Home Forums Hunting & Shooting Ask The Gunwriters Cartridge Efficiency: Why case shape matters

as to

Anybody remember who the "experts" were who were shooting for the 5000Fps mark. Last I heard from several years ago, they had given up due to impractical barrel length, and unforeseen problems with projectiles and other components.
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I can't see a copper lead projectile holding up to that kind of speed. The lead would most likely melt.

AS to Newton; He never did figure out the variables of the speed of sound. In the vacuum of space, he is spot on. We don't live in space. Sound is not C.

Get a .22mag rimfire with a 22in tube. Then watch the group size change with the weather. It's the most fun barometer I have ever had.

The .17M2 is made to stay just under the M2 speed. If you have a 24in tube and your using the faster rounds you will most likely have some group size issues. If you have a 20in tube use the faster stuff. Check this out for yourselfs. Stay away from the .22mag rimfire unless your willing to to do this test.

|Muddog,

You are correct on the jacket/lead projectile. That was the first issue "problem" they ran into with the 4000 plus-FPS. I do remember they tried different projectile material.

Toward the end of their testing, they were using a saboted/titanium projectile and getting a little over 5000fps. Then they started having barrel erosion issues.

At that point, they kind of ended the article by saying back to the drawing board, and if they came up with anything practical they would try some testing. I wasn't too long after I read about this that out military came out with their "tank-killer" saboted projectile (about two years).

By the way, not criticizing the Mach2 cartridge, I think it is a nice cartridge. I just have the opnion the 17HMR is the more likely one to last.

Will try the "barometer" test on the .22 mags sometime this Summer. My most consistent/accurate .22 mag is a 20" barrel.

Whether the powder has already burned or not is irrelevant. It, or the gases, still have the same mass.

2525,

We had to go all the way to Australia to find it but we have found it... the truth. Thanks

Fans of overbore catridges such as myself can rest secure in the knowledge that the laws of physics continue to hold despite a mountain of bull**** to the contrary. <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />

John
Being a shooter and a gunbuilder, I have some experience to add your comments.

The 300 WSM is to the 300 Winchester what the 6PPC is to the old 6x47.

The 6x47 was a cantankerous round that sometimes shot and sometimes did not shoot--one had to work with them diligently to make them shoot well.---Take the same rifle and same barrel and make it into a 6PPC and it shot. The case capacity of the two rounds is very similar and the end velocity is similar. These results took the variables of action, stock, barrel etc out of the tests.

I have had great success with the 7 WSM and 300 WSM-they shoot and shoot well. I have no problems with them feeding through my actions or actions or actions I have modified.

Jim Borden

Jim--

I've had the same experience with the short-fat mags. They don't produce any more muzzle velocity than longer rounds of the same capacity--but the velocities they do produce are far more consistent.

Aside from the WSM's, I've also had extremely good luck with the 7mm SAUM. In fact I have gotten the best short-fat accuracy out of factory ammo with that round, which may or may not have anything to so with the factory Rem. 700 I was shooting it in.

Have also seen some phenomenal accuracy out of the WSSM's, but apparently very few people want to buy the rifles!

I have seen some problems with all the short-fats feeding in factory actions, but not many since the early days. They do seem to feed better in push-feed actions--but I have also seen a few push-feed actions with the feed rails just a little too far apart, so that the rounds popped out early.

Good to see you posting here!

John

Where in Manhattan are you? I am in the village. How did you get Elmer's rifle? Keith is a hero of mine. The 285 OKH was a cartridge that had a tube brazed over the flash hole so the powder was ignited from the shoulder back towards the rim as opposed to the other way as is normal. Supposed to make ipowder ignition more uniform resulting in faster and more accurate loads. The militaery was considering it vfor artillery ammo if I remember my reading right.

The Wal-Mart near me had several Winchester 70s in 223/243 WSSM that nobody wanted until word came out about USRA shutting down the New Haven, CT, plant. Now all the Winchesters have been sold or are on lay-away. I've been really happy with my 25 WSSMs, really, really, really, happy!

