A simpler way to do this if it is not a structural joint is to put 2 blades on your SkillSaw. It will accept them. Make a level line down the center of the log from top to bottom. Cut down this line, put the logs together and after fastening them to the wall, drive a 3" x 12" x 3/16" piece of plate down the joint. It will fit. It is best if you sharpen one end of the plate with a minigrinder first. Drive it into the logs below. This makes a great weather-tight joint. I ALWAYS primer any steel before installing. This is easier than using a chainsaw, especially if you are not experienced at making plunge cuts.
This does seem like a very time consuming and labor-intensive detail to make work. First, I would like to know where in the wall this butt-joint occurs? Apparently, you have a log crossing above the joint. Is this a corner or an interesecting wall? Is this joint sitting on other logs? Does it need to carry any load? Why can't you simply pin this log to the logs below? Are there any settling issues concerned with this butt-joint?
I have a very simple, as well as secure way, of connecting logs at butt joints when needed. Depending on the application and circumstances I have used this method in structural spans. You only need a piece of 1-7/8" x 24" Sch. 40 pipe, 2-3/8" x 8" spikes or pins, a 2" Milwaukee self feed bit/extension. This method takes about 8 min. per butt joint to complete.
If this is a simple butt joint in a log wall:
1) Fasten one of the logs to the wall as per your manufactures specs.
2) At the butt end find the center of this log and with a 2" Milwaukee self feeding bit drill a straight horizontal hole approxametly 13" deep.
3) Drive a piece of 1 7/8" x 24" Sch.40 into the hole. Stop at 12".
4) Slide the log to be joined, up to the pipe and mark it's location on the butt joint.
5) Slide it back so you have access and drill a horizontal hole in this matching location.
6) Slide the log back. Useing a rope come-along draw the two logs together! Done.
If you are concernd about this joint ever seperating, simply drill a 3/8" hole 8" from either side of the butt joint directly down. You will feel the bit hit the pipe. Drill through till you feel it hit wood again. Drive a piece of 3/8" in this hole. It will hold forever. You can also apply a 2-part epoxy adhesive in the 2" holes before you drive in the pipe to give your joint added strength.
Milwaukee makes a great set of quick connect bits in the larger sizes that I use for my deep holes. No more lost bits. Simpson makes the epoxy I use.
I have a complete set of custom hardware based on hidden connections, using pipe instead of plates. If you have any questions, feel free to contact me at firstname.lastname@example.org or email@example.com.