RWS 350 Magnum - shooting high ???

[AmBraCol]

Well, the 350 Magnum rebuild went very well.  See this post. But yesterday was a holiday and the owner took it out to tweak the sight settings.  He sent me some pics of his targets, at 15 and 25 meters.  See the attachments below.

Now, here's the thing - the rifle's set up with a UGT 3-12X44 SWAT scope mounted in an RWS Zero Recoil mount.  This mount has barrel droop correction built in.  The scope adjustment was bottomed out to lower the impact as much as possible - and the results show on the accompanying photos.  OK.  Let's get rid of the droop compensation by using a different scope/mount combo (didn't have a 30 mm mount with me to try).  So I first used a UTG 1" mount with a UTG 4X32 "True Hunter" (35 yard parallax) scope - but the mount was a high mount.  Oops!  Hitting a mile high, of course.  Back to square one.  Put my other "True Hunter" scope in low rings on the rifle.  Bottomed out the adjustment - and it's still hitting high.  How high?  About 4" high at around 15-17 meters or so.  So we've tried three different scopes, in three different mounts (although the second one I never tried to adjust down as it was mounted too high) - and they all have the same problem, not enough vertical adjustment. 

So we ran the target out to about 40 meters, and were still a couple inches high.  Don't recall exactly and didn't take pics as the light was quickly fading, but there didn't seem to be much drop between 15, 25 and 40 meters, although we were shooting with the vertical setting at its lowest.  That's one sweet (for a "Magnum") shooting rifle, and the trajectory seems to be quite flat, as one would expect from a fast shooting rifle.  The final image is one of a group he shot using 4 mildots of compensation.

Anyway, diagnosis anyone?  Suggestions on getting the point of impact lowered in relation to point of aim?  Right now I'm just detailing facts, don't want my cogitations to cloud the pool of ideas.  :-D  Any help in chasing down the matter is quite welcome.

[mpbby]

I would restart trying to know the actual barrel alignment.

With a flat mount and the scope's adjustments 'centered' (for instance, optically, mirror technic), 3 shots at, let's say, 15m.  Where is the group?

[dtdtdtdt]

Since your iron sight shooting was fairly close and those sights are mounted on the barrel, I would suspect that the barrel to action alignment is wrong.  Perhaps it is over extended and the barrel is not meeting the action properly.

Suggest laying straight edge along the scope rail and action.  See how the barrel points relative to that line. 

Others know much more than me about break-barrels.  I hope you get good advice!

[Roadworthy]

Has the gun ever snapped shut while cocking?  The inertia developed by the fast upward motion coupled with the sudden stop upon closure has been known to bend a barrel in the upward direction.  Check with a straight edge.

[landymick]

You could shim the front mount a little to compensate though I don't like shims on my mounts,i would prefer to get to the root of the problem such as a bent barrel or dodgy scope rail.

[DanD]

Is it possible the barrel got bent upward? Maybe it slipped out of a hand while cocking?
The droop compensation is working against you. Drooper mounts are for when the gun shoots low with a regular mount, but that gun is off so much it seems like it would still shoot high with a regular mount.
You could try a shim on the bottom of the front ring to point the scope higher. Or you could optically center the scope and bend the barrel to point where the scope is aimed.
Good luck!

[Artie]

My two cents and a grain of salt:
I was having a similar problem with a D460 but the poi was too low instead of too high. I almost convinced myself I had excessive droop but I was wrong.
I recommend using one mount only with no shims for testing. Don't mix mounts, don't shim. Kiss principle, and eliminate variables. Doesn't matter if it's a compensation mount or not as long as you can print groups on paper.
All your scopes need to be centered with the same method, no matter what method I.e. mechanical click count, mirror reflection method, or vee block method. If counting clicks visibly verify the clicking is moving the reticle by viewing against a mirror same as mirror centering method is done. Many, many scopes have inactive or 'dead" clicks at one limit or the other, windage or elevation, and those clicks move nothing but the adjustment knob and your fingers. Those "dead" clicks must be subtracted from total click count of the vertical and or horizontal click count.  Now you know the true adjustable range of your scope. Most scopes with dead clicks I've noticed are at one limit or the other, not left and right or up and down. The limit that immediately moves the reticle is the one I start from to count total active clicks and divide by two to determine center.
Of your scope selection, one must be centered and known to be a good scope. Shoot groups of each scope, using the same mount with no shims and compare.
I have a scope that is repeatable, shoots tight groups, and in all respects is a "good" scope except for one issue.  It will not group the D460 where it is supposed and by a long shot.

[dtdtdtdt]

Following dand logic. Try putting the droop mount on backwards.  That would reverse the effect and help analyze the problem.

[Artie]

Reversing a compensation mount will certainly reverse the correction. Both the ZR and RWS lockdown have an arrow indicating the direction of angle drop. The arrow is normally pointed to the muzzle to correct for droop.
I'm thinking that reversing the Bullseye Mount is counter productive to the mounts design and will adversely affect performance.

[dtdtdtdt]

Reversing a compensation mount will certainly reverse the correction. Both the ZR and RWS lockdown have an arrow indicating the direction of angle drop. The arrow is normally pointed to the muzzle to correct for droop.

I have both the ZR and regular lockdown mounts on RWS 54s.  I don't see anything to keep you from trying it backwards.

My bet is the pivot and action engagement with the barrel are a bit funky.  Recall that this was a beater when he started on it. It may have been damaged somehow.  that would allow the barrel mounts iron sights to be on target while the scope mounted on the action could be wrong. 

I went back to his original string about working on this while waiting on FWB300 parts. 