Jeff

I have not met Mic, but his collaborator on these cases is Vi Smalley, who is a acquiantence of mine and shoots at the range here in town. Two things you should know, if you are discounting these cases as marketing hype that ignores the laws of physics.
First, Vi is a rocket scientist. Truly--he retired from Thiokol were they make the shuttle boosters. I am willing to assume he knows a little more about combustion and gas flow than most of the rest of us. And no, he didn't do the O-rings.
Second, I have read their patent application. The case shape uses the mathmatical concept of the parabola, which has the property of reflecting anything back to a central point. It is the same physics that makes collecting antennae of all types work.

And I am familiar with the same research as Jim where barrels were chambered first in 6x47 and then shot better once rechambered for 6PPC. Like Jim, it and the combined experience of thousands of BR barrels shot by the most painstaking shooters in the country convinces me that case shape does matter.

So I am not willing to say that these cases are some hokum that cannot be explained based on my freshman physics course 25 years ago. To me, their design takes the short fat case, adds the new wrinkle of the parabolic shoulder, and that combination intrigues me.

John

Thanks for the reply. Gary Amatrudo and I redesigned the Remington style feedrails and feedramps for my Rimrock, Alpine and Timberline actions. I have performed those modifications successfully to Rem 700 actions to keep the rounds "under control" while they are being pushed forward.

In my opinion--these rounds are here to stay--i still remember when Doc and Ferris came out with PPC--the word around the BR circuit was that it was a folly and that the cartridge would not last.

Jim

Just an observation from the peanut gallery, but it is amusing to watch a discussion about an innovation in a group of people so traditional and conservative, they are probably trying to find someone to put their 8-track player in their truck...... <img src="/ubbthreads/images/graemlins/wink.gif" alt="" /> Dutch.

Utah708--

I believe his name is By Smalley. At least that is the way he signs the correspondence he's had with me. I am familiar with the concept of the parabolic shoulder, because I shot quite a few rounds out of one of the rifles chambered for By's round during the past few months.

So far, I am reserving judgement on whether the parabolic shoulder somehow allows more velocity from the same amount of powder space. Savage and Norma are evidently cooperating on the project, so we'll have pressure-tested data pretty soon. However, the results that By and Mic provided showed the case gained just about exactly the amount it should have over the .204 Ruger, given their different case capacities. (I measured the water capacity of both cases.)

All this, however, has nothing to do with the 6x47 and 6mm PPC. Shooting accurately and somehow gaining extra velocity from the came amount of powder space are two different things.

I have seen the finer accuracy from a number of short rounds, from the mundane .308 to all the PPC's, WSM's, WSSM's, SAUMs, etc. I have yet to see any increase in muzzle velocity due to case shape, but am perfectly willing (even eager) to learn about it if it has somehow been achieved.

MD

Jim--

I am certain the .300 WSM and .270 WSM are here to stay. I have hopes for the 7mm SAUM, but the WSSM's are apparently not selling very well at all--apparently partly because of some gossip about how the .223 WSSM ate barrels.

Another part of the problem may be that the average shooter can't find the accuracy advantages of the WSSM's in the typical factory rifle.

MD

savage 99, when the weather warms up a little I may take you up on that chronographing offer. Very kind of you.

Regarding the 223 WSSM Hornady did not do it any favors in its sixth edition citing significant throat erosion in 350 rounds and also stating it is hard on barrels with the word hard in bold italics. Of course they don't mention how fast they were throwing rounds through the barrel either and some of their data is pretty hot. I think this is some of the " misinformation" alluded to on Winchester's and Browning's site.

They also did not say how it would compare to a .22-250 or .220 Swift after 350 rounds.

I have been able to see "signs of throat erosion" in a .223 Remington barrel after 100 rounds, using a bore-scope.

MD