Need help with .270-08

I cant get my rounds to chamber once they are loaded what should be the overall length of the round (.270-08) using .308 lapua brass and a berger 150 gr. bullet once it is loaded. Also my dies wont neck the round down close enough to the shoulder without putting a donut on the top of the shoulder on the brass , what would be causing this? I am using RCBS 270-308 dies that came with the gun I purchased this is my first go round with a wildcat round and handloading for that matter can anyone help me out I cant find the chamber measuring tool I need for this gun to determine how long the overall length should be once loaded so any general info for overall length on this round with a 150 gr. bullet would be greatly appreciated, along with load data using lapua brass,berger 150 gr. bullet,winchester primer, and IMR 4064 powder Im not sure of the twist rate on the barrel is there any way to tell what it is. there is alot more I need to know but I have been messing with it for so long today Im just tired of it and cant think of everything right now.

Make you own OAL case by sizing one, cutting two slits in the neck with a Dremel and cutoff wheel. Slide the bullet you want to measure the OAL and carefully chamber/extract the round and measure to the tip. This will put you close enough for a general Over All Length. You really need to get the Hornady attachment and collets for a dial caliper to be able to correctly measure to the ogive of the bullet. Your barrel should be 1 in 10 twist.

Focus on your brass forming first, then worry about the full length of the seated round.

Can you post a picture of the malformed brass? Sometimes brass is difficult to form if you do not properly lube the outside and inside of the neck. I use hornady spray and it works real good. Get one piece of brass really lubed up and try it again.

Does the brass chamber by itself and the bolt handle go down normally w/o excessive force?

Use cheap 308 brass and work on that so you don't dent/doughnut your lapua brass during this work-up.

Once you get your brass where you want it, then you experiment seating the bullet to different lengths to see where your barrel wants the bullets to be seated. The room you have for bullet length is a factor determined to how the chamber is cut into the barrel. The trick GaCop posted is a real good way to figure out what your COL could be with YOUR barrel & headspace.

You may need to neck turn the brass since the necking down operation might leave the neck to thick and when combined with a seated bullet it won't fit the neck of the chamber.

Have you tried necking up .243 or .260 brass?

Black marker to see where it is rubbing?

Thanks for the tips everyone I found out my sizing die was bad the bushing inside of it was worn slap out so Ive got a new one and Ive got things going smoothly loaded a few rounds at diffrent lengths to fire and see what works best. Ill be going out tommorow so Ill post up and let ya know how it went.

Glad you got it figured out. Never heard of a sizing bushing wearing out.......ya learn something every day.

Yes you do Im learning a little more each outing everything went well had some flattened primers on one set of loads but the others did ok at best I sure could use a good base for load data anyone help me out with that? Im on a huge learning curve right now Im shooting 150 gr. berger boat tails with IMR 4064 powder and loaded a few at 36.7 gr and a few at 36.8 gr the 36.8 seemed to do a little better with my OAL @ 2.262 Im shooting for accuracy or at least trying to until I get a good load :-\

If you're in an accuracy node, 36.7 and 36.8 should shoot into the same group. In a .308 class case +/- 0.2 gn in either direction shouldn't matter at all if the load is a good one.