Excessively Preloaded Springs

[doug]

      I am currently making a stirrup link for a Rigby Snider rifle.  Even though it is a cartridge gun, I am asking the question here because the principle applies to percussion locks in general.
      What is awkward about this lock is that the mainspring is massively preloaded.  When in its relaxed position, the lower leg extends perhaps 1 1/2" below the sideplate.  That makes the spring very difficult to compress and put back in place.  I am also surprised that when the link broke the mainspring did not smash out the wood below it.
      So the question is why were many original mainsprings massively preloaded?  They appear to be preloaded far in excess of what is necessary to fire the gun and because of this put the various parts in the linkage system in considerable risk of breaking.  The claw on the end of the mainspring, the claw on the tumbler and the link itself are all small and relatively fragile pieces not to mention breaking the bridle screws if the hammer fell without striking a nipple (lock out of gun or nipple removed)

cheers Doug

[rich pierce]

No real knowledge but it sounds like an attempt to reduce lock time.

[Dr. Tim-Boone]

no engineers...?

[D. Taylor Sapergia]

English mainsprings of the late percussion era and on into the cartridge era where side locks are employed, are long and thin.  When they are at full bent, the leaves of the spring lie parallel to each other, and almost touching.  Often the throw of the hammer is short by flint standards at least, and in order to get the speed and power they thought necessary, they put a great arc into the lower leaf.  Doug, you may need to make a new arm for your spring vise, so that you can place it at the ends of the spring.  It is difficult to compress a mainspring anywhere in between the ends.
They call them buggy whip springs.

[Dphariss]

No real knowledge but it sounds like an attempt to reduce lock time.

Reducing lock time was a factor with the flintguns probably they worked pretty hard at this for wing shooting.
These locks were made by highly skilled lock filers who knew why they were doing. Gun owners, then and now, and current gunsmiths are not as well informed.
The percussion guns used stiff springs to prevent the hammer from blowing back and breaking something in the lock and promoting nipple erosion. Forsythe mentions the hammer blowing back with enough force to break parts in the lock of one of the lower grade guns he owned.
While this was not important with shotguns it was with rifles and ball guns and the lock makers, I suspect, made the stiff springs as a matter of course. AS Taylor mentions these are usually very well tapered and light weight for their power. This makes a fast spring with excellent characteristics when properly preloaded. Cast springs simply cannot match this performance and we become accustomed the weak springs with little or no preload.

Hammers blowing back  was solved in modern times by the "vented" nipple so the cheap locks on the factory guns would not show pressure signs by blowing to 1/2 or full cock a they often would with a standard nipple.
I think that Forsythe's "The Sporting Rifle and Its Projectiles" is downloadable on the WWW it will explain this to some extent. Evreyone who shoots a ML should read it. Its got some 19th century "science" in it but it has a great deal of valid information in it.

Dan

[bgf]

They call them buggy ship springs.

Taylor,
Are they "buggy ship" or "buggy whip" springs?  I suspect a simple typo, but could be wrong. 

[D. Taylor Sapergia]

Thanks bgf!!

[Daryl]

Us military muskets also had very heavy mainsprings - 3 times "heavier than necessary".  Although very hard on small flints, I suspect musket flints stood up very well.  Sure fire was more important than any 'jar' they might give.
Doug - I'd reduce the throw and strength of the main if I were you. Since it is a target gun, the 'jar' from a heavy spring is not a good thing.

[Dphariss]

Us military muskets also had very heavy mainsprings - 3 times "heavier than necessary".  Although very hard on small flints, I suspect musket flints stood up very well.  Sure fire was more important than any 'jar' they might give.
Doug - I'd reduce the throw and strength of the main if I were you. Since it is a target gun, the 'jar' from a heavy spring is not a good thing.

Shiloh Sharps always shoot best with an original forged spring from DGW (when they had them) over the factory issue. In the Sharps the heavier spring gave more consistent ignition. But the 74 Sharps has a somewhat odd firing pin.
I would never lighten the spring on a cartridge gun unless it was very, very strong.
There may be a reason for this that will not be apparent until the spring is lightened.
I.E. It must be done with great caution.

Dan

[heinz]

I had ignition problems with my Shiloh Sharps.  They furnished a modified breech block and suggested I switch to pistol primers.  The block helped but the pistol primers did the trick.  It works with either breech block when using pistol primers, which I am told are slightly more sensitive and take a lower impact to set them off.  I have no data other than the pistol primers work and I got less than 50% ignition with magnum rifle primers.

