Amyone have any idea what I should use for starting loads to launch 1.5 lb harpoons from a 50-70 size case with smokeless powder? I use 10-14 gr of FF black now with good results on wood shafts and up to 30 gr FF with metal shafts but want to switch to smokeless. Thanks for the help.

Matthew

not sure about the powder, but i'm quite certain that you should use match grade magnum primers

The general conversion to Nitro from Black is 40% of the blackpowder load in 4198. A filler is used to fill the space between the nitro powder and the base of the bullet. It's used as a filler, NOT as a wad.

As to whether or not this method will work with pound and a half harpoons, I have no clue.

quote:

Originally posted by Matthewx:
Amyone have any idea what I should use for starting loads to launch 1.5 lb harpoons from a 50-70 size case with smokeless powder? I use 10-14 gr of FF black now with good results on wood shafts and up to 30 gr FF with metal shafts but want to switch to smokeless. Thanks for the help.

Matthew

Mathewx,

This is one of the greatest questions I've read on here in quite some time. For the love of God, PLEASE share some pictures with us.

I think the suggestion to only use match grade primers by butchloc is helpful, but please don't forget to ream the primer pockets square, debur the flash holes, and use a VLD chamfer on the case mouths! Are you neck sizing only, or just PFLR?

Also, be sure to check the runout and OAL. Crimp, or no?

What kind of groups do you get with that rig?

quote:

Originally posted by SR4759:
What kind of groups do you get with that rig?

Depends on the sea state ...

quote:

Originally posted by Matthewx:
Amyone have any idea what I should use for starting loads to launch 1.5 lb harpoons from a 50-70 size case with smokeless powder? I use 10-14 gr of FF black now with good results on wood shafts and up to 30 gr FF with metal shafts but want to switch to smokeless. Thanks for the help.

Matthew

Have you thought of using a black powder substitute like Pyrodex?

Smokeless powder requires higher pressures than black powder in order to burn properly and generate enough pressure to drive your projectile. That pressure can damage guns not strong enough for it. So, what are you shooting your 50-70 cartridges in, and are they actually 50-70s or just something of the same size?

How good a seal does the base of the harpoon make with the bore? I am not sure what difference that will make, but I bet it makes something.

General rule of thumb with smokeless powder is that heavier bullets get lighter charges (heavier bullets don't move as fast as lighter ones and develop higher pressures than ones that get out of the way faster). I imagine your harpoon is quite a bit heavier than your average 50-70 slug.

I would seriously consider pyrodex. Guns made for black powder don't do well with smokeless powders unless you are VERY careful and if you don't have a few spare guns to lose to the testing process...well, it's up to you. Pyrodex is much cleaner-burning the BP and was designed to be used in guns designed for black powder.

Be safe. Always, all ways. Good luck.

Lost Sheep

I will get some pictures up tomorrow with a few more details.

Of course I always turn the necks, champfer and square primer pockets and flash holes and of corse I sort cases by weight. I bought 10,000 brass and then culled them down to just 23 useable pieces but am getting 6" groups at 20 yards so it was worth every minute and every penny

Actually it does use a 50-70 case and depending on the rod and head shoots well. I am casting up some copies of the original head and will post more when the time comes. I intend to use it with some muzzy Gatorgetters this summer to get some gators.

Matthew

quote:

Originally posted by Matthewx:
I intend to use it with some muzzy Gatorgetters this summer to get some gators.
Matthew

Uhhhh... lemme know if you need a deck hand. I've got to see this shit! Hell, I'll even take you to my favorite gator hole!

Have you ever chronoed it? What kind of velocity can one get with a 1.5lb harpoon? Maybe at least 200 to 300 fps? (I am serious with this question, just curious)

I have not even thought of it but I do have a 35P so I can crono some loads. That will give me something to do next week

Matthew

Mathew, I can't wait to see the picutres.

Not to hijack, but here's my harpoon launcher.




It's a Navy Arms copy of a Greener and uses measly 38 special blanks. I made up some 1 pound dummy harpoons with blunt brass heads to chrono and determine what velocity I should be looking for with my reloads, but haven gotten valid data yet. My mistake was using brass for the screws to hold the head into the steel shaft. That only lasted 1-2 shots each before shearing. I've killed two chronos in my life and am leary about losing a thrid, but it is in the interest of science I suppose!

Without the drag of a trailing line the harpoon would yaw badly when leaving the muzzle, adding to the danger of hitting the chrono and making a valid reading harder. The botton shaft was an attempt to vent a bit of the gas radially prior to fully leaving the barrel. Nice in theory, but I doubt it will have much effect. It did work fine on the seal picutre.

I'd love to see what a 50-70 case does!

Bob

quote:

Originally posted by Omnivorous_Bob:
...It did work fine on the seal picutre. ...

quote:

Originally posted by SR4759:
What kind of groups do you get with that rig?

Nothing under of "minute of whale" should be acceptable.

quote:

Originally posted by Kenati:

quote:

Originally posted by Matthewx:
I intend to use it with some muzzy Gatorgetters this summer to get some gators.
Matthew

Uhhhh... lemme know if you need a deck hand. I've got to see this shit! Hell, I'll even take you to my favorite gator hole!

Me too, me too!

God bless America....

I have seen 3 on Martini actions:
In Jaws....
In Waterworld.....
And at a LA gun show that gave credence to the other 2.
.
And I know where there is a nice Martini action............
.
Bluegills beware!

Not in the Sierra manual?