Another Front Band Question

4136 Views 41 Replies 13 Participants Last post by M1AallTheWay, Jan 26, 2011

G

Discussion Starter · Jan 23, 2011

I did not want to steal the other guy’s thread, so I am asking this in a separate post.

I apologize for perhaps my ignorance, for I know there have seen many threads on “front band tension” but I still an unclear.

I have absolutely NO front band movement between the front band and the stock ferrule. No matter how I press (pressing upper band and lower hand guard together at the stock ferrule), there is no movement at all; the two are ROCK SOLID tight against each other. Again, ABSOLUTELY no movement up or down or side to side.

I have shimmed the gas cylinder so the front band has no movement on the gas cylinder, but the top of the stock ferrule sits against the lower bends of the stock ferrule (where the ends are bent to hold the upper hand guard in). There just is no place for there to be ANY movement, so that is where my confusion lies.

Reading posts (and http://m14tfl.com/upload/showthread.php?t=54400), it seems I should have pressure where if I squeeze the upper band and the stock ferrule together, there should be some movement with pressure. I must be missing something here, for the front band does not seem to have any gap within it where movement of the stock ferrule is possible. If I shim the stock channel, I’m not sure it that will really do anything.

In the link it says "Place a stand off spacer in the barrel channel midpoint between the rod guide and end of cyl." . I’m not real clear on what a "stand off spacer is (or what it would be made out of). I'm also not clear on how to do that, because I sure don’t want anything rubbing against the operating rod as it moves. It seems any shim would need to go under where the OP operating guide rod is, or under the gas cylinder itself, but not between the two. If so, what material would you recommend to shim?

Where do I have a hole in my head? (Please don't say all over :O) )

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21 - 40 of 42 Posts

G

Discussion Starter · #21 · Jan 25, 2011

I believe that Grasshopper finally understands, thank you Masters.

A friend brought over his SAI NM and I looked the situation over. The stock ferrule on this rifle did not touch the bent metal tabs that hold the upper handguard. There was some space, and so when I squeezed the front band and the lower front portion of the stock together, I could feel the pressure and see movement.

I'm convinced that bending the upper tabs will do the trick (or show I'm going in the right direction).

Many Thanks you all that replied!

G

Discussion Starter · #22 · Jan 25, 2011

Oh heck-- one more thought.

If some "play/looseness" is desired, and the intent is for the front band "U" and the stock ferrule to move during firing (but having increasing pressure pushing everything back to center), would it be good to oil/lubricate the area. This would permit them to more easily adjust with the vibrations and center back after every shot?

gunnutbmg

· #23 · Jan 25, 2011

yes the stock farrel and front band is a grease point when you clean and lube you riffle

SmokyBaer

· #24 · Jan 25, 2011

2

GDavis said:
I'm convinced that bending the upper tabs will do the trick (or show I'm going in the right direction).

Well... maybe. My SA stock did not budge when i white knuckled it to get some movement off the front band. i thought it was the most draw tension ever found on a front band. no one had EVER seen this... no kiddin, i was past the three finger squeeze. i'm talking palm to palm gritted teeth squeezin... uh, i found the wood touching hard on the bottom of the gas cylinder. the stock was so thick there it was wedged in when dropping the action in. arg!

Here's how to fix that problem...

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gunnutbmg

· #25 · Jan 25, 2011

i had the same problem with my SAI and came to the same conclusion

G

Discussion Starter · #26 · Jan 25, 2011

And now that I have checked my SAI stock that came with the rifle (heavier target stock than a USGI regular), I realize I have to sand wood as well.

I realize I must shim my other stocks to get the play and pressure everyone has talked about (I did bent the front band "ears (holds the upper handguard in) , but with the SAI one no matter how much shim I try, there is no movement of the stock ferrule with any pressure. I inserted a thin piece of paper through the "drail hole" toward the muzzle, and it stops well short of the metal ferrule. I'm certain it is touching wood.

What do you guys shim with?

M1AallTheWay

· #27 · Jan 25, 2011

GDavis said:
...What do you guys shim with?

