I'm putting together a 6mm Reminton. I've noticed that the SAAMI max pressure for this cartridge is 65,000 psi. Given that the 7X57 derived case has quite a bit of taper, I was wondering if case stretching decreases case life & promotes premature insipient case head seperation?

Since I'm going to utilize this chambering for long range work I'm not really looking to reduce loads to increase case life.

Does anyone have any 1st hand experience W/loading this cartridge @ full house pressure? What is the case life expectancy @ full SAAMI pressure?

As I will have to have the barrel I bought re-threaded, it would be a simple matter of setting it back a bit to do an Ackley Improved chamber.

Now please don't expound on how the Ackley Improved version of the 6mm Rem does not improve Mv much if @ all. I'm not interested so much in that, although I will take whatever I can get in increased Mv. What I am interested in is the increased case life that DOES result from the decreased case taper.

I started out my reloading career on an 8mm/06 A.I. & the "Improved" case DID greatly increase case life in that particular flavor of "Improved" chambering. I would get 12-14 reloads before the primer pockets would open up & I was definately "pushing the envelope" just a bit on pressure,

Still, if one can get 7-8 full power loadings W/the standard 6mm Rem case, I would gladly forego the "Improving" & the reultant feeding issues (in a 98 Mauser) that arise W/it.

Wildcat,

My father re-loaded the same 40 pieces of Norma 6mm rem brass for many years...he used a full power load of IMR 4895 and a 60 gr sierra HP to vaporize varmints.

Case life was outstanding.

Good luck.

If you're building the gun, just make sure the chamber is such that the bolt closes lightly on the go gauge.....

PFL resize the case to push the shoulder back only a few thou and your case life will be excellent.

Many folks attribute the shape of the "AI" rounds to good case life.....that's bullpucky....it's because of the minimal headspace these custom rifles normally encounter!

My first choice in actions wouldn't be a controlled round feed,to be pushing the pressure envelope.
Blanked primers won't be entertaining!!!

Push the envelope with a Rem 700 long action,1:8" twist Bbl chambered 6MM Rem pushing 105-115 VLD's @ 3100+fps w/ ease.
Minimum headspaced & 10-12 loadings is the norm.

In have a custom Mauser in 6MM Rem., and I see case necks cracks after about 6 reloads.

quote:

Originally posted by Dans40XC:
My first choice in actions wouldn't be a controlled round feed,to be pushing the pressure envelope.
Blanked primers won't be entertaining!!!

Push the envelope with a Rem 700 long action,1:8" twist Bbl chambered 6MM Rem pushing 105-115 VLD's @ 3100+fps w/ ease.
Minimum headspaced & 10-12 loadings is the norm.

My 1st choice of actions for ANY hunting rifle IS a CRF action & there's probably none better than the M98.

I have 2 M700s. I like them, but I have had issues when I was fumbling for cartridges while watching a deer that I happened onto unexpedctadly.

Once W/a POS pre '82 ADL (one of the ones that went off, just as mine did, on safety release) I managed to cross up 2 rounds in the magazine & had to remove the action to restore functionality.

Several times I have short stroked the bolt on M700s resulting in a double feed. That's nearly impossible W/a 98.

Granted, those were screw ups on my part, but I have never,,,,, never had a M98 jam up on me for any reason.

As far as blown primers. The one time that has ever happened to me, the gas handling features of the 1944 vintage J P Sauer 98K action handled things W/little drama. It directed the gases away from my face & I only felt a slight sensation on the far reaches of my rather large FIVE head. (pun intended)

quote:

Originally posted by Leo L.:
In have a custom Mauser in 6MM Rem., and I see case necks cracks after about 6 reloads.

Sound to me like that is from a chammber that is a bit large in the neck causing excess work hardenning of the brass upon resizing.

That flags out a potential problem & encourages me to do a chamber cast on the take-off barrel I bought.

Worst case scenerio would be to form brass from the plethora of once fired G I '06 brass i have on hand. I think that would result in thick necks that I could talor to tye cahmber if need be.

Loaded to similar pressures and treated in the same way you'll find no difference in case life between a regular 6mm Rem and an Improved version.

However, there's no real reason not to improve it as you can acheive the same velocities at marginally lower pressures which WILL (potentially) improve case life.

quote:

Originally posted by kreyten:
Wildcat,

My father re-loaded the same 40 pieces of Norma 6mm rem brass for many years...he used a full power load of IMR 4895 and a 60 gr sierra HP to vaporize varmints.

Case life was outstanding.

Good luck.

I love Norma brass, drilled, not punched primer flash holes all but eliminate the need to de-burr. Case head dimension right on the money, not .003" undersized like domestic cases. Great weightb consistancy.

