Cartridge Design

Roger T

Roger T

Member
Useing a modern single shot BR action is it mandatory to have case taper from base to shoulder ?,if so what is min.taper? (2) At what capacity should you go from a small primer pocket to a large primer (in making a new case) (3) would a large primer pocket bennefit from a PPC flash hole dia.? (4) is there an optimum expansion ratio? (5)body/shoulder/neck juncture , conventional (what angle), Weatherby,or single radius? (6)neck length, what percent of caliber?(7) rim dia. conventional/rebated/rimmed /semi rimmed ?(8) would this case work equal in 100-200br and 1000yd br ?
 
Roger T said:
Useing a modern single shot BR action is it mandatory to have case taper from base to shoulder ?,if so what is min.taper? (2) At what capacity should you go from a small primer pocket to a large primer (in making a new case) (3) would a large primer pocket bennefit from a PPC flash hole dia.? (4) is there an optimum expansion ratio? (5)body/shoulder/neck juncture , conventional (what angle), Weatherby,or single radius? (6)neck length, what percent of caliber?(7) rim dia. conventional/rebated/rimmed /semi rimmed ?(8) would this case work equal in 100-200br and 1000yd br ?
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A case needs a little taper in order for it to chamber and extract easily... Usually about 10 thou will work.

Nothing at present beats the 6mm PPC for short range, the 6mm BR and variants of it using the small primer work very well at longer ranges.

I don't think anything is better than the rimless case. The Weatherby radius shoulder is of no advantage... nothing simpler than a 30 degree shoulder for feeding and ease of head spacing.

Just my thoughts...
 
Along with what Dennis said I can't even imagine how much fun it would be to size a straight sided rifle case. Getting the case in and out of a die would be about as much fun as most people could stand. I'd imagine that a straight sided case would be great fun to chamber and extract too.

Unless a person is going to have custom cases made with a minimum order probably on the order of 100k cases, the best way to design a wildcat is to start with an already manufactured case. Unless of course the person happens to work for a manufacturer and has been given free rein to do whatever he thinks would be fun. Most of the "new" factory rounds are based on an already existing case so a new and wonderful design would probably be viewed with some displeasure by the bean counters. :eek:

Ken Howell's book Designing and Forming Custom Cartridges is about the best reference I know of, and it's back in print.
 
Hard task

In the past when I was using my own reamers, the minimum body taper that still worked was 0.127mm (0.005") that's both sides combined and case body was 60mm (2.236") long.

I never had an extraction problem (ZKK 602) even I was loading it to the point that the primer pockets would be gone after 2nd. reload. However, I gave up on this "minimum" taper idea as it was giving me an overall grief.

I've quickly found that the "usual" proven factory taper is there for a reason. Personally I believe that a longer neck will give a longer throat life, but many have proved, that's not the case.

Personally I believe that the shoulder angle/radius is only valid where feeding/case stretching is concern. If the PPC is not the most possible accurate design ever, it can't be too far from it. Would a difference of plus/minus 2 degrees in the shoulder angle make any difference?

There is virtually nothing in a case design that hadn't been done many times before by many. I don't care what anybody say, but the PPC was more a lucky design, rather than scientific. Like many other designs the PPC is based on an existing case and if that existing case had a different head size Pindell would used it and the outcome would be in question.

There are still many of those who believe their own design is THE design of all, but the reality proves otherwise.

I prefer to sit back and let someone else who is smarter, has more time and money to do the hard yards. If it's any good I'll buy it.

Shoot better
Peter
 
Cases

At one time or another, all of us have dreamed of, and even "developed" our own "Wildcat". I think that there is something in the genetic code that compels us to want to be different.
But as Peter said, what we usually end up with is something that has already been done, or is the ballistic twin to something else.
The two single biggest innovations in the past 30 years, (as far as extreme accuracy is concerned), has been the PPC case, and the BR case. They actually do something that other cases will not. That being, they dominate a particular shooting Discipline.
The Ultra Mags, the WSM's, and WSSM's, and the other 'innovations" are just re-arranging the powder column. In most cases, the bullet could care less.
Here is a good example. The 25 WSSM is, more or less, the ballistic twin to a 257 Roberts. The 257 Roberts is nothing but a necked down 7mm Mauser, which was developed at the end of the 19th century. Once you get past all of the hype, and glossy adds about all of that over rated "short fat" stuff, it ends up that we haven't really come that far.
But that does not mean that we are not constantly looking for a better moustrap. Many of us do things within the basic concept, like matching a specific throat length to a particular bullet design, or doing something really radical, like going to a .269 neck,:D or matching a specific bullet-barrel-powder combo together to optimise a given combination.
Sure, it is still a "PPC", but in this game, it is sometimes the little things that reap the big gains.........jackie
.........jackie
 
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Even the PPC and BR can trace their case shape and design roots to wildcats all the way back to the 1930s. What makes todays' benchrest versions different is quality brass, bullets and barrels.

