Scope missalignment issue.

[Bushleague]

I have an old Husqvarna 1600 that has some scope misalignment issues. The groups tighten up significantly if I loosen off the rear scope ring, I did some lapping but the problem persisted. So today I got curious and backed off the rear ring cap, and I was able to fit a .0035" feeler gauge between the scope and the bottom of the ring.

IIRC I did ensure that the rifle had the right Weaver bases on it when I first bought it, but I will double check that. I don't think there are many mounting options for these rifles still around. So what to do? Can this be lapped out, should I try shimming the base up, or is there another option?

[prarie_boy1]

Best thing I think if you have access to alignment bars would be to tighten everything up with the bars inserted and determine where the issue lies and go from there. Lapping only gets you so far if there is a gross alignment issue you will just end up removing to much material and get nowhere.

[Dean2]

Originally Posted by Bushleague

I have an old Husqvarna 1600 that has some scope misalignment issues. The groups tighten up significantly if I loosen off the rear scope ring, I did some lapping but the problem persisted. So today I got curious and backed off the rear ring cap, and I was able to fit a .0035" feeler gauge between the scope and the bottom of the ring.

IIRC I did ensure that the rifle had the right Weaver bases on it when I first bought it, but I will double check that. I don't think there are many mounting options for these rifles still around. So what to do? Can this be lapped out, should I try shimming the base up, or is there another option?

If I am reading what you wrote correctly, the bottom of your rear ring is .0035 too low, with the front ring tight, for your scope to sit on it without bending the tube down. If this is accurate then you either need a thicker rear base or you need to put a brass/aluminum shim under the existing rear base. The alternative is to shave down the bottom of the front base. Lapping is not going to solve this issue, you will end up with a front ring that doesn't hold properly. I also would NOT recommend putting a shim in the ring itself to take up the slack.

If you want some help, pm me your phone number.

[Bushleague]

Originally Posted by Dean2

If I am reading what you wrote correctly, the bottom of your rear ring is .0035 too low, with the front ring tight, for your scope to sit on it without bending the tube down. If this is accurate then you either need a thicker rear base or you need to put a brass/aluminum shim under the existing rear base. The alternative is to shave down the bottom of the front base. Lapping is not going to solve this issue, you will end up with a front ring that doesn't hold properly. I also would NOT recommend putting a shim in the ring itself to take up the slack.

If you want some help, pm me your phone number.

Yes, the rear ring is too low. The receiver top (base bottoms) are not flat, so shaving the base would not be simple. Having lapped the rings that are on there, would you recommend starting with new rings and re-lapping once things are shimmed much closer to alignment?

I made some home made alignment bars last week, once I pull the scope off to shim the base I will see if I have any horizontal misalignment as well. Just judging by the way simply loosening the scope cap affects the groups I think the bulk of my problem is vertical.

[elkhunter11]

Beer cans are about .004" so cut a shim from a beer can, and place it under the rear base. Then see how close you are.

[eschafer]

Another option.... Burris Signature Rings with nylon inserts are made for this very problem... They work well to compensate for misalignment.....

[fps plus]

You are using a feeler gauge to measure ,go buy a cheap feeler gauge to use as the shim. You will know exactly what the amount you are shimming

[Bushleague]

Originally Posted by elkhunter11

Beer cans are about .004" so cut a shim from a beer can, and place it under the rear base. Then see how close you are.

IIRC we are both in the same profession, which happens to give us access to some very precise shim stock... no beer cans will be used LOL.

[Bushleague]

Originally Posted by eschafer

Another option.... Burris Signature Rings with nylon inserts are made for this very problem... They work well to compensate for misalignment.....

Burris signatures do not come in "low" size. I need a low ring on this gun to get a good cheek weld, otherwise I would have gone this route.

[Dean2]

Yes, start with new un-lapped rings. Get your front and rear rings to align by purchasing a thicker rear base or shimming the one you have. If you look up the Weaver base info you can find the exact thickness of bases with the same hole spacing. I have on more than one occasion used a different base than the commonly recommended one to get the right front and rear height to match or to gain some MOA by raising the rear.



