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Discussion Starter #1
Hi
this is my first time so please be gentle :eek:

I've been reading up on the various AI, ICL etc improved cases based on the x57mm mauser / .257 Roberts family.

The claims made in Ackley, are that these cases, at least up to .270 and .280 calibres, are giving equal performance to the .30-03 and .30-06 based rounds, such as 25-06, .270 Win and .280 Rem.

Has anyone measured the pressures that those performances were achieved with?

130gr .270 WIN factory loads have enough difficulty achieving the advertised 3,100 FPS, with SAAMI / CIP listed max pressures up to 65,000 PSI

I'm having difficulty seeing how a smaller capacity case can achieve the same velocities (assuming the same bullet travel in the bore) without increasing the peak pressure

especially as larger capacity cases than the .270win and .280 Rem, do still show some increase in velocity (even if it is only around 150 FPS, going to the 7mm Rem Mag).

has anyone got measurements or calcs?
 

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ICL, Welcome to our neighborhood. My own view is that when Mr.Ackley wrote that, the then available powders supported him. There's only about a grain of H2O difference, and the abrupt shoulders and minimum case tapers held the Ackleys in the barrel better, when sticky bolts were the danger signs.

Today, with so many unobtanium powders, maybe we should re-think some of P.O.'s ideas. But my own take from making wildcats out of stepped Mauser military barrels, is a little different. When Jack O'Connor created the 338 x 57mm O'Connor, he never got into the extra three inches of barrel length, engendered by the now commercial ( tight ) neck and throat.

In auto mechanics' parlance, these would be called "cheater cams". They exist because Mauser made really oversized neck/throats, for long round nosed bullets. When you do one in a commercial barrel, or as Jack did, ream out and re-cut to a 33 cal. bore, you eliminate all of the oversized military ( trench warfare era ) dimensions.

At the same time, our own military 30-06G chambers were pretty loose, and for the M. 1 Garands, our Powder Companies, downloaded them to 47,500 C.U.P. during WWII, and never juiced them back up in the Post War period.

So in his day, Mr. Ackley wasn't wrong. For years after, we could match an available powder and bullet and beat his improved wildcats, but today's shortages puts the ball back into Parker's court. IMO.

I reloaded for the 8 x 57mm, and then the 8mm x 06, before creating my own 8mm Mag. wildcat. With each one, I gained about 150 fps. with the heavier bullets. It may be hard for you to get your head around this, but it comes from a Nineteenth Century design, before Spitzers were common. 220 gr. Sierra Game Kings in my wildcat 8mm Mag. like H-1000, but its been hard to find. In an old BRNO, with a 29 inch long barrel, I am nipping at the heels of my Remmie 338 R.U.M. using old Speer 275 gr. bullets, up against those 220 gr. Game Kings.

In the end, both an Ackley Imp. 8 x 57, and the 8mm x 06 were equally good Elk Rifles, back in the Post WWII era. Jack O'Connor built himself a rimless 33 WCF. but the light weight stepped barrels made these kick really bad, when Speer came out with their 275 gr. semi spitzer bullet. As we speak, I"m having my G.S. build a 257 Rem. Rob'ts out of an old barrel blank, in my former BRNO 8mm x 06 rifle. He's doing a custom stock along with the re-barreling job.

Note; Speer 8mm bullets were always manufactured for reloading them at 50,000 C.U.P. If you could find good barrels, that gave you another edge, over shooting weak commercial ammunition. O.T.O.H. that same "weak" ammo gives you the best penetration, if not the best knock down.
 

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I have reamers for several AI and ICL.The 7X57AI is a very efficient along with the 257AI,the 30-06AI very little can be gained but has other advantages along with the 270AI because it is right at the upper limit already. The ICL's gain their improvement through some really high pressure.I had a 270 ICL Mag and a 300 ICL Mag.I have a 25 ICL reamer but have never used it yet.
I really like both AI and ICL and will accept their problems,like having a hard time making them feed through Mausers and pre 64 model 70,s.There is no free lunch.
 

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The Hog Whisperer (Administrator)
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If a gun didn't blow up, and you could get the bolt open without undue force, Ackley published the load. You take your chances with that data... guaranteed that none of it was pressure-tested.
 

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Discussion Starter #5
Thankyou @Carpooler
I hadn't realised that the capacity of the improved x57mm rounds was so close to that of the factory standard '03 and '06 based rounds
I'll have to check my copy of Donnelly (I had got a bit sceptical and suspected some typos in there, things like 4 getting typed as 1).

