Converting a 300 Win Mag to a 300 WSM?

Shane Lindsey

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Greetings,
Can this be done? I have an older Ruger M77 Tang Safety in 300 WM and I would like to convert it so I can load the heavier/longer bullets. I am limited to the mag length for loading with the design of the Ruger it is not much (<3.34"). I like the rifle design for what it is, but it seems to be getting a little loose in the chamber.
Could I just set the existing barrel back and have a gunsmith run the 300 WSM reamer through it or put a new barrel on it?
Does the bolt need anything done to it? The difference in the two is very little with regards to the case diameter and head.

Has anyone ever done this?

Thanks
Shane
 

BountyHunter

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I love the WSM but you are going to get into this way more than it is worth!

No point in wasting money setting a factory barrel back.

Different feed rails and bolt faces. Way to much money to modify/convert those on top of everything else.

Either sell it or just buy a WSM

Look and see if Wyatts has an extended mag box for a 77 first.
 

MagnumManiac

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Feb 25, 2008
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Even if the conversion was simple, you still won't match the velocity of the 300WM over the WSM, there's no substitute for cubic capacity, unfortunately.
If you want to load longer in your 300, do so and single load it, or extend the mag box.
I had a M77 MK II in 300WM, I don't recall the mag box being that short at 3.34" in mine, in fact, my 25-06 measures over 3.4" (MK II) and my 270 (tang safety) measures 3.375". I think if you can make a MK II mag box fit, it will give you all the room you will need.

Cheers.
gun)
 

Shane Lindsey

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The problem isn't the magbox on this M77, the receiver actually has a "lip/lug/something" where the aluminum mag box seats into. I think that is the limiting factor. I have tried several ways to work around and either I have to single load or grind that piece out and I am not a fan of either in a hunting rifle.

May just be this one is destined to stay 30 cal. I am thinking of 264 WM as well.

Shane
 

mountainman56

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I believe it is certainly feasible. The WSM cartridge base is only .003 larger in diameter. The case itself is however .022 larger diameter so you may have to relieve the rails somewhat. Another option would be the Ruger compact magnum. The base size is identical to the Win mag and the case diameter is the same as the Winchester belt diameter. You would lose some velocity but you could load the long VLD's easily.

I would recommend replacing the barrel though. JM2C

Good luck and good shooting gun)
 

Garycrow

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Jan 30, 2011
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I think you'll have feeding problems and be getting into more problems than you would want. The WSM's are finicky about feeding even from an action designed for them. You'd also have to set the barrel WAY back to get a 300 WSM reamer to clean up a 300 win mag chamber. Setting back a factory barrel usually isn't that great of an idea, a gunsmith will charge you what about he'll charge you to chamber a new barrel from scratch and when you're done you've spent $175 in gunsmithing fees but still have a $10 barrel. Better to just start from scratch with a good quality barrel & have it chambered where you can touch the lands.

The 3.34" actions like the Ruger aren't that great for shooting long bullets out of in cases like a 300 win mag. You really need a longer mag box than that if you're going to run long VLD type bullets in that case. I'd probably look to another action like a remington M700 with the full 3.6" magazine. I definitely wouldn't set it back and turn it into a WSM.
 

jfseaman

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Anything is possible with time and $.

Will it give you what you want?

Certainly the WSM and WM are very close. I shoot WSM and Wby.

I have to believe the guys with Rugers who say it will be a difficult conversion from a feeding standpoint.

If it were me, the project would include changing rather than setting back the barrel.

If you are open to wildcats there are lots of options.
 

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MagnumManiac

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I think the OP has been reading too many magazine articles and interweb forums.
I run Nosler 200gr Accubonds in my 300 WM, even at 3.34" there is ample case capacity, my rifle routinely gets 3100fps, yes, the loads are compressed, but it poses no major problems, just load 'em up before you hunt, don't leave them for months so the bullets have no chance to back out.
Just FYI, the powder capacity of the WSM case is even less with long 200gr bullets seated out than the 300WM seated normally.
If your rifle gets between 2850-2950fps with 200gr bullets, then this is normal per book data.
I see no need to change anything, personally.

Cheers.
gun)
 

EddieHarren

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"It seems to be getting a little loose in the chamber." I still haven't figured that statement out.
 

Shane Lindsey

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"Loose in the chamber"-Gunsmith said it didn't need to be re-chambered yet, but headspace was a "little loose". "Still safe for now but if not re-barreled could be set back."

Like many rifles I cannot take once fired brass from this re-size and shoot from another 300WM. The other is a new 5R so thought this might be up for a new chambering as I love the old Rugers even with the "quirky" designs. My daughter loves the Ruger (shoots it better than me...almost) and wanted to get it cleaned up as new for her.
 

shortgrass

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"Loose in the chamber"-Gunsmith said it didn't need to be re-chambered yet, but headspace was a "little loose". "Still safe for now but if not re-barreled could be set back."

Like many rifles I cannot take once fired brass from this re-size and shoot from another 300WM. The other is a new 5R so thought this might be up for a new chambering as I love the old Rugers even with the "quirky" designs. My daughter loves the Ruger (shoots it better than me...almost) and wanted to get it cleaned up as new for her.
Headspace is either in spec or it isn't. Seems I go through that "once fired brass" thing, with customers, at least 3 times a week Why is that so hard for some to understand?
 

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