450 Ackley build using a Zastava

[Quaticman]

Can I use a Zastava Commercial M70 rifle currently chambered in .458 Winchester magnum for this build? Is it as simple as using a .450 Ackley reamer to re-chamber or am I missing something? What about the feed ramps, magazine lips, etc? That’s assuming that this action can accommodate the extra length of the .450 Ackley cartridge.
For those of you with more experience I’d love to hear your feedback.

 

[CTDolan]

It's been used for the 375 H&H, so yes, you can (if you know what you're doing...lots more than reaming and feeding involved). Go with the 458 Lott, though. It is every bit as good and a whole lot more common.

 

[John P.]

You will have to open up the magazine well for the 450 Ackley. To the front as most do (Horrors!!!)

I have a Mark X in 458 Win, a factory built rifle. I am leaving it as is.

I will also be building a 450 Ackley in the near future. I have the barrel, the chamber reamers, dies, brass, and a BBK Action. The BBK is a big action and will hold 5 down. A bit rough as shown in the photo below, but the long winter hours will take care of the metal finish.

 

[CTDolan]

You will have to open up the magazine well for the 450 Ackley. To the front as most do (Horrors!!!)

I have a Mark X in 458 Win, a factory built rifle. I am leaving it as is.

I will also be building a 450 Ackley in the near future. I have the barrel, the chamber reamers, dies, brass, and a BBK Action. The BBK is a big action and will hold 5 down. A bit rough as shown in the photo below, but the long winter hours will take care of the metal finish.

The action will clean up nice, no doubt. I am curious, though, why not go with the 458 Lott? It's far more common, can shoot 458 Win Mag in a pinch (which you already have, so ammo will have two rifles in which it can be used), and is a ballistic twin to the Ackley.

 

[John P.]

I have two 458 Lott rifles already! I like the nostalgia of the Ackley. I met Parker Ackley years ago and I have always had a respect for his accomplishments.

 

[fourfive8]

I think any of the more or less 375HH-based cartridges can be housed in a standard length Mauser, and not sure there is much difference in any of them- 458 Lott, 450 Watts, 450 Ackley (or even the 458 Express in some actions). I know a 458 Win Mag can be fired in a 458 Lott. And a Win Mag and Lott can be fired in a Watts. And a Win Mag, Lott and Watts can be fired in an Express. But, the expanded shoulder of the Ackley prevents similar flexibility with other slightly shorter cartridges. Another seldom reported downside to the longer case length in regular length actions is the availability of bullets with the crimp groove in the proper place. Seems bullet manufactures have designed many of their 458 bullets with the location of the crimp grooves for the shorter OAL of the 458 Mag- grrr That seems especially true for some of the 500 grain bullets where the groove is placed well to the rear because of the limited Win Mag case capacity. Just too much bullet nose length added to the standard case length of 2.8- 2.9 of the longer cartridges to fit properly into standard length actions. Some of the 480 gr (Nitro) 458 bullets however do have the crimp groove far enough forward allowing for an OAL that can fit into a standard action.

Another issue is the published ballistics re: the "Ackley" cartridges. Ackely was known to publish load data for his cartridges right on the upper ragged edge of dangerously high pressure. I do not use published Ackley data and would never recommend it- especially for dangerous game hunting loads. The data I see for the 450 Ackley Mag is no exception so I would approach it with caution. Plus- what's the point when trying to load for 100% reliable operations in potentially high temperature field conditions anyway??

 

[John P.]

The 450 Ackley, as I said, is a nostalgia cartridge for me. One advantage of the big BBK action is the magazine is long enough to put that crimp groove where it belongs, at the case mouth. Hmm. A free case capacity increase.

I know all about PO Ackley and his claims. Chronographs were rare in his early years. I do appreciate his quest for "bigger is better" though and admire his gun smithing skills. I am 71 years old and have read about everything Ackley wrote and the writings about him by others both pro and con.

Maybe I will write history as I have the Oehler M43 strain gauge system: I plan on pressure testing some of the loads. Will be interesting. Both velocity and chamber pressure at the same time. The M43 is accurate if a guy does his attention to detail in placing the strain gauge in the correct location and knows the chamber wall thickness at the strain gauge attachment point.

I also have a 450 Watts.

Building rifles to me is the retirement thing: Keeps me active and exercises my brain. I do not sit in front of a boob tube while the attendants keep a bowl on the TV dinner stand full of "Geyser Chow".

African Hunter had an interesting article years ago comparing the 450 Ackley, 458 Lott, and a couple other 458's. I printed it off and have it in my files. Do a search, it is well worth the read.

