Determining neck size

[Mauser06]

So, I am still trying to figure this all out. FL neck sizing and then a mandrel...


How are you guys figuring out where to be?


Right now, I have a couple bushings and a mandrel. But still not sure that I have the right sizes. Was looking to goto a custom honed die and get away from bushings but wanna make sure I have the right size figured out. And not sure if I need a different mandrel or of mine is right..

Running a 6.5x47 Lapua with a .293 neck. Loaded rounds are around .289.

Have a few different bushings and a .262 mandrel. Just want to learn to fine tune it. I shoot steel. But at the same time, I would welcome better ammo.

 

[nn8734]

What’s wrong with your current reloads?

 

[Mauser06]

Nothing....that I know of. Maybe chasing a problem that doesn't exist. Or maybe there is room for improvement.

To be completely honest, I've been chasing some accuracy issues. But believe I maybe sorted them out now. Cleaning issues and didn't know I was basically seating bullets with my bolt...concentricty is great. SD and ES were OK. I'd like to see them lower...and I know neck tension can play a role in that. So, that's where this question comes from. But, jamming bullets HARD and making VERY compressed loads probably didn't help either.

(Long story but screwed up measuring my lands. Several different times...)

 

[nn8734]

No worries, mistakes happen esp when you’re just getting started.

Just be careful not to make the mistake many in reloading do: try and fix what ain’t broken. Hence my question.

Also, accuracy is all in the shooter not the system. If you’re having precision problems (ie random flyers, consistently large groups, etc) then that’s a different story.

Don’t fall down the “super-low SD/ES” trap either. SD and ES are important but you want to ensure your efforts/investment in time and money aren’t wildly outsized relative to your requirements. Also, SD/ES figures are really only valuable if taken over 30+ rounds in the same lot of produced ammo, not just 3,5 or even 10 rounds

In other words, if I’m shooting bench rest, I’m going to the Nth degree to exact every last bit of precision and consistently from my loads. In contrast, if I’m shooting PRS (or just steel for fun) I’m keeping it simple.

Define your requirements then compare your load’s results on target to those requirements. Then determine if you really have a problem to solve.

 

[Mauser06]

Thanx for the info!


I was having precision issues. Maybe still am. Gotta do more testing now that I found those 2 more issues.


I understand shoot what shoots well and don't chase numbers. But, crappy chrono numbers aren't going to help shooting at distance.


I'm the kinda guy that what's to understand how and why guys use what they use. Lots of guys say "this size bushing and this size mandrel" but I wanna know how to determine those numbers. This is my first rifle. But won't be my last. I want to educate myself.

Right now, shooting steel out to 1k. Might dabble in smaller PRS matches next season. But I also like to squeeze precision out of my loads. Especially if it doesn't cost me a ton of time or money. If I can simply use a different bushing or mandrel and make it shoot even better...thats a no brainer. If I have to weigh primers and take 6 different bullet measurements and sort them etc etc...eh, my ammo is good enough. Lol. That's kinda my mindset. There's a line drawn for me where adding a ton of time will make my hobby less fun. So I'm learning as I go and trying to fine tune things...finding what is worth my time and what's not. Even if something does as time, I still might deem it worthwhile if the downrange improvement is there.


Hopefully that makes sense.

 

[nn8734]

Your welcome, makes sense. Haha, no need to weigh primers (I’d prob quit reloading if that ever became necessary lol).

what specifically are your issues?

what SD/ES numbers are you seeing across how many rounds?

How do you measure the inner diameter of your necks after sizing?

Quite a few knowledgeable folks on here run bushing dies, expander mandrels, etc. so they can speak to them.

 

[spife7980]

Get a bushing that sizes the neck .003-.004 below loaded round diameter, so .289-.003 or .004= .286 or .285 bushing. That removes unnecessary over working of the brass but still will do a minimum amount of it.

Then a turning arbor is .002 under bullet diameter so .264-.002=.262 Which will open the neck back up to .287 which will give you the .002 interference fit most people go for between the bullet and the case neck.