I'll gladly pay the extra $$$$$, even on my tight budget, for all that. Minimal initial case prep needed & I too experience great case life from Norma brass.

I used it exclusively on my 8mm/06 A.I. & also in my 280 Remmy.

quote:

Originally posted by vapodog:
If you're building the gun, just make sure the chamber is such that the bolt closes lightly on the go gauge.....

Since this barrel will need to be re-threaded, I'll be farming it out to Dennis E Olsen.

I'll make sure to specify that when I send him the barrel/action.

quote:

Originally posted by vapodog:
PFL resize the case to push the shoulder back only a few thou and your case life will be excellent.

Many folks attribute the shape of the "AI" rounds to good case life.....that's bullpucky....it's because of the minimal headspace these custom rifles normally encounter!

All I know is I hardly EVER had to trim my 8mm/06 A.I. cases while nearly all my other chamberings 8X57, 7mm-08, 280 Remmy, 30/40 Krag need trimming every few resizings & as a rule, I set my FL dies so that I can just see the die marks on the powdered mica on the shoulders.

All in all, it looks like I will invest in Norma brass if it is still available & stay W/the standard chamber.

quote:

Originally posted by Stonecreek:

However, there's no real reason not to improve it as you can acheive the same velocities at marginally lower pressures which WILL (potentially) improve case life.

Oh damn, just when I had my mind made up you go & fill my head W/yet another factor.

Case life depends on a lot more factors than just pressure. You need to address ALL of them to get maximum case life.

I had a 6mm Rem way long time ago with a Douglas Airgauged 26", #7 taper bbl I loaded to SAAMI max(and over) all the time, shooting 70 gr bullets. I got well over 10 reloading per case without any trouble. I still have some of those cases today and I use them for things whenever I'm thinging about doing another wildcat. Of course I wasted a few cases getting to the point just below case killing pressure and the point of max accuracy.

These are some of the factors you need to address.

Minimum SAAMI chamber with a chamber neck ID about 0.002" over loaded case OD. Dies that fit the chamber resizing minimally, I keep the sizing to 0.001" - 0.002", Use bushing FL dies set hard against the shell holder...NO SLOP or breakover...to keep everything square and NO resizing button, all that does is stretch the case even more, set minimum headspace and keep the bolt nose away from the barrel face at least 0.005", use Imperial sizing wax INSIDE as well as outside the case...I use a nylon brush for inside the neck and slick up the case and brush by running my finger across the wax and swirling the case and brush between thumb and first two fingers. You also have to benchrest prep the brass and bullets so you start out with dimentionally similar cases.

Pressure is NEVER the problem per se(unless you get stupid) in case life, it is how well the chamber, dies and the case fit each other, what weight bullet in relation to what powder burn rate. I even get a minimum of 5 reloading in most of my large bore belted magnums(MY use limit, not the case's), but I also guarantee I've messed up doing a chamber or picked up a cheap rifle and have case head separation on the first firing.

I disagree with an AI case having no benefits as far as case life is concerned...minimum taper and a 30° shoulder plus or minus about 5° has been well proven over the years and the excellent family of modern cases proves that very well...BUT...that is so argumentive as to be meaningless.

As far as which receiver is the "best",
"IF" there is a feeding issue, that is, again, totally subjective and argumentive and depends on if the 'smith knows what he is doing and how well the chamber/headspace is set up, and is more related to accuracy...a good stiff Rem or benchrest action is usually MUCH more accurate than a relatively floppy M98, but that has to do with structural stiffness, and a solid, enclosed case will hold more pressure before "relieving" itself, but the weak part is the primer...it will "usually" go well before a case head will.

There are a lot of things to think about whenever you start mucking about with standards AND wildcats.

You need to spend some time on 6mmBR, Sabier, Long Range hunting, and some of the other major precision shooting and target forums...THERE's where you will learn about wildcatting, reloading and setting up a rifle to get maximum performance out of THE WHOLE SYSTEM.

By the way, depending on the metallurgy of the case, most brass will keep on trucking until you hit the metal deformation point...THAT's the point where you kill you brass...and that point is not far beyond 65KPSI. Keep the pressure below that point, anneal to keep the case from work hardening(sizing/firing/sizing cycle) and the case will last as long as it will last...WHO KNOWS just what that point will be.

Luck

Sooner or later the truth will be known.....

It's now quite clear how much velocity gain there is in the "AI" cases....and if it's not then one just isn't reading closely enough!

Eventually it'll be clear that the extended case life of "AI" cases is also a myth!