I also hadn't considered long throats / freeboring as a way of increasing the apparent space available for powder burning beyond the case itself.

The gain of around 150 FPS each time capacity is increased from x57mm to x63mm/'06 to your wildcat mag, is about the increase that I would have expected.

The Brno in .257 sounds good. Is it on the Vz 24 (98 style) action or one of the ZKK actions?
 

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Discussion Starter #6 (Edited)
Thankyou @Jim Love and @MikeG

You have confirmed what I suspected; that the claimed velocities involved some fairly hairy, seat of the pants loading.

I'm interested in what you wrote about getting "Imp" rounds to feed reliably

Is this just a case of slightly widening feed lips at the forward end, or is it a more involved process? I have a .270 that I'm starting to consider the idea of setting the barrel back one thread and re-chambering and cutting a fresh throat for one of the improved versions. I'd be doing it as a hobby, The feed lips are in the receiver rather than pressed into a mag box - so any mods there would be dauntingly above my current abilities. I don't claim to understand feed lips at all.

taking my own post OT, the .416 Rigby has struck me for a while as one of the first cases with a 45degree shoulder and minimal body taper (from the 19 teens! when Ross and Newton were producing decidedly wedge shaped cartridges, not that either of them was a particularly good engineer).
In rifles which were properly set up for it, It apparently had a very good reputation as a smooth and reliably feeding dangerous game round.
 

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ICL they're just plain janes

No, both of my BRNO's are just the old pre 1935's with the 29 inch long stepped military barrels. And this is another good reason for not goosing up the pressures. My logic is that although the metal's heat treating may be off, both of these old soldiers have that Mauser third bolt lug under the handle.

This is an important safety factor when you are developing newbie hand loads. Three of my four M-98's have magnum bolt faces. Two are now set up as 6mm, and 7mm x 300 RCM based wildcats. The third is my 416 x 375 Ruger wildcat, which will probably stay as it is. Both my 8mm Mag. and my Rem 700 L.H. 338 R.U.M. barrels are off at present. When I go back to them, I'm sure that I'll use commercial ( Hart ) SS barrel blanks.

In answer to your other question, no, have a G.S. do any rail mods. If you goof it up, the receiver is ruined. These mostly feed staggered, off of the rib in the magazine's follower, so each side's rail has to be ground differently.

Plan B, here is to order a Brownell's B.R. aluminum magazine block, and just load your rounds single shot. This block has a channel in its top so that the claw extractor can pick up the rear of about any cartridge case. So it keeps your Controlled Round Feed features.

My 6mm x 300 RCM wildcat is going into my Ruger L.H. Hawkeye 300 RCM rifle, fitted with a new Hart SS barrel. But I waited for two years to be able to purchase six boxes of this virgin brass. Hornady feels that the handloaders are a secondary market, which they only supply virgin cases to, at their own convenience.

So making up something out of a common 30-06G case has a lot going for it. Pushing back the shoulder so that you have a 26 degree shoulder angle, and with less body taper, will give you a cheaper 240 Weatherby.
 

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The original commercial 257 Roberts were rated for 51,000 PSI. Since then with the development of better metal for the chambers, +P loadings have come out that allow up to 58,000 PSI.

I would hold about the same with any of the 57mm long casings.

As far as velocity is concerned with the 58,000 PSI cap, some research into different powders should get you to a velocity that you desire without going over on pressure.

Example...

With the 257 Roberts out of a Ruger 77MkII, I'm getting over 3000 FPS with 100gr Nosler Ballistic Tips, and Hodgdon Hybrid 100 powder. That is not a max loading either.
 

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the 7x57 Ackley IMP is an outstanding cartridge in every respect..P.O. himself said the 7x57, 257 Robts and the 250-3000 were his best successes and gained about 300 FPS over the standard, I have found that to be true...

Ackley knew his business and could squeeze every ounce of good out of a cartridge, and as such grew a lot of criticism from self styled experts..He stated that each reader should work up their own loads as he expected all of them to know as much as he did..that is seldom the case today, very few reloaders have reached a high level of reloading, with the ability to actually reach a safe full maximum load, some quit to soon and others go beyond safe with gay abandon, and when interviewed their results, the good and the bad float to the top..:)
 

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I load for a 7x57 AI in an Interarms Mark X receiver. I am able to load to longer than specification COL. With longer heavier bullets there is very little difference between it and a .280 Remington seated to same COL but the shorter case uses much less powder. With lighter bullets the shorter case is even more competitive as it handle faster powders better.

