Main spring

[King Medallion]

So I took ol' Thumper out this morning and fired off a box of 50 rounds of 350gr Laser Cast pushed by 25 grains of 5477 and a pinch of lint filler. Worked beautifully,  knocking down steel targets regularly at 150 yards.  In those 50 rounds, the @#!%*^$# main spring fell off 4 times. I need to get this remedied asap. 5x actually,  once it fell off while putting the stock back on. Would a new spring be the answer? I don't understand why it falls off in the 1st place.

[larryo1]

King:

Don't your '76 have a set screw on the lower tang to tighten up that main spring?  I know mine does and you can titen it up with a bit of tension on that screw.  If yours don't have one   a gunsmith could sure drill and tap one in for you.  They are not very big and would not show at all were it blued and stuff.

[Coal Creek Griff]

Mine has a spacer over the tensioning screw.  Take a look at the photos from this thread.  Is it similar?

https://www.cascity.com/forumhall/index.php/topic,58132.msg695537.html#msg695537

CC Griff

[King Medallion]

Yes, it does have the tension screw and I have it as far in as it will go. CC, Mine does not have that spacer. Where would I get one? That is the same tension screw I have tho.

[Coal Creek Griff]

Mine came from Uberti "fully equipped" with the spacer!  In other words, I suspect that they couldn't get enough tension on the mainspring, so they added the spacer.  It looks like a simple piece of metal tubing, cut to fit.  I'd be more upset if it didn't work as well as it does.

I'm guessing that the design is a combination of original 1876 features and some changes that don't work well together, hence for the need for modifications.

CC Griff

[King Medallion]

So maybe a longer tension screw? Or a welder. On a side note, 25 grains of 5477 with a pinch of laundry lint was a nice load, very few unfired grains of powder. No sign of lint downrange either. Whacked the steel with authority I'm told, I can't hear chit, wife/spotter said so.

[greyhawk]

So I took ol' Thumper out this morning and fired off a box of 50 rounds of 350gr Laser Cast pushed by 25 grains of 5477 and a pinch of lint filler. Worked beautifully,  knocking down steel targets regularly at 150 yards.  In those 50 rounds, the @#!%*^$# main spring fell off 4 times. I need to get this remedied asap. 5x actually,  once it fell off while putting the stock back on. Would a new spring be the answer? I don't understand why it falls off in the 1st place.

ah ha - he sez smugly into his half empty coffee cup

Been there done this one

The trigger on my Uberti outta the box was ....brutal/ disgraceful/ awful - so rather than mess about thinning the spring I took the quick fix and released the tension screw (they call it the strain screw in the parts picture) which got it quite nice - I backed it off untill I got a couple of light strikes and then just tightened a bit -- the main spring then proceeded to walk itself forwards out of the retaining slot just a tad each time you work the lever - ten shots - fifteen maybe - till it fell out. After some precise study of the situation I attacked with the Dremel tool (yah I agree with Coffin MAker - no gun owner should be allowed to own one)
I ground the back end of the mainspring just where it engages the retaining slot - sos I had a little raised lump right at the back - didnt take much off - maybe ten thou or so - then I ground a corresponding little groove through across the top of the slot - didnt remove much metal at all - but it fixed it and I still got a decent trigger - if you add to the mainspring tension  that will fix the creeping problem but you make the trigger pull heavier as you go .
Another fix would likely be to make a small mild steel insert so that the mainspring wedges tight in the retaining notch before you tension it - that worked on my Chaippa 86 - I made a new lighter mainspring for it and had to use the filler to retain it.
Wasping your mainspring would work too but would need to add packing to the strain screw.

Easiest way to figure this out is take the stock off and cycle the action and watch what is happening in that retainer notch - its all about the geometry and fit of the mainspring in the retainer notch.
I can draw you a couple pictures and post tomorrow if you would like.   
   

[King Medallion]

I would, and take a few pics of what you did, if possible. I'd greatly appreciate it. thank you so much.

