475 Ackley / OKH Magnum


#1

Looking through my junk I found what I assume to be 475 Ackley /OKH Magnum NPE made from a 375 H&H Magnum. It’s has a 4 overstamped on the 3. Is this overstamping a common thing to do and if so why go to all the trouble?


Paul


#2

I can’t answer your question but you have a PM


#3

Altering headstamps on wildcat cartridges is not common. Reasons for doing so range from vanity to possible liability.

What is with the neck???

Ray


#4

Ray, they also placed a cannellure on the neck about .4" down for the case mouth.

Paul


#5

What is the case lenght?Some say it is identical to the 470 Capstick but the bullet weight,other say it is longer.

I have asked the same question in another thread but nobody answered me…


#6

The case length is 2.736 inches (69.5mm) Neck diameter 0.491" (12.4mm).

Paul


#7

I think that you have a 475 Barnes supreme,not a 475 Ackley.
Case lenght match Barnes’ dimensions.The Ackley round should be longer ( more than 72 mm)


#8

That could be. The only dimension I had were from CoTW which listed the case length for Ackley/OKH as 2.739". It also states “Both can be formed by necking up 375 H&H brass with out any other changes”. They listed the case lenght for 375 H&H as 2.85". Is the Ackley trimmed? I guess I’ll see if I can find some information some where else.

Paul


#9

Donnely reports a case lenght of 2,85" ( from a Ackley book)

Take a look to municion.org website


#10

Fellows, don’t forget that all of the cartridges mentioned were originally wildcats. Most still are. They were made from 375 H&H or cylindrical brass that had a nominal length of 2.85". Cases made from 375 H&H could lose considerable length in the fire-forming process and so it is not uncommon to find examples shorter than what the books say.

Bottom line - putting a label on any of those nearly identical cartridges is a crapshoot at best. Unless you had the box they came out of.

JMHO

Ray


#11

Well…straight wildcats caliber 458" or 475" are a bit difficult to identify.
I found 3 case lenghts for the 475 Ackley with differences of about 5 mm !

It’s like my 458 lott samples.The one made from 375 brass is shorter than the A-Square factory made round