Ray
 
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Ray

I always say that if you took the 220 Russian Lapua case from us, most of us would have to start back at "square one" in the way we approach Competitive Benchrest.......jackie
 
(8) would this case work equal in 100-200br and 1000yd br ?
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I would say no. I shoot both. Until a long-range bullet will agg as well as a short range bullet at 100 yards, or until a "100 yard" bullet will compete at 1K, you need different bullets. And that means different case capacities.

I'd go with Ray & Jackie & all the others. A wildcat means dies & reamer(s), and that's about a $350 to $450 proposition.

Oh. My latest wildcat was a 6mm on a small 6.5 case -- the 6.5x54 M-S. The 6.5x54 is just a touch larger than the "new" 6.5x47 -- the latter has a .308 body, the 6.5x54 a PPC-size body, so the extra 7mm of length isn't as much as you might think. The other difference is large primers on the M-S case, but then some drill out the flash holes on the 6.5x47.

How does my 2-inch PPC shoot 105-grain 6mm bullets? Probably about as well as a 6/6.5x47. My only excuse is I made it just before the 6.5x47 case was offered.

If you get the case capacity right for the current good powders, & nothing else is really out of wack, I don't think much else matters. This is my conclusion after spending a lot of money on various wildcats. But come on it, we're told the economy needs some stimulation!
 
good responces thanks

I don't know if I would actually design a (New) ;) case ,but was curious as to why ,if a specific property of a competitive case works so well that the manufactures don't employ that in all comperable designs. Example the small primer/PPC flash hole in all cases with say up to 50 gr.water capacity or say a neck length of 125% of caliber etc. BTW I do have quite a number of wildcat/improved cartridges from 17k Hornet to 375-284 but the 6mm.and 6.5 have my highest indulgenses by far
 
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Ppc

Charles E said:
I would say no. I shoot both. Until a long-range bullet will agg as well as a short range bullet at 100 yards, or until a "100 yard" bullet will compete at 1K, you need different bullets. And that means different case capacities.

If you get the case capacity right for the current good powders, & nothing else is really out of wack, I don't think much else matters. This is my conclusion after spending a lot of money on various wildcats. But come on it, we're told the economy needs some stimulation!
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Donovan

1) No
2) No

When I was a young imbecile I've spent thousands of $ on various experiments and I've never seemed to improve on anything. If I've gained something in one area I've lost more in other area. After I've spent about $40-50K on what I've thought "were good ideas" I've finally reliazed, that there is no point of "chasing the impossible".

I would tend to agree with Charles that the correct case capacity/powder/bullet will do 99% of the trick.

Those shoulder AI-40*angle/radius theories are only good for a case life, if they had any other value the PPC consistency/accuracy could/would have to be improved on by a change of a shoulder angle.

Maybe Donovan can take on this and show/prove his own parrot advokated believe, that the AI 40* shoulder is better for inner case turbulance/consistency/accuracy than 30* shoulder is. We may have a 6mm PPC AI. I've no doubt, that this also have been done many times by many.

So that's why we still have the PPC with a 30* angle.

Shoot better
Peter
 
Roger

Roger T said:
But what about expansion ratio and neck length ? Is the 2.1-1 ratio as in the SMc cases optimum ?
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Everything is good in the theory. Personally because I like magazine heavy recoiling calibers I like longer necks, but for a single shot sport many believe, that there is no difference and proved that short neck means nothing.

Many claim that longer neck 300Wea. and 6mm Rem. will have longer accurate barrel life than a 300WM and .243W. Many claim that there is no difference and it depends on individual barrels how long they'll last.

My personal advise would be to stick with what's already known and it's here. For an accuracy if the PPC or the BR won't satisfy your needs I don't know what will. For a long range accuracy there are many cartridges to choose from.

Forget about improving the ratios/necks/capacities/optimums and if you have to spend the money hone your shooting/reloading skills with anything that has been proven many times by many.

Shoot better
Peter
 
Roger T said:
But what about expansion ratio and neck length ? Is the 2.1-1 ratio as in the SMc cases optimum ?
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McPherson's source of income is writing about shooting, not shooting itself. I guess with this new patent, he may try the WSM route to making money -- patent something someone else has already done, then sit back & wait for some large corporation try it, threaten them, & hope they pay you off.

For optimum cases, look at performance. If that is hunting, look at what the best hunters use. If highpower, what the top highpower shooters use. If benchrest, read the benchrest match reports.

I don't read too many match reports these days, & when I do, it is usually for "who" not the equipment list, but I will say I've not seen any SMc case listings in the winners column.

Where to look:

There is a big 1,000 yard match coming up, the World Open in Pennsylvania. See who & what does well. We just had the IBS 600-yard nationals, and the NBRSA 600 nats weren't too long ago. Look at the results. There are plenty of big point-blank matches, but you can just about guess the "standard" 6 PPC has won them.

Now for something interesting, Randy Robinett just wrote me about his second-place finish in a Point-Blank group match at 200 yards, where he was shooting a 121-grain FB bullet with a B.C in the .5 region . . . If we can get bullets like that to agg at short range, that will rewrite the record books.
 
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