New AR2078a... Questions.

[nc527]

Hey guys,

Just joined GTA after buying my first air rifle in a long time(mostly due to the high ammo prices at this time), and decided to go with a AR2078a from Archer Air. It arrived monday and since then, I have been putting it through its paces. My best group so far was a bit smaller then dime sized at 10m. I also went today and bought a 2.5lb co2 tank to bulk it with, but it turns out the fill hose that comes with the gun does not fit my 2.5lb welding tank. Ill be going back to the welding supply tomorrow to hopefully figure out a solution.

I have a few questions, so I figured this would be the place to ask.

1. I can see the breech seal protruding a bit on the left side of the gun, but not the right. Is it normal to be able to see the squished seal? Mine is white/clear, so I assume that @SSS$$$ replaced the factory one before he shipped the gun.

2. When I close the bolt, the last 1/4'' or so sometimes requires alot of force. I mean to the point of me having to tighten down the stock screw, or the gun would shift forward in the stock. What can I do to get rid of this?

3. I have a basic understanding of what to do when tuning these guns, but I was wondering, what do I polish/round off to smooth out the cycling of the bolt. It feels like sandpaper right now.

Thanks guys, hope you can deal with another air gun enthusiast in your ranks.
Ryan Baker.

[ac12]

I would contact the dealer about #1 and 2.
He might be able to also help you with #3.

[QVTom]

#2 may not be atypical.  QBs and the Crosman 160 they were copied from cock the hammer on the closing stroke of the bolt and do require some force.  My 7 and 9 year old kids can't close the bolt on their own.

Tom

[nc527]

Took a pic of the left side showing the breech seal. Its not that bad really, but It was just weird to me that I could see it on one side. Of course, if it is a factory seal, it could have just been squished off to that side a bit. I just want to make sure nothing is twisted or bent.

[AmBraCol]

When you said "breech seal" I thought you were referring to the seals around the barrel.  I've not handled a QB78 yet, but that does not look normal.  That would be the transfer port seal, if I'm not mistaken.  You might want to check and see that it gets lined up properly.  You can see it in the file attached below, it would be number 1500.  Things should be well centered when assembling and apparently this piece did not get that treatment. 

[nc527]

Is there anything to keep the whole barrel from twisting in the breech, other then the set screw? Im beginning to wonder if I might have done it when I was fitting a tight muzzle break to the gun and I had to twist to get it back off.

[Raizer]

I'd guess you have cocked the breach over a little on the tube, I've done it before tightening my LDC, need to remove the barrel and loosen the breach screw and rear trigger screw a touch to sit it on the tube straight again.
Or if its not leaking don't worry about it.

[AmBraCol]

Is there anything to keep the whole barrel from twisting in the breech, other then the set screw? Im beginning to wonder if I might have done it when I was fitting a tight muzzle break to the gun and I had to twist to get it back off.

My understanding is that the barrel is held in place with the orings and a set screw.  I don't know if the set screw even has a "dimple" or a flat to help orient and stabilize everything in place - my guess is that it does not.  In which case you might very well have twisted it around while messing with the muzzle brake.  It should be fairly easy to set it all back in place.  Loosen the appropriate screws, line everything up and tighten it  down in place.  I'd be tempted to make a dimple or a flat where the set screw contacts the barrel to help prevent such things in the future.  But again, I've not yet had a chance to play with one of these so my opinion is based on "general principles" rather than direct experience with this particular family of rifles..

[Raizer]

There is a dimple in the barrel where the set screw goes.

[AmBraCol]

There is a dimple in the barrel where the set screw goes.

I figured there SHOULD be one... but now there's the "DUH" moment...

The issue isn't the barrel twisting in the receiver, the issue is the receiver twisting above the valve tube.  A well fastened barrel in the receiver isn't going to change that.   The seal is still visibly out of shape, however.  It'd be good to have it well centered between the valve and the breech.

[Raizer]

The issue isn't the barrel twisting in the receiver, the issue is the receiver twisting above the valve tube.  A well fastened barrel in the receiver isn't going to change that.   The seal is still visibly out of shape, however.  It'd be good to have it well centered between the valve and the breech.

That's what I was trying to describe in my post

[nc527]

Thanks for the advice guys. I have one more day before going on vacation, so Ill use it to just shoot the snot of it before leaving. Oh, and Ill order a seal kit from charliedatuna so that when I get back I can open her up for surgery.

Just for giggles, what kind of velocity increase will I see from a full polish of all internals, breaking those 90degree corners, drilling out the bolt probe, notching the valve washer, and adding extra holes on the valve end?


edited for language