[Coal Creek Griff]

The little spacer that the Uberti "gunsmiths" put into mine looks kind of funky, but the trigger pull on mine is quite good.  The mainspring tension seems about right for smooth cycling, although I did back off the lever and carrier springs a bit.  I did a little smoothing on the internals, but didn't feel the need to work on the mainspring.  If I had your gun, I'd be tempted to take a bit of copper or brass tubing, cut off little sections and put in in place a la mine.  Unless you put so much pressure on as to damage the mainspring, it should be quick, inexpensive and reversible.  It just might solve your problems by holding the spring in place without adding too much tension.

My understanding (although I may have been misinformed) is that the original springs were quite a bit thicker.  The hook for the mainspring was copied, but the Uberti spring is thinner, making the hook a bit larger than it should be.  No doubt someone with better knowledge will correct me here...

CC Griff

[greyhawk]

The little spacer that the Uberti "gunsmiths" put into mine looks kind of funky, but the trigger pull on mine is quite good.  The mainspring tension seems about right for smooth cycling, although I did back off the lever and carrier springs a bit.  I did a little smoothing on the internals, but didn't feel the need to work on the mainspring.  If I had your gun, I'd be tempted to take a bit of copper or brass tubing, cut off little sections and put in in place a la mine.  Unless you put so much pressure on as to damage the mainspring, it should be quick, inexpensive and reversible.  It just might solve your problems by holding the spring in place without adding too much tension.

My understanding (although I may have been misinformed) is that the original springs were quite a bit thicker.  The hook for the mainspring was copied, but the Uberti spring is thinner, making the hook a bit larger than it should be.  No doubt someone with better knowledge will correct me here...

CC Griff

No correcting needed - I reckon you got it right- my Uberti mainspring looks like stamped out of a piece with same thickness from end to end (71 thou my measure) all the original mainsprings I saw for various winchesters always had a thicker butt where they secured and tapered thinner to the front end - my Chiappa 86 also built like that - mainspring woulda been better employed on a truck axle tho.
The Uberti with full screw adjustment stayed in place but 11 pound trigger pull - back it off to get the trigger lighter and the spring walked forward and fell out. 

[greyhawk]

I would, and take a few pics of what you did, if possible. I'd greatly appreciate it. thank you so much.

KM hope this helps
You dont need to remove much metal !!!
The groove across the top of the spring is a touch less than ten thou
The line drawing is rough but might explain easier

Extending the strain screw like some others recommend will fix it - trouble is that adds weight to the trigger pull - (added a lot of weight to mine)
I wasnt sure if my modification here would work when I did it but has worked a treat really.
     

[kwilliams1876]

My original Uberti mainspring was an abomination, so I made a new one that is thick enough to fill the  retainer slot and then tapers in thickness and width. Works great.

[King Medallion]

Thanks, Hawk! That looks like something I can do. I'll use a fresh hacksaw blade too! Might be a good idea to order a spare spring or two also, just in case. If the hacksaw fails, I still got Dad's torch out at the farm!

[greyhawk]

Thanks, Hawk! That looks like something I can do. I'll use a fresh hacksaw blade too! Might be a good idea to order a spare spring or two also, just in case. If the hacksaw fails, I still got Dad's torch out at the farm!

I have a little set of diamond burrs for the dremel tool - cheap chinese stuff - maybe 8 bucks - but they work good
I think you need to work the retainer slot a little also (any small round file should cut that) Good luck with the project - the 76 is a sweet piece of machinery when its working right.

[King Medallion]

We got a new Harbor Freight store in our town, I'll to check out what they have for dremal. There's always Menards.

[King Medallion]

So the new springs arrived today from VTI. The short one is the old spring. I wonder if that has anything to do with the problem?

[King Medallion]

Well, Chit. New springs dont work either. too thin. Old spring is 0.08, new springs 0.06. Put one on the gun, squeeze the trigger, hammer barely touches the firing pin, spring falls off. Can put the spring back on without even loosening the screw.

[Cliff Fendley]

Bummer, I could see where the shorter spring might cause it to pull and maybe pop out. Can you shim the new springs at the base?

[King Medallion]

 I'll have to fiddle with it, see what I can do. 

[Classicflh]

KM... I saw a video where a hammer link was factory installed backasswards.  Are you having any difficulty hooking the spring hooks to the link?  Have you ever had that link out?

I?ll be sipping on my whiskey trying to think what the possibilities are until you getter done!