Ack Improved Cartridges

[Bret4207]

Root, I wouldn't mess with that 99 either! I missed a 22HP a few years back and still kick myself. But if you have an action and a barrel and a stock set all from different original sources, the 25/35 AI make a lot of sense. The one thing I don't know about in a 99 is the spool mag. What a 25/35 AI will do in a standard 25/35 spool I don't know. It's a dream for me. I'd be better off finding a trashed Marlin 336 and building it off that.

Rifle or Handloader, makes no diff to me. It all depends on who writes the story and when. Dave Scoville wrote some real good stuff back in the day. Now, I wouldn't believe a word he says. I can say that if I had hankerin's for a 300 mag type, it would be the H+H. It's just classic.

Bill, the 280 is about perfect just as it is. I would pass up a 7Mag any day in favor of a 280, but I am not afflicted with magmunistis. I have a 280 reamer and an FN Mauser action. Someday I may mate the 2, unless I really decide I want that 375 Whelen...

 

[fiver]

here's how I figured it.
1. 2 rifles in standard 7x57 [using heavier +P brass]
2 rifle in standard 40* ackley
3 rifle in ICL configuration
4 a chronograph and the same lot of powder,primer and bullets.
1.1 grains of powder in a sharp shouldered case that is bigger should not give you 100 fps in velocity increase.
one anomaly was the 1 standard rifle was faster than the other by about 40 fps but still 100 fps slower than the Ackley case even with the heavier +P cases versus standard cases blown out.

this was one of the things I discussed with Felix in a long PM string and he agreed that the sharp shoulders will make a powder burn faster.
it also explains why we use H-322 in the big straight wall [think 45-70] type rifle cases, and why we couldn't get real velocity from many of the 'wild cats' back in the day before stuff like 4831 was available.

 

[Intheshop]

"Cosine error" comes in many forms gentleman. The sharper the shoulder,and less body taper,the easier it is to....

 

[Rootmanslim]

Keep clinging to the idea that case shape means diddly. Roy used it for decades to make $.

 

[Ian]

It can mean diddly....or a lot. Even the .308 Win is a lot closer to the .30-06 than it should be with bullets up to about 170 grains. Again an instance of relatively modern powders and something about the case shape.

I'm surprised nobody has brought up how neck length, powder choice, and shoulder angle affect throat wear. Oops.

 

[fiver]

ain't got there yet...LOL.
can't draw pictures to illustrate the point either.

 

[Rootmanslim]

When anyone can produce a detailed study that will stand up to analysis, that proves the angle of the shoulder has anything to do with velocity, I'll be listening.

OR can disprove that X amount of powder in cases of equal capacity produces the same velocity regardless of the shoulder angle, I'll be listening.

Hint: powder does NOT burn in the case.

 

[Intheshop]

Fiver.... grab a crayon and start drawing. Then take a pic of it,or let the Gbaby do it.

I'm saying it's easier to form the case to a predetermined measure with less body taper and a sharper shoulder..... vs,chunking a case up in a FL sizing die and hoping it all goes well.....

But,if you don't see it that way..... fine by me,carry on.

 

[Rootmanslim]

Guess "speaking in tongues" is the new normal.

 

[Bret4207]

I think you'd have to start with the same rifle and test before and after using same powder lot, primer lot, etc. Testing different rifles doen't tell you all that much. I'm sure case shape plays a large part in how a particular powder burns, but just changing a shoulder angle without gains/reduction in case volume is about the only way to tell if it's going to having a meaningful effect with each powder, and you'd need to do more than one rifle. Blowing out a shoulder and gaining, say, 10% volume and adding more powder isn't proof of anything except more powder gets more velocity.

 

[Rootmanslim]

That's what RIFLE did to test the 300 WSM and the 300 H&H. Even used the same barrel. Seems to be the last word on the case shape debate.

 

[waco]

I passed up an older Ruger tang safety M77 in 257 Bob AI long ago. Slick rifle with a 3x9 Redfield. This was 20 years ago. I still think about that rifle....

 

[Jeff H]

I passed up an older Ruger tang safety M77 in 257 Bob AI long ago. Slick rifle with a 3x9 Redfield. This was 20 years ago. I still think about that rifle....

"Tang-Safeties" had the plunger ejector. In mine, that spoiled the rifle because it jammed the fired improved 7x57 case into the right lug race at the receiver ring as it was extracted and tied the gun up. It took a long, long time, lots of patience and gluing small patches of crocus cloth to the pad of my pinky, and some and some painful contorting of the same to cure that to the degree that it wasn't a show-stopper every time I shot. I dislike plunger ejectors to begin with and that one just rubbed it in my face.