[Daryl]

I was not suggesting reducing the blow to the point of poor ignition and Doug has the expertise to do this properly.  Antoher thought is to make a new spring, with shorter throw but heavy blow.
A muzzleloading-type English spring has a long throw.  They may have been trying to reduce lock time through a heavier spring, but the longer normal throw will counter this.  Reducing the throw but increasing the strength will hit both goals - strong ignition and reduced lock time.

As to light springs, the one on my 'in-the-white' - Italian action that I finished has a lighter than normal main spring.  It has a nice 2 pound trigger pull as well, and shoots moa at 100 meters with BP, under than with jacketed. Seems to work OK.

[Dphariss]

I was not suggesting reducing the blow to the point of poor ignition and Doug has the expertise to do this properly.  Antoher thought is to make a new spring, with shorter throw but heavy blow.
A muzzleloading-type English spring has a long throw.  They may have been trying to reduce lock time through a heavier spring, but the longer normal throw will counter this.  Reducing the throw but increasing the strength will hit both goals - strong ignition and reduced lock time.

As to light springs, the one on my 'in-the-white' - Italian action that I finished has a lighter than normal main spring.  It has a nice 2 pound trigger pull as well, and shoots moa at 100 meters with BP, under than with jacketed. Seems to work OK.

I know guns can shoot well with light mainsprings.
But a simple spring change can and has worked wonders in rifles with accuracy problems.
Guns that go off every time will often show accuracy improvement with a stiffer spring and/or a more uniform  pin strike.
Firing pin impact can be a major factor. I have a Win. low wall  22lr that with a single trigger will shoot very small groups with Green Tag but will fall off a 4 ft high target backer at 100 when a set trigger is used with a fly in the hammer. It goes bang every time but accuracy is pretty "amazing". I found this out when I put a single set trigger in it for a offhand match. Shot fine used as a "straight" trigger but if I set it accuracy "deteriorated".
An experienced friend thinks that a fly in a tumbler of a cartridge rifle is a source of inaccuracy.
One would not think that a rifle with a small straight line pin like the Win SS would have this problem but it IS there. 22 Rf is very susceptible to both strike and pin nose shape but so are  centerfires. My Win SS match rifle with set triggers has no 1/2 cock and thus no fly as do many original rifle of this type used for competition. They were ground out so the rifles are full cock only.
In building match rifles I learned that anything that might cause a variation in pin strike should be avoided or fixed if it existed. It was always good for a MOA or more especially at longer ranges.

Dan

[northmn]

When you compare the late English locks to the early German and English locks you see the difference in theory.  The stirrup system permits a shorter hammer throw, even in flintlocks, but uses a strong spring. By persussion days you had to almost pull back the hammer to full cock to place a primer on the nipple and some were hard on nipples to the point that I had to ocaisionally turn the tip in a drill and turn it down again to get a good seat with the cap.  I have a percussionlock like this and it is avery quick and reliable.  A production CVA lock I had one time required a couple of mainspring replacements to get one strong enough to set of a cap and did not have the stirrup system.   The repos I have used with the stirrup system in flintlock still work very well. The Siler I now have on my latest creation is very reliable so I do not know how much of an improvement they are.  The late flintlocks also went to smaller locks including frizzens and flints.  The early ones and the muskets Daryl mentioned used very massive locks, flints and had very large frizzens.  You could about time a musket lock time with a calender but they went bang.  The large flints could also withstand the stronger springs.  I am still impressed with a repo Brown Bess I had and how reliable it was.  I had to work over a L&R Durs Egg one time as it would totaly destroy a flint within 3-4 shots, so you cannot necesarily say todays springs are weak.  In another discussion I had a while back it was explained that the system for casting springs, includes putting them under a very heavy psi during the cast.  I still do not think they are as good as a forged spring, but forged springs would bring the price of a new lock up considerably.  Might be worth it

DP

[westbj2]

Doug,
Your observation concerning replacement of the Shiloh mainspring is very interesting. I assume that the forged spring replacement you note was "stiffer" than the factory spring resulting in a shorter hammer throw time?  Did you find any other alterations of the lock improved accuracy? 
On the 'fly' subject.  Do you know if the Sharps rifles used in the long range matches (1870's and 80's) had locks with a fly even tho a single trigger was required?  English Match Rifles did have locks with a fly regardless of the maker.  One would assume that by this time in the evolution of British locks they thought there was some advantage to  using a fly.  Not sure what their thinking may have been however.....thoughts on this?
Jim Westberg

[westbj2]

In the post above, the heading should have been for Dan Harris.   Sorry
Jim Westberg

