Must Have Tools

[churchmouse]

Long bed Mills aren't cheap! A music wire pulled tight gives you a NO LIE straight line for gauging and it's inexpensive.
It's also good for the guy doing sights/rings on a bench top.

This is an OLD 'Trick' I picked up from a gunsmith that was brilliant...
Want to check for cross hair optics vertical, directly over the bore, use a string & plumb-bob.

Clamp the action in a vice, forget the levels, depending on the clamp on the level and where it's clamped, it can lie.
Once action is in a vice or shooting cradle, hang a plumb-bob out about 15 yards off a sign or something, gravity never lies.

Plumb-bob, a vertical line every time, 100% of the time, your first point of reference.
Center the bore on the string, your second point of reference.
Rotate action, keeping bore on string, until the optics reticle cross is on the string.
Once reticle & bore are both centered on the string, rotate optics tube until the vertical line is directly inline with the string.
At this point, you CAREFULLY tighten the caps on the tube making sure you don't move anything, string line still centered in the bore, vertical line of the reticle still centered on the string.

Then add the Anti-Cant Device (Usually a bubble level) to the optics tube or rail, or where ever it goes.
This allows you to have an ACD that is precise to the optic/bore arrangement.
Tube clamps are the easiest to adjust since they rotate around the tube.
For the rail/mount clamp style, this is where you use a file or shimming to make the ACD show level when screwed on.

Keep in mind, the Marine Corps Sniper Manual says 1 minute of cant (1 minute mark on a clock face off 12:00/vertical) is 1/2" miss at 100 yards (giving Prairie Dogs a new lease on life), and at 1,000 yards it's a 55" miss!
Getting the optics square over the bore is important, and if you are going to precision shoot, an ACD THAT'S ACCURATE is a real good idea...
Keep in mind my manual is very old, that would have been the UNERTL 10x optic on the M40, and I don't remember how far over bore the rings were on it anymore. The taller the rings over bore, the more Cant is increased.

ACDs & bubble levels depend on the top of an optics turret cap being true, and they often aren't, the tops of receivers often aren't true with where the rings wind up.
Caps are often pressed instead of lathe turned, domed, have engraving/logos,
The rings can shift centerline, have quirks of there own.
This let's you get a directly vertical alignment of reticle & bore, then add the ACD so the shooter can see when optics & bore are directly vertical.

Since gravity never lies, it's a simple, cheap, easy and foolproof way to get it done.
I find that if I center the optics adjustments, run the adjustment knob all the way to one side, then count turns to the stop to the other side, then center (half turn count) on both windage & elevation, centering reticle, results are better.

I find the more obnoxious colored string helps... Mine is hot pink!

My plumb bob's are both loaded on hot pink string. Not for this reason but just saying I am 1 step into the process. I like this.

 

[churchmouse]

The schizophrenic nature of the military...

Rem 700 Bolt disassembly, it was recommended we use a dime & shoe lace.
You don't carry loose change into combat!

The military wants higher velocity, more penetration.
They use heavier bullets and CHOP THE BARREL OFF!
That's sure going to increase velocity of heavier bullets!

JAG has run 14 investigations into why Marines in particular, and grunts in general are producing more precise shots, head shots, exactly center mass shots.
Keep in mind these shots started immedately after the common issue of magnified optics!
You take the best infantry shots in the world, add magnified optics, and then question the results.
Apparently the lawyers missed 'Marksmanship 101'...

Schizophrenic behavior to be sure!
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Upper & lower AR blocks are pretty well a necessity, not a huge deal because they are cheap...
Painters tape is also a REAL good idea.
Vairation in the castings & forgings keep blocks from being 100% tight, layers of tape will snug things up.
You REALLY don't want your workpiece moving around when you are trying to drill/mill/drive pins, etc.

AR clones are the 'Erector Sets' of firearms, nearly anyone can assemble the parts.
It takes a gunsmith to get parts fitting correctly.
I don't know how many people have shown up in the past 10-15 years with all sorts of issues all related to assembly without attention to fitment.

Gas tubes not reaching the BCG key, gas keys sticking on gas tubes, gas leaking around front gas block/sight, upper bores so over run with excess anodizing the BCG won't cycle from the friction, wrong or cheap buffer springs, the list goes on and on...

The clone makers aren't any better, instead of a friction fit gas block, they heap lock-tight in the gap between barrel & gas block, using roll pins instead of taper pins to secure gas block/sights, etc.
The fittment between upper & lower is stupid, rattles like rocks in a tin can, but you can buy it for $299 at the farm store so they bought it...

It's a challenge to make some of these clones actually function correctly sometimes, and the customer doesn't help things by constantly complaining about price or the fix isn't 'Tactical' Black...

Folks tripping over $5 bills to pick up nickels.

 

[JeepHammer]

I've tried to point things out gracefully before, and got no end of grief for it, so I didn't know how it would be received.

Until the last 75 years or so, everything was built with plumb line, string, square, etc., From pyramids to aqueducts that aligned from both ends with more precision than the English channel tunnel had.
Lapping is the oldest precision way to align parts known to man, no reason to think it stopped working when lasers were invented...

When a friend of mine started building high precision parts (high precision being relative) he was dumbfounded by the cost of an inspection block.
I simply pointed out that plate glass was floated on liquid tin, and gravity precisely leveled both.
A sheet of plate glass (properly supported) was a VERY good substitute for a lapped inspection block.
The 0.0001" difference between an inspection block & sheet of plate glass worked for him.

If you want to lap a flat surface, a piece of plate glass & lapping compound will do the job nicely.
Get with the local glass installer and he will be glad to sell you pieces cut from 'Take Outs' for your projects since a 'Take Out' is a scratched or broken window anyway, cash for a couple cuts on scrap is something he'll jump at!

This goes down to something as simple as a ogive adapter or Datum line adapter for calipers.
For what ever reason, the makers of such adapters can't seem to understand a ROUNDED or radius edge on the adapter changes the seating point and renders the readings useless.
The case or bullet sinks further into the adapter, you can't zero the caliper in a recess, so you can't get a direct reading.
Comparison readings, yes... Direct, absloute readings, not possible...

 

[lrdudley]

I have a bunch of plate glass mirrors that I took out of a coworkers house many years ago that has just been looking for a use. If anyone would want some of it I would just need to know what size. I am on the southside of Indy.

 

[JeepHammer]

Thank you for the generous offer! Good on you for helping out.

For inspection table, the thicker the glass the better.
If the glass you find isn't that thick and flexes, stack two or three pieces.
What I do, A box, sand bed with some cloth over it then lay the glass in the cloth.
Cloth keeps sand off the glass while supporting the glass fairly well.

For lapping, which I normally do on a bench top, I simply lay a short loop carpet/rug so I can move it easily.

Some people will scoff at a nearly perfectly flat surface, others will see value in it.
Don't lap on your inspection table!
(Yup! Had an employee lap on a $7,000 inspection block. The only thing that saved his life was the block could be resurfaced and didn't need completely replaced, lapping a $10 part too boot!)