mechanical fit projectile

[rampa room artillery]

well a new project has caught my attention.  a mechanical fit projectile for my mountain rifle.  everyone tells me its to hard. and wont work,  well that makes me want to do it even more.   so i have  a peice of rifled liner about 3.25 inchs long. to begin my plan.   I plan to cast zinc rounds.   anyone else every tried this here.  and with any luck?

  I am looking for something to win 1st place at nationals with and shooting what everybody else is shooting wont get me there. 
   so its time to think outside the box.

 rick bryan

[dan610324]

you mean to cast the zink in that piece of barrel ??
Ive seen something somewhere of a guy doing that
but cant remember how where when or anything
I guess its possible to do it , but You got to think out an good idea on how to complete that piece of barrel to make complete bullets and not just a piece of zink that fits your barrel
if its a good or bad idea I cant say

[KABAR2]

I would Cut a 1" wide peice of the rifled section and add it into a mold simular to what you have,
so that you have a 1" lug on the sides of your projo.... if you cast longer you are going to have to
fight with it to get it down the bore and after a few shots with fowling even with sponging it might
be a problen getting them down there..... lugged projo's had deeep rifling to follow I don't know how
well it will work with a more normal rifling.

[seacoastartillery]

      Rick,   Mike and I have seen such projectiles fired by competitors in cannon shoots in Westero, NY and Casper, WY.  I got up within a few feet of one loading procedure with permission at a practice session and noticed that the zinc projo was a very tight fit and not only had to be indexed perfectly, but the attitude of it's axis had to be pretty close to coincident with the tube's axis.  In short, this makes loading a very finicky thing to accomplish.

     Is your plan to use the exact same liner that the cannon's bore was made from?  If so, form errors aren't going to zap your efforts, unless your tube has gain twist rifling.  The shrinkage rate of the projectile as it goes from molten to cool is .007" per inch, so you theoretically will have a total gap of .01575" or only .00788" all around. NOT MUCH!!   Even an increase of .010" or .012" in size diff. would make loading a heck of a lot easier.  The closer you get to a line-to-line fit, (same projo dia. as the bore dia) , the difficulty of loading increases exponentially.

     If you are thinking of something completely different from what I have described, please let us all know.

Sounds like a terrific project, Rick.  Pay no attention to the naysayers, Just Do It!.

Tracy and Mike

P.S.     Ref. this post about ZN shrinkage:             

http://www.gboreloaded.com/forums/index.php?topic=234419.0

[gunsonwheels]

Some folks are casting into a short barrel piece but some are swaging... one fellow that wins a lot casts a wheelweight metal (higher density but softer than zinc) slug with an enlarged skirt (about the diameter of the rifling GROOVES) at the bottom (land diameter is used with the upper portion along with lube grooves).  Taking a barrel section, he cut a recess into the lands and a taper going into their full profile and then had the section hard chrome plated... He then would set the cast slug in the recess and swage (with a hydraulic press) the slug through the rifling.  Due to the chrome plating, the slug's rifling would be slightly undersize of the barrel (both lands and grooves)and fit snugly into it while engaging the rifling.  Zinc will also swage but requires more pressure.  He also had a hollow base mini-ball style geometry so the gas pressure on firing would expand the rifled skirt completing a good tight seal.  Shooting discipline does require going into the barrel with about three or more wet swabs from sopping to just damp and with varying levels of soap concentration finished by a white dry swab... which if still white signals "okay" for powder and projectile for the next round (hey if you cannot fire again for ten minutes you may as well spend your time making sure the next round goes where you want it). 

Now... shall we talk about windage...??  I think NOT!!

I got up within a few feet of one loading procedure with permission at a practice session and noticed that the zinc projo was a very tight fit and not only had to be indexed perfectly, but the attitude of it's axis had to be pretty close to coincident with the tube's axis.  In short, this makes loading a very finicky thing to accomplish.

Know another shooter who cut out a couple of inches of rifling at the muzzle end to allow the proj. to align the two axEs so all he had to get was the "clocking" engaged.

[Cat Whisperer]

Two principles.

One:  accuracy is gained from controlling and trying every option.  There are MANY.

Two: If you think of a new keen idea, someone has already trired it.

Three:  don't let 1 and 2 slow you down, just take meticulous notes on what you did so you can change one thing at a time.  Know what you change, what you don't, and what the effect on accuracy is - so you can repeat it.

MUCH of winning the match is not having a super accurate rifle (pistol, cannon) but of READING the effects of WIND.

[rampa room artillery]

well the lead furnas is heating up right now, to cast my first prototype  i have just finished most of othe mold, enough to cast a few to seehow they will fit.

 rick bryan

[Cat Whisperer]

There are some Scheutzen rifles with false muzzles that also use front loaded bullets either cast for or fitted into the false muzzle to ensure a precise fit.  Make precise measurement, take copious notes.  Good Luck!
 

[GGaskill]

Since you did this already, my suggestion is a little late but I would have gone with a bore rider design with a relatively narrow groove diameter engraving band located between a half inch and one inch ahead of the back of the shot.  The rear cylinder would give good loading alignment and the narrow engraving band would make for easy pre-engraving.

Sponge, sponge, and sponge some more for this to be loadable.   

[rampa room artillery]

well i have cast the first one, prototype,  it fits great, has .03 windage, which doesnt sound like alot but but my other pellot i shoot only has .02 windage. so its great for me.  I have a bore brush to really get into the rifling so it will be ok. 
   I hope to get my other pellots ready for the shoot., then i will try to finish the mold so i can bring a few to the shoot to test them out. i have to reduce weight so a conical base is in order.  I am going to clay one of the trash can style pellots of my buddys to get a good shape and amount of metal to remove to make weight requirements for n-ssa. 
  it looks great. takes some time to let cool so i can remove them from mold but once they are cool they slide right out.

   this was alot easier then i thought it would be.


 rick bryan

[Double D]

If these are lead, you need to handle them very delicately it won't take much to damage them and stick them in the bore. been there...

[Cannon Cocker]

well i have cast the first one, prototype,  it fits great, has .03 windage, which doesnt sound like alot but but my other pellot i shoot only has .02 windage. so its great for me.  I have a bore brush to really get into the rifling so it will be ok. 
   I hope to get my other pellots ready for the shoot., then i will try to finish the mold so i can bring a few to the shoot to test them out. i have to reduce weight so a conical base is in order.  I am going to clay one of the trash can style pellots of my buddys to get a good shape and amount of metal to remove to make weight requirements for n-ssa. 
  it looks great. takes some time to let cool so i can remove them from mold but once they are cool they slide right out.

   this was alot easier then i thought it would be.


 rick bryan

Rick,  What did you end up doing with the mechanical fit idea and mold.    Also, what is the nssa weight requirement for a mountain rifle.