Need advice on making AI brass

[Stats Shooter]

In another thread I mentioned I am having a 6mm AI built. I have never owned an AI. Nor have I made brass for one, or seen anyone make brass for one.

So I need a few tips on making the brass. I have the dies taken care of.

But my question is this. Should I just buy some factory ammo, same brand obviously, and fire form it?
Or buy 6mm brass, load it, and fire form it?
Or try the cream o wheat method? Though I have heard the COW method may take a few tries.

[Scoits]

I had two 223 AIs that I used for PDs. I fire formed all brass by reloading new brass to std 223 max loads. Kept them separate and used the same brass for about 8 to 10 reloads.
Should check for case length.

[HiBC]

I have formed a pretty fair amount of AI brass.What I do works for me.
I'll begin with the Cream of Wheat idea.I have done a lot of that,too.
While it is a great technique for some things,its just not what you do to make AI brass.
Several years back,the .405 Win Hornady brass did not exist.30-40 Krag brass was still common. The COW method would blow 30-40 or 303 Brit straight to basic brass.
It was also great for blowing 30-06 out to 35 Whelen.I got MUCH better concentricity and uniform neck thickness than by using a sizing die.
Per Ackley's plan there is ,geometrically,a circle at the junction of the neck and the shoulder of both standard and AI brass.In theory,your smith chambers the AI carefully so this circle is at the same length from the bolt face for the standard brass,the AI brass,and the chamber.
So,in theory,that circle of contact will hold standard brass against the bolt face for fireforming.
It can work quite well.
Of couse,there IS Murphy's Law.
Suppose you start with a rifle of factory tolerances and want yours smith to run an AI reamer in.Thats not really the approved method,so maybe that "ring" is in a place that ,for a better term,is"headspace loose"

Brass stretching upon firing tends to thin the brass and create "stretch rings"

Shooting factory loads to form brass is ,IMO,perfectly acceptable ,and is as P.O.planned it,if the rifle was chambered right.

I was aware of all this when I chambered my .257,and it works fine with handloads. Don't bump the shoulders back.

A critical point: With controlled round feed actions,DO NOT put single rounds in the chamber.Feed up under the extractor from the magazine.Forcing the extractor to cam over the rim will crush back the shoulder.

Just think in terms of the case head being snug against the bolt face at firing.

Now,I can feel it coming! Some will advise necking your 6mm up to maybe 7mm or 30 cal,then sizing back down to create a small shoulder.If you want to do all that,OK.But,not me.
Its also fair to say the 6mm is a necked down 7x57.This may apply to 257 R brass,too.You could buy virgin 7x57 ,run it through the 6mm AI die,and create a small auxillary shoulder for firefoming...just watch neck thickness.

But,IMO,just find some bargain heavier bullets and load 6mm virgin brass. If you can long seat them to contact rifling,that holds bolt face contact.Which,ups pressure, Load conservatively.

Load lower midrange with a powder in the quicker range. Burn up what you need to get rid of,within reason.Something maybe between Varget/4895,RE-15,and maybe 4350. Think moderate/starting,but no squibs.
First time out,load 10 for a trial,not 200.
I never had any problem...but glasses are prudent Good luck!

[Stats Shooter]

One of my biggest motivations for buying factory ammo, and fireforming that way, is that I have a bigger selection of brass.
Right now, I can only find Hornady, which I hate, or some supposedly once fired stuff. But if I buy factory ammo, I can get mostly whatever I want.

And if I cost out components, since I am just getting the ammo for fireformed brass, winchester super x is about $1.20/loaded round. Reloading in win brass, if it were available , would cost about $80-$90/hundred so really it isn't that bad......if it works that is. I would just buy 160 rounds or so, then shoot it, then cull what needs culling in hopes of having 100 pieces.

I have actually used win brass in my precision rifles with great success.....but only after culling, turning necks, weight sorting, uniforming pockets, deburring flash holes.
However, it is pretty durable and that is what I would choose if Lapua, or RWS, or some other premium brass isn't available.