Reply 9 or 10 shows a group fired using some scope he had available.  The target shows the group low and right.  Can't tell exactly but am guessing 1-2" each way from the size of the pellet holes.  Can you try that scope arrangement again???  Idea is to see if it is going the right direction.  Does it have droop correction, is it flat, are the rings backward???
Another possibility could be his repair of the muzzle by spinning it in a lathe may have bent the barrel out of line some how???

[Artie]

Wouldn't be the first time I was wrong. My ZR rests with the sled retracted completely to the rear. The scope cannot move to the rear in this position, only forward. If I reversed the mount the scope could not move forward as designed, only backward.

[dtdtdtdt]

Artie,  You are right on the ZR.  It won't work properly backwards.  I was thinking about my conventional RWS base.  I am going to go find the one I have loose right now to be sure I'm not blowing smoke! 

Ok, I looked at both of the mounts.  ZR and Lockdown.  If you mount the ZR backwards, the recoil will hold the flooting unit against the fixed base making it act like a conventional base rather than absorbing the recoil as designed.  I doubt any damage would be done with a few shots for a test - NOT a permanent solution.  The Lockdown should have no problem mounting backwards and could be a permanent solution if the owner wishes to to it that way.  The best, of course, is to figure out what to do about the issue: bend barrel, adjust pivot point to correct the alignment. 

Another way to test this would be to temporarily shim the front base on one of the flat base sets that he has.  Temporary shims of known thickness can be easily made from a cheap feeler gauge set used in car repair. One "tongue" is long enough to get a couple shims from.  I use ones I had in my tool box from 40+years ago but any auto parts place should have something that would work. 

NOT a permanent solution but a diagnostic tool!!   

[Artie]

Hector Medina's action video of the ZR shows what looks like the action and mount moving, not the scope. Either way, the mount is compensating for recoil or double recoil I should say..
Why I don't recommend shims under the mount is while it changed my elevation it also changed my windage by quite a bit. No amount of fiddling with the shim (s) would remove the unintended windage shift.
A break barrel, unlike my under lever, has the challenge of the pivot point dynamic too...

[dtdtdtdt]

Hector Medina's action video of the ZR shows what looks like the action and mount moving, not the scope. Either way, the mount is compensating for recoil or double recoil I should say..
Why I don't recommend shims under the mount is while it changed my elevation it also changed my windage by quite a bit. No amount of fiddling with the shim (s) would remove the unintended windage shift.
A break barrel, unlike my under lever, has the challenge of the pivot point dynamic too...

The ZR I have is one of Hector's improved ZRs. He built my 20 cal rifle. 

I was suggesting shimming under the scope inside the ring rather than under the base.  Also, not a good way to do things but might help in analysis of the problem. 

[Artie]

I've heard good things about the HM improved ZR mounts. As far as shimming the rings it's a "do as I say, not as I do" thing for me. Only on scopes I'm willing to risk though.

[dtdtdtdt]

Hector drills and taps the base above the rod (back end) puts a Teflon button and a set screw to minimize wiggle in the ZR recoil rods/  Very small changes needed to settle them down.  I understand that the latest version of the ZR doesn't seem to need that treatment?  Not sure on that. 

Dave

[AmBraCol]

Guys, thank you for the input.  I, too, suspect a bent barrel.  While looking for info on the subject, came across this very informative video.  He shows how to diagnose and then to correct the issue if, as I suspect, the issue is an upwards bent barrel.

Will inform as this progresses, the owner lives south of here, next state over.  He won't have a chance to bring the rifle back 'til next week, maybe.  Time, as they say, will tell.  Again, thanks to all for the input.

[Yogi]

Thanks for posting the video!
It made me look up some of his other stuff.

Good for you to help a friend in need.

-Y

[mpbby]

In a way or another, once confirmed the barrel is pointing upwards, I would bend it.

I would take in consideration that the owner already bought the ZR, and it can be a great help regarding the recoils.   So, I would bend the barrel until it has a barrel droop (downwards) to get ‘almost even’ with the built in compensation of the ZR.

It’s a trial and error process.  You have to be VERY patient, and, at each trial, put a lot of force to the barrel.  Then, reassemble the rifle, put the ZR and scope on, shoot about 3 rounds and see the remaining difference between POA and POI. The objective is to get them ‘as close as possible’ without any adjustments at the scope turrets. To this process, the scope needs to be 'centered' (mirror method or counting clicks).   

However, the ‘trial and error’ is stressful.., so, how much close would be ‘enough’?   

The UTG scope (owner) has the 1/4 MOA (1/4" click value at 100 yds).  So, when you still have about 2” between POA and POI at 20 yards, it means you should need about “40” clicks to match them.  Just a feeling.. - it should be ‘reasonable’ when you adjust about 40 clicks over a total of “300+” clicks (guessing).  Anyway, closer, fewer clicks away from the center, should always be better for the scope lifespan. 

In my case, I prefer to bend the barrel forcing its middle point, instead its 'beginning’ (close to the action); although the bent barrel ends being curve, it ‘seems’ to me as a less risky effort to damage the barrel engagement point.

My bending device is similar to these pics (from nced, GTA member).

[AmBraCol]

Obrigado por as fotos, Marcos!  (Thanks for the pics, Marcos - for the non-portuguese readers...) I've a few days to cogitate on how I'll go about it, once I confirm it's actually bent.  Time's running out before we travel, however, so don't know how much time I'll be able to put into the project.  Learning a new skill is always a good thing, however this one's giving me a few butterflies in the stomach before engaging in it...