[M1AallTheWay]

Looking at my new LRB build I noticed that the tab on the front band is not touching the ferrule, maybe 1/16"-1/8" gap. I'm using a USGI synthetic stock. The lockup at the trigger group is perfect getting tight at the tip of the trigger. The receiver heel is in contact with the stock. The gas cylinder is not unitized or shimmed, but the front band is solid and doesn't move at all. There is the proper vertical clearance at the front band...

First, to be clear, since there's been some confusion about this on past threads discussing a similar issue: We're talking about a 1/16"-1/8" gap between the front band lip that hooks under the ferrule and the ferrule itself, not the distance between the front surface of the ferrule and the back surface of the front band?

There isn't an awful lot of room between the inside top surface at the bottom of the "U" shape of a standard ferrule and the bottom of the gas cylinder sitting just above it. So part of the purpose of any tension is to pull the ferrule down and away from the GC. That much of a gap suggests the ferrule is already either resting against the GC or really close to it.

One way to get both tension and some distance between the ferrule and the GC is to take advantage of the see-saw relationship which can exist between the stock and the barreled action when the trigger group is locked up. You can accomplish that with the shims that NoExpert mentioned (I guess I'm at least one of the guys since I use such shims regularly).

If you look carefully at the stock, you'll notice the area just forward of the bolt lock on both sides is raised slightly. Adding shims there will increase the lockup tension and move the ferrule down towards the front band lip. If lockup tension is already considerable, you might want to use something like a furniture clamp to pull the heel down on the stock rather than making the trigger guard do the work.

 

[M1AallTheWay]

Yes, that’s correct, the gap is between the lip of the front band that hooks under the ferrule and the ferrule itself. So it sounds to me that the goal isn't just getting the proper tension between the two, but also pulling the barrel unit away from the stock for clearance, so building up the ferrule or tab so they make contact isn't reaally addressing this.

I think I will try shimming at the fulcrum and see if that helps. Can I do something more permanent if the shims work, like using bedding material instead of shims? Not a full bedding job, but just to raise the fulcrum?

Since I've never bedded a rifle myself, I can't speak to how resilient bedding material is to considerable compression but I'd worry about it being crushed since the contact point is pretty small. If you're using metal shims (I just cut a narrow strip of aluminum from a big sheet .020" thick that I keep around for more extensive shims), just attach them with a little piece of double sided tape. Once it's locked up, they won't be going anywhere. Note that with the shims, lockup can get pretty difficult, so some grease on the trigger guard where it grabs the receiver legs during lockup helps, as does http://www.harborfreight.com/24-inch-ratchet-bar-clamp-spreader-46809.html.

Once you get the tension, so that the curve of the ferrule wants to sit in the curve of the front band lip, you're most likely going to find that squeezing the stock at the ferrule up towards the barrel will cause the side of the of the ferrule to rub against the side of the gas cylinder. Ideally, the only contact in that area should be at the front band lip/ferrule, and one step in match conditioning is to route out that whole area so that there's clearance between the inside of the stock and gas cylinder. But I'd suggest just getting the tension and seeing how she shoots before doing anything drastic.

 

[M1AallTheWay]

...Also, for the heck of it, I swapped the stock and trigger group from my other rifle (also a GI fiberglass) and the lockup was significantly tighter and there's tension now at the ferrule/tab. When I locked down the trigger guard I had to push the heel of the receiver down with my thumb. Maybe this stock is a better match for this receiver?

All of the USGI synthetics out there are old, most are used, and some are pretty much worn out. Moreover, they aren't made to nearly the level of precision the barreled actions are, so fit and performance are bound to vary from stock to stock on the same rifle. As others have suggested, I'd try shooting it in this new configuration to see if the better fit actually makes a difference. I suspect that if you use the trigger that came with the LRB in combination with the stock that's on there now, it'll still lock up pretty much the same.

 

[M1AallTheWay]

Recently finished shimming the GC on my std SAI it did
snug up the forend tension slightly but not quite enough.
I can still fit sheet of writing paper inbetween ferrule and tab with a bit of effort.Of course I need to shoot it first as the gc was all sorts of sloppy beforethe shimming.What Im wondering has anyone even considered removing material from the heel so my GI TG can put more tension on the forend rather than shim the 'fulcrum' area?About bedding the TG?As it sits the TG starts to tighten just as the tip trigger and T guard hook get close together.If that isnt decipherable just like the book says its supposed to!
LOL As it sits I can tell theres some clearance between GC and the stock as I can push the front of the stock up till I feel contact with the GC.Clues as to how SEI sets up thier weapons w/o traditional bedding?Im of the same opinion glass is for target rifles.Sadly I cant afford thier work.

