How can I level out the bases on a M98-based sporter?

Reinstate the bases and post a pix. Looking at your bases they have been fitted to your receiver. A28 is a rear unmodified for the PH 1200 and the A5 is for Cooey 71/Winchester 670 with the parent metal showing (it's been fitted). I've got a ton of PH bases....not many rings. Ring selection is dependent on the scope. Let's get the bases squared away 1st then determine the scope and rings lasts. Ron
 
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Ive put can shims under bases before on level surface. On my K98 it was D&T and they grounded the stripper clip guide down more, so rear base will slope down.. So I used steel putty to build up a level surface.
 
rgg_7 said:
Reinstate the bases and post a pix. Looking at your bases they have been fitted to your receiver. A28 is a rear unmodified for the PH 1200 and the A5 is for Cooey 71/Winchester 670 with the parent metal showing (it's been fitted). I've got a ton of PH bases....not many rings. Ring selection is dependent on the scope. Let's get the bases squared away 1st then determine the scope and rings lasts. Ron
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Here are the measurements. First is the A5 base mounted, dimensions in inches. Second is the A28 rear base, dimensions in inches

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Need to determine the thickness of the front base. Take the front base off and measure front from the underside of the receiver to the top of the receiver. We will deduct this from your 1.506" total. This way we can calculate what has to be done. Ron
 
rgg_7 said:
Need to determine the thickness of the front base. Take the front base off and measure front from the underside of the receiver to the top of the receiver. We will deduct this from your 1.506" total. This way we can calculate what has to be done. Ron
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Receiver measures 33.02 mm, close as I could tell.

Receiver with base measures 38.27 mm, close as I could tell. I'd have to take another gander at it tomorrow and make sure I got all the epoxy cleaned up. I also wasn't sure if the base had a taper to it, I forgot to measure the thickness at each end.
 
The difference is 5.25mm or .2066929" so lets call the nominal thickness of the front base .207". The A5 base originally started life at a nominal thickness of .225" ( from Parker Hale Base Chart) so it most likely has be fitted to the contour by losing .028". The front never was the correct height as it was shy by .020". The difference between your 2 heights ie 1.544 - 1.506" = .038".... that's a lot to adjust. Let me think about this for a couple hours and I'll give you my fix. Ron
 
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rgg_7 said:
The difference is 5.25mm or .2066929" so lets call the nominal thickness of the front base .207". The A5 base originally started life at a nominal thickness of .225" ( from Parker Hale Base Chart) so it most likely has be fitted to the contour by losing .028". The front never was the correct height as it was shy by .020". The difference between your 2 heights ie 1.544 - 1.506" = .038".... that's a lot to adjust. Let me think about this for a couple hours and I'll give you my fix. Ron
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I'll take a measurement again later this evening if I have a chance.
 
Pls remeasure your bases from the top flat where the ring will rest to the apex of the circle (Highest point on the curvature. If your receiver dimensions are correct the difference is .100" (1.298 - 1.198" )? or Let's try this. If you have 1" wide masking tape start to build up under the front base until you get it level with the rear base. This will determine what shim thickness is required for the front or what has to be removed from the rear. No masking tape use cardboard. Let's see what this reveals. Ron
 
The holes in the front base show as off center too.

Just sayin'. Might have been an error that could be adjusted out, might have been done to compensate for an off center drill and tap on the front holes, might have been...???

Might be nothing. But might not.
 
rgg_7 said:
Pls remeasure your bases from the top flat where the ring will rest to the apex of the circle (Highest point on the curvature. If your receiver dimensions are correct the difference is .100" (1.298 - 1.198" )? or Let's try this. If you have 1" wide masking tape start to build up under the front base until you get it level with the rear base. This will determine what shim thickness is required for the front or what has to be removed from the rear. No masking tape use cardboard. Let's see what this reveals. Ron
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The apex of the inner curvature of the A5 base is .2" below the top flat, give or take a couple of hundredths. A little hard to measure it accurately, but that seems to at least be what they were aiming for when they machined it.

I notice the screw holes in the Parker Hale mounts are a bit, well, screwy and out of round. Really wondering if a Williams SM70 base or similar side mount might be my best bet at this point. Although the only choice seems to be obscenely priced WW2 repros or unobtanium, must-be-shimmed, no-longer-in-production SM70s.
 
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Can you post a pix of the bases with the screws in position. The A5 base looks washed out - maybe using the wrong screws? Do the screws pull the bases when tightening them up? Do the go straight in or are they canted.
From pix of holes is hard to tell. Can you just start the screws in the receiver so we can see what that looks like. I'm thinking a higher front base as the rear looks Ok. Ron
 
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rgg_7 said:
Can you post a pix of the bases with the screws in position. The A5 base looks washed out - maybe using the wrong screws? Do the screws pull the bases when tightening them up? Do the go straight in or are they canted.
From pix of holes is hard to tell. Can you just start the screws in the receiver so we can see what that looks like. I'm thinking a higher front base as the rear looks Ok. Ron
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UPDATE:

Took a good long look at everything before I got too busy with hunting season. Ordered a vintage Williams sidemount with quick-detach rings. May go that route instead, as it's less problems to fix.
 
With holes already tapped on top... you will be drilling and tapping more holes on the side? Why not have a qualified smith fix/mount Weaver bases on top...
 
guntech said:
With holes already tapped on top... you will be drilling and tapping more holes on the side? Why not have a qualified smith fix/mount Weaver bases on top...
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It doesn't hurt a thing to have the option in hand when going to see a smith. If the existing holes are as balled up as they appear to my naked eye, why chase 'em? By the time a smith, or I, gets around to buying the oversize bit for the sloppy 6/48 holes, I'd be in for more money than the sidemount cost me ... and I wanted quick detachable rings anyway.

But if a smith figures they can fix existing mounts, they can do so. I just don't have time to tinker with it right now, and if I have to get into milling parts, I don't have the capacity to turn down a scope base.
 
I bought a swede that had a scope mount crooked. I put the rifle in the mill and recut the edges of the bases. Then for good measure i cut the tops. Took half an hour. Fixed.
 
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