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Discussion Starter · #1 · (Edited)
I wanted to start a thread that can give any average M14/M1A rifle owner a method to give their rifle a quick health check that could help them identify accuracy degrading problems with their rifles. Some problems don't announce themselves with any form of symptom other than the results on the paper downrange.

The tilt test
The first simple health check than can be performed is the tilt test. Since there is already a sticky with a full discussion of the tilt test, I will only post the link..
http://m14tfl.com/upload/showthread.php?t=69061

For those of you who don't know what that test is, believe me, it's well worth reading. GI7

Stock clearance:
Another quick check would be stock clearance all around the barrel. What we are looking for are spots that the wood or fiberglass could be coming into contact with the barrel, op-rod guide or gas cylinder. Remove your hand guard and assemble the rest of the rifle. From there, slide a piece of paper or an index card between the stock and the barrel and move it from front to rear or vice versa...

Look for spots where the paper will not pass. If there is a spot, then the forearm of the stock needs to be sanded or cleared to allow the barrel, op-rod guide or gas cylinder to remain clear of the stock channel. The only spot that the barrel should have contact at the stock is at the front band and stock ferrule. And even then, there should only be contact between the concave and convex surfaces at the bottom of the FB/SF.

The vertical surfaces should have a .010" to .020" clearance between the both of them.

FB/SF alignment:
Another item to check would be the front band to stock ferrule alignment. When looking at the front band from front to rear, there should not be any overhang to the left or right between the FB and SF. If they are not centered, then your rifle needs to be bedded. This will fix the alignment.

Edit: If your alignment is off, then also check that the front band is tight against the gas cylinder. If it's loose, shimming the gas system is in order. In most cases, this will help increase accuracy. See these posts for more on shimming the gas cylinder:

http://m14tfl.com/upload/showthread.php?t=83742
http://www.m14tfl.com/upload/showthread.php?t=67322

Flash suppressor alignment.
Look for copper marks on the front orifice of the flash suppressor. If there are marks, then your flash suppressor needs to be aligned properly. Your bullets may be hitting the flash suppressor on the way out of the barrel and throwing off your shot. This can be tricky so just ask someone here and they will advise you on the proper resolution. A FS strike can crack or break your FS.

Screws and loose hardware:
Check your flash suppressor nut set screw and your front sight set screw to make sure they have not come loose.

Op-rod and gas cylinder alignment:



With your barreled action out of the stock, ease the bolt closed. Look to see that the tail of your gas piston and op-rod are in a straight line. If the op-rod is hitting the GC off center, then the problem could be one of a few things.
  1. Your barrel could be over-indexed. If it is, there is not much you can do except have your gunsmith look at it or send it back to SAI
  2. Your op-rod guide may be out of alignment. Although there is a pin that retains the op-rod guide, it does not have any alignment function. There is still a bit of play and the alignment can be adjusted.
  3. Your splines on the GC and barrel are loose. If this is the issue, then post here and we will help resolve the issue
This is just a quick list to start things off. This post is intended to be one where other forum members can pitch in their list of quick checks that can help other members identify problems before they become problems!

So let's hear your ideas!
 

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Great post. Not a newbie, but well worth repeating.
 

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Discussion Starter · #6 ·
Thanks gents. Here are some more inspection tips...

Extractor quick check:
Another quick check is with the extractor. On rare occasions, M1A owners have had their bolt completely disassemble while firing, sending the extractor, extractor spring and plunger into no man’s land. Since USGI extractors are becoming harder to find, rifle manufacturers have had to resort to making commercial extractors. One problem with commercial extractors is that the leg of the extractor can sometimes protrude out the bottom of the bolt too far. It should be as close to flush with the contour of the bolt as possible.

If it is not, the bottom of the extractor leg can come into contact with the magazine feed lips or the next round and it can be pushed upwards and out of the bolt while cycling. To remedy this, you need to file or stone some material off the bottom of the extractor until it is flush with the bolt surface.

