Neck turning Alpha brass in 6mm GT

Mystic Precision said:
Why bother spending money to "play" with neck tension when the case can vary in tension from top to bottom of the neck?
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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.
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1) short answer is that I believe, having read Litz' tests ( Litz, Bryan. "Neck Tension." Modern Advancements in Long Range Shooting – Volume II". Applied Ballistics, LLC, 2016, pp. 154-156 ), that I want .003 grip and can get there with bushings. If there is variance on a uniformed (skimmed or fully-turned) neck, I think it would be immaterial. The section is not definitive (and is acknowledged as such) but is intriguing and aligned with Lee Precision's long-standing position that a good crimp provides more-accurate ammo (crimping being more applicable to hunting, not target-shooting).

2) Even if I could get the right-sized ball expander - I suppose that one can count on about .001 spring back with a ball expander and fresh brass (?), so I would want, hypothetically, a .241 diameter expander and the one in the freshly-arrived Whidden die set is about .2392 - in the distant past I read a study showing less runout with neck bushings and believe that to be the conventional wisdom.

Given that a) and b) are in play, if there is more modern information showing that ball expanders are okay for runout, I'm all ears :) and would love to read it.

As my barrel will be at the gunsmith on Jan 10 and they have a multi-week backlog, still a bit of time to decide how to process the brass / reload.
 
#1 for accuracy, I would not want more then 2 thou neck tension... just survey the competition shooters in F class and BR and I expect you will find 1 to 1.5 thou is plenty. Crimping is a byproduct of poor annealing and very rough use. I would avoid crimping even with hunting ammo... if accuracy is the goal.

If you want truly uniform case necks, use a Lee collet neck die.

If you have to use a sizing die with an expander ball, just measure the runout after the case is sized. It is not the end of the world but some dies will cause runout.

#2 really easy to test how and what is causing runout. Just get a runout gauge and measure it. You will also find that high neck tension WILL create more bullet runout after seating vs less tension.... why accuracy minded shooters will use only enough to both hold the bullet securely and get it into the chamber.

Jerry

PS if you have been told that you must have high neck tension in a PRS rifle, find someone better at setting up the mag and feeding of the rifle.
 
Mystic Precision said:
If you want truly uniform case necks, use a Lee collet neck die.
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PS if you have been told that you must have high neck tension in a PRS rifle, find someone better at setting up the mag and feeding of the rifle.
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1) Looking into that. It would be a custom die (they don't catalogue the 6mm GT)- might be worth it, I've heard good things about this method, and I think it's worked well for you for a long time. My barrel would have to be here, Lee wants fired cases for custom dies. FYI on the custom dies one can request that collet resize the entire neck, without that a small portion near the mouth is left unsized (as of when I don't know).

One thing tbd full vs. partial sizing of the neck.

2) it was Litz' findings that at .003 the velocity SD was slightly better. It was a weak finding, but on the edge of statistically significant; he says he'll dig into it in future volumes. If you haven't picked up his series - highly recommended. "Modern Advancements in Long Range Shooting", three volumes for now, starting here: https://thescienceofaccuracy.com/product/modern-advancements-in-long-range-shooting-volume-i/

Having said that, I'd be fine with .0025 up to .003. I'll check the runout of course and reduce if it's high, but should be okay with chamfered cases, HBN-coated boat tails, and some dry lube inside the neck.
 
Funny Litz would offer a 'solution' that no one in the world of F class would choose. I have ZERO interest in ES/SDs... just watch the target and plot each shot, it will tell you more then any Chronie ever will.

I wonder if all those lubes can offer a consistent slip? I gave up on coated bullets a very long time ago.... the way I clean my brass, graphite is not needed. Chamfering isn't going to solve the tight neck issue. But easy enough to test for yourself. Note, I am not a fan of soft squishy necks.

Lee collet neck dies are simply the best way to size a case neck. I would definitely size the entire length... right to the base. Remember that you are sizing from the inside out... and then you turn the necks and remove any excess that has been pushed to the outside.

The way the Lee die works, they must have a precise dimension to the base of the neck to make the collet... this is the only reason they want a fireformed case. Nothing in the collet neck die touches the case (decapping pin will fit into the flash hole). They will provide a seating die so seat a bullet or two so they can help with the seating stem cup... most usually fit longish bullets. Some have worked great, some not so much... usually, I just run a Forster seater and problems, if any, solved.

I would send down a couple of fireformed cases with and without a seated bullet with an OAL to suit your chamber.

Have fun with your new rifle.

Jerry

PS, see how long the neck on a 6 Creedmoor is vs your GT. Also, the shoulder angle. If they are close, you can shorten a 6CM collet neck die and voila, custom neck die.
 
Just received an email saying Lapua will start making brass for the 6gt. I have 200 pieces of the alpha, but having more available options is good. There’s really only one place I found the alpha available and always seem to have an issue when ordering from them. I haven’t seen the Hornady stuff available anywhere either. Not that I would race out and buy it.
 
I would argue that neck turning is a fruitless endeavor, unless you are running a tight neck chamber.

And you don't need a tight neck chamber to get excellent results.
 
acrashb said:
Reference(s) to tests from credible sources?
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This is an incredibly subjective topic. There are many accurate rifles and rounds that use neck turning. And many that don't.

Try it out for yourself. Load up a few hundred rounds of each, and do a bunch of testing over numerous shooting sessions and see for yourself if it's worth it or not.

