CCI 35s have not been legally exported from the US for several years so are hard to find here.
I assume there must be some reason you want 35s, but I can not think of a good one.
It is commonly held amongst serios 50 BMG shooters that the RWS primer is far superior and much easier to find in Canada.
I am not going to get into a debate as to why the RWS primers are better, but there is a ton of info on the FCSA site from well known shooters in the 50 community who have stated this.
Thankfully Rick at ATRS has a constant supply of RWS primers and the pricing is about the same as the CCIs used to sell for.
He has a good of stock on all other 50 cal components which makes it nice for us 50 cal shooters and to have an extremely knowledgeable 50 cal shooter here in Canada that is willing to share info and help new 50 cal shooters is an added bonus.
RL25 is not only too fast for most uses in a 50 but there may be a case capacity/loading density problem to look at too. If you are loading spotter or trace it may work, but I would not try it with a 647 or heavier bullet unless ou can find data.