during further shooting.
joe

[JTank70]

I'll keep an eye on it all right.

Since everyone seems to point toward oil, bolt or o-ring I will check those things the closest.

When I did the Barrel, bolt, o-ring swap I may have wiped the components down with a patch & light drop of pellgunoil.
I know I never put any "in" the gun or barrel, but I may have wiped the outside parts such as the top of the air tube/ bottom of breech area and outside of barrel before reassembly. 
I do not remember if I did or not but going slow and cleaning up as I go is very much like me.  So , I may have.

It seems odd that that this could be the problem since it has been 10-12 days and many many shots since?

Good info and replies thank you all

JT

[Progun]

JT, I can only add one other possibility to the suggestions you have already received and that is the possibility that your tin of pellets contained at least one or two "pee wees". If that's the case you wouldn't be the first to have that experience. An undersized pellet inserted  into the breech can result in mayhem such as you've described. I hope you get it sorted out.

[JTank70]

JT, I can only add one other possibility to the suggestions you have already received and that is the possibility that your tin of pellets contained at least one or two "pee wees". If that's the case you wouldn't be the first to have that experience. An undersized pellet inserted  into the breech can result in mayhem such as you've described. I hope you get it sorted out.

Thanks for this suggestion Progun

This is a good possibility.
I guess "Premium" would fool me into believing that there is some sort of quality control.
 
It just seems to me if it were the gun or oil in the gun it would have happened more that twice out of 90 shots
 and would not have waited 10+ days to show itself.

I am going to check it all over good though.  Probably Sunday as we have a fairly busy weekend up til then.
I'll post my findings.

If anyone has other suggestions / advice I'll take it .

thanks
JT

[LeadHead]

I agree about the peewee pellet. Like shooting a PBA out of a springer. I don't think it is/was an oil issue. Be safe and I hope you get the issue corrected fast.

[JTank70]

Well,

I took a dry paper towel and checked/ wiped all of the pellets in the tin....no oil at all...bone dry.
upon naked eye inspection all the remaining pellets look good too.
 Although I am sure I would not notice a small size difference that could exist.

I went to run a dry patch through with trimmer string starting at the breech and I could not get the string to move past the TKO brake.  
No obstruction in there but the string was hitting something.
I removed the brake and was then able to use A few patches and got a bit of gray pellet residue on the patches but they were dry.  
Took care and used a soft pipe cleaner up in the breech where the bolt seals and the air nipple are....dry.

The end of the barrel had a bunch of gray pellet residue on the end of it (under the brake).
The crown looks fine.

Looking into the brake from the back about 2-5/8" in was a funnel or cone it was bear metal and looks silvery but even in shape.  
I am sure this is normal and part of the design but I emailed TKO just to be safe and sure.

I have to go to a family reunion but plan to shoot the gun and possibly disassemble for furher inspection tomorrow.

The small pellet theory seems possible but was thinking if this were the case that it would be more commonly discussed around the forums.

Looked at the bolt and oring again too and all seems well there.

?? dunno....... I'll keep y'all posted.

Thanks
JT

[JTank70]

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   

[aack73]

verify that the breech o-ring is there and in good condition.

[JTank70]

verify that the breech o-ring is there and in good condition.

I will do that aack73 thanks for the heads up.

[rsterne]

verify that the breech o-ring is there and in good condition.

Are you talking about the transfer port seal or the bolt O-ring?.... Those are the only two seals between the valve and the pellet in a Disco.... I can't really see how a transfer port seal can be "intermittent", and the OP already checked the bolt O-ring....

Bob