.223 Rem Neck Tension Issues with 75gr BTHP,Help)

[Conrad]

I’ve recently switched from shooting 69gr smks to 75gr BTHP’s out of my RRA 20” Predator Pursuit to capitalize on the better ballistics but still remain magfed. I’m achieving good accuracy and velocity and the bullets are BN coated.

My problem is that with the 75gr BTHP’s,Hornady) I’m experiencing a pronounced “cannelure” at the O-give from the seating die,Forster Competition). I experienced this only slightly with the 69grer’s,and seemed to fix it). The brass is from a batch of 1000 once shot LC,presized and deprimed). I noticed when I first started loading the 69gr smks that there was too much neck tension, and I opened up all of the necks with my regular Redding FL die with carbide button. Doing this gave me a neck measurement of roughly .245 on average, and the 69 smks seemed to seat better after this. I can’t even say that the 69 smks had any deformation afterwards but being coated the sizing die ring will show slightly. The 75’s are definitely deforming more so though. Again, I think I still have too much neck tension.

My fired brass from my rifle measures .251 to .252 at the neck and from best as I can tell my brass thickness seems to measure .013 to .0135. I only have calipers, but I’ve measured neck thickness by both direct measurement, and then also measuring the OD of the neck and subtracting the ID to get neck thickness. I did this on multiple pieces of brass. On my shot brass it seems like the brass thickness might be slightly thicker than the unshot,from my rifle) as it seems more like .012. I would assume the shot brass from my rifle is the important measurement. This was just an observation.

My two questions that I have are:

1) Does it seem like I should get a Redding FL Bushing die with a bushing of say .247 or .248,.224+.013+.013-.003 = .247) to reduce neck tension,any preference between the two, remember I’m shooting BN coated bullets)?

2) For the remaining ~250 pieces of “tighter” brass that I’ve already primed, should I just load it up and shoot it, or should I look into getting some kind of expanding mandrel? If so, which mandrel?

Any ideas?

Thanks,
Conrad

 

[kevinbritvec]

Conrad,
I use an .224 expandiron that I chucked in a drill and spun while applying a relatively fine emery cloth. My final diameter is .221, this gives me .003 to .004 neck tension which is plenty. Accuracy remains excellent. Using this type expander makes for a more uniform neck tension for the entire length of the neck.
You mentioned that you use Forester's competition seating die. If you use their resizing die you're in luck. Simply measure the loaded round's neck, subtract .004, and ship the die to Forester with the measurement and ten bucks. They'll hone your neck to that dimension for just ten dollars,plus return shipping). This will give you a die that only creates .003 to .004 neck tension without an expander of any type. You can use the expandiron too just to gaurantee uniform internal dimensions.
Finally, you might want to disassemble your seating die, chuck it in a drill and turn it slowwly while lightly applying emery cloth to the interior of the bullet seating stem. Try to smooth the area that first meets the bullet making sure there isn't any sharp angles there. You might be surprised how much dirt has accumulated around the bullet seating stem where it meets the interior of the die which may be contributing to your problem. I've noticed some stems don't work well with certain bullet profiles, the Hornady 75 is very close to Sierra's 77 in profile, however the Hornady 68 looks more like a VLD when compared to Sierra's 69. Let Forster know about your experience, I'm sure they can help you out.

kevinbritvec

 

[ronemus]

I had the same ring when using a standard die and expander with 75 gr BTHPs. Hornady uses a jacket that isn't as tough as Sierra's, but that probably contributes to the superb uniformity of Hornady bullets. I neck-turn my brass,Gracey neck shaver), so the Hornady sizing die doesn't reduce the neck diameter much below loaded diameter. I use a custom expander ball that Hornady's custom die shop made for me that is full bullet diameter; that produces maximum bullet pull and avoids using the bullet as an expander - it's not nearly as tough as a steel expander ball.

 

[jthyttin]

IMHO, real problem is the bullet seating stem. Contact Forster or modify your existing stem to properly fit your bullets. Many stems fit OK for shorter bullets but put too much stress on single "ring" when using bullets with "pointier nose".