Shimming the GC to keep the front band stationary isn't going to give you any tension unless the front band lip is already in contact with the ferrule, in which case pulling the front band vertical will tend to pull it's lip up tighter against the ferrule. Removing material from the stock's heel will probably do it but it'd be hard to put it back if you take off too much. With a shim, you just take out the shim or put in a different thickness.

When you mention tension, if you can slip paper between between the ferrule and front band lip, where is the tension being applied or felt?

I'm with you in wondering how SEI can get 1 MOA without tinkering with the stock!

 

[M1AallTheWay]

Should I take all the paint off the ferrule so it's metal on metal?

The basic idea is that the barrel will move when you shoot so the gas cylinder will move too as will the front band if it's unitized or shimmed tight to the GC. Since the stock and ferrule are supposed to stay stationary, the front band lip will move relative to it, and if the surfaces in contact with each other are smooth, they'll move easily, and the tension will then slide them back together into the same position. It's the consistency of that position which aids accuracy. So, yes, the portion of the ferrule that might be in contact with the front band lip should not only be free of paint but kept as smooth as possible. I've used a Dremel 320 grit finishing abrasive buff (512E), which is rough enough to take off paint but fine enough to still polish the metal underneath. The edges of the lip are sometimes fairly sharp so softening the edges is often a good idea too. Once that's done, putting a little grease between the lip and the ferrule is the finishing touch.

At the same time, the ferrule material itself isn't all that thick so be careful to only remove paint. And where the front band lip can't possibly reach the ferrule surface, it's OK to leave the paint as is.

 

[M1AallTheWay]

The stock ferrule on my std has had the paint removed
by shooting.Fortunately centered exactly enough Id have to use a tape measure or caliper to detemine if the wears exactly centered.Eyeball method shows tab/forum centered exactly.
I suppose I should use some emery cloth to smooth the contact areas along touch grease.

If there's tension between the ferrule and the front band lip, the two will always end up centered relative to each other unless there's a terrible misalignment of the stock and the barreled action and/or terrible friction between the two (perhaps caused by a dent in the ferrule material). The trick is to achieve that centering before the tension is applied so that there's no sideways pressure until things settle down.

Ive got some Pro Bed 2000 from midway IIRC it uses a carbon fiber filler the consistency of putty/I have been coonsidering using a carbon fiber arrow shaft material in concert with the glass bedding.Does it need to be a high temp
material?...

If you're referring to what would hold the carbon fiber arrow shafts in place, a high temp material certainly couldn't hurt. I used the J-B Weld slow cure epoxy, which is good up to 600 degrees F. just to be sure. It can get pretty hot around the barrel, and if one of the arrow shafts came loose, it could block functioning. Also, those carbon fiber arrows are remarkably stiff and can add considerable stiffness to a stock all by themselves.

 

[M1AallTheWay]

...Is there something wrong with this barreled action?

I guess there could be. But consider that what's up against the inside of the ferrule is really the gas cylinder, so if the splines on the GC or the grooves in the barrel were timed wrong, you'd have the same symptoms. With the action out of the stock, how does the front of the op rod line up with the back of the gas cylinder? And looking at the chamber, is the center, between the two feed ramps, sitting directly over the tail of the op rod spring guide? Finally, with the iron sights zeroed, where does the front sight sit on the dovetail of the flash suppressor - is it centered, hanging off one side, somewhere in-between?

 

[M1AallTheWay]

It takes maybe 4-5 clicks of windage to get zeroed... But it looks like the whole barrel action is over to one side at the ferrule, not just the gas cylinder...
Is this pretty common? I'm assuming bedding it would fix this?

...I tried another rifle in the same stock and it was perfectly centered. I then tried the bad rifle in the good rifle's stock and it's pressed over to the side in that one too...

Your swapping test suggests the problem is with the rifle, not the stock. Since the goal is to get the orientation of the receiver and the portion of the stock it's sitting in such that the barrel (and GC) ends up centered at the ferrule end, bedding would take that misalignment into account because, as Dave P says, the routing of the stock in the bedding process gives the receiver some room to move in the stock.

