what does your protractor say if you take out the barrel and just read the face of the upper?
Barrel alignment problem?
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Do you have a way of checking the run out on the face of the barrel extension that mates with the upper receiver and the concentricity of the barrel extension. The barrel extension should be machined from 8620 and is heat treated after machining. Improper heat treating can warp the surfaces.
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OK.
So with my very limited tools i was able to check the run out where the barrel meets the receiver face. I could not detect any run out. YEAH!
I have no real way that i can figure out how to check the receiver face however i did use some prussian blue on the receiver face and lapping tool. It looked decent but there are a couple dark spots showing indicating more lapping is necessary and i will lap it vertically from now on.
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Every upper I've built after lapping usually results in my mechanical zero in the scope being almost dead-on when I go to bore sight at 10yds.
I'm on paper with my bore-sighting jobs at 100yds every time.
I use math for my offset at 10yds, with POA being 90% above the bore.NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
www.AR15buildbox.com
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So i did figure out a way to measure the run out on the receiver face.
Turn out the lapping tool inserted from the the rear worked great to get a reading. Taking the reading it showed almost 2thou reading from flat. Lapped the receiver some more until i had a flat reading.
Put the receiver on and leveled the barrel. Now i have a 0.0 reading on the scope rail and on the barrel.
Turns out when i first lapped it i seen shiny all around the receiver face and thought it was done when in fact it needed more lapping. If i did not have a few precision measuring tools i would never known the difference and my have thought what a POS gun that cant hit a thing.
Wonder how many other people just assume everything is good and in line?
Next up Scope mount aligning!
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All you have done is eliminate a little angle. Rifle is going to shoot no matter what. If it was off, it would be consistently off - which zeros that aspect of the assembly out, and it gets factored into your dope chart.
I had to math that out. 10 feet at 1000 yards. So .2* is substantial. I could have gone the rest of my life without knowing that number.Sticks
Catchy sig line here.
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Im certainly no perfectionist but i could not leave it alone as i feel it is not right with the alignment off.
Now its aligned with out compensating a misalignment with the scope.
The scope mount i will work on tomorrow. With a 1in steel bar mounted in it, it measures 0.1deg off from the barrel/receiver
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If we ignored all errors and misalignments, something known as tolerance stacking begins to accumulate. Each error, considered on their own, may seem insignificant, but all combined? Well, there it is: the reason why some shooters and assemblers take the time to eliminate as much error as one is able.
Assuming the errors SpairParts identified are all biased in the same direction (downward), then a .2 degrees error in the barrel + a .1 degree error in the scope mount becomes .3 degrees overall. This then potentially becomes an 18 MOA error (60 MOA per degree of arc). That represents an extra 18 MOA one would have to account for in either a scope base or a rifle scope with an additional 36 MOA of elevation, if long distance shooting was something you planned to do. Either solution represents additional $$ that need not be spent.Last edited by NugginFutz; 12-29-2017, 06:24 PM.If it's true that we are here to help others, then what exactly are the others here for?
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Know all about tolerance stacking. Work with aircraft. If its not right it don't fly. Period.
Guess that kinda training is what makes me check everything i work on.
My plan is to use this gun as my main hunting rifle and also my just for fun long range, can i hit it kinda gun. My 5.56 will be the main plinking gun.
Next summer my plan is to build a AR10.
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Originally posted by SpairParts View PostReally, So thats what 2-1/2 at 500, 1-1/4 at 250, 8in(ish) at 125.
Seems like WAY to much to me for something i can fix i think pretty easy.Sticks
Catchy sig line here.
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