My gun has a 26 inch barrel and with 120 grin Hornady it chronographs 3,281 fps. Easy to remember as it is exactly 1,000 meters per second. With a 162 grain bullet it chronographed , IIRC, 2960.
 

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There has always been reloading data of some sort for the AI since the mid 50's. Speer started it with Reloading Manual # 1 for Wildcat Cartridge 1956 which included some of Ackley's favorites. I've got # 4 1959.

First printing Ackley's book was 1962 and Vol 2 was 1966.

Velocity is nice but you need accuracy first and I'm loading for 3 AI's now. My first was 7x57AI and I used data from Speer # 4 and I used start load and worked up to max and I never did get his velocity but got some pretty accurate mid loads.

Later I changed how I load for AI and now I use start load for parent case then work up.
 

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Discussion Starter #12 (Edited)
Thanks @Big 5
I was checking the listed case capacities in my old copy of Donnelly;
normal x57mm cases approx 54 grains of water
AI and ICL improved x57; about 59 grains
normal 06; about 65 grains of water
AI 06; about 68
Gibbs; about 74 grains of water,
Although it's not listed in my copy of Donnelly, I'm guessing that the 6.5mmx65mm RWS is about the same capacity as the Gibbs, but with a longer neck and .474" base diameter. http://www.cip-bobp.org/homologation/uploads/tdcc/tab-i/tabical-en-page29.pdf

So yes, almost a 10 percent gain in capacity over the factory case for the improved x57mm cases.

and only about a five percent gain in capacity over the factory case for the improved 06, and bigger gains on the same base diameter cases requiring either pushing the shoulder or going to expensive RWS factory ammunition.

I guess that in a way we are spoilt for choice with factory re-loading gear and info, possibly at the expense of never needing to learn the level of skills that Ackley's generation had to pioneer.

@Ozarks,
That is some performance, you are getting the same or higher velocities as an 06 based case out of a case with ten percent smaller capacity!

@ Old Roper, are you starting with the starting loads for the parent case?
 

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Yeah, try to AI a cartridge from the 308 family..
About 4 percent more useful capacity. Hardly any load data.

I did a 7mm-08AI (yes, I know Ackley never improved the 7mm-08)... Would not recommend doing it again.
 

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First and foremost a reloader has to realize that the reloading books vary to degrees as to a max load, so balically you fly by the seat of your pants..Its up to you alone to hone your skills and knowledge to be able to load to max in each rifle you own and a rifle is an inity unto its self as someone once said.

I start with new brass and in some cases a book max load minus two grains and work up a grain at a time to start with. I use a chronograph as I know about where max velocity is as the book shows that. While reaching that velocity I look for flattened and cratered primers and that's iffy information as primer metal varies, but its still an indicater if combined with another pressure agent such a case head indention, with both apparent your probably max and need to cut back a grain...watch for a sticky bolt, a clear indication of pressure, some folks mic case and I do that also but you must fire form a case before you measure the base to know what kind of expansion your actually getting, and I strive for _0_ expansion, some go for no more than .0005..After I reach what I believe to be max, I reload that case and Im looking for loose primer fit, if so Ive gone a bit too far so its time to cut back a grain..the I try to load that same case at least 5 to 10 times successfully..if so I have a max load for that rifle and I know where max is, that's the important part...I'll probably load up a batch of that load minus a grain just for the heck of it as 25 to 50 FPS means nada...BTW another indicator of pressure is a crack as opposed to a boom, cut back a grain. I almost forgot this one.

I also seldom weigh a charge as over the years Ive mastered my powder measures, I do this by using the same repetition each time I toss a charge..I observe the the loaded case under a strong light before seating a bullet and I strive to use powders that fill the case to half way up the neck or at least to the shoulder, depending on the caliber. If at any point in shooting something isn't right, I sure need to figure out what it is and the cause, but that seldom if ever happens.

For what its worth, this has been my way of handloading for the last 70 years without a blowup and oney a few ruined cases. Im sure others have a different procedure or simply load below book max, and I suspect that works just fine, especially for a beginner..I personally want/need to know where max is in my rifles, even though I may not load to max pressure, but in some cases that is where extreme accuracy is found, especially with slow burning powders. Books could be written on this subject and have..Good idea to read them all...Fortunatly most good rifles are test fired at pressures beyond where we go in handloading and most accidents are caused by carelessness like leaving the wrong powder in your hopper, using by neglect pistol powders in your rifle, pushing the string beyond what you know is max to get that worthless extra little bit of velocity trying to make your 06 a 300 win. or make your wildcat the cats meow! and your just being ignorant at that point.
 

