Finding and using the proper neck tension

[Bigsky108]

Hey guys, I am trying to work up some loads for my 300PRC and I have a question about neck tension. I am pretty novice when it comes to reloading so pardon my lack of knowledge here.

I am using the RCBS Matchmaster dies and have chosen a .334 bushing to use with it from the information I gathered online. The sizing die came with an expander ball installed, but I replaced it with the de-capping pin holder that comes with the die for better results while using the bushing (as per RCBS instruction)

I have cleaned my once-fired brass and checked the neck size before sizing it for curiosity's sake and it shows 0.3400 diameters. I then ran a few pieces of brass through my sizing die and bumped the shoulder back 0.0020". My neck diameter is now 0.3345 on my cleaned and resized brass. After loading some bullets into my brass the diameter is now 0.3365. It is my understanding that this 0.002 difference is the sweet spot correct?

So my question I suppose is, should I use an expander mandrel? Or just stick with the method I am currently doing?

Thank you for your time!

 

[ID_Matt]

You are spot on with your thinking as far as I know. As for the expander mandrel, I think opinions will vary. I have never messed with them but can see the benefit if your necks get dinged sometimes.

 

[Keith Stone]

If it’s shooting quarter minute and single digit ES I probably wouldn’t change anything. Two thou neck tension is a guideline just like 30 thou off the lands. If you are having issues try different things and see what works for your setup.

 

[Mag_7s]

Short answer I think is yes. If your not turning necks, your neck thickness will vary, giving inconsistent tension, the expander ball would "help" with this. I would still run over the mandrel, which will also help correct runout.
I'm guessing you mandrel is .306?

 

[wind gypsy]

I've loaded the majority of my ammo with bushing dies and quality brass with zero neck expansion. I've also set neck tension on a fair bit of ammo with mandrels because the internet told me to. If I told you i noticed any difference in performance between the two i'd be lying.

I could see it making a bigger difference if using brass with a lot of variance in neck thickness.

One of these days i'll get a progressive press and then I could see having a station to expand with a mandrel again but for single stage press i'm leaning back towards using forster standard FL sizing dies honed to desired neck diameter with expander ball for simplicity. One pass through the press to size, decap, set neck tension. I don't think this will induce runout that will cause me to shoot any worse than I otherwise would.

 

[Bigsky108]

Thanks for the feedback guys! I can see how a mandrel could negate some variables, but I think I will see if I can dial in a load before I give them a shot. It always seems like there are a million little details that can alter load development.

I just got back from the range where I did a 13 shot test from 75gr-78.9gr. I wanted to see if I could find a couple plateau's to do further work on. I am using Ramshot Magnum powder, 215M federal primers and 225gr. ELD-M bullets. From what I found, it looks like there might be a promising node around 77-78 grains. So, next stop is 3 shot groups spread .2gr apart to see where I can find the lowest SD/ES and play with seating depth to try and hone in a group.

 

[ResearchinStuff]

Nodes aren't real, they're just small sample size noise. You can save yourself a lot of hassle, time, money and heart ache by listening to this podcast then following the method laid out in the post linked below.

Painless load development (mine)

I have had multiple people ask me to lay out how I do load development being that what I do is different. Since Shaen @Shooter71 just rebarreled a Tikka 595 in 6XC I thought it would be easy to show how I do it. It’s a Master Sporter with a T3 lite profiled 20” barrel- keep in mind it is a T3...

rokslide.com

 

[Harvey_NW]

for single stage press i'm leaning back towards using forster standard FL sizing dies honed to desired neck diameter with expander ball for simplicity. One pass through the press to size, decap, set neck tension. I don't think this will induce runout that will cause me to shoot any worse than I otherwise would.

This.

Nodes aren't real, they're just small sample size noise. You can save yourself a lot of hassle, time, money and heart ache by listening to this podcast then following the method laid out in the post linked below.

And this.

Alex Wheeler has quite a bit of data on bigger cartridges having a positive response to more neck tension, upwards of .005". That was in reference to vertical and group size at 1,000 yards though, so it would be hard to distinguish that at 100.

 

[Jesse Jaymes]

Overall I think you are doign a fine job and right on track. I've used bushings for maybe 15 years. I do disagree with bushing selection and the math. There is a ton of "spring back" and other variables. I rarely get the correct bushing size first go. I have several now.

Lots is "feel" and lots is the gun/ammo telling you what's correct.

For $22 I would say don't be afraid to try up or down a bushing size.

If you're next steps after powder charge is seating depth....I really giggle at guys saying " I was running .005 off the lands but .007 really tightened up my groups".

The inconsistency in Ogive between bullets can be bigger than that.

Try Lands, -.010"......-.030......-.-060......-.090". You should see a pretty dramatic change in group size.

Watch your magazine length while you're doing it. If the gun doesn't run cuz the loaded round's Sweet Spot is 1/8" longer than the magazine will allow....it's all for naught.

 

[Ernie]

Great start.
As mentioned some cartridges desire more neck tension.
If it shoots great the way it is-Awesome!