Neck turning Alpha brass in 6mm GT

[acrashb]

So moving to 6mm GT from 308 is turning out to be an adventure all unto its own.

For context, I've turned a lot of brass, mostly Lapua 223 and 308, and mostly just skimming to remove high spots, but also a lot of tight-chambered 6mm PPC. This Alpha 6mm GT brass has presented a new challenge, and before I accost the Alpha people, perhaps the collective wisdom of this forum can help.

The new challenge is tapered neck thickness. The necks start at .013" or less near the mouth and thickens to .014 or a bit more near the shoulder/neck junction. I'm reluctant to turn it all down to .013, because that means a finished OD of .269 and the SAAMI spec is .273, which in theory works the brass a fair bit with each firing - but I'm not an expert on how much free play in the neck is too much. On the other hand, turning it to max .014 - just skimming near the shoulder - makes it .013 near the mouth and .014 near the shoulder, so a .001 taper in the neck tension, which can't be a good thing.

Pics below.

Thoughts? Should I turn it to .013? Should I complain to Alpha and get new brass (given that I'm in Canada and this could take weeks or months or longer)? For all I know a tapered neck isn't terribly out of the ordinary, but I think it is.

Thanks in advance!

Sequence showing neck thickness - notice it goes from just over .012 to a solid .014:

Results of turning to about .0138":

 

[Janeau]

I am turning neck for .30BR, 6PPC - 6BR, 6.5x284 to name a few.
Not only for me but for other competition shooters.

On .30BR I like .002 clearance, on 6PPC .003, and 6.5X284. .004
Nobody have reported split neck but sure the PPC and 6.5 like the extra clearance.
This is what work for me and many others.

The real measurement is not SAMI but your rifle chamber neck diameter and the measurement of your brass neck with a bullet inserted.

Your brass will take shape after fire forming - and final shape after 2-3 firing. You can then touch them again if needed.

The 6GT is a hot round and my guess is that primer pocket will give before you have neck abuse. If this bother you, anneal after each firing. This will help. Myself I would turn to .0132 or .0133 and see if it clean up completely. If not, I will go to .013 and don’t look back.

Nice tool and nice clear pictures by the way !

 

[adamg]

Isn't the latest word from Cortina and some BR shooters that make youtube videos, that lots of neck clearance is good? I think they have been moving to larger diameter neck dimensions on their reamers to get more clearance there, and liking it.

Another point of interest here is, how do we think the thickness will change after a few firings? Will it continue to get more thick at the shoulder-side, or even out?

 

[yodave]

I've got multiple shots on my Alpha brass, and I never had to turn it, nor did I measure it, and I don't even know what the chamber reamer spec was, I'd shoot it as is, if a bullet drops inside a fired case with little to no resistance, don't worry about it.

I also don't turn some of my necks lower then what I can size with the bushing and or where the base of the bullet sits, sooner or later without a full length or full neck sizing die you will cut the neck right off the case above the shoulder junction. I am running 2980 giver take with a 105 grain, zero issues with necks, primer pockets, pressure

 

[jimbo14]

Isn't the latest word from Cortina and some BR shooters that make youtube videos, that lots of neck clearance is good? I think they have been moving to larger diameter neck dimensions on their reamers to get more clearance there, and liking it.

Another point of interest here is, how do we think the thickness will change after a few firings? Will it continue to get more thick at the shoulder-side, or even out?

Peanut gallery comment: given how much brass expands to fill a chamber, I’d think a bullet stuffed inside a neck would project any thickness variations to the outside, and then under firing, would tend to level out the brass thickness. It’s hard to see it mattering too much.

 

[Lead hammer]

Isn't the latest word from Cortina and some BR shooters that make youtube videos, that lots of neck clearance is good? I think they have been moving to larger diameter neck dimensions on their reamers to get more clearance there, and liking it.

Another point of interest here is, how do we think the thickness will change after a few firings? Will it continue to get more thick at the shoulder-side, or even out?

I have heard and read this as well. 4-5 thousand clearance. I am sure it will work many different ways, like bullet seating depth, lands or jump.

 

[Janeau]

I've got multiple shots on my Alpha brass, and I never had to turn it, nor did I measure it, and I don't even know what the chamber reamer spec was, I'd shoot it as is, if a bullet drops inside a fired case with little to no resistance, don't worry about it.

I also don't turn some of my necks lower then what I can size with the bushing and or where the base of the bullet sits, sooner or later without a full length or full neck sizing die you will cut the neck right off the case above the shoulder junction. I am running 2980 giver take with a 105 grain, zero issues with necks, primer pockets, pressure

You says in the first sentence you never turn and then in the second paragraph ‘ I don’t turn my neck lower ‘ . You turn or not ?
Second - turning just were bullet sit is a sure way to get a donut and bad neck tension. As for your comment the full neck sizing die will cut the neck right off is just not true and not based on any fact. It’s not the way to turn neck for accuracy and consistency.

Even Benchrest along with F Class and PRS shooters full lengh resize their brass..nobody who wants to win anything and get the best performance of their rifle neck size only.

You are proven wrong by hundred of thousand of competition shooters since the 50’s who turn neck to the shoulder on the most accurate guns there is.

