Well as best I can remember, (it was 15 years ago or so) I sent the rifle to Allen Carr, the smith that built it for me and he had to pull the barrel to get the action open. He then re-assembled after carefully checking the metal work for any visible damage. He then re-installed the barrel and checked the head space which was slightly larger indicating lug set-back. He then re- headpaced the barrel and test fired and returned to me. There were no further issues. I continued to use the rifle for many years without any probs.

The lugs being set back means that the lugs are compressed thus increasing the distance between the bolt face and the rear of the chamber, therefore increasing head-space. The barrel has to be then turned further in to correct this increase in dimension. Mausers have a very coarse thread so it means that not much of a turn is required.

I am no expert in these matters but have not seen any evidence of any 1908 or 1909 Mausers blowing up because they are "soft". I wouldn't hesitate to use one in original condition. If you are really worried why not send it in for heat treatment if you can find someone in Oz to do it. Or get really carried away and send it to Germany and have the whole receiver and bolt colour case hardened. That looks way cool and will alleviate any potential concerns. Good condition 1908's are beautifully slick actions and with new bottom metal are an excellent choice for a high end custom rifle.