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Discussion Starter #1 (Edited)
Hello,
I'm fairly new to wildcatting, having only dabbled with an Ackley Improved round before, but I've had this idea in my head for some years. I am considering a round based on a shortened, blown-out 6.5mm Carcano for use in the Mini-Mauser, available again from Charles Daly. Basically very similar to a lengthened PPC case, slightly fatter, probably keeping the 6.5mm bore diameter. Application will be in a lightweight sporter for coyotes and whitetails. Not looking for a benchrest round. Expecting about 2500-2700 fps with 120-130 grainers from a 20-22" tube. Similar to a .250 Ackley only with a .450" (instead of .473") head diameter. I may just go with the 6.5PPC but there'd be little or no cost savings as it's a pretty custom affair itself. Since I've got a little more magazine space, I might as well use all I got and of course there's the distinction of naming your own round :). I'm kinda looking for feedback on who to contact to start this process and looking for ideas on how to form cases. Would it be possible to use off-the shelf dies to shorten the Carcano cases, cut to length and then fireform, or would I need a set of custom case forming dies? Also, if anybody could comment on the dimensions listed below, I'd appreciate it.
 

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Certainly not as distinctive, but the same wildcat has probably been done on an improved 250Savage case. For a difference of .023" of head diameter and easier brass, I would stick with the '06 head size.

However, I think the point of this excercise is to use a bolt face already set up for the smaller diameter. I would then go with your idea of the Carcano case since the PPC is a fair bit smaller. How is the availability of the Carcano brass? Could affect the lifespan of this project.

Enjoy the wildcat.

Jerry
 

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Discussion Starter #3
PPC Idea...

If I could use the standard rim diameter, I no doubt would squeeze a .250 Ackley (or 6.5x250AI) into this action. Unfortunately, as I understand, the bolt face cannot be opened up enough. The Carcano brass is being made commercially by Hornady (reasonably priced) and Norma (not reasonable at all...).
 

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Here is a crazy idea. Do you have access to a lathe? Why not turn down the rims and extractor grooves to fit? Now you have a crazy wildcat that only you could love. The control feed should still work as it is not that rabatted.

Actually, I would look at the bolt face. The Mauser based actions that I have played with are much easier to convert to a larger bolt face. You don't even need a lathe.

If this rifle is a true mini Mauser, it will have a large extractor and a static ejector at the back of the action. All that is needed is to grind the bevel on the extrator and the sides/top of the bolt face to fit the larger rim. Just use a Dremel tool and appropriate bit. The mag may need some work on the feed rails but the follower should be fine.

If you have access to the rifle, have a look. I bet you can do it. Remember that Mausers have be changed to the H&H magnum bolt face for a century. That is a very large change.

I have a Bruno Fox (mini mauser) in 222. The same action is used for the 7.62X39case which is a big change. It is possible.

Jerry
 

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Discussion Starter #5 (Edited)
[I have a Bruno Fox (mini mauser) in 222. The same action is used for the 7.62X39case which is a big change. It is possible.
Jerry,
You're lucky, I love Brnos! That sounds like the exact size of this action (made by Zastave in Yugo.). It's available in .22 Hornet, .223 and 7.62x39. The bolt face for the7.62x39 is 0.453". I was told this is as fat as it can handle. Oh, I have considered turning down the rim ala .284. Is it that easy?
Dave
 

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The Hog Whisperer (Administrator)
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The rim on a .35 Rem is about 0.460" I think. Now that would be a head-turner, to shoot benchrest with a wildcat based on the .35.

Bet you could squeeze another 0.007" into that boltface.... or rebate the rims very slightly.

As a bonus, when you neck down, you'll have plenty of brass to turn off the neck to fit the chamber exactly.
 

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I, too, have been very interested in more powerful rounds for mini actions.

Good Luck and keep posting your progress,

Fireplug
 

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Shooter, the Bruno and CZ are the same action. Just a name change at the factory. Probably to take advantage of the popularity of the CZ handgun. Who knows? The big difference is the single set trigger (mine is double set triggers) and the stock shape which is more for NA hunters and scope use.

Now knowing what action you have, I would not want to open the bolt face too much. I would stick with the PPC or slightly larger and limit the "strength" of the wildcat.

