To lap or not to lap ???

carlchevalier

carlchevalier

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Just got my rifle from ATRS. Should I have the rings lapped to install the scope or not? They are TPS 30mm on a 20 moa ATRS rail holding a nightforce scope.
 
I was reading the NIGHT FOFORCE SCOPE INSTRUCTIONS.

The say no laping for the unimount. They state you may lap if needed for the steel rings. They recommend a gunsmith though if you are not comfortable.

There is a complete page in the owners manual about lapping.
 
You should have pretty straight base so as long as the action is not wonky, you shouldn't need to lap.

If the action is wonky, Burris Sig ZEE rings will solve your woes.

I do not like lapping as grinding well machined rings to make them out of round and likely oversized seems like the wrong thing to do.

Besides, if you ever need to remove those rings, they may be useless even if installed on the same wonky action/base.
Jerry
 
Jerry, I am always interested to see your input on discussions. You certainly don't follow conventional wisdom and always have an out of left field common sense view. Keep em coming!

I was all set to get my rings done too :D
 
Most rails are properly made.
Most actions are bent from heat treating.
Put a straight rail on a bent action and what do you have?
 
Posted this previously on optics forum. Recently installed 2-piece IOR M1913 bases on a Sako M591 and IOR 30 mm rings. The initial lapping process produced chatter, as only the rear edge of the rear ring was making contact with the bar. After considerable effort, the rings were showing about 90% contact. Mounting without lapping in this cases would have a ruined a Nightforce BR12-42X56. This is standard procedure with gunsmiths.
 
Sinclair used to provide instructions with kits. We are looking at having these made in Canada, and due to amount of waranty problems, proper installation may become a condition for Sightron. This is being discussed.
 
carlchevalier said:
Just got my rifle from ATRS. Should I have the rings lapped to install the scope or not? They are TPS 30mm on a 20 moa ATRS rail holding a nightforce scope.
Click to expand...

IF it was a stock 700 action and someone elses rail, I would agree that lapping would be required.
Given that we completely trued your action including aligning the scope mount holes to true center of bore and then fitting 1 of our rails which I know has less than .001 total deflection in it, I would set the lap bar in to the TPS rings just to settle in your mind that the rings are true.
TPS claims that they hold their tolerances well enough to not require lapping assuming 1 aligns the rings as per their instruction.

I have seen many lapping jobs that have caused more problems than they solved by incorrect lapping or over lapping.

Peter keep me in the loop regarding the making of lapping bars, we have been pondering making them, just not sure if there was enough interest to bother.
 
Lapping Bars

I made a set of lapping bars , one 1.0 "" bar and one 30 mm bar i made them out of 4140 htsr , turned them between centres to within .005 " of finished size then finished them between centres to a 63 micron finish on a Cincinnatti o/d grinder they measured .0001+/- over their 12.00" length when finished , i used the 30 mm to lapin the TPS rings that hold my nightforce BR scope , i had approx 80 % contact before lapping and full after about 20 min of lapping with 320 grit clova,
( i mixed a bit of telus 32 in the lapping compound ) i find it easier to work with that way.and then clean it off with m.e.k, that gets rid of all of the messy compound, so on my rifle it was worth it IMO to have full and even holding force on my expensive BR scope .
** PETER ** by the way i love the scope i bought from you :)
 
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A little lapping will quickly determine if any or more is required. It will remove any sharp edges that may mark a scope tube. Burris Signature rings do not require lapping. I would not mount any of my scopes without trying the lap to see the fit... Usually it takes very little lapping.

It would take a lot of lapping to 'cause' a problem. I really don't understand how that may occur...
 
As I have noted before in previous similar threads, we always lap steel rings. The use of a lapping bar confirms the allignment of the two rings (we seldom use ring allignment pointers because this is accomplished with the lapping bar). We often find rings that are either out of allignment, are not even round or have high ridges on the edge(like every Ruger ring we have mounted). You soon find out what actions (or bases) are true and how the various makes of ring/bases vary in quality. High end rings like Leupold Mark 4 and Nightforce rings need very little attention while othe rings like Weaver Grand Slam and Burris (not the Signature) require quite a bit of attention. We even invested in ring reamers for really bad rings (like Ruger) and use this infrequently but it is sure nice to have when lapping would take an hour, a reamer can solve this in a few minutes. If you chose to ream you have to be careful because over eager use can destroy a set of rings that will be out of dimension and not properly hold the scope. Phil.
 
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Phil, guntech, machinist and Rick, thanks. I'm not a gunsmith, but have used lapping tools for years and especially like Phil's professional approach, as many dealers simply slap on scopes and this causes the majority of problems according to scope technicians, leading to unneccesary expense.
 
peterdobson said:
Phil, guntech, machinist and Rick, thanks. I'm not a gunsmith, but have used lapping tools for years and especially like Phil's professional approach, as many dealers simply slap on scopes and this causes the majority of problems according to scope technicians, leading to unneccesary expense.
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I agree, that in most cases some lapping is required and certainly there are some rings that are not true at all out of the box as Phil points out with Ruger rings.
The point I was making to the OP was he is NOT in a case where the parts are questionable.
 
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