[doug]

      Just a note that with a lot of jiggery pokery, I was able to put the spring back in the lock and my link held together.  Somewhat as Taylor noted the spring is relatively light but not exceptionally thin as he described.  With the spring in the gun but not hooked to the link, I am able to push the lower leg almost up to the bottom of the side plate which surprised me.  A lot of original springs are a lot stiffer than that.  When compressed the legs of the spring are touching and the end of the lower leg actually starts to bend up to reach full cock. 
      Now I have to work on a slug that will shoot straight.  Percussion Enfields and military Sniders (many are converted percussion guns) seem to have some variation in bore dimensions and this particular sporting gun appears to be about .015 over the nominal caliber. 
      I continue to wonder how people ever shot the percussion enfields accurately; so far they have been an exercise in frustration for me

cheers Doug

[Dphariss]

      Just a note that with a lot of jiggery pokery, I was able to put the spring back in the lock and my link held together.  Somewhat as Taylor noted the spring is relatively light but not exceptionally thin as he described.  With the spring in the gun but not hooked to the link, I am able to push the lower leg almost up to the bottom of the side plate which surprised me.  A lot of original springs are a lot stiffer than that.  When compressed the legs of the spring are touching and the end of the lower leg actually starts to bend up to reach full cock. 
      Now I have to work on a slug that will shoot straight.  Percussion Enfields and military Sniders (many are converted percussion guns) seem to have some variation in bore dimensions and this particular sporting gun appears to be about .015 over the nominal caliber. 
      I continue to wonder how people ever shot the percussion enfields accurately; so far they have been an exercise in frustration for me

cheers Doug

If properly designed and used with BP .010-.020 undersize may work surprisingly well.
I know of an original Sharps longrange used by a then factory shooter no less that is .464 groove (nominal for 45 Sharps was .451") and will not chamber a bullet in the case over .451". When loaded as the LR ammunition was loaded, PP bullet 1/16" in the case, it shoots fine according to Dr Gunn's letters to me. Bullet could then bump to the proper dimension.

I won some prizes years ago with PP that were .010" under groove of the barrel.
If you choose to shoot smokeless its gotta be the right size though.
If you need a quality mould and have a diameter and length needed check out brooksmoulds.com.
Not cheap but they will not warp the first time they are heated as most will.
Dan

[Daryl]

Taylor and I found PP bullets in our .45 3 1/4" chambered rifles shot best with a pure lead underiszed bullet, that after being patched, barely was marked by the lands.  The cases had to be sized quite tightly, just to hold a patched bullet, which would only be in the case 1/16" or whatever depth one wanted, as they would chamber no matter how much stuck out.  This shooting of undersized bullets, allowed up to 20 rounds to be fired without blowing into the barrel beteen shots, nor needed any wiping.  Accuracy was 1 to 1.2MOA at 100 yards for 5 consecutive shots off the bags using iron sights (apertures) and 116 to 122gr. of 2f depending on the make of brass. My rifle was a Rolling Block w/Hoch barrel, while Taylor's was a Shilo Sharps, stock barrel with .0015" deep rifling - yeah - thou and a half.

[Dphariss]

Taylor and I found PP bullets in our .45 3 1/4" chambered rifles shot best with a pure lead underiszed bullet, that after being patched, barely was marked by the lands.  The cases had to be sized quite tightly, just to hold a patched bullet, which would only be in the case 1/16" or whatever depth one wanted, as they would chamber no matter how much stuck out.  This shooting of undersized bullets, allowed up to 20 rounds to be fired without blowing into the barrel beteen shots, nor needed any wiping.  Accuracy was 1 to 1.2MOA at 100 yards for 5 consecutive shots off the bags using iron sights (apertures) and 116 to 122gr. of 2f depending on the make of brass. My rifle was a Rolling Block w/Hoch barrel, while Taylor's was a Shilo Sharps, stock barrel with .0015" deep rifling - yeah - thou and a half.

Some of the early Shilohs had various barrels, some were pretty grim.
I have shot parallel sided bullets, PP, with pretty good results. So small I had to use a 38-40 sizer for my 40-70.
But looking at original bullets shows they were tapered. The 45s were about .451 as patched and under bore size at the front of the patch.
This allows using normal case dimensions and dies and still shoot pp without the "paper patch throat" that is needed with groove sized parallel sided PP bullets. I have never seen an original Sharps or Remington with a such a freebore and I looked at everyone I could for years. I have seen one 32-40 Win Hi-wall with a throat but doubt it was from the factory.

Dan