Extended case life is not a function of geometry.....it's a function of minimal "working" of the case between firing and reloading.....the less the brass is worked the longer it will last.

quote:

Originally posted by vapodog:
Extended case life is not a function of geometry.....it's a function of minimal "working" of the case between firing and reloading.....the less the brass is worked the longer it will last.

Yep,
Just one more reason to anneal.

quote:

Originally posted by rcamuglia:

quote:

Originally posted by vapodog:
Extended case life is not a function of geometry.....it's a function of minimal "working" of the case between firing and reloading.....the less the brass is worked the longer it will last.

Yep,
Just one more reason to anneal.

I'm convinced that cases from the factory come in widely differing states of anneal. This is a cause for loss of case life or conversely.

Since we have no real method of measuring this we make judgements based on experience of case life....blaming or crediting what ever seems to make sense.....as an example, I'm convinced that neck splits are caused by the nickle plating process (in the case of plated cases) but have no real method to connect those dots....cause and effect....I can't prove it at all....but try to say so instead of saying it's true!!!!!

I'm wondering if it makes sense to anneal new cases from the mfr?

I don't know, but if they are in different states of hardness it would make sense to do so.

I simply anneal every third firing. I wore out the barrel with 300 starting cases of 6.5 Creedmoor (about 2400 rounds) and have not lost even one to a split neck. I'm planning on using the same cases for the new barrel. I would guess that you'll wear more barrels out with the exact same brass if you anneal regularly.

Great consistent neck tension

The 6MM is no different than most other cartridges. With your dies set up properly you will never have a case head separation.
If you anneal the necks a little they will not crack. The 6mm cases will eventually develop loose primer pockets if you load at maximum pressures.
I have handled thousands of of once fired cases of almost every caliber. The 6mm Rem and the 25-06 are the only two which often have loose primer pockets in factory loads.

quote:

Pressure is NEVER the problem per se(unless you get stupid) in case life,

Pressures that are not at all "unsafe" in a strong bolt rifle will expand primer pockets to the point of uselessness in a relatively few firings. Also, case head hardness varies, and if you are using expensive, but soft-headed, Norma brass you can lose a case to excessive head expansion in a single firing with the same load that might go indefinately in a harder-headed WW or Lapua case.

So, while I certainly agree that work hardening (which can come from a number of causes) is the greater enemy of case life, pressure can also be a significant factor.

Lots of good info here.

From the feedback I think I will definately forego "improving" the 6mm Rem.

Still, I suspect that a pronounced case taper does promote "flowing" of the brass.

My 8mm/06 A.I. hardly ever needed case trimming before the prmer pockets got loose after 12-14 loadings & I was pushing it W/compressed loads of IMR 4064.

My 8X57 brass on the other hand, required a trim after the 3rd pass through the resizing die. I am useing Vv N550 in the 8X57 & acccording to Quickload, Vv N550 on average is not prone to pressure spikes in a case/bore of that size W/a 200gr bullet. It should not be generating overly high pressure even when slightly compressed as it is in that particular load.

Both cartridge are only partially FL resized & it takes a slight bit of pressure to close the bolt on either.

I plan to do some checking of fired & unfired brass from each chambering to see IF perhaps the 8mm/06 A.I. does indeed have a tighter "custom" chamber as Vapodog subggested.

quote:

I plan to do some checking of fired & unfired brass from each chambering to see IF perhaps the 8mm/06 A.I. does indeed have a tighter "custom" chamber as Vapodog subggested.

For the record....AI chambers normally are very tightly chambered in terms of headspace....and why not?....they are all custom guns and the ability to custom chamber to the "go Gauge" plus .001 is actually not difficult at all.

Many of them are actually chambered to a light crush fit on a factory round and then reloaded with controlled dimensions.....

Again.....case life is primarily the result of minimum working of the brass during firing and resizing.....and Stonecreeks comments certainly are valid about excess pressure opening the primer pockets.

quote:

Originally posted by vapodog:
Again.....case life is primarily the result of minimum working of the brass during firing and resizing.....and Stonecreeks comments certainly are valid about excess pressure opening the primer pockets.

I agree that case life is determied by the amount of "working" that the brass is subjected to. Resizing would be the major contributor to case working. But, the flowing of the brass & subsequent trimming would be "working" of the brass to some extent.

Not nearly as much as stretching & resizing, but it would be working the brass albeit to a lesser extent.

Here are my measurements of unfired compared to fired case dimensions.

8mm/06 A.I.

