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I thought I might start a thread related to issues we face in the shop with M14s.

I'll do a new quick reply whenever I have the chance update.

"Timing"

Timing and point of impact are one of the major considerations for M14 rifles. The timing is critical. Often, a perfectly timed rifle will not shoot point of aim when the front and rear sights are at mechanical zero.

If timing is a few degrees off and you have a unitized gas cylinder, that front band is not going to mate up perfectly with the stock ferrule.

That is why it is critical to not unitize a gas cylinder before you build and test fire.

Barrel timing has many variables. The splines, gas port, shoulder, tenon length, and threads. Here is a tough question to answer though; what is being used in timing as the point of origin "zero origin" Many use the rear sight pocket, and some time off the bottom of the receiver. I have found the internal cylindrical portion of the rear sight ears has the greatest correlation to getting timing right the first time around. A hardened rod is inserted through the rear sight and a v-block machinist level is placed upon the rod. Although the base of the rear sight pocket intuitively seems like the best location for determining alignment, it's the rear sight ear's cylindrical portion that determines how the rear sight lines up.
 

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Thanks Jon. Can you post a pic of the V-block level being used? Not sure I know what they look like.
Is the hardened rod used a snug fit into the ears or does it not matter as long as it's sitting at the bottom of the ears?
 

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Jon,
and now a slightly different "foreign perspective".

This post deals with the often out of spec issues found on front and rear sights of the Chinese/Canadian import M14s, and if this posting is not appropriate here in your shop thread, let me know and I will delete it.
(;-[)

I never worried too much about sights and POI alignment until the recent Chinese/ Canadian M14 imports started showing up with GROSSLY out of index front sights. The decades old original Chi/Can imports rarely had any problems with barrel indexxing, and POI was usually close with both sights centered.

However, a very large percentage of the newer Chi/Can 14s have all sorts of mis-alignments. On many new rifles, when looking through the iron sights, often it is immediately obvious to the naked eye that something just ain't right.

Most common issue is the barrel has been under or over torqued during installation. Apparently the newer Chinese assembly procedures do not bother with any degree of accurate quality control alignment while screwing in the barrels.

To add to the aggravation index, the Chinese barrels are locked into place with a hidden little set screw at the side of the receiver, and some of these screws have been screwed in with "extreme enthusiasm". That set screw also may have a shallow slot that varies in width and depth, so you need to use a perfectly fitted bit, and an impact driver. In worst case scenarios, the screw will strip, and need to be drilled out. In even worse than worst case, that screw will be harder than most drill bits, and a carbide mill will be required to get rid of the screw.

Another issue is that even if the barrel is indexxed correctly, the flash hider may have the internal splines off center from the sight tower vertical. And/or, the top of the sight tower and the dovetail may be machined at an angle. AND, THEY WELD THE FLASHIDERS TO THE BARRELS, so you can't easily check to see what exactly is the cause of the symptom.

At the back,
the notoriously poor quality Chinese rear sights may have very sloppy adjustments for both elevation and windage, and windage may simply decide to freeze or skip at random.

So getting a new Chi/Can M14 that aligns sight and POI correctly is definitely a bit of a crap shoot. Which is one reason I designed the M14.CA CASM mount to completely replace the rear sight. However, a small percentage of the most recent Chi/Can 14s has shown some with the internal rear sight pocket machined at an angle to the bore line. This is easily seen when the CNC machined CASM mount lines up to one side, and thin shims are required to fit it correctly. So far, the holes in the rear sight ears seem to be aligned correctly for longditudanal and horizontal. We use big tapered head screws through these rear sight holes to "self align" the mount, for both vertical and hirizontal, and any significant variations here would be noticeable after tightening.

Hope this adds to the knowledge base ..
LAZ
 

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Thanks Jon. Can you post a pic of the V-block level being used? Not sure I know what they look like.
Is the hardened rod used a snug fit into the ears or does it not matter as long as it's sitting at the bottom of the ears?
Going to be my question also, What size hardened rod?
 
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