I recently put a brake on my 6mm AI. Before putting the brake on, my dies could never bump the shoulder back. Bad chamber, or dies I guess. When putting the barrel back on after installing the brake, the smith said he left the barrel loose on my once fired brass, so the next shots would stretch the brass, forcing the shoulder farther forward, so I could resize the brass.

Anyways, I just got some new 6mm Remington brass, and when I fireform with some Unique and Cream of Wheat, my cases look good, but the primers are backing out a pretty fair amount. I'm pretty sure this means I have excessive headspace.

My question is, when I fire the fireformed brass with real loads, will the shoulder maintain that headspace to prevent this from happening anymore? Is it dangerous in any way?

Tyler

Do yourself, and your eyes, a favor and find a new gunsmith.

If your cases had the primers back out a "pretty fair amount" you have probably already stretched the solid head and no amount of shooting is going to bring the cases back to where they should be.

Any AI case can be sized, including bumping the shoulder, if you have the correct dies and follow the correct steps. If you were unable to do that before, you certainly aren't going to be able to do it simply by making new brass with even greater base to shoulder length than before.

Ask your gunsmith exactly what he meant when he said that he left the barrel loose. I'd like to hear his answer. It would surely be a novel alternative to bumping shoulders.

Were you getting a good crush fit when you fire-formed the new brass? I'd bet that you didn't.

Ray

"left the barrel loose"??? Why didn't he put it back exactly like it was before? I'm curious to hear how he did that and WHY he did that.
The primers backing out CAN mean in your case that he left a LOT of head space or you didn't use a stout enough load of powder to completely fire form the cases.

quote:

Originally posted by Cheechako:
Tyler Do yourself, and your eyes, a favor and find a new gunsmith.Ray

What Ray said, and IMO the above is the most important part of what Ray said.
Regards, Joe

If you don't have a good crush fit on the brass when fireforming, you will sometimes (often) end up stretching the brass to the point where head separations occur. You need to either have a good crush fit on the brass shoulder itself or else seat a bullet backwards in the case to ensure a good crush fit that way.

If you use a fireforming load with no bullet and no crush fit, the firing pin blow will drive the case forward and then the primer explosion will cause the primer to back out of its pocket while driving the case even further forward under the pressure of the primer gases. This will move the shoulder to the rear and WILL cause head separations as a result.
Regards, Joe

Tyler

With regard to bumping shoulders on AI cases, it can be done but takes a little experimenting, and the correct dies.

If you set up a die to bump the shoulder back a few thou, chances are that the case will bulge out behind the shoulder. Then you'll find that you still cannot chamber the case. If you size the case down to eliminate the bulge, the shoulder will move back forward where it was before.

What you need is a combo die that bumps the shoulder and sizes the body at the same time. Or, do some testing until you develop a procedure that will do both. It ain't easy but it's all part of shooting AI cartridges.

What I do is set my die to bump the shoulder a teeny little bit and do it after each firing. That way, the shoulder does not have a chance to get progressively worse until you reach the point where it's near impossible to bump it back.

Or, Plan B, use cartridges with 30 degree shoulders.

Ray

Ok, here's the explanation:

My dies are too deep to bump the shoulder, or my chamber is too short. Either way I can't bump my shoulders back. They get nearly impossible to chamber after several firings.

The smith said he didn't tighten it down on my once fired brass so that the case would form the shoulder farther up, so my dies could size them.

As an interesting note, the last 7 cases have not backed out primers at all, but they do look a bit flat.

FYI, this is on a Savage, so headspace would be easy to change, but the brake on it is timed, so if I adjust headspace the dang brake will be pointing any way but up.

Tyler

I like it!!! Instead of bumping those pesky shoulders I'll simply unscrew my barrel 2 thou each time. That should get me through several firings, and then I'll make new brass. Your gunsmith is a genius.

Get someone to face off the bottom of your sizing die or try some of the different size shell-holders.

Ray

With my fancy case head seperation indicator (paper clip) I was unable to detect any seperation occuring. The last cases haven't had the primers back out...I'm confused as to whatever is happening.

I have fireformed more than a little brass in my life. Nothing really totally exotic, but, I would make my 6mm Rems from 270, 243, even 06 brass sometimes. I had a full set of dies and assorted collets that would make anything into anything if it was from the 06 family.

I shot a 6x47 for bench for a couple of years until the PPC'S came along and made me obsolete. These were for a tighnecked chamber so I really was careful forming these.

I owned a total of 3 AI's in my life. On fire forming AI's for my 22-250, my 30-30 and my 06, I just ran factory ammo through the gun and although I lost a touch of velocity and a touch of accuracy, they were all "working shots".

To me, one of the advantages of PO Ackleys designs was that you could always run factory through your AI, and then reload the fireformed result along with any Virgin Stuff.

My points are:
1. For only bumping the shoulders in an AI conversion, why are we down to breakfast cereal and reduced loads?

2. Why would the gunsmith POSSIBLY leave the barrel loose of an AI conversion? This would be dangerous and defeats part of the advantage of PO's design.

I do not knock the extra care being taken in fireforming for the AI. I am probably just from a different time and wasn't as informed as some are today.

Enjoy your Ackley Conversions, I am a believer in them. thanks rc

Well, I formed about 30 more cases...no more primers coming out. Maybe my chamber had some oil in it or something? (NO CLUE how, as I've shot it since the last cleaning)

I also fired a full power load, no seperation that I can feel, primer looks good. However, since the brake was put on, firing pin marks are way "bigger". They aren't cratered, but they look deeper and over all just larger than before. I guess this isn't hurting anything since I've fired several full power rounds, and nothing has happened.

quote:

Originally posted by Tyler Kemp:

As an interesting note, the last 7 cases have not backed out primers at all, but they do look a bit flat.

