A couple months ago I posted an inquiry as to wether or not the 336 30-30 Marlin could be converted to 308 Win. Well after all the replies I converted mine. It shoots 2" groups with Winchester PP 150gr ammo.
The conversion involved rechambering and bobbing the lifter a little to accomodate the different length. The max OAL is about 2.56 so using cheap ammo is not possible. There is no sign of pressure problems and feeding is great with 308 or 307.
Now a 35 Remington is aobut to be a 358/356 Winchester.

Thanks for the update. I've been wanting to convert a 336 to .300 Sav. Was there no work required with the extractor? I don't own a 336; do you think it would be possible to increase the COL any, by removing a bit from the back of the carrier? Who was your gunsmith; or did you do the work yourself?

We removed about .125 from the front of the cartridge "lifter/carrier" and tapered the little pivot. I think a 300 Savage would work just fine with out much alteration. The bolt needed no change at all.
You will respect the Marlin when you take it down. Everything is well made and thought out.

I just checked some dimensions and the Savage is Max COL of 2.60. The 307 Win is 2.56. 2.60 is about what you can get with the conversion. The mod of the cartridge carrier is the most difficult part. YOu need to saw or mill a piece out of the front of the carrier and reprofile the little pivoting piece on the side.(Don't know th name).The whole thing took about 5-6 hours with the disassembly and reassembly to check feeding and OAL. No alterations were needed to the bolt or extractor/ejector. It pulls 'em out very well without any slipping off the rimless case.
I took the barrel out to cut the chamber. You might be able to do it with the barrel in if you are careful. I bow to superior knowlege and experience.
All in all a very straight forward conversion. Just needs a little fiddling here and there.
I need to polish the chamber a little bit because I'm getting some sticky cases when the chamber gets hot- I ran 2 boxes of ammo through it pretty quick and it got HOT.
I got a bunch of 307 brass and I'm going to load some of Ken Waters recommended loads for the weekend.

Noted; thank you. I'll study your comments along with the description of the working of the action as contained in the original patent (available free on the web).

quote:

the little pivoting piece on the side.(Don't know th name)

Forgot to mention, that pivoting piece is the carrier rocker. It controls the up and down timing of the carrier. It follows the finger on the lever. It's a very clever design.

Actually, it's not obvious to me why the rocker would have to be changed. OK, I must also admit I'm not sure why the front of the carrier would have to be notched.

I knew what that little rocker did but I didn't know the name. You have to shorten the carrier to accomomodate the length of the 308. The rocker is the same length as the carrier. I reground it to match the original profile(as close as possible).
The Marlin is indeed an ingenious design. If it is not in battery, it won't fire.
BTW, I was in Peterborough once in the early '80's. I was wandering through the Midlands.

I'm here in the UK for a 2 yr assignment, then it's back home to the US, which is why I've time to daydream about rifle conversions, etc. -- no shooting for me here.

By "out of the front of the carrier" do you mean the very front tip of the carrier, up near the mouth of the magazine entrance, or do you mean the ledge on the carrier which is about one COL back from the tip? Again, I don't own a 336, but in looking at the drawings, I imagined this ledge in the carrier is what stops the cartridges from going back so far that the next round protrudes from the magazine. In the drawings, this ledge on the carrier is about where the rocker ends as well.

If it is the ledge you milled, then I understand all the points you're talking about, but it seems it must have been dicey getting the rocker to work properly again at its shorter length -- impressive even.

Yes, In the back where the cartridges butts against the rear.

Thanks again, and if I may, what COL do you now have? If you removed .125, you must be up near 2.67". Do you think going to just 2.60 would require monkeying with the rocker? (Of course, the standard 2.55 would be plenty for the .300 Savage)

When I said .125 I was approximating. We just loooked at it and said'That's about all we can take off and still get the little rocker to work". It gaave me an overll length to work with of about 2.58-2.60. You have ot be careful with pointy bullets. The sp type seems to feed better. I has some Federal loaded with Grand Slams that were perfect. The Win PP are just a fraction too long but work OK.