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There is no reason to expect brass for any of the '57mm family of cartridges' to be any weaker than 30-06, 308, 25-06, 270, etc. Manufacturers are not going to make weaker cases for older calibers originally loaded to lower pressures. It does not make economic sense. The reason factory pressures in the older calibers may be a little lower is not that the brass in weaker but because there are many older guns floating around and manufacturers don't want a +P load getting into them by mistake.
 

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The Shadow
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The "bigger issue" in the pressure discussion is what was actually being tested, and a previous post touches on the other issue; What is max charges.

1 - For a period of time, Copper Crushers were reported in PSI, rather than CUP(copper units of pressure). Then we moved on to piezo transducers, and strain guages for what is known to the world as PSI. For a somewhat large amount of time after the system change, the military was listing "PSI" but were actually measuring CUP. The system change happened after the major players in SAAMI(Federal, Remington, etc) did some very carefully controlled tests. What they found was that Copper Crushers are very inaccurate when used over @ 45,000 psi. Inaccurate to the tune of 15-20,000 psi swings of actual pressure! I know Denton has done some correlation between CUP and PSI, but the inaccurate reporting will limit you to correlation only. So in the 270 as an example, what you *thought* was a safe pressure, very well may have been quite hot. Such as a test proved when conducted on one of Ackley's loads in his rifle.

2 - Max load discrepency. This is another old wives tales from folks who don't fully understand what Canister-grade powder is, or what the reloading world is. Canister grade powder is blended to a range of nominal specs. However MOST of the brands that you know of, don't even list what those specs are; and they don't actually build the powder anyhow. So there is a VERY good reason why everyone selling powder cautions you to "Drop loads 10%, when switching lots". Powder isn't a fixed, never changing animal, so A load in grains will never produce exactly identical results; because the powder is different. In the extruded world, powder has it's burning rate controlled by Geometry, and so is loaded by volume to account for said lot variations. Grains don't account for this, which will change case fill volume and further aggrevate burning rate differences. Another reason why they tell you to drop your charges between lots.

Unless you have a Pressure Trace or similar accurate strain system, the only reasonable close way for the average joe to accurately measure pressure, is against the velocity. People CONSTANTLY forget/don't know/ignore this. They use the same charge in grains across different lots of powder, and then write that they have a "fast barrel" because the velocity is higher. There certainly CAN be fast barrels, but 98% of the time it is because they are simply over-pressure. Most good data is fired in a SAAMI minimum spec components, which will be more efficient and produce higher velocities, than a mass produced rifle.
 

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If a gun didn't blow up, and you could get the bolt open without undue force, Ackley published the load. You take your chances with that data... guaranteed that none of it was pressure-tested.
Ackely was known for his high pressure loads, but i doubt that he would publish a load that would injure the shooter.
Jim
 

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I doubt Ackley knew hat pressures his loads generated. There is also the difference in strengths of different actions and individual guns. The fact that his gun didn't blow up of fail prematurely doesn't mean that another gun might. What he was doing is reducing the margin of error for safety and pushing the limits.

There is a limit for potential power at any given pressure level. There are two usual methods of increasing that power level. One is to increase case capacity while maintaining the same pressure levels. The other is to increase pressure while maintaining the same case capacity. I believe we intuitively know which approach is more likely to result in undesired consequences.
 

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The Hog Whisperer (Administrator)
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No. Ackley had no clue what pressures he was running. To be frank.... most of the rest of us don't know, either. Entire load manuals have been written without pressure testing equipment. See Darkker's post. Get a pressure trace, or get very good at correlating your velocities with the load data. Quickload gives some insight, too (it should no be trusted as absolute but it is exceptionally useful).

When I toured the Sierra facility (highly recommended, by the way), our host said they worked up loads with 'usual' pressure signs, then had them tested ... and sometimes they were lower than they thought, and sometimes higher than they thought. Remember, that statement from guys who shoot all day long, have hundreds of test guns, and fire more bullets in a week than some handloaders will do in a lifetime.

If they can't eyeball pressure... the rest of us have no idea.
 
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