what is CBTO?
Hello,
This my first post so I apologize if I screw up.
I just purchased a 2015 10FCP-SR .308 24in 1-10 twist. I am going to build up some hand loads for this. Here is my concern/question. Using the Hornady OAL and comparator w/ 168gr Amax, I have consistently come up with a 2.195 CBTO.......does that seem extremely short? My ultimate goal is to setup with the 175-185 Bergers and ping steel at 1000yrds but I have 500 Amax's just sitting around for the time being.
thanks again
what is CBTO?
Case bottom to ogive. It's the length where the ogive of the bullet hits the lands
2.280 is my CBTO on the 168 SMK in my 308...
2.248 is my CBTO on the 175 TMK in my 308...
I'm not sure what would be considered a short throat, I'm just giving you this information so that you can compare...
Thanks, I'm thinking it is shorter that usual. I have read where some of them come from the factory short. I'm just wondering what impact it will have with trying the larger grain bullets.
Well, thats .085 shorter than the throat in my barrel (assuming 168 amax and 168 SMK have similar measurements to ogive). I just ran that CBTO on my load in QuickLoad and it adds about 3600 PSI to the chamber pressure. That equates to 0.9 grains of charge with IMR-4064 which is what I'm using.. So almost a full grain of charge..
This is just some information to think about.. That rifle may be a shootin' mofo once you get that thing dialed in.. I see you concern, but I'm not wise enough to tell you one way or the other... Good luck with it...
Thanks for the feedback. I guess I really won't know until I start working up the loads. If all else fails I could take a trip to the gunsmith.
What is the Over All Cartridge Length of the 168grn round that touched the lands?
The COAL with the 168 AMAX is 2.813
That would seem to be within SAMMI specs, however it could be on the short side of what you want to do.
Thanks, I have figured out that the 168 Amax and the Berger VLD175-185s are shaped quite differently, with most of its length in the nose. The base-to-ogive of the berger is much shorter that the amax. That was great news when i discovered it, those will ultimately be my pills, the only issue i foresee is they probably wont mag feed. For now I will shoot up the 168 Amaxes I have left.
The 168 gr Amax's shoot pretty good in my rifle with 42.5 grs of Reloader 15 in Federal cases. they are loaded .010"-.015" off the lands
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