Ruger 300 RCM re-chambered to 300 WSM?

[calinb]

The price was right so I bought an future orphan (a Ruger M77 Hawkeye Compact Magnum).  It's 3-1/2 inches shorter overall than my M70 Featherweight .30-06, while offering perhaps slightly better velocity in the 150 to 180 grain bullet range, and that appeals to me.  I also bought 15 boxes of Hornady Superformance ammo.  If I reload the cases a few times, the brass should last the rest of my hunting lifetime.

But, if I ever had to, could I re-chamber this barrel in 300 WSM (assuming the 300 WSM doesn't become orphaned too)?  I've heard that the 300 WSM, with its rebated rim, will work with my bolt and it sure looks like the barrel could be re-chambered:

http://www.saami.org/PubResources/CC_Drawings/Rifle/300%20Ruger%20Compact%20Magnum.pdf

http://www.saami.org/PubResources/CC_Drawings/Rifle/300%20Winchester%20Short%20Magnum.pdf

My take on this cartridge is it's a "WSM" patent dodge.  There's nothing special about it.  Given that it's just a slightly lower capacity 300 WSM, it's not surprising that the loads I've explored with Quickload are comparable to 300 WSM loads--even from a short 20" barrel, where Ruger and Hornady claim the 300 and 338 RCM are superior.  It appears that any RCM superiority is due to the proprietary Hornady factory powders.  Hornady tunes the powder for each Superformance factory cartridge and bullet.  One of the reasons I chose the 300 RCM over the 338 is the Hodgdon Superformance powder appears to produce nearly the same velocity as the Hornady Superformance factory loads in the 300 RCM--at least in the 150 to 165 grain bullet range.  I see no way a handloader can duplicate the performance of the 338 RCM factory load velocities because the Superformance powder that we can buy isn't appropriate for the 338.

Thanks for any answers to my re-chambering question!


-Cal

[gunnut69]

I really don't know but if the diameters are the same or the compact is a bit smaller and it's shoulder is closer to the bolt face it should be doable. Will the magazine take a slightly thicker and longer WSM round??  I consider the entire short magnum group as a whole to be (to steal a phrase) a reasonable answer to a question that didn't exist! In some instances the actions on these rifles are taylored to the WSM length cartridges and that really limits action versatility.. On the plus side they will kill as well as any 300 magnum already existant.

[calinb]

I really don't know but if the diameters are the same or the compact is a bit smaller and it's shoulder is closer to the bolt face it should be doable.
<snip>

Thanks, gunnut69!  Good point about the magazine.  Even though the cases are the same length, the 300 WSM permits an extra 0.020" in COAL.  That's not much, but I'd have to check some WSM cartridges.  The shoulder of the 300 RCM does start 0.0201" closer to the bolt face and it has a smaller angle so I think the WSM chamber exceeds the dimensions of the RCM in all respects.

As you said, there doesn't seem to be any reason for the 300 RCM to exist (perhaps the 338 can be justified), except for royalty fees or Ruger just wanted a  cartridge with their name on it.  Quickload confirmed that it performs like the WSM, with a bit less case volume to work with.  Given the similarity of the cartridge dimensions, that's no surprise, despite the marketing hype.

Hopefully, my brass supply will last me and it's something that I won't have to ever consider doing, but it give me a little extra comfort to know there might be a way to extend the usefulness of this potential future orphan.