Bolt roller impact :
Another rare occurrence is that sometimes the op-rod will travel so far forward that the bolt roller is bound up inside the roller cutout in the op-rod. Normal function should be that the op-rod reaches its full forward travel and the bolt is rotated into full battery. The roller should not have any forward to rear stress. It should merely be resting into battery and being held from rotating by the horizontal surface of the op-rod roller cutout.

Another symptom of this is that the tab of the op-rod will have a rounded forward edge. This means that it is hitting the end of the track for the op-rod. Contact a gunsmith or SAI.

When into full battery, you should be able to wiggle the bolt just slightly front to back, and rotated left to right. The possible causes of this are that your op-rod is traveling too far forward. The common causes of this are the piston being altered to increase dwell time or the barrel may have an out of spec shoulder for the gas cylinder. When the piston reaches the end of its travel inside the gas cylinder, it stops the op-rod from moving forward. This is how the timing is set for the bolt.

Another type of bolt roller impact defect was because of out of spec receivers which did not have enough clearance for the bolt roller. When the bolt rotates into full battery, there should be enough clearance on the receiver that when the bolt lugs are fully bottomed out in the lug recesses, the roller should not be contacting the receiver at all.

To check for this, field strip the rifle. Insert the bolt into the receiver and move it into battery by hand. If the roller is hitting the receiver, you won’t be able to roll it freely. There may also be impact marks on the receiver from the bolt roller. This can damage the bolt roller and cause it to wear and even fall off. To remedy this, go to the sticky section and look up “bolt roller impact defect” by Art Luppino. He gives detailed instructions on how to remedy this. If you don’t feel like you can fix it yourself, send it to a gunsmith or send it back to SAI.
 

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FB/SF alignment:
Another item to check would be the front band to stock ferrule alignment. When looking at the front band from front to rear, there should not be any overhang to the left or right between the FB and SF. If they are not centered, then your rifle needs to be bedded. This will fix the alignment.
The front face of the stock ferrule should not touch the rear face of the front band. There should be a gap wide enough to easily slide a slip of paper into.

The lip on the bottom of the front band should touch the bottom of the ferrule, with some pressure pulling down on the barrel called "barrel draw." This pressure on a standard rifle should be about 5 pounds or so. For a quick check, put the tip of your index finger on top of the barrel and the tip of your thumb on the bottom of the stock and pinch the two together. It sould take some pressure to make the front band lip pop away from the bottom of the ferrule. The pressure on your fingertips should feel about like the same pressure it takes to pull the trigger.

If this pressure is not there, or is much higher, or if the front band seems to slide to one side or scrape as you pinch, then there is an issue with the bedding or fit of the receiver and trigger group into the stock. GI6
 

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Here's another one..

Trigger guard lockup:
For the M14/M1A to maintain consistent accuracy, it is typically a unanimous opinion that a tight fitting stock will help maintain accuracy. This is gauged by how tight the trigger guard locks up into the receiver and clamps down on the stock.

A good gauge on the ideal tightness of the trigger guard is when the tirgger guard is latched, you begin to feel tension just as the latch passes the bottom of the trigger as shown in the picture below...

If it tightens before this spot, then there is the risk that your rifle may not function properly and you could have a runaway rifle on your hands. If it's too tight, then the hammer hooks may not engage the sear properly and the hammer can follow the bolt home after cycling, or you may experience doubles. To remedy this, you need to take some material off of the bottom of the stock where the trigger groups wings or pads contact the stock (where the magazine latch is).

If the lockup is too loose and there is little to no tension when clamping the trigger guard down, then your stock fit is loose and your receiver is going to shift around in the stock giving you inconsistent results downrange. In this case, bedding will remedy the problem. Another option is to add some shims under the trigger group wings to tighten things up. These can be made out of aluminum cans or tin foil.
 

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Another option is to add some shims under the trigger group wings to tighten things up. These can be made out of aluminum cans or tin foil

This works ! I had that problem with my first birch stock.
 

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Tony asked me to put down what I recommend for minimum length of springs.

Op rod spring minimum length - 15 inches
Extractor plunger spring minimum length - 7/16"
Ejector spring minimum length - 2 inches

If you compete in Matches, I would strongly suggest you put new springs in every year and then you won't have problems caused by springs going bad all year.
 