 

[yodave]

You says in the first sentence you never turn and then in the second paragraph ‘ I don’t turn my neck lower ‘ . You turn or not ?
Second - turning just were bullet sit is a sure way to get a donut and bad neck tension. As for your comment the full neck sizing die will cut the neck right off is just not true and not based on any fact.

You are proven wrong by hundred of thousand of competition shooters who turn neck to the shoulder on the most accurate guns there is.

maybe your English to French isn't working, try reading the original in english and dissolve what it says LOL

I don't turn my GT brass, no donut if there is no bullet that far down the neck, only turn where the drive band sits in the neck, I don't know much because I am to busy shooting between 8 and 12 thousand rounds a year so don't have time to run a youtube channel, I teach those that want to learn, but in order to learn, you should at least have half a clue and share the ability to both read and write

 

[Janeau]

I would not attend your class for sure…

 

[yodave]

neck turn to the shoulder after repeatedly sizing with a bushing and, you'll cut the neck off.....we've proven this a thousand times

hmm, how many PRO's chamber their rifle so the bullet sits just above the donut so it doesn't effect seating or neck clearance issues? all the ones I know do, why are you sizing the neck down below the driving band of the bullet? even sinclair figured this one out and make micrometer adjustable bushing neck sizing dies so that you don't have to, I can go on, but you refuse to want to learn

 

[Janeau]

‘’neck turn to the shoulder after repeatedly sizing with a bushing and, you'll cut the neck off.....we've proven this a thousand times’’ - Go tell that to the thousand of Benchrest shooters that ALL neck turn they've will all laugh at you.

In our sport - we and (I) shoot Benchrest custom rifle and need brass to fit custom chamber neck. Running an expander to set neck tension will not work if you have material thicker inside the neck below the base of the bullet. I use custom full length sizing dies made for those chambers.

I shoot (also) a 6BR with 105 scenar L at 2950 and those bullets goes the full neck length just to the shoulder to case junction. Your ways will not work.

The primary reason to turn neck is to make the brass fit the tight chamber in use and then uniform them. None are perfect out of the box. None.

Maybe you should start looking at youtube. You will learn from F Class and PRS PRO’S what they are doing even using IDOD inside outside neck turner now. Those are not my game, but I am open to learn what they are doing and why.

I compete and also shoot close to 10000 rounds a year and burn a couple barrel in the process.
You found a way to get by for your game..I have nothing to learn from your ways for mine.

 

[yodave]

In our sport - we and (I) shoot Benchrest custom rifle and need brass to fit custom chamber neck. Running an expander to set neck tension will not work if you have material thicker inside the neck below the base of the bullet. I use custom full length sizing dies made for those chambers.

The primary reason to turn neck is to make the brass fit the tight chamber in use and then uniform them. None are perfect out of the box. None.

I compete and also shoot close to 10000 rounds a year and burn a couple barrel in the process.
You found a way to get by for your game..I have nothing to learn from your ways for mine.

stop contaminating other peoples' sports with yours, life would be simpler, you don't just neck turn to fit a tight chamber, you also neck turn to make necks more concentric for better more even neck tension, regardless of chamber size, this also allows brass to more evenly expand and let go of the bullet in a more concentric path to the lead of the throat, those thick spots in the brass around the neck are not going to grow or expand at the same rate, it's one of those little tricks we use to turn any brass into match brass

 

[Mystic Precision]

Turn them all down to at least 13 thou thickness... 2 thou per side clearance is VERY small. Assuming the alloy is the typical tough stuff in premium brass, I would turn to 12 or 12.5 thou, anneal often and enjoy the consistent neck tension.

And I will definitely cut lightly into the top of the shoulder... provides clearance for brass flow. With reg turning, no donuts can form as the material is removed before it can become a problem.

If you can't drop a bullet into the fired case, you need to turn the necks more to create more clearance... at least in an application where you aren't cleaning your barrel every few rds.

Jerry

 

[acrashb]

I am turning neck for .30BR, 6PPC - 6BR, 6.5x284 to name a few.
The 6GT is a hot round and my guess is that primer pocket will give before you have neck abuse. If this bother you, anneal after each firing. This will help. Myself I would turn to .0132 or .0133 and see if it clean up completely. If not, I will go to .013 and don’t look back.
[...]
Nice tool and nice clear pictures by the way !

1) thanks, I may try cutting a bit deeper to even out the neck tension

2) It is! I have enjoyed using the K&M for years - it cuts cleanly and is very easy to adjust. And re: pictures, this is my eBay photo setup repurposed

Isn't the latest word from Cortina and some BR shooters that make youtube videos, that lots of neck clearance is good? I think they have been moving to larger diameter neck dimensions on their reamers to get more clearance there, and liking it.

Another point of interest here is, how do we think the thickness will change after a few firings? Will it continue to get more thick at the shoulder-side, or even out?

1) I've heard that on another board, will dive into it and see what directly comes from Cortina's feed. He doesn't know everything, but he's worth listening to.

