Home Forums Hunting & Shooting Ask The Gunwriters Clarion Call: .270 WSM "Crush" and Load COAL's for 160 gr. NP/140 gr. TSX

Am building a cartridge around these bullets and the SAAMI spec. .270 WSM leade.

Needed for these bullets: (Nosler Partition/160 gr., Barnes TSX/140 gr.)

- "Crush" COAL. (hard against the leade)
- Any COAL for these bullets that shoot really well.

This information will help determine COAL/leade location given 1 dia. case seating depth.

TIA.




GR

Why wouldn't you start w/magazine COAL capacity and work backwards into the chamber dimensions? Or are you intentionally building a potential single-shot?

Started w/ magazine COAL, and then worked backward to get case seating depth (.280") COAL.

Now I need to bring the leade to that, plus setback, using the bullet tip as a datum.

TIA.




GR

Seat bullet to mag confines. Measure length w/bullet comparator installed on calipers.

Developing a cartridge/chamber.

Need to know where these bullets contact the leade on a SAMI spec .270 WSM chamber.

Either a dimension on the bullet, from tip or base, or a COAL seated hard against the leade, will allow me to translate that into the new chambering.

TIA.




GR

Look at the reamer diagram and with a comparator you should be able to determine overall length. The 270 WSM has almost no throat or lead for 2.850" actions, but most are built on 3-3.2" actions. I would throat for the magazine minus 0.2-0.4" and I would also go with a 1 in 7 or 8 twist to shoot the longer 270 bullets available now.

Here is some info that might be useful: https://www.brownells.com/aspx/learn/learndetail.aspx?lid=12897

Couldn't find a reamer dimension sheet but just ask one of the makers and they can usually send you one and also an order sheet for specific dimensions.
Easy way would be to do the standard chamber then open it up to match your specific bullet and seating length.

I think I know what it is you're looking for and why, but sadly I do not have either of the bullets you care about in hand. But referencing my notebooks, here are the max OALs that result in the listed bullets just barely being a wedge fit into the lands of my stainless Win M70 .270WSM made in early 1998. These numbers are not a "crush" fit into the lands, just pushed into the lands enough to allow a reference rod to rest vertically on the bullet tip for taking OAL measurements at the muzzle. I do not know if my chamber started out "SAAMI-standard" or if so, if it still is.

130 Part - 2.83"
150 Part - 2.83"
140 NBT - 2.84"
150 ABLR - 2.90"
140 NAB - 2.845"
130 NAB - 2.85"
130 Hor GMX - 2.825"
130 SGK (old stock) - 2.78"

Maybe this will help you some.

Rex

I don't have the bullets you specified, but just to add another data point I do have a Tikka T3X .270 WSM with less than 20 rounds down the barrel. Using the Hornady AOL tool and pressing the bullet firmly into the lands, I came up with a COAL: of 2.940 with a 140 grain Nosler Accubond bullet. FWIW the unmodified magazine is about 2.85 inches so as it sits I can't quite get to the lands with a 140 NAB unless I use it as a single shot.

Thanks y'all.

To minimize variables, increase flexibility, and stave off disaster - used a different vector to approach the problem.

And, by giving up a little capacity, this should be a solid cartridge.

Thanks for the help.




GR