Suddenly my airgun is really inaccurate

[gunnewb]

Hi,

Not too long ago I bought a QB78 Deluxe. Bought it with some extras, installed a hammer debounce kit, shipped it to get it tuned and installed a sound moderator. It was shooting fine at approximately 700 fps, and perfectly accurate.

A few days ago I brought the airgun to my friend's place. In taking off the scope, he drops the scope and it hits the ground. The gun never touches the ground. The scope appears to be in good condition, so I install it back on the gun. There wasn't a whole lot of CO2 in the gun, so I degass the gun and later on that day, I try to sight it in. I used some Crosman CO2 cartridges with a tiny amount of Pellgun oil on it, as recommended. However, after 20 or so shots I have absolutely no luck sighting it in. I can't even hit my target. I try shooting it at 8 or 9 meters, and all the shots are wild so I assume the scope doesn't work and order a new scope, exactly the same model.

Well today the new scope came in. I tried to sight it in, and even at close range (about 5 meters) the shots are still completely inconsistent. At that range, the shots vary in distance by as much as 1-3 inches! So it appears that the gun is totally inaccurate, but I can't understand why??

Does anybody else have any ideas? As my handle suggests, I really don't know squat about airguns.

[crosman999]

Very sorry for your frustration with the gun,I know from what I have read that the bolt Oring can sometimes fail along with the transfer port seal being crushed during assembly from the factory. Too,when I got mine the barrel was horribly dirty so cleaning it was the first thing I did. These three things could all effect the guns performance. You can find lots of info on this forum regarding this gun and I'm sure others will chime in here. Best of luck and hope you can sort your troubles and get to shooting. I'm very happy with mine and haven't had any troubles. 

[UCChris]

I'd start by cleaning the barrel

[Rivers3Plinker]

I'd start by cleaning the barrel

+1 and actually I get reasonable results sometimes with nothing more than felt cleaning pellets.
I'll fire a couple of them out of my PCP or pumpers ( do not use on springers ) with some oil on the first one and that's it.
If you have a better, more thorough process then all the better, but I'm lazy and start with those first.

[gunnewb]

Thanks for the replies. I went on Amazon and found some RWS .22 cleaning pellets. So I guess I'll try and order that and see how it works. It'll probably come in a few days, and I'll update the thread once I try it out.

I'm just confused as to how the gun barrel could possibly have crud in it though. It was ordered new, had a tune performed on it...the only thing that's been through the barrel is CO2 and pellets.

[UCChris]

Thanks for the replies. I went on Amazon and found some RWS .22 cleaning pellets. So I guess I'll try and order that and see how it works. It'll probably come in a few days, and I'll update the thread once I try it out.

I'm just confused as to how the gun barrel could possibly have crud in it though. It was ordered new, had a tune performed on it...the only thing that's been through the barrel is CO2 and pellets.

Most airguns come with horrendously dirty barrels. Unless whoever did the tune cleaned the barrel out, it's dirty

[gunnewb]

Well, I bought some RWS .22 felt pellet cleaners and put 3 pairs of two pellets through the gun. The pellets as it came out didn't really look all that dirty.

Tried to fire at the target, but couldn't locate where it was hitting, so I put my old scope on and a fresh piece of target paper. I figured my scope probably wasn't damaged by the drop, and it would at least be closer to zero. Groups are all over the place. Shots 1-3 were within 2 inches and shot 4 was something like 6 inches away. This was done at the same distance as before, approximately within 5 meters.

I believe it's only had about 250 pellets through it. All the prior pellets were pretty darn accurate, I'm not sure why the sudden change.

[robertr]

Try shooting a group with the thing on the end of the barrel removed, maybe it got jostled in the commotion.

[Taso1000]

Eric,

I concur with Robert.  Take some shots without the pickle.

Taso

[gunnewb]

Yeah, it might be the moderator.

I looked at the end of the tube and I can see little marks where the pellet at some point hit the edge of it. This is kind of surprising since the moderator is on really tight and I can feel no play at all. I mean it's so tight I haven't even been able to remove it yet so I hadn't thought it could be the moderator.

I'm going to put a little bit of painters tape on the inside rim of the moderator and see if that's where it is hitting.

[The Nutty Professor]

Are you using the same scope rings? Check them if you are for cracks or stripped screws. If it's not a baffle strike that's the next best guess.

[gunnewb]

I did check with a new scope with new scope rings, with the same result. I also tried to shoot the gun at the same spot without sights and was pretty sure it was off.

Well shining a light down the moderator I don't see anything wrong with the baffles. There could still be a problem though. I have to try removing the moderator, but man is that moderator stuck on the barrel. If you have any simple ideas on how to take it off let me know!

[Gerard]

Not knowing how the device was attached to the barrel makes it anyone's guess how best to safely remove it. A bit of heat maybe? Solvents? Twisting one way or the other? No way to know.

[Taso1000]

Eric,

You said you sent the gun to have the moderator installed.  Reach out to the tuner to see how he installed it.  Usually they are screwed on or held with a grub screw or friction fit.  If it is a shroud it can be secured differently.

I don't know how the air dynamics work inside an ldc.  But I think it is possible that if the baffles aren't evenly centered around the pellet path, the uneven turbulence? may push the pellet off its intended path. 

I need to read up on this more because I have a couple ldc's that do this.

Taso

[gunnewb]

It's entirely a friction fit. Basically I used a mallet/hammer to force the moderator over the barrel. I had a tuner tune the gun, but ordered my moderator elsewhere and installed it myself.

Anyways I was told to cut some wood in the exact dimensions of the barrel and use a hammer to tap it out the other way. I'm not going to do that, as I don't have any wood working equipment, but I'll try to figure something else out later. This weekend is busy though as I won't even be in town, so I won't get to try it for a few days.

[Taso1000]

If you have a heat gun it may be hot enough to expand the area of the moderator where it attaches to the barrel.  Hopefully the moderator material will expand enough to allow you to twist/pull it off.

Taso

[kbstingwing]

if you dropped the scope, it's done, it probably damaged it internally, put a "NEW" scope on it and that should solve the problem.............the Gun is most likely fine....think about it... do you change a tire for a broken head light, "NO"............ is the " NEW " scope a New scope or used, are the rings tightened to tight over 20 in/lbs, unless the gun was damage during transport such as (large heavy object on top during transport) try using a laser boresighter to get the scope set close and then resight, if that doesn't do it then it's probably the gun.

Disregard this Post, I missed the first part of the original post and didn't read it all, got distracted from what I was doing. sorry.....

[Gerard]

He has stated that the gun shoots just as wildly with a different scope, and that he thinks it's just as bad without a scope. So clearly not a dropped scope problem. The moderator is badly aligned, end of story.

[kbstingwing]

I missed that part, got distracted and over looked the rest of the posts
so Disregard my last post please, Sorry.........

[MJP]

Barrel band tight? Breech and barrel tight to the frame?