Not saying that would be the case with every single specimen, but maybe it could make you feel better about missing out on one.

Mine started as a Tang-Safety Ruger Ultra-Light 257 which "wouldn't shoot." My dad had made that determination and sent the action to Colorado to have it rebarreled with a tapered, 24" octagon Douglas premium 7x57 Improved barrel by John Pell. It wasn't ultra light after that but still light and those stocks fit me. The slight shift of weight forward made it a sweet-handling rifle. I've never owned or shot the newer MKIIs or Hawkeyes and don't know how they compare. The M77s were pretty, sleek and handled well. Very nice rifles.

 

[Bret4207]

Jeff, my 250 is a Ruger Ultra Light in a glass stock. Only glass stocked rifle I own. It has done 1/4" groups and will reliably stay under an inch with 90gr Partitions. or would back when I could see.

 

[Bret4207]

That's what RIFLE did to test the 300 WSM and the 300 H&H. Even used the same barrel. Seems to be the last word on the case shape debate.

Yes, you would ahve to use the same barrel or the test would be meaningless. Sounds convincing to me. If they'd done it with 5 rifles, it would be even more proof.

 

[Jeff H]

Jeff, my 250 is a Ruger Ultra Light in a glass stock. Only glass stocked rifle I own. It has done 1/4" groups and will reliably stay under an inch with 90gr Partitions. or would back when I could see.

Here, I'm trying to make Waco feel better about a twenty year old decision and someone mentions a 250 Ultra-Light. I had a chance to trade a used Ultra-Light in 308 straight up for a brand new 250 Savage Ultra-Light. No one knew what it was and didn't want a "puny" caliber so it had sat on the rack for a couple years. Told the guy I'd think about it over the weekend even though I pretty much had my mind made up. Well, you can probably guess that someone spotted it over the weekend and recognized it for the gem it was and it was gone Monday after work. They guy at the shop was almost as disappointed as I was because we were two of the few in the area who appreciated really light, compact rifles and "puny" calibers.

I have one in 308 in my safe right now which was my mom's. Like new. My dad had me come get it the day she passed and I told him I'd hang onto it until he had time to think it through more carefully.

 

[fiver]

you know the 250 Savage Ackley improved doesn't have the feeding or ejection issues mentioned in the Tang safety rifle above.
mine don't anyway.

 

[Jeff H]

you know the 250 Savage Ackley improved doesn't have the feeding or ejection issues mentioned in the Tang safety rifle above.
mine don't anyway.

That's good to know. It's possible that the 7x57 Improved has slightly different body taper - or at least the version I had. I think it was .010" taper from base to shoulder. It also could have just been how tolerances stacked up in my particular rifle. I don't mean to scare anyone away from a rifle they like, so thanks for mentioning that.

Mine fed just fine too and with no alteration of the feed rails. My dad's 257 Improved (Mauser 98) and a weird wildcat he devised by necking down the 8x57 to .308" and blowing it out like the Ackley cases both fed fine with no fussing as well.

Didn't get that lucky converting a Chilean 95 to 6.5x55. I did not figure it out - my dad (again) spent about ten minutes on it with a couple slender stones and it fed flawlessly. And (again) instead of divulging the magic trick, he just grinned when I asked "how?".

 

[fiver]

occasionally you get one like that.
I have that 257R with the radiused shoulders that was giving me all kinds of grief for a while.
I finally tracked it back to the extractor slightly binding against the barrel when it had a case under it.
I kept thinking I had high pressure because of the bolt lift until I tried an 86gr bullet on top of some 4895 going like 2400 fps.
hmm? yep,,, some magic marker and some file work later and smooth as butter.

 

[GEMIHUR]

Rootman,
If you have the time to read this 1996 article from Gun Digest https://gundigest.com/wp-content/uploads/GunDigestPOAckley.pdf
you will gain a bit of insight on how the 'improvement' of an AI design affects a cartridge's properties upon detonation of charge and propulsion of projectile.
I agree that powder does not burn in the case but the design of the case dictates it's volume of containment and how it behaves as it stretches and springs back upon ignition.
Note the chart that compares equal loads to improved and standard chambers.
Not only is the angle of the shoulder changed to increase case volume but the case walls are affected for a more parallel design.
In essence, creating more grip to the chamber walls thus alleviating pressure especially backthrust toward breech.
Thanks,
Jimmy