110 fcp hs reloading question

I just recently purchased a 110 fcp hs lapua with the intent of reloading for just this particular round. I have never reloaded before due to the fact I just buy factory loads for my other guns (which will probably change now). I am using once fired sellier&bellot brass as of right now. I was pleased with these cheap factory rounds so I figured I'd reuse the brass until I can find some lapua brass in stock. I do not own a C.O.L gauge so I figured I could do it the old fashioned way. I used a piece of prepped non primed brass and necked it so that the bullet (300 gn Berger OTM hybrids) would fit snugly in.

I loaded the kind round and closed the bolt. This should technically give me my O.L touching the lands right? I did this procedure 5 times to get a good average. Every time I got 3.825 except one that was 3.820. I want to start my loads .0015 off the lands so I set seating die to 3.81. I thing SAMMI specs are in the neighborhood of 3.681?? Everything went smooth untime I starting looking around on this sight and saw most people's C.O.L were in the 3.7's. Did I do something wrong. I double and tripple checked my measurements. Showing I try applying some marking dye to the bullet and chamber the round and see if it is hitting? I am a little hesitant about chambering a live, first time re-loader, round in the house. Please help.

Thanks,
David

COAL is dependent on the bullet used. If you are using Berger bullets your OAL will be longer than pretty much all the rest. What wool be more consistent would be to measure OAL to the ogive.
From memory, however, having reloaded for my 110ba in 338lm, i believe i was about 3.805 COAL for a .015" our so jump.