Might sound obvious but the difference between the inside diameter and the outside diameter is the neck thickness.
.289-.264=.025 of total neck material/2=.0125 of neck thickness per side.

Spring back etc can vary things but that’s why I go in .002 increments instead of trying to divine the thousandth. It’ll still work well and be easy with little questioning.

Edit: If you want to know how to improve on that, you’re just gonna have to get the equipment and test to find out. We could only venture a guess the same as you.

 

[Snuby642]

Running a 6.5x47 Lapua with a .293 neck. Loaded rounds are around .289.

Have a few different bushings and a .262 mandrel.

Your numbers seem off ?
You have a mandrell (-0.002) under but neck measurement is +0.004 loaded?

(Assuming you got the .293 and .289 backwards)

It's late what am I missing here?

Edit: I'm doing exactly what @spife7980 said on every caliber I load now but just sand the expander in my standard fls die's to get there.

Expander yields 3-4 thousands under and then mandrell brings it up to the -0.002 nt.

I'm a poor.

 

[spife7980]

Your numbers seem off ?
You have a mandrell (-0.002) under but neck measurement is +0.004 loaded?

(Assuming you got the .293 and .289 backwards)

It's late what am I missing here?

Edit: I'm doing exactly what @spife7980 said on every caliber I load now but just sand the expander in my standard fls die's to get there.

Expander yields 3-4 thousands under and then mandrell brings it up to the -0.002 nt.

I'm a poor.

.293 is the chamber neck, ala the fired case neck diameter or at least close enough

 

[Snuby642]

Ahh.

I get it now thanks.

Since I went to the sinclair -002 mandrells I quit measuring necks at all.

Every load I had got better especially with different headstamp lotts.

Never could understand why it works better than just setting an expander at -002 but give up trying to figure it out.

 

[spife7980]

The ball is a small surface area that’s only in contact with a small particular portion of the neck for only a small timeo as it’s sliding through. The mandrel allows all of the neck to be sized to the mandrels diameter evenly and all at the same time and for a much longer duration which is however long you chose to let it dwell.

You may drag the ball through the base of the neck at a quicker rate than you do the top part of the neck leading to a discrepancy there vs every other piece each with their own quirks and it’s actually only in contact for that split second it’s forced through. The mandrel is there solid the whole way through, the whole time.

And it’s pushing down on the case rather than pulling up on it. Brass with its wider base and narrow cone shape resists compression and deformation as you push a mandrel down into it much better than it does stretching with a ball getting drug out of it pulling whichever way the brass is weakest.

 

[Snuby642]

The use of mandrells gave me instant satisfaction of 20 % tighter groups and some more than that.

For aproxamatly a 1/4 moa even my 223 ar plinkers get the extra step of the mandrell.

Seems like other fine tuning processes are showing results that can now be measured and before lost to inconsistent neck tension.

I have no doubt that sticking with one brand of brass and working it the least ammount possible would be even better.

 

[Mauser06]

Thanx guys!


Sounds like I'm on the right track. Just need to do some testing and see if anything shoots better. Just didn't know if there is certain things to consider as far as neck size goes. I know BR and F Class shooters sometimes run really light tension..doesn't really work for us mag feeding and such.

 

[K80/6.5]

Get a bushing that sizes the neck .003-.004 below loaded round diameter, so .289-.003 or .004= .286 or .285 bushing. That removes unnecessary over working of the brass but still will do a minimum amount of it.

Then a turning arbor is .002 under bullet diameter so .264-.002=.262 Which will open the neck back up to .287 which will give you the .002 interference fit most people go for between the bullet and the case neck.

Might sound obvious but the difference between the inside diameter and the outside diameter is the neck thickness.
.289-.264=.025 of total neck material/2=.0145 of neck thickness per side.

Spring back etc can vary things but that’s why I go in .002 increments instead of trying to divine the thousandth. It’ll still work well and be easy with little questioning.

Edit: If you want to know how to improve on that, you’re just gonna have to get the equipment and test to find out. We could only venture a guess the same as you.

Thank you for that response I had the exact same question.