[Don Fischer]

I've never tried an AI cartridge but have read on it. Seem's that if the AI chamber is a bit big, the thing to do is load lighter charge's up with the bullet seated out to touch the lands and that hold the case to fire form it. Ackley's way was to cut the chamber very tight so the factory care would actually rub on the shoulder a bit. That way the case supported itself and factory ammo could be used to fire form case's. There was a number I'd read that was how small to cut the new chamber and make the case shoulder rub, but I forget what it was. I've got two Ackley books and in one of them somewhere is what you'd be looking for. I've never understood the COW method. To blow out the case requires pressure. I found with fast powder and rather light loads with 180gr cast bullet's in 30-06 that if the load is to light even with the heavy bullet the case doesn't blow out but rather leave's you with black walls on the case. What does COW weigh anyway? How to you keep it in the case to shoot, wax plug in the mouth? Well maybe a toilet paper plug down at the base of the neck?

[HiBC]

Don,the Cream of Wheat technique is ,IMO,not applicable to making AI brass.

I understand true case forming dies can do a better job,but in my experience "necking up" using a sizing die/expander ball for the desired cartridge...such as 30-06 to 35 Whelen...I have had mediocre results .Eccentricity and all the stretch/thinning on one side. I get concentric,uniformnecks with creamof wheat.
Today,30-40 brass is precious.I used to blow 30-40 Krag out to a slightly short 40-70 Sharps Straight using cream of wheat.It required virgin brass.
The COW works as a semi solid,media that will flow.It opens up necks quite well.

[FrankenMauser]

I've always formed with standard loads - usually handloads, but sometimes factory (such as with my 6mm wildcat that won't chamber anything but unfired Remington .243 brass, because it's well under SAAMI minimum spec).

Check dimensions afterward.

Fully forms the cases.
Usually results in exceptional accuracy. (I think this is due to the initial pressure spike being 'smoothed' a bit by the extra expansion allowed.)
And you get to spend some time getting to know the rifle, and breaking in the barrel.

[F. Guffey]

Depends on the chamber. And then there is the complicated part. The neck on the Ackley chamber is longer than the neck on the parent case. Meaning when the Parent cases if fired in the Ackley chamber the shoulder on the parent case head spaces at the neck/shoulder juncture, when fired the rest of the shoulder and case body form. The neck on the shoulder shortens when the shoulder and case body forms.

I have formed and then fire formed cases that shortened .045" from the end of the neck to the case head.

There are smiths that cut the Ackley chamber without doing anything to the parent chamber. When that happens forget head spacing on the neck/shoulder juncture.

I do not know what 6MM, I will assume it is the 6MM/244 Remington.

Or try the cream o wheat method? Though I have heard the COW method may take a few tries.

I am not beyond using a standard /starting load with a heavier bullet; factors allow me to get away with it and reloaders believe they are into some risky stuff when they try it.

I have forming dies, to avoid fire forming I form 6mm Remington cases from 30/06 cases. I also have a neck reamer die for the 6MM. It comes in handy when forming 22/6 MM Remington/ Improved type Wildcats.



F. Guffey

[Stats Shooter]

I do not know what 6MM, I will assume it is the 6MM/244 Remington.

Yes, 6mm Remington....an offspring of the 7x57 Mauser

One thing I have heard folks do is use Lapua 7x57 cases and make their 6mm Remington AI cases from that, simply because necking them down to 6mm makes the neck longer. Then, turn the neck because it will be too thick, then form from that.

[oldscot3]

Shoot factory ammo and chronograph it, then you'll have a benchmark to see how much of an improvement you're getting when you load your fire formed cases.

BTW Lapua's website doesn’t indicate they make 7×57 cases; 8x57 but not 7mm mauser.

[Jim Watson]

Not AI, but a guy here had a wildcat that frustrated him.
His fireform load was quite accurate, but he never got a load in the reformed brass that equaled the fireform. He was an experienced reloader and shooter but he never did figure that one out.

[Stats Shooter]

Senior Member


Shoot factory ammo and chronograph it, then you'll have a benchmark to see how much of an improvement you're getting when you load your fire formed cases.

BTW Lapua's website doesn’t indicate they make 7×57 cases; 8x57 but not 7mm mause

Factory Brass won't hit as high of pressure in an AI chamber, so it will be slower than factory ammo in a standard 6mm chamber.