I bet if you do the above, you won't really see a noticeable difference between neck turning and not.
 
acrashb said:
I'm not going to argue. If you have a reference to a credible source that has run credible tests and described them well, I'm all ears.
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This is kind of my point - it's all subjective. Not even BR shooters can agree on whether it's necessary to turn necks. People are basing their opinions off of anecdotal low quality observations, not any sort of rigorous testing employing scientific principals.

Let me turn the question around to you - do you have any sources of credible scientific testing that shows that you need to neck turn? That there's an observable and quantifiable effect on performance with neck turning, versus without?
 
The extra challenge with demonstrating that neck turning is productive, is that simply shooting factory brass, then turning it, shooting it again, and comparing results, is not a valid test. Instead, you'd have to have factory brass in a chamber with a certain neck clearance, shoot it. Then have neck turned brass in a different chamber with that same neck clearance, shoot it, compare.
And now you are inherently dealing with either two batches of brass or two barrels, and at least one chamber change, which further calls into question what the real cause of the difference downrange was.
 
adamg said:
The extra challenge with demonstrating that neck turning is productive, is that simply shooting factory brass, then turning it, shooting it again, and comparing results, is not a valid test. Instead, you'd have to have factory brass in a chamber with a certain neck clearance, shoot it. Then have neck turned brass in a different chamber with that same neck clearance, shoot it, compare.
And now you are inherently dealing with either two batches of brass or two barrels, and at least one chamber change, which further calls into question what the real cause of the difference downrange was.
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There's certainly a lot of confounders present in a lot of reloading "tests".
 
kthomas said:
This is kind of my point - it's all subjective.
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Potentially, with a decent study, it is not. If I was aware of a credible study, I'd post it, but all the internet has kicked up is a variety of statistically-invalid 'tests' and a lot of ranting opinion and few reasonable but not credible (not really a study, just good results shooting) opinions. A reasonably-uniform neck diameter should, intuitively, for all the usual reasons I'm sure you know and therefore won't repeat, result in a smaller mean radius. As you and others know some intuitively beneficial prep / processing things turn out to not have real-world results. And that's, I think, all I can reasonably add to that, because no-one wins if this thread turns into yet another "why neck turn" slagfest.

Someone might show up with real data vs. an opinion, looking forward to that.
 
acrashb said:
Potentially, with a decent study, it is not. If I was aware of a credible study, I'd post it, but all the internet has kicked up is a variety of statistically-invalid 'tests' and a lot of ranting opinion and few reasonable but not credible (not really a study, just good results shooting) opinions. A reasonably-uniform neck diameter should, intuitively, for all the usual reasons I'm sure you know and therefore won't repeat, result in a smaller mean radius. As you and others know some intuitively beneficial prep / processing things turn out to not have real-world results. And that's, I think, all I can reasonably add to that, because no-one wins if this thread turns into yet another "why neck turn" slagfest.

Someone might show up with real data vs. an opinion, looking forward to that.
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That test data is never going to present itself, unless someone like Applied Ballistics decides to test it.

Ultimately, it's up to you to decide if you want to spend all the effort and time neck turning. I think for your own purposes, and lacking of any real proper test data currently available, is do your own pseudo-testing with reloads made from neck turned and non-neck turned brass, and decide for yourself if it's worth it or not. See if in your rifle and chamber, and for your shooting style, if there's any measurable and repeatable difference in performance (ES/SD and group sizes).

There are people who have really accurate rifles that neck turn, and people with really accurate rifles that don't. You don't need to neck turn to have a precise rifle, or to have small SD. Does neck turning help? Maybe. Maybe not.
 
kthomas said:
That test data is never going to present itself, unless someone like Applied Ballistics decides to test it.
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Exactly. Litz has done interesting, valid test on any number of things. Looking for something like his work, kind of like on the flash hole tests, but on neck turning. Having said that, "never" can sometimes be a few hours, and hope springs eternal.

I won't be doing my own testing because of cost and the challenges of doing double-blind tests. A great example would be Litz' theory of precision tests - many hundreds of rounds across five different shooters.

Every round, especially considering barrel life, is pricey, so the type of testing required to really get at this would cost more than any normal person is willing to spend. I'll likely follow the herd on this one. Or my inner voice. Or a coin toss ;) Still figuring out dies.
 
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neck turning has to do very little with the rifle, but more about the quality control or lack thereof in the brass itself, first and foremeost, if you're using a sizing die with an expander are you likely to see the same results as using a sizing die with a bushing?
When you size the neck of an egg shaped piece of in a standard die, the resulting neck is round on the inside after it is drawn over an expander ball, but with a bushing, the neck is now egg shaped on the inside and neck tension can vary greatly from one case to another.

neck turning becomes a question of how uniform do you want your box of ammo, and is rarely a question of does my rifle shoot better with 2 thou clearance or 4 on the neck. We're trying to remove as many variables as we can, regardless of whether they make us more accurate downrange, what it does do, is remove any doubt in certain aspects of the craft when we get results that don't pass our expectations......
 
10s of millions of rounds fired by thousands of shooters around the world at a 1/2 MOA circle at 1000yds.... with every shot marked and scored on paper.

Seems the top shooters have a similar loading process to maintain the accuracy they need to get on the podium of some very tough competition

Maybe they are all just lucky.. who knows, but you gotta think, that is a pretty good sample size

Maybe not... :)

Jerry
 
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