the loss of accuracy with 150gr ammo is more than likely just a slow twist rate unable to stabilize the heavier bullets however much past 100 yards and 7.62x39 isn't going to do much good anyway so taking that 3 inch group into account you are still well within the kill zone for an elk. I've read posts on here where the shooters have used everything from a 475 nitro express to 5.56x45m. your 7.62x39 is lighter than what I would like to take hunting but that is only because a majority of elk hunting where I live requires VERY long range shots.
if you live in an area where you can get within 125 yards then more power to you, I also can't stand the guys that tell you a certain caliber is unethical, marginal, underpowered or my personal favorite illegal based on their impeccable knowledge of the hunting laws in all 50 states. however I think that the first remark was just an attempt at humor. after all, some of the funny comebacks on here is one of the things that brings me back to TFL day after day, so far I am not seeing anything that even resembles unprofessional-ism or lack of decency/dignity. I will say having been a member of several gun forums; ar15.com, m4carbine.net, defensivecarry.com, milsurps.com, thehighroad.org, the firingline.com, snipershide.com, xdtalk.com, glocktalk.com and 1911addicts.com I will tell you that this is among the most civil gun forums out there with a strong knowledge base among it's members and with the exception of THR is the only forum where you can discuss everything from from muzzle loaders to glock, from how to fix your smith and wesson revolver to what ammo works best in your new-to-you MP44 sturmgeweher. if you expect more from this forum then I'm afraid the world of internet gun forums may not be for you.
now just so I can add something pertinent to your question at hand. I inherited my fathers remington 700 with wood stock as a teenager. he had that thing on several week long excursions in idaho, north dakota, south dakota, montana and wyoming. I've seen pictures of some of these trips and all of them either involved being rained on or being snowed on. since I've owned it I have never had it out for more than day trips but it has been packed through rain and snow, it has been banged off trees, dropped in mud and cow dung, covered in dust and been dropped in creek beds. the stock has never had anything done to it since it left the remington factory. it sure doesn't look pretty anymore but your bigger concern IMHO, is going to be stopping your metal parts from rusting more than keeping your stock from rotting.
go out, do your business, kill your elk, bring it home and just remove the stock from the action and set them near your fireplace/heating vent/space heater for a little bit to make sure that it's dry. that should be more than enough attention for a new CZ that's just spent 3 days proving that the internet doesn't know as much as it claims when it comes to elk hunting.
ignore my complete lack of capitalization. I still have no problem correcting your grammar.
I never said half the stuff people said I did-Albert Einstein
You can't believe everything you read on the internet-Benjamin Franklin