W.R. Weaver Company Mount Base Specifications
DETACHABLE MOUNT BASES
No. of Base Length Hole Spacing Diameter Thickness
11 .812 .504 1.290 .147
12 .812 .504 .925 .155
13 .812 .504 .730 .238
14 .812 .504 Tapered for Savage 99 only
15 .812 .504 .946 .195
16 .812 .504 .840 .205
17 .812 .504 .770 .219
18 .812 .504 1.050 .182
19 .812 .504 1.160 .125
20A 1.168 .860 1.360 .127
21 .812 .504 .710 .273
22 .812 .504 .700 .201
24 .812 .504 .900 .271
25 .812 .504 1.125 .248
27 .812 .504 .930 Tapered .161/.185
28 .812 .504 Flat .239
29 .812 .504 Flat .292
30 .812 .504 .845 Tapered .205/.230
31 .812 .504 Octag. .182
32 .812 .504 Octag. .357
35 1.168 .860 1.290 .147
36 1.401 .604 3.900 .272
39 .812 .504 Flat .165
40A 1.840 .860 1.290 .147
42 .812 .504 .730 .298
43 .812 .504 .840 .265
44 .812 .504 .770 .279
45 .812 .504 1.050 .396
46 1.168 .860 1.290 .222
47 1.168 .860 2.692 .368
48 .812 .504 1.290 .395
49A 1.058 Win. 70 in 375 H&H, 300 H&H only .368
50 4.500 .504 Flat-Tapered .200/.232
53 4.983 Win. 88, 100 1.290 .222
54 .812 .504 1.290 .222
55 .812 .504 1.050 .310
57 2.340 .960 1.220 .250
58 4.624 3.275 Flat .283
59 .812 One hole only Notched .366
60 4.500 Browning .22 Auto, H&R "Topper" .361
61 1.168 .860 Flat .360
62 4.430 Rem. 740, 760 1.290 .222
63A 6.125 Marlin 336 Flat .283
63B 5.450 Marlin 336 Flat .370
65 2.000 None Spec. * .322
66 2.650 None Spec. * .322
67 1.650 None Spec. * .332
68 .812 .504 .916 .399
70 5.900 Rem 600 1.290 .275
71 1.168 .748 1.180 .215
72 .812 .504 2.590 .376
74 5.723 Savage 24V 1.125 .275
75 1.168 .860 1.050 .310
76 .812 One hole only 1.050 .310
77 .812 .504 .700 Tapered .248/.267
78 .812 .504 .880 Tapered .171/.198
79 .912 .604 3.900 .272
80 6.125 .500 1.892 .147
81 6.000 H&R 360, 361 .946 Tapered .237/.252
82 6.000 H&R Topper 158C 1.050 .396
83 .812 .504 1.252 .250
84 1.168 .860 1.252 .250
85 1.168 .860 1.124 .275
86 .862 .555 .925 Tapered .366/.396
87 5.000 H&R 700 1.050 .400
88 5.900 Mossberg 500AS 1.500 .496
89 .862 .560 1.062 .347Fr/.301Rr
90 5.000 Marlin 39A .300Fr/.428Rr
91 1.400 .504 .946 .280
92 4.500 Thompson Contender Hand Gun .361
93 4.430 Rem 4/6/7400/7600 1.290 .222
94 .812 .500 1.124 .170
95 1.168 .860 1.124 .170
TO-9 4.750 Ruger 10/22 2.000 Tapered .155/.170
TO-10 5.00 Grooved for most 22's Spec. * .175

[elkhunter11]

Originally Posted by Bushleague

IIRC we are both in the same profession, which happens to give us access to some very precise shim stock... no beer cans will be used LOL.

For a test shim to see where you are, the rifle won't know where the shim came from. Put a shim under the low base, and lay a straight edge across the rings to test your alignment, If that gets you where you need to be, you can even purchase commercial precut shims made for the purpose, if it makes you feel better.

https://www.brownells.com/gunsmith-t...t-prod914.aspx

[qwert]

AFAIK,
most/all factory receivers are fully machined before heat treating.
heat treating, combined with residual and internal stresses, can cause distortion and degrade alignment.

IMHO,
All mounts should be laterally level and aligned with the bore.
Shims are a VERY poor means to correct and/or adjust poor alignment (or slope),
I MUCH PREFER to epoxy bed ALL mounts, (and avoid any ‘lapping’ of rings).
Misalignment should be corrected at its source, (usually the receiver to mount interface,) and not at the ring to scope connection.

The Burris Signature rings with curved insert seats are a great idea, but AFAIK are not available with ‘tip-off’ connection to mounts, (which are MUCH superior and allow easy removal from mounts without disturbing connection to scope).

IMHE,
Proper mount alignment is seldom ‘plug and play’.
Alignment of receiver mounting holes can be variable, (especially when not factory drilled)..
It is VERY difficult to properly align and epoxy bed multi piece mounts, as it requires construction of a complicated fixture.

I MUCH PREFER to install properly epoxy bedded P-rails on all rifles.
The P-rail provides fixed slot spacing, and longitudinal & lateral alignment, and greatly assists torsional alignment (when P-rail epoxy bedding is allowed to fully harden before tightening mounting screws).

Once the P-rail is properly installed, the section over the loading port can be removed or reduced if desired/required to increase clearance for top loading and ejection.

IMHO ‘lapping’ destroys rings.
Any rings that have been lapped will require replacement,
(or at very least re-lapping) for proper alignment and stress free connection of scope to correctly aligned mount(s).

Caution: all P-rails are NOT correct 1913 spec.

Good Luck, YMMV.