 

[John P.]

Strain gauge and my 100 pound "sled". Note the chrono screens out past the muzzle. The barrel is purposely small diameter at the chamber to give a good "flex" at firing for the strain gauge to read. 50 Caliber. Yes, the sled does move back a bit at firing. Note the wood strips to allow returning the sled to "battery". There is a big gravel pile in the brush that the bullets go into, nope, I am not spraying lead into the trees. Nearest civilization is 45 miles away.

Question: If a big bore rifle is fired way out in the deep woods, with no one within hearing distance, is a noise produced?

 

[Tam Dl]

If nobody is within hearing range I think the more pertinent question is what is the bear doing with your rifle?

 

[Shootist43]

John P it is obvious that you enjoy taking rifle building, testing and comparison to a whole new level.

 

[AZDAVE]

It is nice to see the level of testing you are doing. I would rather read one article that is written by someone that does REAL testing and provides a analysed details of the testing methods and data gathered and conclusions. Than a million of the other kinds of articles. I am envious of your testing equipment and location for testing.
Keep up the great work.

 

[Mick Moriarty]

Like Ackley? Build a 17Ackley Hornet, they are a ton of fun and cheap, sleeve the 458WM (sleeve it alone, haha).

 

[John P.]

If nobody is within hearing range I think the more pertinent question is what is the bear doing with your rifle?

'Ol Bruin likely will be chewing on the oil soaked stock.

 

[Doc25]

I think the 458 is on a standard length action. The 375's have been enlarged by the manufacturer. If you don't want to do action work then the 375 with a new barrel may be a good start.

 

[Nkawu]

Is it safe to assume that a zastava 375 could be converted into a 458 Lott with a new barrel?

 

[Doc25]

I am not a gunsmith so can not guarantee it. From what I understand is the lott is just a blown out 375 h&h. The increase in case mouth diameter causes it to be slightly shorter ( case length ) maybe not COL.
I don't own a 458 zastava maybe there is enough room already for the lott. I do know they sell magnum actions here, they list most of the magnum cartridges but not the 375 leading me to believe that the only opened up action is the 375 one. I do not see them for sale separately though.

I'm not sure but you may be able to have the zastava barrel rebored and rechambered to the lott. If not then the barrel could just be replaced. These are questions to ask someone more competent than myself.

 

[kayaker]

Terry Weiland has written about his .450 Ackley on an FN98, same action dimensions as the Zastava but I am not sure what he did for a magazine.

 

[Dale Wade]

I realize this thread is a bit dated but I will offer some information. There is a good article by Joseph R Donnelly in the book "Big Bore Rifles and Cartridges" by Wolf Publishing. He describes in some detail the modifications he made to a type "C" Mark X action. This is the standard length, magnum bolt face action. He modified his action to feed the 338-378 Weatherby cartridge. In addition a very good article was written Paul Marquart in Rifle Magazine #30 on correcting feeding problems with magazine fed bolt action rifles due to caliber changes.

I have the feed rail and magazine box measurements of the Mark X rifles in .243, .25-06, .270, 30/06, 375 H&H, and .458 calibers. If you are interested I can post the dimensions here for the 375 and 458 so you can see how they differ.

Dale

 

[CTDolan]

Please do (post the dimensions)!

Thank you!

 

[Dale Wade]

Since almost any surface of the M98 action can be modified to accommodate a cartridge it is important to select a immovable (within reason) datum point. An easy to access point is the front screw boss. I selected the rear surface and first measured the distance to the bolt face from there.

Interarms (Zastava) 375 H&H Measurements

Rear of front screw boss to bolt face at rear most travel position: 4.53" Inches
Rear of front screw boss to front of magazine opening: 0.700"
Rear of front screw boss to rear of magazine opening: 4.63"
The following measurements are the distance between feed lips taken at the specified distance from the rear of the front screw boss
Width 0.574" at 1.00"
Width 0.590" at 1.50"
Width 0.610"at 2.00"
Width 0.615" at 2.50"
Width 0.615" at 3.00"
Width 0.615" at 3.50"
Width 0.615" at 4.00"
Width 0.615" at 4.50"

The magazine box is 3.675"internal length
The internal width is 0.916" at the rear
The internal width 3.50: from the rear is 0.708" and then enters into a radius for the front corners

The recess milled into the bottom of the action is opened accept the larger magazine box.

It appears that Zastava gains all the necessary clearance for the longer cartridge entirely from the front of the action.