Neck Sizing .300 Rum (any issues)

[rhouser]

I have a new .300 Rum and am doing my first workup's. I have a neck sizer that I will use after the first firing of my new brass. I keep running into statement in different .300 Rum threads that cause me to now ask if their are 300 Rum issues with necksizing brass (specifically the shoulders bumping so far forward that the neck sized case won't chamber?) I may just be reading into some of the posts. In my own experience, I have never had a case expand to the point that the "spring back" wasn't less than the chamber diameter and headspace (short of high pressure where you have to "hammer" a bolt open). If the bolt opens and the round ejects, the neck sizing should work (?) right?
Anything weird I should know about the RUM? I am working a brand new Remington .300 Rum police with a factory 26" 1:10 barrel. I have both Nosler Custom and Remington brass.
Thanks in advance...
rc

 

[Michael Eichele]

I can tell you that if you move the shoulder back too much you WILL have major problems such as stuck cases and even split cases. If you dont move the shoulder enough, after a while the become sticky as well.

IMHO the best way to deal with the 300 RUM case is to get a body die which doesnt touch the neck and set it to bump the shoulder .0005 to .001" back. This will also shrink the diameter of the shoulder area a tad. Then neck size. You will maximize the life of your brass this way AND have very reliable/smooth feeding and extraction.

You may be able to neck size only for a couple of firings. It will depend on the quality and demensions of your chamber AND how hot you run your loads. When they start to extract and chamber with some resistance, then it is time to run them through the body die.

It may take some trial and error to figure out what works best for you but definately DO NOT use any cases who's shoulders get bumped back too much. IMHO .005-.006 is way too much in a 300 RUM. Keep the headspace close and things will go smooth. The larger the headspace of the rifle, the more you bump the shoulder back the more compound the issue. The tighter the headspace is, the less critical and more forgiving it seems to become.

 

[rhouser]

Michael, I hate to show the extent of what I don't know, but, I hate not knowing even worse. I am new to ballistic programs. Please answer a couple of quesions about the following terms used in your post:
specify angle degrees or numbers from your ACI.
1. Do you mean the degree angles for a specific shot or something completely different?
2. I have NO IDEA what ACI means.

Thanks in advance. rc

 

[Michael Eichele]

Michael, I hate to show the extent of what I don't know, but, I hate not knowing even worse. I am new to ballistic programs. Please answer a couple of quesions about the following terms used in your post:
specify angle degrees or numbers from your ACI.
1. Do you mean the degree angles for a specific shot or something completely different?
2. I have NO IDEA what ACI means.

Thanks in advance. rc

ACI stands for Angle Cosine Indicator. Angle indicators are marked with either degrees or angle cosines. Which ever one the shooter uses is what he would enter into his software.

Right now, actually, I only have angle available as the version that uses cosines is being overhauled.

Yes it is for the shot angle compensation.

 

[rhouser]

Michael, thanks, I understand now (the letters, not the functions). rc

 

[300R]

I have only ever FL sized my 300 rum not for any reason other than it shot well enough not to bother neck sizing,i think you should try FL sizing first and if you find no luck try with neck sizing ,it might save you alot of headache with headspace issues and extracion problems plus i dont think NS will save your brass from this big boy.I use rem brass and have found great success with 210 vld's and RL25,fgm215m primers and 180 e-tip noslers,ar2217(aussie h-1000)fgm215m.Good luck.