Slugged My Longbranch #4 MkI*

[BudRow]

It is a 5 groove that I slugged with a pure lead 103 gr. Boolit that I cast in my RCBS Nambu mould. I cast up a bunch of these to use for slugging purposes only. My Longbranch No. 4 Mk.I* is like brand new with a perfect bore. I wanted to shoot cast in it so I throughly cleaned the bore of all copper fouling and slugged it this morning. Of course it is difficult to get accurate figures due to the odd number of grooves however I decided to see if the slug would slip through my Lee .314 Boolit sizer. It fell through with room to spare. Next I expanded the neck of an old 30-06 case with a LONG TAPPERED EXPANDER MANDREL in .0005" increments. I polished the inside of the neck with fine steel wool and then started: .3145", .315", .3155" and on till I got to .317" at which point the slug would pass. OUTCH! I carefully measured each increment with precision small hole guages. I am conviced that this gun left the factory with this barrel as it is. Now this gives me the groove diameter and thats primarliy what is of interest to a cast shooter but if the the grooves are typically .005 - .0055" deep, then the BORE must be .307" or so. I need a dial indicator with a small nib to check the difference between the groove and land. I am shocked, I guess I won't try to make a cast shooter out of it - too far out of the norm.
Merry Christmas, Bud

[Phil]

Not really unusual but it is on the high side. I've seen lots of them that measure .316" and I think the record that I have measured is .318". The only problem is when they get so big you have to start neck turning. This isn't all bad as you can set up the neck so all you have to do is reprime, recharge, and seat a new bullet.

I have one No.4 barrel that has a .314" throat and .314" grooves with .304" lands. It is really a treasured barrel that I only shoot cast in.

Heck, play with it a bit, it may surprise you!

Merry Christmas,

Phil

[PAT303]

It's not unusual for a groove that size,they made them that big to lower the pressure in the tropics and desert.In a mates long branch we shoot lymans 311291 bullet unsized and it shoot's spot on,we also tried paper patched lead and jacketed bullets that shot equally well.It was only the groove diameter that was enlarged, the bore stayed .303-.304.my mold cast's boolit's that are .314 at the base, but the top band is .317 so we don't have to turn down the necks. PAT

[mag_01]

--------Welcome aboard BUDROW-----My #4 likes a .316 boolit and shoots well .3165 will not chamber---I opened up a .314 die to .316----removed the head space problem and it now shoots well and dose not separate cases---boolits are 180 and 190gr.-------Mag

[Buckshot]

.............BudRow, Welcome to the board! I have a 1909 Arg Cav carb that has a .314" groove but a bore that defied anything I could come up with at .303 or .304", I forget now :-) I tried bumping up noses in the size die to no real gain (other then some bent noses). I didn't have any 32-40 bullet moulds (.321")so the next step up for me was 8mm.

I lube sized the Lyman 323470 boolit (165gr) in a .323" die and then ran it up through a Lee .314" push through die. Since it was a Loverin with no bore rider to worry about, I was hoping this might work. And so it did! The rifle became a real shooter. Check your throat and see what it will take.

...............Buckshot