More help with AR2078... barrel band loose

[SeanMP]

I completely agree agree with both of you....It's on the list.

#437 ...Install grub screws on AR breach

[Dukemeister]

I'm wondering if there is room for a couple of 8-32 setscrews, one on each side, immediately in front of the loading port....

Bob

Position 1 or 2...
1 has more meat and may be easier to do.
2 gives more "leverage" and perhaps a tighter fit.

Would 2 #5-40 serve for these 2 setscrews? (I have a bunch and a tap).

[rsterne]

I think using position #2 might position the setscrews below the centerline, which might have a tendency to force the back of the barrel up, or prevent them from staying tight?.... I was thinking on the centerline at position #1 as far back as reasonable, but I haven't checked the back O-ring position so I might very well be talking through the (other) hole in my head right now....

I would think two 5-40s would be fine.... I'd use either 6-32 or 8-32 'cause I have them....

Bob

[AirGunEric]

I would agree with location #1. That being said, even if you place setscrews between a couple o-rings instead of behind I don't think this would be an issue- those rings aren't "sealing" anything really. If you wanted to get really creative- what about putting a hold through the bottom of the loading tray- similar to a Crosman 13xx/22xx breech screw? It's more complicated, and I don't have a QB in front of me at the moment so maybe there's not enough "meat" for this to work- but just another possible idea...

[Gippeto]

Will suggest you remove the barrel and lay it alongside the reciever. Place the grub screws such that they will land in between the orings. Something like this;

|o|o|

Two in the top "should" be enough...can also put two in either side if your overly ambitious, the nervous type, or maybe you just like tapping small holes.

For the record...I absolutely LOVE tapping small holes.

Al

[Dukemeister]

I absolutely LOVE tapping small holes.

Al

That's what he said.

[SeanMP]

I would go with position #1

I would put them barely above centerline at about 9:30 and 2:30. Aimed at the axial center

This would ensure the situation that Bob mentioned does not happen. You don't want the barrel to shove upwards at the rear as it binds the bolt. I've experience this in various attempts to get a tighter connection.

I would not bother dimpling the barrel to get a positive socket. I would stone the end of the allen screw to a nice smooth arc rather than the stock gripping edge.

5-40 would be fine as this is for positioning more so than securing

[Dukemeister]

Will suggest you remove the barrel and lay it alongside the reciever. Place the grub screws such that they will land in between the orings. Something like this;

|o|o|

Two in the top "should" be enough...can also put two in either side if your overly ambitious, the nervous type, or maybe you just like tapping small holes.

For the record...I absolutely LOVE tapping small holes.

Al

Well, thanks for all the advice. In the end I replaced the original grub screw and tapped a 6-32 grub screw behind the original as suggested above. I had to do it at home, by hand, so I was leery about attempting too many and at different points. The result is 100% satisfactory. Except my grub screws are 1/4" long and they stick up 1/8" above the breach. Since I have it scoped I may just drill accommodating holes on the scope ring. I did dimple the barrel to take the second grub screw as well. Sighted it in with the rings mounted at the rear (not perfect fro eye relief) and was shooting ragged holes at 10m, grouping under 1" at 25 yards, and hitting a 4" can every shot (with holdover) at 50 yards! 15 C today so I am back to the backyard shots. Oh happy day....

[SeanMP]

That does sound like a happy day!

Awesome