How big of an ordeal (and how much metal would be left) if I wanted to open the bolt face on a Rem 700 375 RUM to fit the 9.53 Saturn or .378 Weatherby? I've been toying with the notion of getting the RUM, and having a barrel chambered for either two of the aforementioned rounds, and having the bolt face opened up...is there enough metal? I figured there would have to be, at least for the lazzeroni, since John started making his rifles off of 700 actions.

Dan Lilja has his opinion on his website. There's a number of articles there that are worth reading.
As far as work, it's as easy as packing it in a box and licking a stamp.
I assume the rechamber would be done by a pro smith, no? Any competent one can do open the boltface.
(Not all will, though.) Factory Lazzeroni and Weatherby loads are both pretty high pressure, and the M700 wasn't designed around that sort of performance. There are many who've done it, and there are many who will tell you not to.
As an aside, check out performance gains with sporter-length barrels before you go too far.
Many feel the benefit of increased speed doesn't come close to the detriment of heavier recoil, unless using big bullets in long barrels. The RUM might send a 270g out at around 3025 fps with maybe 95g of powder from a 26" bbl, and either of the other two will go 3150 using almost 110g.
That's about a 15% increase in recoil for a 5% increase in speed. There's even less in the 260's and 250's. The 300g bullet is a bit of a different story, however. All depends on how your boat floats.
That'll be 2 cents, please.

444,

If you open it up for the Weatherby, 338 Lapua, 416 Rigby, Laz cases, using one with a 30-06 size boltface doesn't require the boltnose to be sleeved to get rid of the extractor groove when installing the Sako or M-16 style extractor you need. Feeding will take work, but I assume you'll be single feeding the longer ones? George Garderner at GA Precision will do the conversion correctly, he's built a ton of them.



I have one in 30-338 Lapua Imp, my brother has one in 338-378 WBY, 32" bbl. I'm building another light weight rifle this coming winter in 30-338 Lapua Imp again. The one I have now has a 30" 1.35" barrel on it, not quite a hunting rig, but shoots in the 2's to 4's consistantly with no barrel block yet.



Interestingly enough, Remington built some 338 Lapua sniper rifle prototypes on the 700 called the SR8, ask George about it sometime.



Depending on the "loaded" OAL, you may have to shorten the ejector on a M70 action, and both actions may also need the rear of the ejection port taken back some. Shortening the bolt stops and some milling is required if using a longer Wyatt center feed box. George and Chris do this all the time too.

I have watched my brother alter a bolt face:
He could not get the the hard bolt face to cut right [the tool force was high and it made a screaming sound], even with a carbide bit. So he put a die grinder on the tool post with a grinding wheel bit. He dressed the tool straight with a diamond. He then ground the bolt face with the lathe running counter to the die grinder running. If this is done slowly, there is very little tool force.

Bwana-be...thanks for the Lilja info...it was quite informative...so I guess it would mostly be a question of using the 9.53 Saturn, since it is almost the same case dimensions as the Rigby, which was the lesser of two evils it seemed like in Lilja's article.

The 700 action isn't designed for higher pressures? I was definitely under the impression that they could take any pressures that a round could dish out. What kind of pressures are the Laz and Wby operating on? The RUM?



Plus, the 700 action in question would be for the 375 RUM, not 30-06 as was mentioned before, so length is not a problem.



These plans also include a 26 or 27" medium heavy fluted Pac Nor barrel, installed by a competent gunsmith, so no worries there...but perhaps I could just try the RUM with a 27" and see if it gives me the desired velocities.

Ah, new barrel. I thought you were saying simple rechamber. I wouldn't mind one of the big cases with a 28" bbl. 'Bout as long as portable to me. But keep in mind, the speeds you see for the RUM will be increased by another 75 fps or so as well.
As for the pressures, the word I used was "performance," i.e., the bolt thrust and ring flex around such a big piece of brass. Someone else can say exactly, but I think the Weatherby and Lazzeronis are factory loaded at 65-7k psi? Is the RUM 62? Anyway, even handloading to same pressures will get you much more bolt thrust as well as having less steel on the barrel tenon.
Please note, I don't know what I'm talking about, just parroting what I've heard folks say. And there's lots of folks on both sides of the fence....
Me personally, I think if I wanted a big case like that, I'd have no trouble starting with a CZ magnum, with plenty of room on all sides. Good idea for the RUM even, since a good 270g could easily be seated to about 3.7" if there was room.
The 375 RUM does to the H&H what the '06 does to the 30-30, no small feat. Might be a really good idea to play with one first, see if you can save yourself about $500.

444,

What I probably didn't explain well was, the 700's action length is the same whether it's 30-06 or 300 Ultra Mag. Not the case with the M70, the magnum length is needed, as it is longer. The 30-06 bolt face is smaller, yes, and the Remington extractor groove is also smaller in diameter, thus when the bolt face is turned out to accept the WBY, Rigby etc. case head size, it also cleans up the whole extractor groove doing so. This is not the case with a magnum size bolt face, it leaves some of the groove in the boltnose ring. So, it's common to turn it out oversize then solder a sleeve in place to eliminate the groove, then open up the ID to the correct size. Sleeving the bolt nose is just not necessary if you start with the '06 size boltface, that's all I was trying to say.

Bolt thrust is increased with the larger casehead size, yes, but it still retains more than a two to one safety margin. You'll not reach that even with a full casehead seperation. Even running hot loads (70k psi), which most guys do and don't even realize it, the brass is still the weakest link. The difference in thrust at 63k psi (RUM) and 65k psi (Wby, Laz) is minimal, and most guys handloads exceed both!

If I were you, I'd seriously look at the 338 Lapua brass, much higher quality and stronger than the others, cheaper ($1.30 ea. at Sinclair )than the Wby ($2.00 ea.) or Laz too.

One could always open up the RUM to the others if it didn't do what you want, just cost another chamber job and dies.

Here's a 700 boltface opened up.

Thanks Brent, et al.
For some reason I just took for granted that the Magnum actions were longer than the standard 'long actions' on the 700s, much like the m70...learn something new everyday.

I guess I'm still confused as to the whole sleeving process you're talking about, but I guess that's something I need to sit down w/ my gunsmith and have him show me. The more I've been thinking about it, the more I'm wondering why I want more than the RUM anyways...*shrug*

The 444shooter,
The M/70 long actions are all the same action length. The only difference is that the receiver used for the longer cartridges (7mm STW, 300 RUM and 375 H&H etc) have a longer ejection port and use a shorter ejector, bolt stop and a magazine without the filler. You can convert any of the standard length actions to accept the longer cartridges by opening up the ejection port to the rear until you just remove the forward scope base hole then redrill to the short hole spacing.
Good luck,
Headache