7/270WSM - 7/300WSM

[Curious]

Guys,

Am I right in thinking that these two are in effect the same other than I would be necking up 270WSM brass as opposed to necking down 300WSM?

My reamer is marked 7/300WSM, I understand how this differs from the 7WSM in terms of having a bit less capacity and a longer neck but can't see where 7/270 relates to it all?

What is your preferred way of getting there, necking up or down and what dies do I use?

Many thanks and Merry Christmas to ya'll.

 

[RDavies]

Guys,

Am I right in thinking that these two are in effect the same other than I would be necking up 270WSM brass as opposed to necking down 300WSM?

My reamer is marked 7/300WSM, I understand how this differs from the 7WSM in terms of having a bit less capacity and a longer neck but can't see where 7/270 relates to it all?

What is your preferred way of getting there, necking up or down and what dies do I use?

Many thanks and Merry Christmas to ya'll.

Yes, they are the same. I use either brass in mine, though I suppose it is slightly easier to neck 270 brass up than 300WSM brass down. Both cases are same headspace and OAL.

 

[Curious]

Yes, they are the same. I use either brass in mine, though I suppose it is slightly easier to neck 270 brass up than 300WSM brass down. Both cases are same headspace and OAL.

Thanks for confirming what I thought.

What dies do you use?

 

[ShaunBrady]

Guys,

Am I right in thinking that these two are in effect the same other than I would be necking up 270WSM brass as opposed to necking down 300WSM?

My reamer is marked 7/300WSM, I understand how this differs from the 7WSM in terms of having a bit less capacity and a longer neck but can't see where 7/270 relates to it all?

What is your preferred way of getting there, necking up or down and what dies do I use?

Many thanks and Merry Christmas to ya'll.

Yes, the 7/300 can be made from 270wsm with a simple neck up.

You're probably aware that a big reason that wildcat exists is 7wsm brass is hard to find, while the 270 & 300 are not. 270 and 300 used one shoulder dimension, the 7 is longer to prevent chambering in the other 2.

270 brass has been cheaper to obtain. Its not really much of a wildcat since you're only necking up from .277" to .284". Dies are easy too. I use a 270wsm bushing die with appropriate bushing to size and a 7wsm seater. I had Whidden make a sizer in the Dillon trim die format. It simplifies trimming when needed and gives me a fixed neck sizer to use before neck turning. A cheaper option is Forster can make a 270 die with the required larger neck. I was using a Redding 7WSM fixed neck sizing die with 0.045" turned off the bottom before buying the Whidden die.

Compare the neck diameter on your reamer with the diameter of a loaded round before you shoot the first one. WSM brass can have very thick necks and some of those reamers are made with diameters that would be no turn on most 7s but do require turning for the WSM. The brass from a chamber cut with PTG reamer T10467 is 0.316" diameter after firing. It's 0.319" on the reamer drawing.

The case capacity of Norma 270 brass once fired as 7/300 is ~ 3 grains of water less than Winchester 7wsm brass fired in a 7wsm chamber. The combination of H4831SC and 210M primers gives me low velocity spreads. With the 162 AMax, the 7wsm was the original budget 1 mile gun. I'm using the newer 180 ELDm the same way.

Accurate makes a short action AICS pattern magazine that will feed rounds loaded to nearly 3.0".

 

[RDavies]

Yes, they are the same. I use either brass in mine, though I suppose it is slightly easier to neck 270 brass up than 300WSM brass down. Both cases are same headspace and OAL.

I use an unmodified Wilson 7mm WSM seater and a Redding 300WSM FLS dies, just swapping bushings when I move it between my 300WSM and 7mm/300WSM (7mm/270WSM)