One of my best friends is sick. He just got the news he has a blood disorder where bruising is really bad for him. He bruises so easy now it sucks. The clots could kill him.
He is into firearms and just got the sweetest sporter 03' in a trade, I've ever seen. The problem is he cannot shoot the big 30-06 rounds.
Are there bad things that come with using such an adapter?
Thank you for any real world experience in the matter. I'd really like to see him be able to enjoy this rifle.

dont know anything about the chamber adapter but what about getting him a recoil absorbing rifle rest? i think it is the led sled by caldwell. it uses lead weights on the rest to absorb felt recoil. i know it was not the answer you were looking for just another possible solution that he can use on all his rifles.

30 06 is a very versatile round. It can easily be loaded light so that the recoil would be comparable to a .308. I have actually fired some 06's that were heavy guns and recoiled less than a short barreled light weight .308. I assume that is what you meant by 7.62. A 308 is just a shortened 30 06 case by the way and both shoot the same 7.62mm (.30 caliber) rounds.

You can also buy a plastic sabot that will allow you to load a 22 caliber round in the 30 06. Not sure who sells them but I know someone who used to use them regularly for varmints and target shooting.

Edit: here are some of them in a kit: http://www.eabco.com/reload02.html there are others out there, just do a search for accelerators or 30 caliber sabots.

There are lots of problems with the adapters. I would not waste the time or $ trying to use one. Besides, if he ever wants to sell that sweet '03, the value will be markedly diminished unless the adapter is removed (which has its own set of problems). Even if going the 30-06 to .308 adapter route was successful, the difference in recoil is negligible, so you won't have gained anything.

By far the best thing to do is start reloading, as noted above. With proper selection of powders and bullets, it is child's play to create low-recoil, safe loads for .30-06. Plinking loads can be be made with virtually no recoil (especially if you use light cast bullets), and hunting loads with only minimal recoil. A single-stage Lee setup is all that's needed for the relatively small volume of shooting he'll do, and the whole thing can be had for about $200 ready to roll.

From the standpoint of preventing a bruise (which is, after all, the whole point of this): contusions occur because of localized stretching of small blood vessels, causing them to tear. If the force is spread out over a larger area, there is less stretch on the vasculature, and therefore, less tearing and less bruising. One of the PAST recoil shields would help a lot in this area.

Adding weight to the rifle will also help dramatically, whether it's integral to the rifle or as part of a rest like the aforementioned Lead Sled.

Muzzle brakes or porting will not be terribly useful. They work best when there is high gas pressure, and light loads will not develop sufficient pressure for the brake to make much difference.

Thank you for the replies. I am sorry for the confusion, I meant to type 7.62x39 in the title. I saw some adapters to change the 06' to the Russian round.

Coupla fairly big problems with that adaptation.
Rim diameter of 7.62x39 is 0.447 inch, while the .30-06 is 0.473 inch. There will be considerable slop on the '03 boltface, probably not enough to prevent the firing pin from hitting the primer, but likely enough to make extraction and ejection unreliable.
Feeding of the short, very tapered 7.62x39 cartridge from the '03 magazine is also going to be less than reliable. Mauser magazine boxes (from which the '03 Springfield is derived) have a width and taper specific for the intended cartridge.
The adapter is also going to create an extremely long freebore, which is not conducive to accuracy.
Finally, standard bullet diameter for 7.62x39 is .310 - .312 inch, not .308 inch. It would not be unsafe to shoot them because that long freebore will keep pressures from spiking, but again, you can't expect top accuracy. Additionally, there are hundreds of bullet types in .308 inch, but relatively few in .310 inch.

It's quite easy to load the '06 with a 125gr bullet cruising at 2400fps (7.62x39 ballistics); no need to mess with all the problems inherent in an adapter.

as pigbat said
a 123 grain slug or there abouts - doing 2400 fps is x39 ballistics. perfectly safe and doable in a 30.06 case if one hand loads it, and will not alter the resale value of the rifle in any way.

which on target, if using a SP/HP bullet will perform similar to a 30.30 on light skinned north american medium game. plenty of punch to do small to medium hog, or deer humanely out to about 200 yards or so (IMHO), or effectively drop a man out to 300 yards if self defense is a consideration... and it always is. (humans are far more delicate than game animals...)

if I were in your friends shoes, I'd spend the funds on a hand loading setup and go that route.

hopefully your buddy can recover from his malady someday.

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Thank you for all the replies. I guess I was just looking for a quick fix. The rifle is so beautifully done it looked to be a commercial made hunting rifle until I saw the giveaway on/off switch for the magazine.
Neither of us has any reloading experience but now is a good of a time as any to learn. Those 06' rounds are not inexpensive.
We are hoping and praying he gets well.
Thank you again, this is a good place to hang out. I'm glad ya'll let me join.