You'll find a discussion here dealing with shimming the area that'll increase tension as well as giving a snugger fit of the receiver in the stock, along with results reported by an impartial experimenter. I'd suggest reading through the thread since the sizing of the part of the shim that provides the tension is different from what's shown in the first pictures.

bunsen27

· #28 · Jan 25, 2011

(raises hand) I'm still confused.GI3

I have a standard SIA circa 1994 in a SIA synthetic stock. I have 1/16 in clearance all around the sides of the stock ferule and front band except at the front band lower lip. I have shimmed the gas cylinder to the front band so that the gas cylinder lock is snug at 5:30 and can be thumb tightened to 6:00. Grasping the top of the barrel and squeezing on the bottom portion of the stock yields about 1/16in of movement with minimal pressure (thumb and index finger) until it contacts the upper potion of the front band. The hand guard is not touching the stock until I squeeze up on it. The trigger group in this stock locks up extremely tight (it's a bugger to cam over and lock) and there is no gap at the heel of the receiver even with the trigger group unlocked.

I have been trying to improve the 2.5MOA groups the gun is shooting by installing a Sadlak NM guide rod and gas piston. I've gather from reading this thread and others that one issue may be the fit in the stock. I've relieved the stock somewhat in the front where the gas cylinder was rubbing. Any help or suggestions would be greatly appreciated. I can post pictures of specific areas if that would help. Thanks.

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M1AallTheWay

· #29 · Jan 25, 2011

bunsen27 said:
...I've gather from reading this thread and others that one issue may be the fit in the stock. I've relieved the stock somewhat in the front where the gas cylinder was rubbing. Any help or suggestions would be greatly appreciated. I can post pictures of specific areas if that would help. Thanks.

Improvement in accuracy comes from a combination of many modifications working together until the inherent accuracy of your rifle is reached (recognizing that sometimes you just can't get there from hereGI4). The fit in the stock is important because keeping the receiver and stock tight helps the front end of the stock to always present the same position for the barrel to return to. Bedding is the recognized way to do that, but check out the link in post #27, which presents another technique that has proven to work for some TFL members.

One simple way to check for that tight fit is to grasp the GC with your fingers, with your palm resting on the stock and ferrule. While watching the heel as it rests on the stock (focus on wood grain or paint imperfections), push the ferrule area sideways with your palm. If the fit of the receiver in the stock is not tight, you'll likely see the heel move over the stock. That's what bedding is intended to eliminate.

jens5

· #30 · Jan 25, 2011

I must be from Missouri and don't know it. I'm a picture kind a guy. Show me! I start reading too much techno and my head swims.The photo in this thread showed me more than 10 or more posts.

bunsen27

· #31 · Jan 25, 2011

M1AallTheWay said:
One simple way to check for that tight fit is to grasp the GC with your fingers, with your palm resting on the stock and ferrule. While watching the heel as it rests on the stock (focus on wood grain or paint imperfections), push the ferrule area sideways with your palm. If the fit of the receiver in the stock is not tight, you'll likely see the heel move over the stock. That's what bedding is intended to eliminate.

Thanks for the feedback. What would the status of the TG be for this test? Locked in or just cammed over?

As I mentioned previously the TG on this rifle locks up extremely tight so I'd be surprised if the heel was able to move with the TG locked in. However, I've been wrong before.

I'll check it when I get home this evening and I will try to post some photos to go along with my questions.

My reason for originally posting is that "I think" I don't have enough tension on the front band/stock ferule. I did read the entire thread on shimming with the metal flashing, but am uncertain if that is an option with the already tight locking TG.

Ultimately I am going to put this rifle in a JAE G2 stock, but until I save up all those pennies I'll continue to tinker and learn about this platform.

M1AallTheWay

· #32 · Jan 25, 2011

bunsen27 said:
Thanks for the feedback. What would the status of the TG be for this test? Locked in or just cammed over?

As I mentioned previously the TG on this rifle locks up extremely tight so I'd be surprised if the heel was able to move with the TG locked in...

The test would be done with the TG locked up. (BTW, an easier way to lock up is to use something like this to pull the heel down on the stock before you close the trigger guard.) The basic idea is to prevent the receiver from rotating sideways in the stock, even a little bit. Unless it's rear or double lugged, the only parts of the receiver that are in contact with the inside surface of the stock are the outer faces of the receiver legs and the section just forward of the legs. If the fit there isn't extremely tight, a small amount of rotation is possible (which is what the test of movement of the heel over the stock is designed to disclose). And if there's a little rotation at the receiver, imagine how much displacement there is way down at the end of the stock/barrel contact point (front band lip/ferrule). The tension intended to guide the barrel back to it's rest point on the ferrule would be guiding it to a different place every time, not a good thing.

Even if the heel is really tight against the top of the stock, if there's some slop between the legs or the section forward and the stock, you can still get a bit of sideways movement there and a lot at the ferrule.

