Resized dimension of inside of brass case mouth?

[RHOTWING]

I have recently reloaded some 260 Rem. and things have gone ok, but now on my second reloads when I started seating some bullets I found it was difficult.

It was definitely harder than it was before so I stopped after say six rounds. I took some resized brass and with my calipers checked the dimension on the outside of the neck and they were running at .291 to .291.5. So I subtracted .030 for the thickness of the brass and got .261 to .261.5. Knowing the bullets were .264 actually when I measured they were .264.5.

I remember checking the first reloads and I believe the dimensions were .292 to .293 on the outside and .030 less .262 & .263 inside and they felt just about right in my opinion when I was seating the bullets.

I'm wondering if there is a standard of sorts to go buy?

[Alleycat72]

I do .003 neck tension on hunting ammunition and .001 on F Class loads.

[LongRange]

what is the riffle mainly used for? what brand dies? full length resized or just neck sizing? what brand of brass?

ive only shot lapua brass in my 260 and loaded neck size is .295 i neck size to .293 but if its hunting rounds like alleycat said i would add a little more tension.

[RHOTWING]

Well first of the gun is a Savage 12 LRP and I am disabled so I'm currently benching at 100yds and want to go out to 1000 eventually. I am starting with new Lapua brass.

I am unfortunately limited to bench. I'm using a full length Hornady Custom Grade two die set. This is the only one rifle of mine in 260 so I could neck size only, but not sure if that is a 100% advantage or not from all that I have read, I know your brass will last longer, but in my case don't know if that is the number one priority. I have a Hornady Headspace Comparator that I have used for the first time and have set the sizing die to bump the shoulder about 1-1/2 - 2 thousands from a fire case. I don't remember for sure what the O/D was on the neck of a fire case (next time will document) but I think it was either between .297 & .298 or between .298 & .299. It seems like I read somewhere that when resizing with a neck bushing die set you wanted to be around 4-5 thousands under your fire brass.

I remember thinking that .292 was good and that was what the new brass was, and when I first got the new brass somewhere I read to run the expander through the brass for concentricity so I did. Also when I re-sized the once fired brass, the first few rounds that I checked with the calipers were around .292 so I just ran the whole 100 out and then proceededed priming and reloading. The first reloading went ok and had some developmental loads that did less than 1/2 MOA which is what I duplicated this time when I noticed the tight tension. So after about the sixth tight tension is where I stopped and discovered most of the O/D's were running .291-.291.5.

I decided (not sure if it was a good decision) to just run the expander in and out of the mouth, and in doing so that changed them to around .292-.292.5, and then started loading and it everything seemed fine like it did the first reload.

Let me know what you guys think.

[gotcha]

The only way to accurately measure neck wall thickness is with a ball micrometer or similar. the only dimensions you need to be concerned about are sized neck dia. VS. bullet seated neck diameter. As the other guys say .001" to .0015" for target ammo, .003" to .0035" hunting. Keep in mind that varying neck tension can have an effect on accuracy. Yours might actually shoot better at .002" :) ..... If you jam your bullets into the lands .002" neck tension, for me, is minimum to prevent bullet set back when chambering a round. My 6.5X47L measures thus: .290" (bullet seated dia.) - .264" (bullet dia.) = .026" divided by 2 = .013" wall thickness. Apparently the .260 has thicker necks........ Or maybe you formed from .308 brass??

[gotcha]

RHOTWING, Thanks for the clarification on type of die used. What you experienced is due (in part) to the bushing die pushing irregularities of the case wall to the interior of the neck. The expander (good decision) pushes case wall irregularity to the outside of the neck and makes the interior case wall uniform and slightly larger in diameter. Beware, expander balls can get tweaked and pull the neck out of plumb with the case body. Many reloaders will use a separate expander die to uniform and align the interior dimension of the neck. Personally I think the bushing die is more appropriate for cases neck turned to a specific wall thickness. (just my .02) You solved your own problem. Keep lots of dated notes to refer back to and many of these mysteries will become self evident. Itty bitty groups to ya'

[RHOTWING]

Thanks Gotcha, definitely need to keep better dated documentation for future reference as you suggested!