My attempt to find the lands of my sako s20 in 6.5 prc has been wildly inconsistent. Using 2 methods i got eratic results.
Hornady OAL guage using the Hornady modified case (base to Ogive).
2.3525"
2.3900"
2.3720"
2.3635"
2.3760"
Hornady OAL guage with homemade modified case using fire formed brass (base to ogive).
2.3840"
2.3820"
2.3835"
2.3840"
2 3830"
Using fireformed brass, loctite, a bullet, and the bolt to push it into the lands. Wait for the glue to dry and then measure the base to ogive
2.3710" (coal - 3.011")
2.3180" (coal - 2.9580")
I am very surprised at how inconsistent these methods are. I was fully expecting to see a fairly tight data group with the possibility of a few outliers. I have machining experience and am very familiar working in tight tolerances. When we are talking about changing seating depth by .020” i want a better zero.
The best data i got was using Homemade fireformed modified case and the OAL guage. That yielded an average of 2.3833" CBTO with an extreme spread of 0.0020”.
Anyone have any thoughts on the matter? Im using 143gr ELD-X so they shouldn’t be jump sensitive. I just dont want to waste a bunch of materials and time chasing my tail.
I’m not totally sure what could be causing that. I usually measure twice and they’re usually pretty close and I take the average. Are you pushing the same tightness into the lands each time? I stop right when I feel resistance.
Watched a video tonight from ultimate reloader where he talked about 3 different ways to measure this.
First way was using the Hornady OAL guage. Second way was use loctite on the bullet and inside neck of the case, seat a bullet long, chamber it, let the lands push it back into the case, let it dry, then measure and repeat a few times. Third was basically the same as the second method but without the loctite.
The results all seem fairly close, is the OAL gauge really worth buying? Has it made an accuracy difference for those that have tried a couple of these different ways?
I have done it all three ways the UR guy details. Seems like when seating long with or without loctite and using the bolt to move the bullet into the lands it is a fairly hard push to close the bolt and often without loctite the bullet will stick and remain in the lands when the bolt is opened. To quote Cortina, it is just a relative point from which to start the process so why chase your tail on a relative target. Not much different than having a magazine that will not even begin to hold a longer cartridge like my Browning BBR in 300 WM. That starting point is now the maximum length that the magazine will accommodate. For a long time I would start 10K - 20K off the lands if the magazine will allow, then seat in .003 increments looking for a velocity node and often a grouping node every 9-12K. Lot of fun and lots of components down range. I have a REM 700 30-06 that doesn’t like any of that no matter what length, primer, powder, bullet, case combination used. I ended up loading a 165 TTSX , max charge IMR 4350 and SAAMI COAL ……… it’s not a tack driver but finally around 1.5 MOA.