Using shims to raise the heel even further off the stock would make locking up even harder or maybe impossible. But using the "L" shaped shims just inside the stock would tighten the fit without tightening the lockup. In any case, thinking of that tension as part of the "see-saw" motion has the ferrule end of the stock being pulled down (creating tension) as the back end of the stock is pulled up to meet the heel. Since that's what's happening to you, I bet you've got the tension, just not the clearance so it can be demonstrated or operational.

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G

Discussion Starter · #33 · Jan 25, 2011

M1AallTheWay said:
You'll find a discussion here dealing with shimming the area that'll increase tension as well as giving a snugger fit of the receiver in the stock, along with results reported by an impartial experimenter. I'd suggest reading through the thread since the sizing of the part of the shim that provides the tension is different from what's shown in the first pictures.

---------------------------------------------------------------------------------------------------
Great info (and a lot of reading). It talks about aluminum and steel not being good together, and "paper" (match box) can retain moisture, what is your thought on "plastic" shims? My thinking is that you would be able to heat to a point where they are pliable / shapeable and would not retain moisture. Not sure of examples of plastic items than could be used though.

M1AallTheWay

· #34 · Jan 25, 2011

GDavis said:
Great info (and a lot of reading). It talks about aluminum and steel not being good together, and "paper" (match box) can retain moisture, what is your thought on "plastic" shims? My thinking is that you would be able to heat to a point where they are pliable / shapeable and would not retain moisture. Not sure of examples of plastic items than could be used though.

I'd be a bit concerned that a plastic which could be softened enough by heat to be workable might be softened on a hot day by a hot receiver.

I was surprised to learn about the potential problem mixing steel and aluminum, but I've been using the combination for over four years now and haven't seen any ill effects at all. YMMV.

G

Discussion Starter · #35 · Jan 25, 2011

It may not be thick enough, but there is plastic you can put into ovens (thinking of the oven bags but there may be other plastic oven containers). Just a thought.

One post says the problem with aluminum and steel is with moisture between the two. Have you poped up out of a lake/pond/river lately and surprised your target? That may cause a problem :O)

ripsaw

· #36 · Jan 25, 2011 (Edited)

overall fit

Here is an example of the liner fit to receiver leg issues I mentioned previously. The bass drum of the symphony. See the corresponding rub marks on both receiver and liner ? Also note the bevels on the stock, front portion.

In this picture, I don't know if you can see it, but I had to remove material off the very top of the liner rear portion, that was in contact with the receiver and throwing an intermittent flyer.

Apologies for drifting off topic, but just found the pics that apply. If you are going to fix it, you have to start in the basement and build a good foundation, just like a house.

M1AallTheWay

· #37 · Jan 25, 2011

GDavis said:
...One post says the problem with aluminum and steel is with moisture between the two. Have you poped up out of a lake/pond/river lately and surprised your target? That may cause a problem :O)

Can't say that I've ever gone swimming with my M1A, but if I had to, I suspect my troubles would extend well beyond a dissimilar metal interaction and would move a lot faster, too.GI4

Old PO2

· #38 · Jan 25, 2011

I'm no chemist, but in my experience the problem with fitting aluminum and steel together is electrolysis. Salt water (or maybe sweat?) makes it worse. Down here on the Gulf Coast, fitting aluminum and steel together is truly bad juju. In fairness though, most damage is to the aluminum. When it mates with steel, it immediately begins turning into aluminum-oxide (a fine white powder).

I use thin brass sheeting for shims. It seems to work well and holds up under most conditions.

Old PO2

G

Discussion Starter · #39 · Jan 26, 2011 (Edited)

Brass- that's a good idea. No detrimental affects with brass and steel I assume?

Thin brass sheet would cut like aluminum, with the ability to shape. I think you have a winner that I'll jump on.

Thanks

Old PO2

· #40 · Jan 26, 2011

GDavis said:
Brass- that's a good idea. No detrimental affects with brass and steel I assume?

Thin breass sheet would cut like aluminum, with the ability to shape. I think you have a winner that I'll jump on.

Thanks

No problems with corrosion, that I've seen. Brass is softer and heavier than aluminum, but I've never found that to be an issue with shimming a scope, etc.

I've never tried to metal shim a stock, but I can't think of any reason why brass wouldn't do well for that use.

I should point out that brass and steel have been used together in firearms since almost the beginning. The only problem is that if any brass is showing, you may feel a need to polish it. GI8

Old PO2

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