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Discussion Starter #1
I cant find a reference anywhere so any help would be great.

Assuming the face of the receiver and the face of the barrel are within spec there should be an acceptable relationship between the two once threaded together.

What is the correct way to check the fit ?

Should the receiver "bore for the bolt" be in perfect alignment with the "bore in the barrel" ?

Or should the "top and sides of the receiver" be in perfect parallel with the "bore in the barrel" ?

Next question is... what is the acceptable tolerance ?
 

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lot_45 said:
I cant find a reference anywhere so any help would be great.

Assuming the face of the receiver and the face of the barrel are within spec there should be an acceptable relationship between the two once threaded together.

What is the correct way to check the fit ?

Should the receiver "bore for the bolt" be in perfect alignment with the "bore in the barrel" ?

Or should the "top and sides of the receiver" be in perfect parallel with the "bore in the barrel" ?

Next question is... what is the acceptable tolerance ?
Yes, I liked your first question, how would one go about checking it?
 

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truckboss said:
Both,I couldn't imagine it any other way.How to check it?If'n you can see it with your eyes it's FUBAR!
I'd say if you can see it with your eyes it is well beyond FUBAR.. A misalignment I would think might rear its head with a receiver mounted scope @ 50 yds and be beyond the ability to sight it in and still not be able to see it just by looking at the barrel/receiver without some sort of specialized equipment..
 

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lot_45 said:
I cant find a reference anywhere so any help would be great.

Assuming the face of the receiver and the face of the barrel are within spec there should be an acceptable relationship between the two once threaded together.

What is the correct way to check the fit ?

Should the receiver "bore for the bolt" be in perfect alignment with the "bore in the barrel" ?

Or should the "top and sides of the receiver" be in perfect parallel with the "bore in the barrel" ?


Next question is... what is the acceptable tolerance ?
Yes, both faces are square to the bores, but the part drawings are a bit lacking for actual specs.......they were drawn, and re-drawn decades ago......

The bore for the bolt and the bore for the barrel threads are concentric, that is, on the same center line.

The top of the receiver, front face and LH side are Datum surfaces, used in setup for most all operations, and should be parallel and or square to the bolt bore.......

As to acceptable tolerances, Without the prints, I can't get you any solid numbers........The bolt bore should be about .675-.678....IIRC..........You could machine a pc of drill rod to fit snug in the bolt bore and measure the parallelism to the top and LH side .

That's the best I can do for you .............

Tom
 

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Discussion Starter #6
Tom,

Thanks for the additional info. From what you indicated... for all practical purposes, one could extend a straight line on top of the receiver and expect it to be just about perfect parallel to the barrel bore. Likewise one could extend a straight line on the left side of the receiver and expect it to be just about perfect parallel to the barrel bore.

I shall do just that and report the "run out" from the "base" of the barrel out to the muzzle end of the barrel.

I think just going off the outside surface of the barrel will be close enough since the center of the bore at each end would be a little hard to "locate". Yes I will compansate for the "tapper" (which in my case is about 0.091"). My barrel base is 0.927 and the muzzle end is 0.745 so ((0.927 - 0.745) / 2) = 0.091 to allow for the tapper.
 

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Discussion Starter #7
I got a chance to take some measurements.

The barrel diameter at the receiver where the (0.301) shim was placed is 0.931
The barrel diameter at the muzzle where the (0.718)shim was placed is 0.745
That makes an adjustment of 0.093 to be subtracted out from the ddifference in shims.

As you can see the "droop" is 0.324 from about receiver to muzzle. (barrel is 22") TOTALY UNACCEPTABLE.
 

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lot_45 said:
I got a chance to take some measurements.

The barrel diameter at the receiver where the (0.301) shim was placed is 0.931
The barrel diameter at the muzzle where the (0.718)shim was placed is 0.745
That makes an adjustment of 0.093 to be subtracted out from the ddifference in shims.

As you can see the "droop" is 0.324 from about receiver to muzzle. (barrel is 22") TOTALY UNACCEPTABLE.

It appears to me, you are working off the outside of the barrel.............You need to work off the C-L of the bore and the top of the receiver.

Tom
 

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It's a good question, and would explain why so many of the folks who try and mount the Lever Rails and why it fails without shims and a whole lot of headache.
 

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Discussion Starter #10
Tom,

Thanks for taking note on where I made the measurements. But, do you really think there is going to be a huge error in the method I used? Like I mentioned, I subtracted out the difference in barrel diameter from end to end. Unless the bore in the barrel is way off (not concentric), I would think my method is ok to say it needs fixed. The top of the receiver is "flat" on the straight edge as pictured. Im not sure how I would go about "locating" the CL of the bore.


Thanks
 

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Im not sure how I would go about "locating" the CL of the bore.

I would turn a piece a few inches long so it juuuust fit into the bore, and measure from that. That's harder to do if you don't have a lathe :-(.
 

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How about a bore sight laser chambered and a laser equipped torpedo level on the top or side of the receiver and see if the beams cross or go away from one another?
 

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I'd think it should be acurate to add 1/2 the difference in barrel dia to the front dia to create a line paralell with the bore. If the bore isn't concentric with the outside of the barrel it wont be inline with the rest of the gun when the barrel was installed straight.
That said I'm not sure how things could be almost a third of an inch out of whack unless something got bent after the gun was assembled.
 
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