Full-Length Resizing New Brass

[Flogain]

So I’ve been full-length sizing new brass. I’m new to this. I’m not as new to this as I once was. But I’m new enough.

Anyway, I’ve been FL’ing new brass. I am thinking I should stop. I figure I’ve been bumping new shoulders back and probably creating headspace issues. Right?

I used a hornady comparator and measured some new brass at the datum of the shoulder. I figure this isn’t super precise because it’s a $15 tool, but maybe it is. Anyway, my measurements of new brass are less than the SAAMI specs for .308. Simon SAAMI says between 1.627 and 1.634. A random piece of new IMI match brass measures 1.619 with hornady comparator. Is that a problem? Is that a side effect of the measurement tool? I know this is the smallest the brass will ever be. I now know I shouldn’t be full length sizing new brass. But is this short brass a problem? What’s the reason?

 

[918v]

It’s a comparator, not a measurer.

 

[Flogain]

It’s a comparator, not a measurer.

Thanks for all of the help today, 918v. You must think I don't know how to put my pants on by myself. Am I correct in thinking that I should stop resizing new brass? Is there a better tool I could get to measure shoulder? I really am under the impression that the shoulder is relative and hard to measure.

 

[918v]

Your die is prolly not even bumping the new case shoulders. Did you compare them before and after? It could be but factory brass is on the short side. I would just use an expander mandrel on the necks that’s all.

 

[Flogain]

Your die is prolly not even bumping the new case shoulders. Did you compare them before and after? It could be but factory brass is on the short side. I would just use an expander mandrel on the necks that’s all.

And then for my optimal neck tension, use the bushing? Or use the .305 expander off-the-bat, and it's good to go? The latter makes sense.

 

[Jordanwickham]

918v is pretty short with his answers typically. You don't need to full length size new brass. Some people say to do it but don't really give the reason they say do it. The reason they say to do it is so that you run the expander ball through the neck to take out any dings and to try to get ID consistent. They don't say that the only part of the die that should ever touch virgin brass is the expander ball and nothing else. To bump virgin brass you would really be going above and beyond. If you are changing the die setting from your regular sizing operation (fired brass) you may be doing bad things but if you didn't crank a few turns down on the die you wouldnt have touched the shoulder.

The basic answer to your question is yes, don't full length resize your brass. The better answer is to get an expander mandrel like Sinclair or 21st and run that through the neck of your virgin brass. If you don't want to get one of those ( they are cheap) then just run the expander ball through which is a shallow ram stroke on a FL die.

 

[FLIGHT762]

Your Hornady tool is a "comparator" it's NOT a headspace gauge. You're NOT going to get the "1.630" SAAMI minimum reading from that tool. The only way to see what your tool measures @ 1.630" is to take a real 1.630" GO gauge and measure off of it. I have done that and from two of my .400" Hornady inserts, one measures 1.611" and the other one measures 1.621". That's because each insert has a chamfer on the edge of the insert. One has a .019" chamfer and the other has a .009" chamfer.

New, factory brass can be @ 1.630" or can be up to .003" or so below 1.630". It's likely that your insert measuring off of a new IMI case @ 1.619" is going to be pretty close to SAAMI Minimum (1.630"). You should NOT be F/L sizing the new cases below that.

Once you fire your cases, you will measure the datum from them (with the primer removed) and note that reading. You will then set your F/L die to bump your case shoulders back .002" or so for a bolt gun, .003" + for a gas gun.

You really don't need to know what the exact 1.630" SAAMI minimum is. If you want to know, take your tool + calipers to a local gun smith and ask if you could measure off of one of his 1.630" Go gauges. I had a friend who owned a gun shop. He let me take measurements off of his Go gauges for 223, 308 and 30/06. I took notes of the measurements. I wouldn't go out and buy a 1.630 Go gauge. You don't NEED it for this.

You can take measurements off of a variety of new, factory 308 ammo and note the numbers for reference. I've measured a variety of domestic and foreign 7.62 X 51 NATO ammo and found some to be below, at and even .002" + of 1.630".

 

[Jordanwickham]

And then for my optimal neck tension, use the bushing? Or use the .305 expander off-the-bat, and it's good to go? The latter makes sense.

If you are running an expander mandrel (separate than the expander ball in a FL die) it should be no smaller than .306 but if you aren't turning necks then a bushing is pushing imperfections to the inside of the neck so the expander mandrel should be the last thing your case sees from a sizing standpoint.

 

[straightshooter1]

Your die is prolly not even bumping the new case shoulders. Did you compare them before and after? It could be but factory brass is on the short side. I would just use an expander mandrel on the necks that’s all.