As to lapua brass, I think I mistakenly confused 8mm for 7 mmx57. But Norma does for sure make 7x57, as does RWs I think?

[HiBC]

Starline has intro'd a number of bottleneck cases. You might look.

Check for subtle variations in dimensions,but the 257 R is also a necked 7x57.

I have not used a lot of it,but I have been OK with Hornady brass.What did you not like?

[Stats Shooter]

I have not used a lot of it,but I have been OK with Hornady brass.What did you not like?
HiBC

It's a long story with many examples, but in summary, I have had stuck cases with hornady brass at velocities/pressures that I got over 9 loads with different brands in cartridges such as .338 Lapua, .30-06, .223, and .270.

I do not load above QL max, but I will absolutely load up near it, and Hornady brass cannot handle it.

My .338 LM load is a 300 gr SMK at 2880 fps in lapua brass and have gotten over 10 loads out of that. I can't get within 100 fps of that with hornady brass without pounding out the stuck case with a dowel. And case water overflow testing says the volume is nearly the same as the Lapua brass.

Similar story with other cases

[30Cal]

Starline isn't doing 7x57mm based cases; at least not as of last week.

I got a Savage in 257 AI of unknown provenance a couple months back. I think the shoulder is a little forward of where it should ideally be. I had a fair number of misfires shooting 257 factory, but that may have been more of a gunked-up rifle issue. However, the other thing I see is some cases that form 5-10 thousandths shorter to the shoulder.

I tried COW per some youtube video, and it worked OK, but with the questionable HS issue, I've since gone to:
1. Seating a bullet long enough to be into the rifling (warning: you cannot extract the round once you've chambered it without dumping powder)

That worked well, but was still getting variable HS on the fired cases until I started:
2. Lightly oiling the case with CLP prior to firing.

All this I do with a cast bullet over a mid-range load per standard 257Rob data. The oiled case makes me weary of putting too much thrust on the bolt, and I'd rather not burn up barrel life just for the sake of making brass.

This fills out the shoulder well (say 90-95%) and I just run from there.


I like the 6mm AI idea. 257AI is cool, but brass is unobtanium. I can find 6mmRem online anyday, and often locally.


Knowing what I know now (in your shoes), I'd push a box of factory 6mmRem through it first and then check to see where the shoulders end up. If they're fairly uniform, I'd skip the oil.

Haven't looked hard at the data to see what is most accurate at the end of the day. All of my brass (from factory 257Rob and 6mmRem COW and 6mmRem cast bullets) shoots really well, but my suspicions are that the 257Rob would edge out the others.

[30Cal]

The 6mmRem brass I'm using is all Hornady stuff. I annealed them after necking up and again after fireforming. They've held up fine. The couple that I lost were in the process of necking up. I'm on 6+ firings now with an even mix of 2000-2100fps cast loads (close to max) and the gamut of jacketed bullet pressures. I've got some smokin' velocities with no issues with the Hornady 6mm brass.

I did have clear signs of separation failures midway up the case on 2 out of 20 Hornady factory 257 Rob when fireforming dry (again, I suspect HS is longer than desired). Wasn't interested in oiling factory loads.

I have a fairly casual, but somewhat calibrated anneal. I used tempilaq 750 to measure the required time on a handful above a 1.5" propane torch flame tip, and spin them by hand on a whittled-down chopstick.


Also, I had problems with Lee dies--I want to say it was when I was messing with squeezing down 7mm brass. Redding ones have a smoother finish and worked markedly better. Cannelured bullets (jacketed) will buckle case shoulders if I don't lightly lube bullets, but that may not be an issue for you in 6mm. That 40deg shoulder is steep so be ready to shift gears out of your normal methods.


HiBC's posts are right on point.

[Geezerbiker]

Another approach is to make a light cast bullet load with the bullet seated into the lands to hold the case all the way back.

It would be a bit harder with 6mm since there's not a lot of cast bullets in that size.

Tony

[std7mag]

Loading for 7mm-08AI.
I had started reloading for the rifle before i reamed the chamber to AI. So still have my notes of the accuracy nodes from the standard cartridge. I load to those and fire form.

Due to budget constrictions i've been using PPU casings purchased from Grafs.
Work just fine with my AI, and also necking down 7X57 to 257 Roberts.

