I'm at a loss and very frustrated (1377 issue)

Tater · December 27, 2015, 12:54:00 AM

I've been fighting this problem for a while and I'm out of ideas.
The issue: The gun shoots way low and left at only 20'-25' feet away. I have a Crosman steel breech and a 12" barrel. I've tried two different scopes and it's the same issue with both. I injured my back (badly) last week, and just now got around to putting on a Davio 3D barrel band. The barrel band locks everything in beautifully and the pump arm finally has zero wiggle to it but the POI is still way off. I've tried a stock barrel band and free floating the barrel too but it's always the same.

The only "fix" so far has been adjustable rings, but they only fit a red dot and I'd rather use a regular scope now that I have an AR stock on the gun. I never really liked the idea of aiming the scope sideways and up with rings to compensate for other problems.
Has anyone ever had a steel breech that just wasn't machined right? The barrel is probably too short to be bent as much as the aim is off. What else could it be?

P.S. The beech and barrel seem level and aligned straight, no visible problems.

Brutuz · December 27, 2015, 01:00:43 AM

Try a poly seal valve to breech, icemaker tube

BigTinBoat · December 27, 2015, 01:03:28 AM

Other then the breech being drilled off center the only thing I can think of is the barrel being drill off center. Whats it look like on the end? Is it centered on the barrel?

Gary · December 27, 2015, 01:51:53 AM

Have you checked the ring to dovetail fit to be sure one or both rings are fully seated? If you have a length of 1" dowel, mount it in the rings so that it extends to the end of the barrel so you can see if the barrel and dowel line up. Another thing I have done for misaligned rings is to turn one of the rings 180 degrees on the dovetail.

And, one more check for ring alignment can be done with two sections of dowel by mounting one in each ring so they meet in the center of the dovetail. If everything is correct, the dowels will mate uniformly. If this is not the case, then the rings can be lapped (or replaced).

Have you tried another set of rings? And, does it shoot low and left with iron sights? Almost forgot, Burris Signature rings with the proper offset inserts can fix the problem too.

It would seem to me if the breech and tube are in alignment, the problem lies with the dovetail or rings. But, whatever the reason, it'll be interesting to know how you get it corrected.

Tater · December 27, 2015, 02:17:56 AM

Thanks guys. A poly tube transfer port came to mind but the breech seems perfectly flush to the tube. The barrel seems to be center drilled and it looks like it's coming out of the breech centered.
I mis-typed in the first post, it's actually shooting low and right by about 3".

Tater · December 27, 2015, 02:30:10 AM

Quote from: Gary on December 27, 2015, 01:51:53 AM
Have you checked the ring to dovetail fit to be sure one or both rings are fully seated? If you have a length of 1" dowel, mount it in the rings so that it extends to the end of the barrel so you can see if the barrel and dowel line up. Another thing I have done for misaligned rings is to turn one of the rings 180 degrees on the dovetail.

And, one more check for ring alignment can be done with two sections of dowel by mounting one in each ring so they meet in the center of the dovetail. If everything is correct, the dowels will mate uniformly. If this is not the case, then the rings can be lapped (or replaced).

Have you tried another set of rings? And, does it shoot low and left with iron sights? Almost forgot, Burris Signature rings with the proper offset inserts can fix the problem too.

It would seem to me if the breech and tube are in alignment, the problem lies with the dovetail or rings. But, whatever the reason, it'll be interesting to know how you get it corrected.

I've remounted the scope several times and it does seem fully seated. I also tried a red dot with a mount similar to this red dot and it's hitting way low too. I tried turning the regular scope rings around and swapping front to back.
I have Sun adjustable rings on it with a smaller red dot but I want to use a scope now. I haven't tried open sights because I don't have a rear sight for a steel breech and my eyes are pretty bad anyways.
All I can think of the dovetails like you mentioned for windage problem. The low shots, I have no idea.

BillK · December 27, 2015, 02:36:15 AM

How did it shoot before the steel breech was added? Can you switch it back to the plastic breech for a comparison?

Tater · December 27, 2015, 02:41:29 AM

Quote from: BillK on December 27, 2015, 02:36:15 AM
How did it shoot before the steel breech was added? Can you switch it back to the plastic breech for a comparison?

It shot "OK", but I had to grind/sand a lot off the bottom of the rear sight. Not sure if I had to take off more or less material then most people have. My eyes aren't good at all with open sights these days.

JMJinNC · December 27, 2015, 03:00:08 AM

Is it consistently grouping shots low and right? If so, it's not a bad crown or pellet damage issue (assuming the pellets load fine). If you have a laser bore sighter, you can see where the barrel is aiming versus the scope.

I use chairgun to calculate scope to bore angle, then shim my rear scope ring according. This assumes you know muzzle velocity of course. Then, with the scope optically centered, You should be pretty close to the laser dot at a specific distance (may not be your preferred target distance BTW - tan of the angle, etc.).

If you're not even close, then obviously there's an alignment issue. Scope to rings, rings to each other, rings to dovetail, dovetail to breech, or barrel to breech.

Sounds daunting, but this way you eliminate variables until only one variable is left.

I don't know if this helps you, but this is how I go about it.

JMJ

Tater · December 27, 2015, 03:11:40 AM

Thanks JMJ. The groups were fairly consistent but I admit I didn't take too many shots today, my back hurts that bad. It shot good groups when I had the adjustable rings on it so I don't think the barrel is an issue, unless it's possible a 12" barrel could be bent. Unfortunately I don't have a bore sighter, but I did optically center the scope with a mirror.

mudduck48 · December 27, 2015, 03:53:18 AM

Where did you get the barrel? Anyone got another 12" barrel they aren't using to send him? Let's help this member out.

Gary · December 27, 2015, 03:58:45 AM

Maybe it's been addressed somewhere already, but, how does it shoot with the factory barrel?

Tater · December 27, 2015, 04:46:07 AM

I think it shot OK with the original barrel Gary, but it's been a couple years since I had it on. Not even sure where it is now but it's in the house somewhere.
The gun shot fine with this barrel using the Sun adjustable rings and a red dot, but the hosps and chipmunks are very cautious now when the patio door is open so I want to shoot further back from the door now that I have a (cheap) scope and butt stock

DaveB50 · December 27, 2015, 07:06:08 AM

Have you tried tightening just the lower scope ring halves on the dovetail, and then laying the scope in them to see if it's sits flush and even in both rings? Does the poi change much from 15' to 30'?

Tater · December 27, 2015, 09:17:24 AM

One of the times I mounted the scope, I did start ith the lowers and the scope seemed to lay in fine. I shot earlier from about 20-22' and I'm afraid to go much further back. The target box is only the size of a sheet of paper and I'm shooting from the hallway to a bedroom so I don't want to hit a wall.