Likewise, I like to use an expander mandrel. . . or use a Lee collet die for the neck, as I've found that doing so lightens and smooth's out the seating force, which helps in reducing runout and in getting more consistent seating depth and much better results on paper for the first firing of virgin brass.

 

[Evlshnngns]

If it chambers smooth I usually just load it and go. If the necks are too tight or fubar the lee collet does the trick.

 

[Flogain]

If you are running an expander mandrel (separate than the expander ball in a FL die) it should be no smaller than .306 but if you aren't turning necks then a bushing is pushing imperfections to the inside of the neck so the expander mandrel should be the last thing your case sees from a sizing standpoint.

Why no smaller than .306. A .305 would give me my desired 3k neck tension. Or that ain’t proper?

 

[Jordanwickham]

Why no smaller than .306. A .305 would give me my desired 3k neck tension. Or that ain’t proper?

If you want 3k neck tension then it is proper.

 

[Flogain]

If you want 3k neck tension then it is proper.

At 2-2.5, there was some minor bullet jump. I figure 3 is a decent middle ground for the aggressive chambering of the SCAR 17

 

[Jordanwickham]

At 2-2.5, there was some minor bullet jump. I figure 3 is a decent middle ground for the aggressive chambering of the SCAR 17

Oh yeah if you're shooting a Scar you definitely want 3k.

 

[918v]

And then for my optimal neck tension, use the bushing? Or use the .305 expander off-the-bat, and it's good to go? The latter makes sense.

Just the expander mandrel. It will iron out the dents in the case mouth.

 

[Flogain]

Just the expander mandrel. It will iron out the dents in the case mouth.

Makes sense, thanks.

 

[Flogain]

Oh yeah if you're shooting a Scar you definitely want 3k.

Yeah, my loaded rounds measure .3375. I tried a .335 bushing and accounting for slight spring back I considered that 2k neck tension. Wasn't optimal. I ordered a .334 bushing and with spring back accounted for, I'll consider the 3.5k neck tension to be three thousandths. I have a .305 and a .3055 mandrel from 21st on order, but they are on holiday, so sometime next week it'll show up. Maybe by the end of the week. I am thinking I could have skipped the .305 because again I'm trying to factor in about a half thousandth of spring back. But at least I'll have both for down the road. I suppose I just don't yet know what is right.

It's been right hard trying to source different components these days. My LGS is great, and the guys are really helpful. But they too have been struggling to keep stuff in stock, like I'm sure you and everyone else is aware of. Redding for example hasn't fulfilled an order with them in like three fortnight. But yeah, I'm hoping the .334 bushing paired with the .3055 mandrel will set me up pretty for 3k neck tension and I can get back to loading a bunch of rounds. Maybe I'm overthinking on the half thousandth of spring back, but I'd rather have a mildly certain feeling about the numbers I'm trying to achieve. I'm kicking myself a bit for even ordering the .305, but it was only $18 USD. I am kicking and not kicking. With the thousands I already have invested in the hobby/sport/lifestyle/nonsense, it's a minuscule drop in a larger bucket of fiscal hemorrhaging.

 

[spife7980]

I'm kicking myself a bit for even ordering the .305, but it was only $18 USD. I am

.308-.003=.305

I don’t get where any trouble or confusion is coming into this.

 

[pucker]

Also, keep in mind, the number etched on the bushing isn't always what you'll end up with for neck OD... variables such as brand of brass, # of firings, whether you anneal, etc. will play a role. Hence the often-mentioned recommendation of running a mandrel (good discussion here) through the neck as the last step (after using a bushing ~.001 under your desired mandrel).

This negates variance in bushing-derived results.

I like/use 21st Century's new black nitride.

 

[A&8's]

I FL new brass, but ensure there is no shoulder bump. Once I've 1x fired all my new brass, I readjust to achieve desired bump.

Main reason I do this is because I brass prep on a 650 and the die is already in the tool head, along with the expander mandrel (which is really all I'm concerned with on new brass.)

 

[Flogain]

.308-.003=.305

I don’t get where any trouble or confusion is coming into this.

Because my loaded rounds at .3375 and a bushing at .334 make 3.5k neck tension with a .305 mandrel. The .3055 makes even 3k with my accounting for half thousandth of spring back. 305 is gonna end up being slightly less than .305. .3055 will be closer.

 

[918v]

Don’t assume that you’ll have .0005” on every case. They’re all different. Going for half-thou is silly.

