I will admit that I have been spoiled by high quality, long range oriented optics. They allow me to get away with some things that would have caused problems years ago. This week I was reminded of one of those problems.
Sig Optics was kind enough to send me a Sierra 3 rifle scope with their new BDX system. We just finished putting together “Project Stumpy” (more about that guy later) and I decided to mount the Sierra 3 on this rifle. I grabbed a Sig One-Piece 30mm mount from the box-o-goodies they sent and I mounted the scope on “Stumpy’s” scope base. The receiver for “Project Stumpy” is an Ultimatum Precision U300. The scope base that is included on the U300 has a 20 minute of angle incline to it. The one-piece Sig mount that I grabbed also has a 20 MOA incline to it. This resulted in a total of 40 MOA of incline for the system.
Forty minutes of angle is pretty significant, but it is something that I have knowingly done before. The Ultimatum Deadline project wears a 20 MOA Nightforce mount on its 20 MOA scope base. That rifle is topped with a Nightforce ATACR F1 with a ton of internal elevation travel. It makes it a simple task to obtain a 100 yard zero despite the angle in the mounting system. This gives me back that 40 MOA when I try to dial elevation for extreme ranges with that rifle.
The role of “Stumpy” and the design intent of the Sierra 3 is not for extreme long range shooting. The Sierra 3 sample that we have appears to have less than 40 MOA of total internal travel. The BDX system is designed to work as a ballistic holdover based on a 100 yard zero. This is not a limitation of the BDX. It is a malfunction in my brain-housing group that caused me to not check the incline of the mount I was using before installing it. It didn’t take any time at all to switch it over to the 0 MOA mount that I had sitting on the bench, but due to my mistake we lost a range day.
The purpose of this post is to again reinforce that there can be too much of a good thing. Canted bases with built in MOA are great for long range shooting. You can get away with a LOT of incline when dealing with scopes with tons on internal travel. If you can work with a 200 or 300 yard zero (many ELR Shooters do), then a ton of incline may not be a bad thing. With most shooters in most situations, if you cannot obtain a 100 yard zero, you need to re-evaluate how much incline is in your mounting system.
You can find more info on the Sig Sierra 3 6.5-20x BDX here: http://bit.ly/2zFmQGh
It would have been easier to understand IF you explained how much total internal adjustment the scope had. Then where the POI was with the scope’s reticle centered in that adjustment range sitting on the receiver with its 20MOA built into its design. Even better would be a little graphics or drawing showing your predicament .