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Thanks guys. This was what I was looking for when I joined the forum. I wanted to make sure everything was good before going to the range and maybe making things worse. I found most of this stuff spread out in different parts of the forum. Thanks again for putting it all together in one post. One thing you didn't mentioned and I found on my rifle. Makes sure all the working parts are greased and not oiled.
 

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Handguard clearance:

Handguard clearance 1): be sure the back end of the HG is not jammed into the receiver. Allow room for thermal expansion/contraction - file it down to leave some room.

Handguard clearance 2): be sure the bottom edges of the HG are not too close or touching the top edges of the stock. I like to have 1/16" clearance between the two, to allow room for "barrel whip".
 

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Discussion Starter · #15 ·
A couple of more checks for the list...

Rear Sight Assembly:

I don't know why I didn't think of this earlier, but check to make sure that your rear sight components are tight. Grab your apperture and see if there is wiggle in all axis. Also, see if your knobs wiggle or if the screws on both sides of the rear sight assembly are loose.

If your apperture can be wiggled up and down, then your apperture or elevation pinion can be worn, This may also be caused by a weak spring (the cover that goes over the apperture and fits into the grooves by the windage marks). In my lubricating post, I posted that the teeth are not to be lubed as this can cause your sights to shift with little vibration.

If you see that your sights are loose in any way, post here and we will help you resolve the problem.

Let's face it, a loose rear sight assembly will severely degrade accuracy!

Gas Port:
It is also a good idea to check the gas port for both obstruction and alignment. If it's plugged, you will be plagued with short stroking or feeding problems.

Pull the op-rod back and lock the bolt to the rear. Tilt the muzzle up until you hear the gas piston slide all the way back. Invert the rifle and lay it in your lap or in a cradle. Insert a 1/16" allen wrench into the hole at the bottom of the gas cylinder. Wiggle it around until you feel it go inside the gas port hole and gently stick it in as far as it will go. BE CAREFUL NOT TO LET THE BOLT STOP DISENGAGE!!! IF SO, THE OP-ROD WILL FLY HOME AND YOU CAN DAMAGE YOUR PISTON AND GAS CYLINDER ASSEMBLY!!! Now that I think about it, it would really stink if your allen wrench sheared and you had half an allen wrench stuck in your barrel. I use a cleaning port to eliminate the risk. You can also throw a block of wood in the action to keep damage from occuring. If you don't want to take that risk, then remove the gas plug and remove your gas piston.

Once the allen wrench is all the way inside the barrel, then look down the barrel and you should be able to see the allen wrench protruding into the barrel. I did this the other day and saw a big glob of carbon lying in the barrel right after I just cleaned it. The allen wrench knocked the carbon build up out of my gas port.

So even if you know your gas port is aligned, it's a good idea to do this from time to time to make sure your port is not clogged.
 

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Failure to Feed from left side if the mag

I've had similar problems w/a loaded model. It was actually a failure to feed problem, all from the left side of the mag.. Sent it off to SAI and they polished the chamber. Still had unreliable feed problems. Removed the op rod spring, installed a mag and fed by hand. What was occurring was that the left bolt lug was contacting the backside, and top, of the bolt stop during each feeding cycle. Enough so that a peen mark was left on the bolt stop in this area. As they left lug moved forward in the rail, it pushed the bolt stop downward. When it did this, the bolt stop bottom pushed the next left side cartridge downward in the mag. This in turn caused enough of a misalignment between the cartridge and chamber, as to cause erratic feeding. Cartridge cases were somewhat deformed through this erratic feeding. If the cartridge is pushed down far enough, the bolt will not catch the cartridge at all. I've measured the thickness of the bolt stop at the top and it was .025 thicker than any of my spare bolt stops. I'm under the impression that the bolt should not contact the bolt stop at all, until the last round is fired. As the bolt stop is a PIA to change out, even with the proper punches, it is awaiting return to SAI this week. Hope you are able to follow my description of the problem. If you have a FTF from the left side of the mag, best to disassemble the rifle and perform the same tests.
dozier

Updated 12/17/09: Well got my rifle back from SAI in November for the above feeding problem. They changed out the bolt stop for one that clears the left bolt lug when it goes onto battery. SAI stated that they fired 80rds out of it at their facility. I checked the finish product, and the bolt does not touch the BS till the last shot is fired. Haven't been able to get to the range till yesterday. Fired 40rds out of two brand new CMI mags. Went thru those rounds w/o a hitch, and no deformed bullets. So if you do have a problem w/your M1A not feeding properly out of the left side of the mag, check for proper clearance on the Bolt Stop. See above post. dozier
 

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Discussion Starter · #17 ·
Just saw another one from another poster...