 

[Flogain]

Don’t assume that you’ll have .0005” on every case. They’re all different. Going for half-thou is silly.

i know this comes a few months later, but today I was playing around. I’ve a .334 bushing. It sizes it between .3335 and .334. I then used a .305 mandrel which for whatever reason makes the ID about .3035-.304 and the OD .335. When I use the .3055 mandrel it makes the ID .3045-.305 and the OD .3355 usually.
So my .305 mandrel ain’t doing what it’s supposed to, but my .3055 mandrel is getting closer. Obviously when you mandrel the inside, the OD gets a little bigger. But what’s more important, staying closer to your ID or OD?

 

[TheOfficeT-Rex]

But what’s more important, staying closer to your ID or OD?

I'd say ID, since that's what interfaces with your bullet. If you're running a mandrel, in theory, any difference in neck wall thickness would manifest in OD, unless you neck turn them.

Were you measuring with pin gauges, or calipers?

 

[Flogain]

I'd say ID, since that's what interfaces with your bullet. If you're running a mandrel, in theory, any difference in neck wall thickness would manifest in OD, unless you neck turn them.

Were you measuring with pin gauges, or calipers?

Yeah, not turned. Knowing we’ll change the ID, why bushing the OD even? Less variation I guess. Seems my .305 mandrel just isn’t giving me the right dimensions.
Using calipers.

 

[TheOfficeT-Rex]

Yeah, not turned. Knowing we’ll change the ID, why bushing the OD even? Less variation I guess. Seems my .305 mandrel just isn’t giving me the right dimensions.

Because the neck ID has to be smaller than the mandrel, otherwise, you won't get the accurate sizing you want. People like bushing dies because they can choose exactly how much smaller than the mandrel they size the brass, to minimize how much it gets squeezed and 'not over work it.'

Using calipers.

That's not really the right tool for the job. Get some no-go plug gauges from mcmaster-carr for $5 each if you really want to nats ass it. Ballistic tools also makes a tool that is like having 4 pins in one, but it's pretty pricy for what it is.

 

[Flogain]

Because the neck ID has to be smaller than the mandrel, otherwise, you won't get the accurate sizing you want. People like bushing dies because they can choose exactly how much smaller than the mandrel they size the brass, to minimize how much it gets squeezed and 'not over work it.'


That's not really the right tool for the job. Get some no-go plug gauges from mcmaster-carr for $5 each if you really want to nats ass it. Ballistic tools also makes a tool that is like having 4 pins in one, but it's pretty pricy for what it is.

Ah, so the OD sizing is just to let the mandrel do better work. Totally makes sense. I appreciate that a lot. Okay I’ll look into the gauges. Thanks so much, man.

 

[308sako]

If the new brass readily chambers in your rifle, why in Gods name would you further reduce it's dimensions? Yes I understand getting the necks into round before seating a bullet, but changing headspace, really?

 

[Flogain]

If the new brass readily chambers in your rifle, why in Gods name would you further reduce it's dimensions? Yes I understand getting the necks into round before seating a bullet, but changing headspace, really?

If the brass is the smallest it will ever be from the factory, “resizing” it with a bushing die to focus on the neck tension isn’t really adjusting headspace, is it?

 

[kingaling]

If the brass is the smallest it will ever be from the factory, “resizing” it with a bushing die to focus on the neck tension isn’t really adjusting headspace, is it?

Depends on how far into the die the brass goes. Obviously if the brass shoulder hits the inside shoulder of the die, there gonna be some push back. Personally, if I was gonna run brand new brass through a die to assist in making sure all my necks were uniform OD, I'd use a neck sizer with bushing. But also, if it's new brass, I turn it, thus making it so after my bushing has ensured my OD is uniform, my ID is uniform by proxy.

 

[straightshooter1]

Depends on how far into the die the brass goes. Obviously if the brass shoulder hits the inside shoulder of the die, there gonna be some push back. Personally, if I was gonna run brand new brass through a die to assist in making sure all my necks were uniform OD, I'd use a neck sizer with bushing. But also, if it's new brass, I turn it, thus making it so after my bushing has ensured my OD is uniform, my ID is uniform by proxy.

That would assume the neck wall thickness is uniform.

With typical brass, there's a lot of neck wall thickness variation as much as .002 (in some instances, more). Bushing die sizing die moves that irregularity to the inside typically resulting in concentricity issues. This is why I use a collet die to neck size new brass and get the neck tension I'm after and in some instances, it smooths out other irregularities in the neck that may be there.

 

[kingaling]

That would assume the neck wall thickness is uniform.

But also, if it's new brass, I turn it, thus .... etc.

As I stated, turning the necks ensures neck wall thickness uniformity.

 

[straightshooter1]

As I stated, turning the necks ensures neck wall thickness uniformity.

 

[vincent7]

if they fit, load them up.

 

[Heffo]

Just use a mandrel die to get necks uniformed and load/shoot! Keep it simple.