Diameter in front of the web..unfired = .471..fired = .472... difference = .001

Shoulder diameter..unfired = .453..fired = .456..difference = .003

Neck diameter @ shoulder junction..unfired = .347.. fired = .362.. difference = .020


8X57IS

Diameter in front of the web..unfired = .467..fired = .470..difference = .003

Shoulder diameter..unfired = .431..fired = .435..difference = .004

Neck diameter @ shoulder junction..unfired = .345..fired = .359..difference = .014

The interesting thing here is that yes, the A. I. chamber is slightly "tighter", but some of that difference particularly ahead of the web has to do W/the closer to spec' case head diameter of the Norma brass. The neck diameter of the A.I. chamber is noticably "looser". Perhaps this is due to the fact that the chamber was cut W/30/06 A.I reamer W/the neck/throat being done in a seperate step W/ a different reamer.

I did measure the case body length from the head to the shoulder, but that would be somewhat subjective as I have no way of determining the transition point other than by eyeball. Besides, I resize both cartridges for a slight "crush fit" on chambering anyway & the dimesions seemed to be unchanged from unfired to fired in both instances.

WJ.....I'd have thought most AI shooters are neck sizing only! This would be minimal working of the brass!

quote:

Pressures that are not at all "unsafe" in a strong bolt rifle will expand primer pockets to the point of uselessness in a relatively few firings. Also, case head hardness varies, and if you are using expensive, but soft-headed, Norma brass you can lose a case to excessive head expansion in a single firing with the same load that might go indefinately in a harder-headed WW or Lapua case.

There are several pressure limits out there. The SAAMI std Max. Which sometimes looks like they just pulled a number out of their hat.

In a normal bolt action the two critical ones are the max safe pressure for the bolt and then the max safe pressure for the brass.

To me if the brass keeps letting go then the strength of the action is not going to be the limit.

As to the brass a lot of things come into play. The fit of the brass to the chamber. Tighter is better. The manufactuer, even the lot, is it work hardened, has it been exposed to amonia?

In my young days I ran my 280 so hot I was getting two loading from the brass, never had to worry about annealing or split necks.

I also learned that the difference in FPS between a pressure that ruined brass and the pressure that allowed you to reload 8-10 times wasn't much.

As to Norma brass. I used 280Norma brass for about 80% of my wildcat work. Sometimes using strain guages and later the Oehler system. I have used two lots of 280 Norma brass over the last 30yrs. What I found is if you kept the pressure at 65,000 or lower it would last just as long as anything else. However a couple in the 67,000 range and the pocket was gone. Norma brass is also 2-3 grs larger in capacity heck you could gain a big portion of your AI capacity increase just by switching brass.

As to the orginal question if you don't over load the brass as to pressure, if your chamber fits as tight as a custom AI you work your brass as little as possible when you resize and then anneal you will see very little if any shorter life than you would see with a AI. As to the neck triming issue. Heck when you form AIs you get a short neck so it already has a head start on the number of trimings.

That said if you really push your brass to the limit as to pressure the AI will hide the effects of pressure longer. Just like any minimum taper case.

I'm sorry this is getting long I must need my morning . The last thing I let impact my decison on what to chamber my rifle in is will the brass last 4 loading or 6. This comes from a guy that has to form about 90% of the rifles he reloads for.

quote:

Originally posted by ramrod340:
As to the neck triming issue. Heck when you form AIs you get a short neck so it already has a head start on the number of trimings.

You know, just after I made that last post, I realized that very fact.

quote:

Originally posted by ramrod340:
That said if you really push your brass to the limit as to pressure the AI will hide the effects of pressure longer. Just like any minimum taper case.

I'll go along W/that.

quote:

Originally posted by vapodog:
WJ.....I'd have thought most AI shooters are neck sizing only! This would be minimal working of the brass!

On the contrary. The minimal case body taper makes resizing even more critical. At least for a hunting rifle.

Everyone is on the same page I think, just stating and restating the information in slightly different mannors.

And you are of course, right, Stonecreek...that was the reason for the "per se"...and why I said that pressure is only ONE factor in the formula. Anyone who has "been there, done that" for any length of time has come across most if not all the various and mostly quite correct statements.

There is absolutely NO WAY anyone's response could cover ALL the various things that can happen in one pass and EVERYONE's experience can't include ALL the things that can happen... unless you've lived more than one lifetime.

I have found that in resizing a sharp shouldered case you need to keep your wits about you...most of the sharp shouldered cases I have delt with will size down to the shoulder without any problem and little pressure on the handle, but getting that last bit of setback always takes a bit more umph to keep from getting a couple thou "false" shoulder...even using my RCBS Rockchucker press...and also the reason I keep hollering for anyone involved in reloading to get a set of relatively cheap headspace gauges, it make things so much easier.

