NEF BP project gun

[omgb]

So here is my project: to take an NEF/HR Ultra 12 GA slug gun, brass Win 12 ga cases and about 180 grains of BP and fire an 850 grain slug. HR says their bore is .718" My cases mic at .726 I.D. I will do a chamber cast when the gun arrives. Then Veral Smith at LBT is going to custom make the mould. I have a FL sizing die I made so that I could use those hulls in various double shotguns I have. Even after passing a case through that die, the I.D. at the case mouth is still .726. If the bore slugs out at a true .718, my bullet will have to be .720. That should allow me to finger seat the bullet in the case without needing a seating die...right? Any thoughts on this? Anyone slugged an Ultra bore?

R J Talley

[nanuk]

what is your Groove diameter?

are you sizing to bore, or groove? or to just over bore diameter?

[omgb]

I want the bullet to be equal to the depth of the grooves but since I don't have the gun in my possesion yet, I can't slug the bore. I asked H&R what their bore dia was and they replied .718. I asked about groove depth and they said they didn't have that figure.

[turbo1889]

The groove diameter on your H&R will most likely be between 0.729" and 0.731" based on my own personal experience with multiple examples of 12ga. rifled slug barrels made by their company. There is a tolerance range and you will have to slug the gun when you get it to determine exactly what the groove diameter of your particular gun will be.

You should have your mold cut to drop a slug that is 0.001" to 0.002" larger then the groove diameter of your gun not the bore diameter. Thus you shouldn’t have any trouble getting some neck tension upon seating the slug in your brass cases.

You will need to slightly bell the case mouth. The method I use is to find a 1/2” drive socket that is bottle neck shaped to fit a small diameter bolt head where the smaller neck fits inside the case and give it a tap or two with a rubber head mallet to slightly bell the case neck. Here is the kind of socket I am talking about; I think you can see how if you find one of the right size it can be used to bell the case mouth fairly easily:

http://act-handtools.com/images/005-421DA.jpg

[Andy Griffith]

You will need to slightly bell the case mouth. The method I use is to find a 1/2” drive socket that is bottle neck shaped to fit a small diameter bolt head where the smaller neck fits inside the case and give it a tap or two with a rubber head mallet to slightly bell the case neck. Here is the kind of socket I am talking about; I think you can see how if you find one of the right size it can be used to bell the case mouth fairly easily:

http://act-handtools.com/images/005-421DA.jpg

I'm speechless.
I wish I'd have thought of that!!! So simple and it works!!!
:D

I always have to complicate things. :confused:

[omgb]

Man, I can only hope it is .729-.731 that would be perfect. A pure lead slug at .731 will go finger tight into the case...that would be perfect. I am prepaired to contact Rockymountain Bullets to have custom cases made if need be. I'm thinking this should be a real Black Powder thumper. I know I won't be able to reach smokless velocities but that's not really the point. The point, if there has to be one, is just to have fun with what amounts to a modern version of a late 19th century 12 bore game gun.

[Andy Griffith]

Rocky Mountain cases are great, but are very heavy because they are turned. They don't lend themselves easily to doing much with them because of their very thick body walls. Also, their inner diameter is very small compared to the think walled Magtechs. I'd suggest sticking with plastic or paper hulls- a lot less equipment is needed.

[turbo1889]

I know you already stated that you intend to have Veral Smith at LBT make your mold for you but you might want to also consider Accurate Molds since he already has four designs that are suitable for 12ga. rifled barrel slug guns:

http://www.accuratemolds.com/catalog.php?page=6

I have an AM#73-775S and an AM#73-900S mold and White Eagle (another member on this forum) has an AM#73-770S and an AM#73-780M

The AM#73-780M has a reverse taper to the design since it was originally intended for a muzzle loader but all you would have to do is just specify in the notes field on the order form that you wanted yours without any taper with all the drive bands the same diameter to use it in a regular breach loading cartridge shell gun.

Tom @ Accurate Molds is a genuine craftsman and his molds are excellent quality. Since he uses a CNC lathe boring process each mold is cut to your specified diameter in 0.001” increments with a tolerance of -0.0000/+0.0015. He is reasonably priced and has quick turn around. I should note that he only does solid base pore molds and doesn’t do hollow base or hollow point molds although you can order a mold from him and then have Eric or Buckshot convert it to a hollow point mold.

[white eagle]

My USH bore miced out bigger than .718
I had Tom do the first slug mold for me
mine is similar to Turbo's
mine is .7315 my mold is .733