Glenn,
I came across the Motorace website the other day. They stud Cheng Shin, Michelin, and Trelleborg tires. They list the base tires that you could use as reference. I have also seen the Maxxis IT tires used. Basically, you need a larger lug pattern and intermediate compound. Soft compounds will flex too much and the studs (or screws) will tear out or crack the lugs at the base.
Here is the Motorace website:
http://www.motorace.com/miva/merchant.mv?Screen=CTGY&Store_Code=M&Category_Code=tre
A couple years ago, I bought a studded CS tire from a friend. It looks like the Motorace type. I have a 18" studded Trelleborg that I purchased through Hall's. Both have worked excellent. Kold Kutter screws are fine for several rides, but the carbide studs are the only way for best traction and longest life.
I have a 19" rear wheel on my CR125, so now I need to buy a 19" studded tire or find a used 18" wheel. A stud gun like your friend's would be great, but it is very labor intensive (drill each lug, apply glue, and insert stud). After all the material costs, $200+ tires such as Motorace's is a fair price.
FYI... I also priced out the "Best Grip" carbide stud options. Those are carbide studs that screw in. They run about $100 for a bag of 100 studs. You would need about 250-300 studs for a rear tire. So again you are at the price of a studded Trelleborg from Motorace.
Winter riding is a blast! The only downside is the initial investment in studded tires, but the carbide versions last many seasons.
Regardng rocks...we do a lot of riding in a super secret limestone quarry. Plenty of rock there. The carbide tipped studs of the Trellie's hold up fine.
These days Trelleborg tyres are made in Czech republic. Same factory produces Mitas tyres. Older Trellies were different and "hand made" in Sweden. I don't say that new Trellies are bad, but different. Mitas makes their own studded endurotires too. I'd try Mitas as soon as I have used my Trellies and Michelins.
Someone said that you can use one pair of tires for many years. Ok it depends how much you ride with them and how you ride with them. In my personal use one rear tyre is good for one race. Sure I can train with it about half winter after that, but it's not good enough for race. Front tyre may last half winter (or not).
Most thing that spoil spikes is transitional riding from one stage to another. Roads are often tarmac and spikes get hot if time schedule is tight. In practice they melt.
In March we have Paijanteen ympariajo (Around Lake Paijanne race). It lasts from friday morning to sunday evening. Total course is about 900km. It includes 26 stages and the rest of it is mostly icy tarmac roads. It's possible to succeed with one pair of tyres if driven carefuly, but most riders use two rear tyres. I'm going to be prepared with two sets and extra rear... (Thats the most expensive part of that race because I have to pay it from my own pocket
Pics of mine. Two seasons and almost shot. I ride once a week throughout the winter, as long as it's not below 10F. I've got them on the back of my 450 and that bike is definitely hard on them.