My 6mm-284 and 250 Sav AI will stick it to me if I don't watch out and I have to be careful with my 300 WIN to boot. I have to look between the case and the shell holder to be sure there is full contact with the base of the die and put a lot of my weight on the handle.

Without doing this I end up with a couple thou longer shoulder and the case WILL NOT CHAMBER. Basically I'm talking ~0,002 - 0.005"...one to two thou "normal" shoulder setback for the chamber fit and the rest because the sizing didn't push the shoulder back far enough.

This is one of the reasons I always say set you reloading press up with NO SLOP AND NO BREAKOVER at the top or botton of the stroke depending on how you have the press set up.

One problem with neck sizing only...for anything other than "hunting" accuracy, 1 - 2" groups is many people also back off the sizer die so the case never gets "squared" up...usually not a problem with benchrest or highly accurate target/varmint custom chambered and blueprinted rifles as more care is taken producing the ammo and maybe higher quality, "benchrest" type dies... but a factory chamber is not cut absolutely square or the receiver/bolt absolutely square and perpendicular to the barrel bore centerline. I guarantee cases shot in lopsided factory chamber will be out of square when ejected and necksizing will only cause it to get worse. Never argue with a "neck sizer"...they won't have it.

I ran a series of tests many years ago with a "blueprinted" 223 and 308 against a factory Ruger 223 and 308...using a 3 die set of Redding 223 and 308 dies, Wilson bushing "Hammer" bushing dies and Redding type S bushing dies.

I posted the results of that test on several forums, but instead of that information being used in a meaningful way all I got was the "normal" BS from a lot of "experts"...but maybe someone out there DID actually get the jist and used it but never bothered to reply.

So far almost all the old "secret knowledge" and the reasons "why", has been posted somewhere on the net...much of it on 6mmBR, Sabier and some of the precision/varminting/1000yd target forums...but few seem to bother with searching it out...or maybe it just seems that way by the questions I read.

It's a good thing some have large egos and tend to be verbose, otherwise it would be back to the "hard way"...doing it "by guess and by golly".

Luck

I bought my first 6mm Rem in 1967 and reloaded for it and a couple of more since then. I am still using some cases marked 244 Rem.

I watch the case length closely. I also watch for inside neck "donuts" and frequently inside neck ream them.

I had to rebarrel one of my 6mm Rem rifles and used a 243 take-off barrel. I decided to make it a 6mm AI because it was the least amount of gunsmithing. I'm glad I did - I use Lee collet dies and get minimal brass working for long case life. The AI gives me an extra 100-150 fps (measured on a chronograph).

Wear on brass is more from the resizing than the firing, so if your chamber closily matches the sized case life expectancy greatly increases. I shoot a 1 in 8 twist Hart 28" 6 Rem, the second barrel on my 40X which began life as a 6 rem 1 in 12, shot that one out, now ready for the thrid barrel. I digressed, sorry.. point is, I'm still shooitng brass with excellent accuracy after being loaded 8 to 10 times while pushing 107 SMK's at 3150 ft/secs, and 115 Bergers at 3,050 ft/secs.

I have learned to anneal the necks and find I get more consistant neck tension and better precision, but case life for me has always been based upon primer retention.

Set your headspace to be as close to .0005" setback and your cases will last a long long time.

My take on minimum working of the brass led me years ago to the Hornady carbide ball expander/decapper assembly.

At the time (late 80's) hornady actually made them in most common sizes and actually made them to fit RCBS dies...

The idea behind the carbide ball was to eliminate case neck lubrication (a false hope), but I never went for that anyway....

What I've always done to avoid excessive "working" of the brass is to clean the case neck with a light touch of bronze bore cleaning brush, One pass on and off the brush mounted to a bench block

then one pass on and off a cotton bore mop soaked with case lube, then into the lube die and then onto the sizing die with the carbide expander ball.

I have tool heads set up for my Dillon550 to lube and size rifle cases and I can lube and size 100 cases in less time than it took to type this reply....

"case lube inside the case is bad" you say?

NOT an issue because the next stop for the cases
after the sizer is a hot water bath to remove the WATER BASED (RCBS) case lube (inside and out) before they go back into the tubler for their fine polish


The other thing I do to avoid neck cracks is to NOT use winchester brass more than five times

Winchester brass has just ever slightly more zinc in the mix than Remington or Norma, note the lighter color in it's polished state, and thus it is harder and more brittle.

I can seperate Winchester brass from any other of the brands of brass out of the tumbler by color faster than anyone I know can sort them by headstamp.

Norma also stands out because it's slightly redder than Rem or Federal