308 setup - Forster FL sizing

[blue_ridge]

I've been loading 308 with my Forster match die set and getting great results from my rifle. In fact, working up loads has become difficult because the darned rifle shoots almost everything sub 1/2 MOA at 100 yds! Walker Custom Rifles made me an awesome rig!

Question #1 - After firing, the case necks measure .343 OD. After FL sizing they measure .333 OD. So they are being resized .010. Should I send the die into Forster to have it honed so the brass is not resized excessively? Or leave it as is, since I am getting good results?

Question #2 - I have a K&M neck turner. If I start turning necks, will it reduce beck diamter by a few thousandths or more? If so, how do I determine what neck diameter to have the Forster sizing die set up for?

e.g - original O.D. is .343, then subtract .002 for brass springback = .341, then subtract .003 for neck turning and I would ask Forster to hone it to .338? or am I missing something?

 

[doc76251]

Re: 308 setup - Forster FL sizing

I wouldn't mess with the die itself but I would seriously consider "polishing" the expander ball a bit (or a bit more). The ball is the last thing to leave the neck of the cartridge and is giving you the 0.010" "growth". That and they are the least expensive parts of the die to replace.

Cheers,

Doc

 

[blue_ridge]

Re: 308 setup - Forster FL sizing

So the expander creates the diamter of the neck instaed of the diameter of the die walls themselves? Forster will hone the inside of the die to a specific neck diameter. They only charge about $10 for this service. The idea is described here:

http://www.accurateshooter.com/technical-articles/reloading/fl-bushing-dies-vs-honed-fl-dies/

I guess my main question is about neck turning because I don't know if I should turn necks at all. If so, how much smaller is the diameter of a properly turned neck?

 

[bm11]

Re: 308 setup - Forster FL sizing

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: blue_ridge</div><div class="ubbcode-body">

e.g - original O.D. is .343, then subtract .002 for brass springback = .341, then subtract .003 for neck turning and I would ask Forster to hone it to .338? or am I missing something? </div></div>No, you are doing your math wrong. Your post firing (blown out) case neck diameter is .343. What you want to do is measure a LOADED, unfired round. If your loaded round measures .338, and your sized brass measures .333, then you have .005 neck tension (probably a bit excessive.) IF, on the other hand, your loaded round measures .335 (win brass, for example) than you probably have about the bare minimum neck tension. The only way to change the .343 fired size is to change the barrel and request a tighter neck.

 

[MALLARD]

Re: 308 setup - Forster FL sizing

i dont use an expander at all ,except if im neck turning ,then i expand with the same mandrel that i will be turning on.

i dont know how the k&m tool works , i got the sinclair and it comes with an expander die , you can use the same mandrel that you turn on to expand the necks. Does the k&m come with an expander die ? is it possible for you to expand the case mouth with the same mandrel you'll be turning cases on ?

i wouldn't get the die honed because your need for a specific diameter will change if you change brass , or when the brass has been fired multiple times. My advice is to get a bushing die, if your loading a bolt gun you get get a bushing neck die and still use your F/l to push the shoulder back. IF its a gas gun ,sell or keep your f/l die , but look into a bushing f/l die , the redding s type is great.

for now , i would remove the expander from your die , and size the case without expanding the neck, then get creative and expand the case mouth using the same mandrel you will be turning the case on, ok ? ( i imagine the ID of a case after you sized it on the mandrel will be around .306-.309,) now turn that , if you never turned necks , start slow , dont cut to deep , just shave off slowly , keep increasing the blade depth , until the case looks pretty, ( if you have a tool , measure for uniformity, but you need a good one ) , once that is done seat a bullet in there ( it should seat) , measure the OD of the loaded round , minus .001-.003 for tension , that will be the specific diameter you want for now, Or im wrong

 

[blue_ridge]

Re: 308 setup - Forster FL sizing

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bm11</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: blue_ridge</div><div class="ubbcode-body">

e.g - original O.D. is .343, then subtract .002 for brass springback = .341, then subtract .003 for neck turning and I would ask Forster to hone it to .338? or am I missing something? </div></div>No, you are doing your math wrong. Your post firing (blown out) case neck diameter is .343. What you want to do is measure a LOADED, unfired round. If your loaded round measures .338, and your sized brass measures .333, then you have .005 neck tension (probably a bit excessive.) IF, on the other hand, your loaded round measures .335 (win brass, for example) than you probably have about the bare minimum neck tension. The only way to change the .343 fired size is to change the barrel and request a tighter neck. </div></div>

Got it. That makes sense to me. I was thinking the fired brass diameter or chamber neck diameter was the measurement to work from. But now I understand that the bullet diameter + brass thickness (measured from a loaded round) is the measurement to work from. It isn't going to change much unless I turn necks or switch to brass of different thickness.

Sometimes it's good to bounce this stuff around the Hide because just having it stated a certain way makes the solution click. Thanks.

 

[blue_ridge]

Re: 308 setup - Forster FL sizing

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MALLARD</div><div class="ubbcode-body">i dont use an expander at all ,except if im neck turning ,then i expand with the same mandrel that i will be turning on.

i dont know how the k&m tool works , i got the sinclair and it comes with an expander die , you can use the same mandrel that you turn on to expand the necks. Does the k&m come with an expander die ? is it possible for you to expand the case mouth with the same mandrel you'll be turning cases on ?

i wouldn't get the die honed because your need for a specific diameter will change if you change brass , or when the brass has been fired multiple times. My advice is to get a bushing die, if your loading a bolt gun you get get a bushing neck die and still use your F/l to push the shoulder back. IF its a gas gun ,sell or keep your f/l die , but look into a bushing f/l die , the redding s type is great.

for now , i would remove the expander from your die , and size the case without expanding the neck, then get creative and expand the case mouth using the same mandrel you will be turning the case on, ok ? ( i imagine the ID of a case after you sized it on the mandrel will be around .306-.309,) now turn that , if you never turned necks , start slow , dont cut to deep , just shave off slowly , keep increasing the blade depth , until the case looks pretty, ( if you have a tool , measure for uniformity, but you need a good one ) , once that is done seat a bullet in there ( it should seat) , measure the OD of the loaded round , minus .001-.003 for tension , that will be the specific diameter you want for now, Or im wrong

</div></div>

Okay, understood. I will look into the K&M expander mandrel. I know they have these. Thanks for the explanation, this helps.

 

[blue_ridge]

Re: 308 setup - Forster FL sizing

Okay, I measured fired brass after F/L re-sizing with the expander ball and without and a loaded round.

With expander - 0.330
Without expander - 0.325
Loaded round - 0.332
empty fired brass no resizing - 0.340

It seems the expander may be sizing the neck just about right for .002 tension. Any thoughts or advice based on these measurements would be appreciated.