[qwert]

Originally Posted by Dean2

Yes, start with new un-lapped rings. Get your front and rear rings to align by purchasing a thicker rear base or shimming the one you have. If you look up the Weaver base info you can find the exact thickness of bases with the same hole spacing. I have on more than one occasion used a different base than the commonly recommended one to get the right front and rear height to match or to gain some MOA by raising the rear.

IMHE, using shims or improper height mounts to adjust mount system slope moa is a recipe for misaligned ring to scope tube connection, as both front and rear mounts will be flat (parallel to but not in the same plane or aligned) rather than the required taper, and will result in stress to any scope tube, (don't try this with a Swaro Z3 or Z5 or similar thin tube scope).

Good Luck, YMMV.

[Dean2]

Originally Posted by qwert

IMHE, using shims or improper height mounts to adjust mount system slope moa is a recipe for misaligned ring to scope tube connection, as both front and rear mounts will be flat (parallel to but not in the same plane or aligned) rather than the required taper, and will result in stress to any scope tube, (don't try this with a Swaro Z3 or Z5 or similar thin tube scope).

Good Luck, YMMV.

There is nothing humble about u, never has been. I never suggested using rings that are not properly aligned and sloped. That is just basic common sense. The whole point was to get rid of the misalignment the OP has now. Getting the rear base high enough to make the bottom of both rings level and aligned is the whole point.

[Ariu]

I always apply electrical tape on the bases and rings when I mount the scope. It will fill (small) imperfections and help with scope not sliding forwards.

[Double Dropper]

Epoxy the rear base, I have a slight issue with my custom P-17 Enfield in 300 win mag, the solution was to epoxy the rear with the front snug and let it dry/set up. Its spot on now.

[Pathfinder76]

Originally Posted by Double Dropper

Epoxy the rear base, I have a slight issue with my custom P-17 Enfield in 300 win mag, the solution was to epoxy the rear with the front snug and let it dry/set up. Its spot on now.

X2

[Bushleague]

Originally Posted by Double Dropper

Epoxy the rear base, I have a slight issue with my custom P-17 Enfield in 300 win mag, the solution was to epoxy the rear with the front snug and let it dry/set up. Its spot on now.

K, cool... I was just about to enquire whether this could be done. So I'm assuming that you scuff up the bottom of the base to get the epoxy to stick and use a release agent on the action... did you need to use plasticine to keep the epoxy where it belongs or was this neccessary?

[catnthehat]

Originally Posted by Bushleague

K, cool... I was just about to enquire whether this could be done. So I'm assuming that you scuff up the bottom of the base to get the epoxy to stick and use a release agent on the action... did you need to use plasticine to keep the epoxy where it belongs or was this neccessary?

many of the older gunsmiths used to use epoxy and I watched as My father created dams with Plasticine.
Most of the older gunsmiths I knew as a kid never lapped rings, but used epoxy instead.
Charley McDonald of the 3M Rifle Ranch once told me he used to use it when he built his bigger McDonald Wildcats.
Cat

[obsessed1]

Originally Posted by Bushleague

K, cool... I was just about to enquire whether this could be done. So I'm assuming that you scuff up the bottom of the base to get the epoxy to stick and use a release agent on the action... did you need to use plasticine to keep the epoxy where it belongs or was this neccessary?

I have done this with a few rifles. I did fill screw holes with plasticine but I let the epoxy squish out the sides of the base and just left it a bit proud as it cured then took a diamond stone to the edge to clean it up. Finished it with a strop and jewlers rouge. I used my lap bar as my guide to set my rings but I guess a scope tube would be just as good.

[Pathfinder76]

Use a good non or minimally shrinking epoxy that is a gel. Don’t use too much and you should be able to clean it up with a Q-Tip dipped in rubbing alcohol. It might take a dozen of them, but it should make for a nice clean edge.

[Tactical Lever]

Used Loc-Tite blue thread locker on the bottom of rings once. Easy to clean before it dries. Not sure if it would be as good as epoxy though.

Think I mainly used it for non slip purposes, and I'm sure it was overkill. Changed the scope out later, but it stuck pretty well to the bottom rings even once I took the tops off. Seems to me, it wasn't too hard to clean up after.

Saw thin brass that you could buy in tubes before, but nothing wrong with beer can! *Might* mar the paint if you use it right on the rings, but it probably is a more effective shim that way than underneath. Just fits better, more surface area, and less deformation.

[Double Dropper]

Watched this, looked like a release agent on the screws, built a little dam on the sides of the rear base, did not put release agent on the action or the base, snugged the front screws, loosely installed the rear screws, to ensure proper alignment but not snug enough to impact the epoxy. Let that dry for 24 hours remove all screws and blue loctite them, torque accordingly. I am no gunsmith I just observed this in action LOL, good luck, BTW it has held to date perfectly although I am told this bedding process may have to be adjusted every 3 years or so to be perfect.....