I am not sure what the yield strength of that bolt is but it is pretty small. The 6.5 in 100 to 120gr bullets at 2500fps would be about max. That would not be much more bolt thrust than the 7.62X39 and 125gr bullets. Overal length should even feed from the mag.


Never rabatted rims but would think with a lathe, you just cut the extractor groove deeper and make the rim smaller. Just keep an eye that the base and web are not thinned.

Jerry
 

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Discussion Starter #9
Jerry,
I've got a couple of the CZ .22LRs and am always on the lookout for the earlier Brno No. 1 and 2s. Fine guns.

These guys safely got 2750fps from the 128gr. 6.5 PPC in the fairly weak (?) AR action. I would expect more than 120gr./2500fps from a cartridge with at least 25% more powder capacity. Admittedly, the mini mauser may be relatively limited in it's pressure capacity, but remember what Col. Ackley taught us about minimum taper and sharp shoulders... I suspect this theoretical round would have LESS bolt thrust than a full-power 7.62x39. I'm planning on getting some brass and fine tuning my case measurements, particularly base and rim diameter.

PS. Am I correct in thinking that I could use the sizing die from another 6.5mm round with the same shoulder angle (and equal or greater shoulder diameter) to shorten a Carcano case? And then couldn't I just cut to length and fireform?
Thanks!
 

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Shooter, you could use a shortened 260Rem sizing die to move the shoulder enough to chamber firmly. Fireforming will take care of the final shaping. Trim to length, maybe neck turn and you are ready to go.

As to the pressure issue, I think you may be wrong about the AR action. While in battery, the bolt is well secured in the receiver. Only gas pressure causes the bolt to rotate and unlock. The action would stay closed if no gas was taken off the barrel. The action is designed for full pressure 223 which is 55,000psi. Who knows what the military stuff is really loaded to.

The 7.62X39 runs at much lower pressures, around 40,000psi. If you calculate pressure over the head size of the cases, you will find that bolt thrust is pretty similar.

If you took the Russian case to 55,000psi, as with your wildcat, your bolt trust will increase dramatically. The changed in surface area from 223 to Russ. is about 50% increase. Just do some number crunching. You may surprise yourself.

The same idea failed quite dramatically when Lee Enfields were rechambered to smaller caliber wildcats. The 303 Brit case was retained but the pressures were elevated. Lead to very short brass life at best and some busted rifles at worst.

Dan Lilja site has some info on shear strengths of bolt lugs. Might give you a general idea of the potential strength of your action. I know that CZ would have proofed those actions for 100,000psi or more in order to ensure consumer safety but with which case head size?

Tread carefully...

Jerry
 

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Discussion Starter #11
mysticplayer said:
If you calculate pressure over the head size of the cases, you will find that bolt thrust is pretty similar.
Good point. I crunched some numbers, based on the SAAMI specs (.223=55k psi, 7.62=45k). This gives a "potential" thrust of 509 ft.lb. for the .223, 596 ft.lb. for the 7.62 and 728 ft.lb. for the wildcat. Unfortunately, Ackley didn't (or couldn't) quantify his bolt thrust/body taper theory. Having read lots about the "significant" reduction in bolt thrust offered by the improved cases, I wonder how much the 22% increase in "potential" bolt thrust would actually equal with an 85% reduction in body taper. Anybody???
PS: Any miscalculations made are purely the result of my public school education...
 

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Shoot,
I don't have a calculation on how much case taper, or lack of it, would lessen the bolt thrust, but if that was what you where relying on for safety, you could be looking for trouble. If you don't get all the oil out of the chamber before shooting, or have a batch of reloads that didn't get the case lube off of them sufficiently, you could be looking for trouble. Just something to think about.
 

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Discussion Starter #13
I've read that the Brits used standard loads that they greased up for pressure testing the Enfields instead of the "blue pills". It can make that much difference. Your advise is universal and not just applicable here. No worries about taking my head off. I fully plan to develop loads carefully and work up slowly (good idea for all, but especially wildcats). The standard pressure signs do apply after all, even with new rounds. Yes this action is smaller in diameter than most bolt actions, but is obviously far from the weakest action in the world. Even weak lever guns firing very tapered, fat-rimmed rounds will flatten a primer before letting loose...
 

