I picked a brand new 8mm Rem mag 700 BDL with open sights. I got a steal of deal on it. Now the issue; I don't want the 8mm mag.
My 2 considerations were -

1) Rebuild in 375 ruger

2) JES rebore to 375 H&H or 375 Ruger? But is the COAL of the 8mm mag too long for a rebore?

It seems to me that the best option is going to the cartridge that is closest to the original. If you rebore to 375, it would be pretty close to a 375 H&H "improved". That would allow you to use 375H&H cartridges. If you want either of the two cartridges you mention, I think you'd be better off re-barrel-ing and it would be the 375H&H that would be best choice in my mind due to feeding issues for one, and for magazine possible issues for two.

Not too many of those left. Sell it to me lol. And buy a Ruger or savage that's already chambered in .375 Ruger.

I'm with Stix, sell the thing original. Those are hard to come by. Just buy the gun you really want. I don't know where your at in the country, but I've seen 375s regularly in the 500-700 range. At that price you'll be ahead with out messing up a perfectly good barrel and paying for a rebore. I've built several custom guns and had multiple rebarrel jobs done and in almost every case it is more cost effective and easier to buy the gun you wanted in the first place.

Mossberg patriot in .375 Ruger. Under 500 bones I believe.

Hmmmm. Have you thought of a different barrel?

I will check my stash of take off barrels, think I have a 375 Weatherby that fits a M700.

Another vote for not altering the scarce 700 8mm mag. You could probably sell it here or on gunbroker for a tidy profit.

that would make a sweet gun