From: firstname.lastname@example.org (John Bercovitz)
Subject: Re: Scope moving in Rings
Organization: Lawrence Berkeley Laboratory
In article <email@example.com> firstname.lastname@example.org
(Henry E. Schaffer) writes:
# Another old trick is to put a pinch of fine carborundum powder
#on the rings before placing the scope there and tightening the
#rings. This helps lock the rings and the scope together.
Hadn't heard of using carborundum (an abrasive powder) but I have
heard of using rosin (It puts the squeak in your violin - you can
get it at a music shop.).
Along this same line of thought, if you have scope rings which
have a horizontal parting line (most makes but not Buehler or
Conetrol, e.g.) you can install the rings, remove their upper
halves, and lap the front and rear rings true to each other with
a scope-sized soft metal tube as a lap and fine grinding compound.
I've done this and used rosin where there were slippage problems.
Works well. The method also reduces the stress on the scope - the
scope's not trying to align your scope rings anymore.
JHBercovitz@lbl.gov (John Bercovitz)
From: email@example.com (John Bercovitz)
Subject: Re: scope ring lapping
Organization: Lawrence Berkeley Laboratory, California
In article <firstname.lastname@example.org>,
Randy Howard <email@example.com> wrote:
#I was reading through my newly arrived Sinclair catalog, and stumbled upon
#their "Scope lapping kits". This is basically a steel bar with handle
#and some lapping compound that you use to make sure the rings fit the
#scope better. I had never heard of this being done before. Anyone have
#experience doing this type of thing?
I've been lapping scope rings for fifteen years or so, ever since I ran
across a SAKO which had scope problems due to the scope being bent by the
rings. I went searching with a micrometer for something appropriate and
found a 304 stainless tube about one thou or so under which works really
well. (Most scopes are under - they vary quite a bit so check your brand.)
I bought a kit assortment of lapping grits from Brownell's but you could
buy the same much cheaper at an auto parts or machine tools store. I use
320 grit to do the cutting and then finish off with 600 so as to not scrape
up the scope. I twist the lap as I reciprocate it giving a crossed helix
look to the lap marks. You want to renew the grit ("charge the lap")
fairly frequently so as to maintain the cutting action. The whole job will
take you maybe ten minutes. I don't mess with the cap as it seems to find
its place OK.
Of course this means you can't use those pretty Conetrol or Buehler rings.
On the other hand, they seem compliant enough that scope bending isn't a
Materials appropriate for the lap are things which are fairly soft so
they will hold the grit - the grit becomes embedded in them. Copper is
traditional but it wears quickly so I like the soft stainless better.
Usually copper is used in a split lap which can be opened up to compensate
for wear. Not appropriate here. I've used split copper laps to finish Ruger
revolver chambers, for instance, and gotten finishes as good as those in
S&W chambers without an appreciable enlargement of chamber diameter. (Hey,
with those huge tapered holes, what's another thousandth?)
John Bercovitz (JHBercovitz@lbl.gov)