[oldscot3]

Factory Brass won't hit as high of pressure in an AI chamber, so it will be slower than factory ammo in a standard 6mm chamber.

Why, isn't the pressure contained in the brass when firing? I'm not necessarily saying you're wrong, but it doesn't seem like there would be much pressure loss as the brass conforms to the (slightly) larger chamber. At any rate, if it so, you should realize a significant difference in velocity between the factory ammo and your reloads, but you'll only know if you chronograph everything.

[Stats Shooter]

Why, isn't the pressure contained in the brass when firing? I'm not necessarily saying you're wrong, but it doesn't seem like there would be much pressure loss as the brass conforms to the (slightly) larger chamber

A 6mm AI supposedly had 9% more volume. Also, cartridges over 30,000 psi expand nearly immediately to fit the chamber such that unfired case volume really only influences how much powder can be fit into the case, and how it is packed.

But an AI chamber being approximately 9%bigger means it will not hit nearly as high of pressure. If you simply consider lake City .308 brass vs commercial in the same chamber, the only difference is brass thickness in that case and commercial brass can require as much as 1 more grain of powder to hit the same velocity as that of lake city... even in once fired and minimally sized brass.

Winchester brass also adds just a little more volume than other brands due to a balloon shaped primer/head area. That can make 50fps difference or not depending on cartridge.

So again, adding 9%more chamber volume at pressures over 30'000 psi will yield remarkably lower velocities. .....confirmed by Quickload

[F. Guffey]

Why, isn't the pressure contained in the brass when firing? I'm not necessarily saying you're wrong, but it doesn't seem like there would be much pressure loss as the brass conforms to the (slightly) larger chamber

Reloaders are not conditioned to think in the form of factors. I was accused of being involved in some risky stuff. I was forming cases with what most thought were over and above and way beyond what was necessary. Do not get me wrong I believe breakfast cereal is cute but I choose not to use it and when I eject the case the case is formed.

Just in case I should take my accusers seriously I called Hodgdon and gave them a rundown, they said I would be OK, as always there was the 'and then'.

Fire forming the cases: The cases shortened .045" from the end of the case mouth to the case head.

F. Guffey

[hounddawg]

pressure and volume are inversely proportional, 9% greater volume means 9% less pressure

If temperature if constant then where P = pressure and V = volume P1V1 = P2V2, as volume increases, the pressure of the gas decreases in proportion. Conversely as volume decreases, the pressure of the gas increases.

[Stats Shooter]

pressure and volume are inversely proportional, 9% greater volume means 9% less pressure

If temperature if constant then where P = pressure and V = volume P1V1 = P2V2, as volume increases, the pressure of the gas decreases in proportion. Conversely as volume decreases, the pressure of the gas increases.

This is what i was saying.

Two ways to see what an AI 6mm remington does compared to a standard 6mm remington is to:
1) Take a standard chamber, and push a bullet until the bolt gets heavy, shooting it over the chroney and get an average velocity. Then, have that same chamber reamed for the AI, and load it until the bolt gets heavy, while trying to keep the brass and other components the same, except the added powder.
or
2) Take the average of several hundred or thousand data points from different ackley vs standard 6mm remington velocity measurements and approximate the gain.

option 1 will tell you how much you have Improved your rifle, option 2 tells you how much it improves the "average" 6mm rifle.

[F. Guffey]

And I said I did not want anything between my case and chamber but air and then I said I did not want a lot of air.

F. Guffey

[oldscot3]

A 6mm AI supposedly had 9% more volume.

Interesting. If you get a velocity increase of 9%, 100% of what your increased capacity is, then on a load achieving 3000 fps you should see a 270 fps gain. Half that would be 135 fps, one quarter (as one gun writer suggests) yields 67 fps.

If you google case capacities chart you should find a listing of most popular cartriges. There is also a calculator there that lets you plug in values to estimate velocity. You might enjoy looking there if you haven't already. That article also suggests you get a 4 to 1 relationship between capacity increase and velocity increase. So a 10% increase of volumn yields a 2-1/4% of velocity for example.

I look forward to hearing what your results are, please post as soon as you get your rig up and running.