Coast Guard line throwing .30 caliber projectiles

Looking for information on the projectiles used in the U.S. Coast Guard M1903 Springfield .30 caliber rifles converted to line throwing use.

Brophy’s 1903 Springfield book has some limited info.

Does anyone have copies of the USCG documentation on these guns and especially on the these projectiles, either the solid type, or the later buoyant types?

I especially need dimensioned drawings, or better yet, a source for any projectiles (even damaged ones) and some of the shot lines.

The commercial .45 caliber line throwing guns (trapdoor Springfield or single shot top break Coston or Bridger types) and projectiles seem to be more common, but I have not been able to find specifics on the USCG .30 caliber versions.

Someone has to have some of these or know something about them. Anyone?

Hi John, here is some information from a USCG manual published in 1965:

Some more from a 1938 manual:

Thanks Fede!

Does anyone have any of the projectiles or dimensions from them?

This is the patent drawing:

That’s the best detail to turn up yet. What is the patent number?
Thanks again!

John, your welcome, wish I had more information. The US patent number is 2,069,276.