I've got multiple shots on my Alpha brass, and I never had to turn it,
[...]
I also don't turn some of my necks lower then what I can size with the bushing and or where the base of the bullet sits, sooner or later without a full length or full neck sizing die you will cut the neck right off the case above the shoulder junction.

1) perhaps your brass necks don't have tapered neck thickness and I just got a weird batch? I've never seen this with Lapua.

2) that's good advice. I would turn only once in a cartridge case lifecycle, this bunch is sacrificial brass to experiment - and I did dig a bit deeper than usual into the shoulder.

I don't turn my GT brass

Perhaps your brass necks don't have tapered neck thickness and I just got a weird batch? I've never seen this with Lapua.


Overall I may contact Alpha and see what they say. No-one (on several boards) has yet said they've had tapered neck thickness.

 

[yodave]

I never checked the cases out of the box, and right out of the gate I had no issues getting sub MOA groups out to 300 with matchburner 105 bullets of all bullet choices

 

[acrashb]

Turn them all down to at least 13 thou thickness... 2 thou per side clearance is VERY small.
[...]
And I will definitely cut lightly into the top of the shoulder... provides clearance for brass flow. With reg turning, no donuts can form as the material is removed before it can become a problem.

1) Thanks Jerry. I'm starting to realize that current thinking about neck clearance is looser than I'm used to. I'll measure the reamer later (got it a couple of days ago), but the real data will be available when the barrel comes back in a good many weeks and I do a chamber cast. I was hoping to do all the brass prep before then, now thinking perhaps I should wait for that cast.

2) in the pictures, would you say I was a bit deep into the shoulder? Not sure, I typically cut less deeply, but I'll listen to your advice given your track record

 

[Mystic Precision]

Just a light cut on the shoulder is plenty... as long as your turning on a reg basis, while annealing, any excess flow will get removed.

When using good quality brass, more room is not going to hurt. 3 to 4 thou PER side is not going to hurt anything.... and greatly reduces the chance of a pressure spike should you shoot more and clean less.

Jerry

 

[acrashb]

Thanks to all - and especially Jerry @ Mystic. We need a "like" button.

FYI, two things to know:
- several people on other forums have confirmed that their Alpha 6mm GT brass had a bit of taper in the neck.
- Alpha tells me that this is "100% normal" and I should just load and shoot, no turning. Of course, I'm not sure how to choose a bushing if the neck is tapered. May go with the average, or I may turn it all anyway. Still thinking.

 

[Mystic Precision]

Simple... if you are using a bushing, you turn and turn often.

Why bother spending money to "play" with neck tension when the case can vary in tension from top to bottom of the neck? And will continue to vary with each firing...and from case to case.

Better to just use a common sizing die with an expander ball... a least you have a chance of having the inside of the neck consistent in diameter.

Brass flows... and if you accept that it does, turning case necks will become a routine step in case maintenance.

Jerry

 

[Maple57]

I feel strongly about neck turning myself depending upon specific factors. The following is pure gold...

If you have a sloppy neck, size your brass in two steps to avoid creating a taper in the neck. First bushing should be 0.002" larger than the second. The second smaller bushing will even out the taper in the neck and provide more consistent neck tension. Pay close attention to the force needed as you retract the case from the bushing when neck sizing... You'll see the difference.

If you have a neck that is sloppy enough for un-turned cases, the benefit will not be as significant as if you have a tight neck chamber.

Neck turned brass will always have more consistent neck tension than unturned brass, regardless of how you size your necks.

The amount of neck sizing required will dictate how much runout you will induce by your neck sizing, so less is better than more... Back to the tight neck chamber. If you have to reduce the neck diameter by 0.002" you will induce less runout than if you have to reduce the neck diameter by 0.012" regardless of sizing method used.

Throat length and clearance diameter is also a factor that will influence the outcome.

A short throat rifle will benefit greatly from tight neck chamber and turned brass. This is because the neck is the primary bullet alignment tool.

If you have a long and reasonably tight throat / freebore, the freebore will become the primary guiding force that influences bullet alignment, so neck plays less of a role, but not no role. A long tight freebore is the defining characteristic of 6BR and 6 Dasher for example and primary reason they are known for accuracy.

If optimal accuracy is my goal, I will order a custom reamer with a tight neck every time. All my competition barrels have tight necks.

As for my neck turning process, I always use two neck turning tools. The first is a rough pass, the second is the finishing pass. If you try to skip the second step and just turn once to your finish size, it will be better than factory but no way as consistent as using the second pass.

Also the mandrel I use for the second pass is larger than the mandrel I use for the first pass... This is key.

As for donuts... Not a concern if you design your chambering reamer so the base of the bullet bearing surface sits forward of the neck to shoulder junction. This is also key.

Also, how you deburr the inside of your necks after length trimming is also key, Best tool is a 1/4 shank cone shaped carbide burr. Forget all inside deburr tools offered by any reloading company... They are all crap.

Certainly the last step is weight sorting brass. Forget weight sorting within a bag of 100 cases regardless of brand. Buy at least 1,000 (4,000 + is even better) cases of whatever brand you like and sort ALL of them into lots of 100 that are closest in weight. The end result will be at least 10 times closer in weight within any weight sorted lot of 100 than each package of 100.