Check those flattened primers for the top hat effect. They well might be backing out just before the case does. Improper set head space on Stevens or Savages (not factory)is not uncommon. roger

I have a 243 Win AI and 257Rob AI. When fireforming hew brass it takes conciderable force to close the bolt. Both were chambered by professional gunsmiths. If your smith had done it right he would have screwed the barrel in tight against the 6MM AI go gage.
Lyle

+1 on what YUMAN said. Always was a SNUG fit on a new case (factory or virgin)on all three of my ackleys. rc

I know you say that your cases were all new and you were fireforming them for the first round, but is it possible that you in fact had some older brass that had the primer pockets a bit loose? Keeping everything well sorted can be a chore, I know, and since you were dealing with a new chamber situation, and your dies weren't resizing the brass very much at all, it would be possible to not notice. That could explain the inconsistent results. Long shot, I know, but plausible nonetheless.

As for your gunsmith, shouldn't he be setting headspace with go/no go gauges, instead of just backing her off a tad? If your chamber isn't withins spec, it isn't hard to believe that your dies aren't doing what they should either, since they are cut around a spec chamber and case length. just my .02

May I suggest something?

Whenever you are fireforming brass, always seat the bullets out so they engage the rifling, pushing the base of the case against the bolt.

That way the case fireforms to the exact shape of the chamber.

Also, I have found that some dies for the improved cartridges are not all the same, and if you have a die that has slightly different measurements than the your chamber you are going to have problems.

We have learnt this a long time ago, and then we started ordering our dies to fit our specific reamers exactly.

Well, Daniel was partially correct, they were "used but not abused" cases, primer pockets were all plenty tight.

I was not using bullets to conserve my already waning barrel life.

Why putting a muzzle brake on a 6 mm? (slightly off-topic)

I have a 244 AI(1-12 twist barrel)and, had exactly the same trouble as you have ,with the die unable to push the shoulder back enough to chamber,and also had primers backing out when sizing brass.
(By the way,I read Parker Ackleys books and the AI chamber should be set up very short to be sure the shoulder of a standard size case is a very tight fit in the improved chamber.)
The first problem was fixed by having a few thousands shaved off the end of the die.This was done by the family member who owned it before me.
I always thought it was the cause of the second problem,but it happens with new,unformed brass,too,so maybe not.
This is where the case is too short for the chamber during the fire forming ,which results in a backed out primer,and the shoulder too far back.
I fixed this problem by necking all my cases to be fireformed up to .257 ,then running them through the 244 AI sizer die ,set so that the bolt will just close on the unfired case.This results in a small shoulder where it needs to be,to tightly fit the chamber.I then had great results with a milder load, a few grains down from max,fireforming cases.If I used full power loads for fireforming ,about 25% of the cases would split.I was able to get under 1" groups with my fireforming load,an 85gr bullet with I think, h414 powder,somewhere around 3000 fps.All these cases have a nice sharp shoulder,no primer extrusion,and no stretch ring.

i just come in on this one.
but here goes your load to fireform was too weak to re-seat the primers.
with an ackley case you sometimes have to do two full power firings to get a full fireform especially with harder brass like win or even federal.
i use remington brass with all my ackleys or other softer brass.
next time you fireform, just partial neck size.
leave a donut to give the neck area some purchase and load up to shoot like a normal round.
this will also help the brass orient to the chamber and let it swell evenly.

I would send the rifle to westpac, or toomanytools, or other real gunsmiths ahd have the headspace set properly. If the headspace is not correct you will always have problems. When I was young and dumb I had a 257 rob rechambered to an improved which I figured out later that they rechambered without setting the barrel back. That rifle drove me crazy for years. I finaly had it rebarreled to a 243 AI by a good smith. What Saeed said is correct if you have a chamber with excess headspace.
Have it fixed!!!!!!!
Lyle

I've formed a ton of brass over the years for a variety of wildcats, and I can tell you that the COW method is not the greatest thing since sliced bread and that I wouldn't use it for anything other than perhaps ironing out the hour-glass shape on a .270 Ren.

What gives you the BEST potential for longest case life is using a bullet long enough to reach & engage the rifling and a powder bulky enough to give a compressed load and yet fast enough to fully form on the first firing. This setup will lend maximum support to the case upon firing.

Well here's some groups shot at 550 yards with the brass that I fireformed.




(YIKES, wind!)

Tyler Kemp wrote:

quote:

(YIKES, wind!)

Hey, those are some super groups, but I don't understand the wind comment. If anything, a grasshopper sneezed somewhere along the way.

Without knowing anything about your load, even a 10 mph wind would probably have drifted your shots at least 20+ inches. At 550 yards, a difference of 2.5" or so is generally not attributable to wind but rather shooter error or load variances/idiosyncrasies.

Care to give us a group size on them 550-yard shots? How big are those squares? I use target dots on white paper, so I have no idea how big your groups are...

1" squares.

quote:

Originally posted by wildboar:
Why putting a muzzle brake on a 6 mm? (slightly off-topic)

It makes it easier to maintain sight picture after firing so you don't miss the "splatter"

As for fireform loads?

Heavy for caliber bullet and the fastest powder that your loading manuals list for that bullet weight.


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