But you might try something simpler first. The horizontal orientation of the receiver in the stock is determined primarily by how the receiver legs engage the cutouts they go into in the stock. If the receiver is positioned parallel to the stock by the legs but the barrel is the least bit crooked to the receiver, you'll get the misalignment you're experiencing. The picture looking up at the GC suggests that if the left receiver leg (looking down and from behind) were pushed a little forward in the stock relative to the right leg, the barreled action would be rotated more towards the center of the ferrule (which is what bedding would be doing). If you added a shim behind that leg, you'd be pushing the leg forward, and the whole action to the right.

How to do it? First, have an aluminum can of beer (soda will work too, but beer is better). With the action out of the stock, you can see where the receiver legs fit down into the stock. Looking forward, you can see a similar cutout where the action also fits inside the stock. Together, it looks like an "L" with a fat foot on its side. If you cut a section of the can to match that shape, you've got a shim for one side of the stock. If you make the "foot" extra fat, you can bend it so that it fits behind the receiver leg as well as beside it, pushing it forward just a bit. Making the "foot" even fatter allows you to double the bend over on itself to push the leg forward even more. Doing this is obviously going to make the fit of the receiver in the stock tighter than it already is, so you may need some help getting the trigger group to lock up. I use something like this http://www.harborfreight.com/24-inch-ratchet-bar-clamp-spreader-46809.html to get the heel down onto the stock before I close the trigger guard.

Of course, another solution is to raise the issue with LRB and see what they say.

 

[M1AallTheWay]

I did some more up close investigating of the fit, and it looks like what is happening is that the front left of the receiver, opposite where the connector lock sticks out, is interfering with the stock at that point, so as the receiver slides in, it gets pushed over to the one side. Any idea why this could be happening? I filled the selector cutouts on the stock. Is it possible that in doing that I somehow warped the stock?...

Forgot to mention that I did make sure that the connector lock isn't hitting the filled in cutout.

Please clarify: the cutout you filled in is in the back near the heel where the selector would go on a FA receiver; the connector lock is up front and keeps the back of the op rod spring guide in place, so they wouldn't be interfering with each other. Also, the front of the receiver sits inside and rests against the stock further forward on the side opposite the connector lock; the stock isn't cut back there as it is to make room for the connector lock. So what's interfering?

 

[M1AallTheWay]

Sorry for the confusion. I filled in both the front and rear cutouts in the stock. The part that is hitting the stock as the receiver slides in is the front left of the receiver if you were viewing it from the back, where the hole for the connector lock is...

I'd say that's good news. That cutout up front allows room for the connector lock; there's no force driving it sideways but if the connector lock did walk out, a loose op rod spring guide wouldn't be a good thing. So the side of the stock is there to keep it from moving too far, should it want to, rather than forcibly holding it in place. Applying sideways force there would tend to push anything forward of the receiver legs in the direction your picture of the ferrule from below shows. Can you open up the area resting against the connector lock enough to give it a bit of clearance?

At the same time, that wouldn't account for this:

...I tried another rifle in the same stock and it was perfectly centered. I then tried the bad rifle in the good rifle's stock and it's pressed over to the side in that one too. Is there something wrong with this barreled action?

Only thing I can think of is that for whatever reason, the connector lock is sticking out further than normal and will push sideways against any stock with a standard sized cutout. Perhaps the retaining pin hole is in the wrong place in the connector lock, or the lock itself is too long.

 

[M1AallTheWay]

...So my question is, could this be the case with a lot of rifles, that the action naturally wants to go to one side or the other, but the narrow ferrule is holding it in place? And when I opened up the ferrule on my two stocks, I noticed this big "misalignment?" Or should it still want to be centered, regardless of the ferrule? I realize that ideally it should be centered, but I'm curious about just a standard grade rifle. Are most up against one side of the ferrule?...

As you've seen, the space on the inside of the "U" of the ferrule is just a bit larger than the gas cylinder that fits in it. Someone with experience with large numbers of USGI M14's can give the definitive answer, but I'd hazard the guess that, as a battle rifle rather than a match rifle, the fit you're finding in the unmodified stock did just fine.

I doubt that either the USGI wood or synthetic stocks were or could have been manufactured to the same level of precision that the barreled actions were. I know that one of the USGI synthetics I've used was a bit longer, receiver leg cutout to ferrule, than the others and the ferrule was pressed against the back of the front band. Given that variability, bedding, or some other method of customizing the fit of the action in a particular stock would be necessary to wring greater accuracy from what started life as an MBR.