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Discussion Starter #14
I've done some research and found out that this action is marketed in Europe as the Zastava LK M85 and is chambered in .22-250 (SAAMI 60k psi). This obviously means the bolt face can handle a standard rim diameter and that the action is strong enough. This changes my plans considerably. I'm thinking hard about barreling one in .250AI, even though I'll be restricted to the shorter bullets due to the 2.37" magazine length. I am currently stuck on the 6.5 diameter, though and may come up with another design. Thanks for all the input!
 

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Shoot,

Since you are using the Zastava .22-250 version, I would look at the IHMSA series of cartridges for the type of performance that you are seeking. These rounds range from the .25 to the .358 IHMSA, and were designed for handgun silhouette. In the one of few mini action rifles that they will fit these rounds have real potential. The IHMSA rounds are based on the .300 Savage case, and have a bit more capacity than the .250 or .22-250 based rounds yet are slightly shorter.

The allowable COL in the mini actions can severely limit bullet choice, and the shortness of the IHMSAs can buy you a larger number of choices.

Fireplug
 

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Discussion Starter #16 (Edited)
Thanks for the input. Looking at the dimensions between the IHMSA and .250AI cases, I can't see where the extra capacity would come from. There's only a 0.05" difference in case length and by pushing the neck back, I would guess they actually reduced capacity. Am I missing something, Fireplug?
 

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You are not missing something. The IMHSA is an improved Savage case. Whether you use the 22/250 , 250, or 300 Savage as the parent case, they all pretty much end up at the same volume (case brand will have the greatest effect). The big difference is the amount of taper you design into the case. The IMHSA still has some body taper, probably to ease extraction out of a handgun like the T/C Contenders. You can easily design an almost no taper case and have a smidge more case capacity.

In the long run, they are essentially the same. One thing I would look for in the design is for max case charge density. When I reviewed my project 6.5, I went with the improved '08 case because it has a higher load density then the 6.5-284 for the vel and powders I wanted to use.

The 284 can easily go faster but that was not a design goal. So I went with the "smaller" case to get 100% load density which should improve accuracy and vel variations.

If the larger case will feed from the mag, build to suit. Afterall, you wanted to name a case so build one just a little different and go for it. As has been mentioned many times, there is very little that has not already been wildcatted. Most designs just change the case dimensions a little here and there.

Jerry

PS where are you getting these cartridge diagrams? How do you get them on the post?
 

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Discussion Starter #18
Jerry,
I get the drawings from reloadbench.com. I use imagestation as my photo host site and use the 'IMG' button when posting to link to them. Charge density is something I haven't considered, but since this will be a hunting round in a featherweight rifle, I don't think it's as critical as it is to a varminter or benchrester, and with these small cases, I suspect airspace will be my last concern. My desire to name a wildcat is far outweighed by the much lower cost of off-the-shelf dies and reamers for the Ackley (or IHMSA) round. I originally thought I was gonna have to reinvent the wheel to get a deer round in this action, but since I found out I don't, I can live without having my own headstamp...
 

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Loading density is seriously over-rated, certainly as far as hunting rifles go (and jacketed bullets, anyway). Now... benchrest and long-range silhouette, I won't go there.

I have fired many a reload with only 75% or so of the case filled with powder, with MOA accuracy. Folks, MOA will get you to 250-300 yards on prairie dogs, let alone deer. Bullet selection, seating depth, and getting the bullets in the case necks straight (in that order of importance) have gotten me to MOA or better in every rifle I've reloaded for, save the .458 Win Mag.

Frankly, when the very first load in the .458 went into 1.5" inches at 100 yards, I decided right then and there that I was DONE with load development! By the way that was a 100% density load, a compressed charge of Varget, which was chosen because it was the ONLY powder that I had which data was listed for! So as you can see I'm not much for trying different powders.

Keep in mind that there are well over 100 different powders available.... if you can't get 100% load density with several, then you have a truely oddball cartridge, or something that started out as black powder.

Good luck with your project, hope to hear that it comes out well.
 

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Shoot,

No, you are not missing much, but I did miss something by comparing the IHMSAs to the standard round rather than the improved. I doubt that any improved design has any worthwhile case capacity advantage over any other improved.

Even the very small length difference can make a difference in bullet suitability in the mini actions with these various larger rounds. COL is very critical in these minis, and thus bullet selection is so limited that anything helps.

Fireplug
 
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