Gas plug tightness...

The gas plug should be torqued to a minimum of 120 inch pounds (10 foot pounds) to a maximum of 23 foot pounds.

The well accepted range is 120 inch pounds to 150 inch pounds. Put some anti-sieze on your plug when servicing.

If you don't have access to a torque wrench, just German torque it (Good-N-Tight!).

With those torques, the gas plug should not be shooting loose. If you need a torque wrench, go to the local auto store and rent one. You will get all your money back anyway and it will cost nothing. Gas plug torque can affect accuracy, so see what torque works for you.

Once you have a good torque, scribe a line or add some fingernail polish or white out to the gas plug and gas cylinder so that you just have to line up the marks upon service reinstallation.

Keep in mind that as the plug is removed and reinstalled, the plug may have to be tightened a little more than before to achieve the same torque you once had.

Keeping your gas plug torqued will prevent cycling issues.
 

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This material may have been cover in another of my Posts but this reminder could be helpful.

Last week two gentleman visited bring three M1 Garands they recently received from CMP. All three of these rifles they stated, would not shoot to the degree of accuracy expected. The problem was the same in all three, sight covers. Two of the rear sight covers were worn out, the third would not seat properly in the receiver.

The tension rib on two covers were worn out and the aperture was not being held level in the base, This problem may be the MOST common issue in both the M1 and the M1a/M14's, and the lest common to be checked. Inspect your cover, the tension rib should be well defined. If you are a shooter that uses the elevation knob constantly, the rib wears quicker then expected, even faster if not lubed.

Poor fitting covers are often the result of the retaining slots having grit or dross present, this is more common in cast receivers. Run a small screw driver blade around inside of the slots, you can feel interference, Clean the slots before installing the cover. I like to stone the rounded corners on the cover to insure a complete fit, To make certain the cover fits properly and is flush, install the cover without the rest of the sight, it should sit flush and firm with no tilt, both sides should be inside the retaining wings of the receiver. Use a small amount of lube in the front and rear slots. It is my practice to polish the top of the aperture, often this curved surface has heavy machine ridges. Cast NM apertures have a raised circle on top, the air vent, this bumps the tension rib in some cases, Don't forget to lube the top of the Aperture. A poor cover is similar to worn out motor mounts, nobody wants to know about it. Art MCORPS1
 

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Discussion Starter · #19 ·
Another addition (torque spec)

If you have a rifle that has a rear-lugged receiver with a torque screw, after seasonal cleaning, be sure to re-torque it from 50 to 55 INCH pounds. I am not sure what the torque should be if you have a double lugged receiver. If anyone knows those torque specs, please feel free to chime in.
 

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Something else on fit of the stock.

If the receiver is loose from front to rear in the stock without the trigger housing in place, it will still cause flyers even if the trigger guard lock up is good.

To test this, take the trigger mech out and turn the rifle upside down with the barreled receiver and stock laying on a bench. Grab the gas cylinder with one hand (and don't touch the stock with that hand) and grab the pistol grip of the stock with the other. Pull your hands apart to see if the receiver will move forward, then push your hands together to see if the receiver will move backwards. On real M14's and G.I. stocks you would see almost no movement because the receiver legs were made so precisely consistant and the stock liners were steel. The steel stock liner took a WHOLE bunch of rounds before recoil loosened it up.

Commericial M14 receiver legs are not nearly so precisely made. Some you have to do a little filing on the stock liner to get them to fit. On others, the receiver legs are too short front to back and that allows the receiver to bounce back and forth in recoil. The only good way to fix that is to epoxy bed the receiver legs or replace the stock.
 
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