Wednesday, August 18, 2010

Stressed out.

A known issue with the little Smith & Walther P-22s is that, given enough time and enough zippy ammunition, their slides can suffer from stress cracks that will occasionally cause the entire front half of the slide to separate and give the shooter a mouthful of zamak (which is the trade name for zinc alloy most commonly seen in Matchbox cars.)

Another gun that uses a slide made of zamak is the Hi Point. This seems to be (and it's painful for me to say this,) adequate in the bricklike 9mm, but the .40 cal variant makes me nervous. I'm sure that the engineers put plenty of mass in the slide, but all it would take is a bum casting to cause this, and bum castings are something I don't want to think about in a gun firing a round that generates 35,000 PSI and can spike to magnum rifle pressures if it experiences some setback with a 180gr bullet.

Needless to say, the thread Caleb linked to at the Hi Point fan forum is full of fanboys claiming that the gun must have been deliberately sabotaged...

35 comments:

genedunn said...

Interesting... do you know if the new PPS uses the same construction?

Tam said...

No, the PPS uses a steel slide.

New Jovian Thunderbolt said...

Yes sabotaged. With zinc alloy at the factory.

The Jack said...

Yeah, you want some real chills look at the material properties of Zamak3

http://en.wikipedia.org/wiki/Zamak

Might as well use aluminum.

reflectoscope said...

We'd have an interesting conversation in person about this.

Jim

Anonymous said...

We might not like crap guns, but they do serve a valuable function in the marketplace as starter guns.

How many P22 crap guns do we see at Eagle Creeks? Plenty and all purchased by Cledi or Seths or Mr. McPhersons down the street who "have this gun."

The P22 and Hi Point, the starting point of the cycle of deviance.

Shootin' Buddy

Tam said...

Reflectoscope,

Huhwhat?

Noah D said...

Does making the slide from zamak vice stainless steel save that much money?

reflectoscope said...

Do you have my e-mail? RX does if you don't; Drop me a line some time.

Jim

Ancient Woodsman said...

What alternate universe has a "Hi Point fan forum"??

Or rather, what deviant slobbering brainless aliens got dumped in this universe to create a "Hi Point fan forum" here?

dwightbrown said...

"...the gun must have been deliberately sabotaged..."

Oh, thanks a whole bunch, Tam. Now I've got to crank up the Beastie Boys.

Anonymous said...

If only Walter had used a real steel slide for the P22...and a normal barrel instead of the wierd thing they have going on...then I'd buy one in a heartbeat.

Or if the Sig Mosquito was worth a shit, I'd have one of those, too.

But both of these makers, known for high quality guns, turn out crap .22s. I just don't get it. I want a .22 styled like a Sig or Walther instead of the fairly plain 22/45, but I'm not buying crap!

jimbob86 said...

"Might as well use aluminum."

Too costly.

"I want a .22 styled like a Sig or Walther instead of the fairly plain 22/45, but I'm not buying crap!"

So you WANT an ugly Krunchen-ticker look-alike, but you want it also to be a quality pistol? Seems akin to wanting a car that looks like a Yugo and performs like a Volkswagen..... style over substance? I'll keep my just plain reliable, monontonously accurate Ruger, thankee.

Bubblehead Les. said...

One would think that after all these years of being in business, and the state of the economy in Ohio that Hi-Point would break down, buy a used CNC machining center,( LOTS of Machine Shops around that went belly up over the last few years) and just make the @^^&^##^ slides out of steel. But Noooo.... I've always done it that way, you can't tell me how to run my business, it might cut into my profit margin....

Eric said...

My wife has a P22 as she wanted a plinker that fit her petite hands.

What's really fun is trying to get the slide back on the frame. Walther provides a plastic rod to help you guide the recoil spring back into place. It's not as easy as it looks!

pdb said...

What alternate universe has a "Hi Point fan forum"??

The same one that has a Olympic Arms fan forum and a Kel-Tec fan forum.

As Dave Barry would say, I am not making this up.

I'm reasonably sure there's a Taurus Judge forum and maybe even a NAA Mini revolver forum, but I'm too terrified to look.

Charles Pergiel said...

Blowback action on a 40 caliber round? Is somebody being funny?

Skip said...

If you can't afford the good stuff, don't.

Dr. StrangeGun said...

Without dragging up my old detail posts...

1 - reassembly: It's not in the manual, but the easy way is to get the guide rod mostly dry of oil, place the spring on it, then put it through the guide rod hole and compress the spring, and grab the protruding guide rod where it protrudes from the front of the slide. Now you can mount the slide on the frame without any spring tension, and once it's locked on you just let go of the guide rod, and possibly wiggle it a little until it drops in it's hole in the frame.

2 - Zamak. I did *tons* of research on it, and I wish people would quit picking on it so much. There are 5-10 different formulations of zamak, it's not 'pot metal', and is actually stronger than aluminum though it is always going to be a little more brittle. And it is vastly cheaper than any other metal for one reason: it doesn't shrink as it cools, meaning a zamak slide comes out of a metal casting die with a ready-to-go finish and may even require NO MACHINING.

3 - after a rash of slide-busted P22s at CCA, I took a very close look at all of them. Zamak isn't the issue so much as it's a very serious design flaw that would eventually show up on an aluminum or steel slide. When the spring weakens, the spring pad under the muzzle of the gun will batter against the collapsed spring and hence the frame. What's in the structure between there and the breech? A very thin section of metal right behind the muzzle where there are sharp-edged serrations that run the entire width of the structure. EVERY SINGLE ONE of the broken P22s appeared to have fostered a crack from the inside edge of a serration at the bottom of the frame, which propogated upwards until there wasn't enough intact structure to hold the force.

All the company has to do to probably completely eliminate that failure mode is slightly modify those slide serrations...

- make them round in profile to eliminate stress risers at the inner corners

- eliminate them altogether

- eliminate the lowest ~1/8" of serration.

Any one of those would add enough material back to the slide to avoid starting the catastrophic crack. The trouble is, a zamak slide is die cast, meaning there's an extremely expensive metal casting die involved, and the beancounters may have figured it's cheaper to accept a high failure rate than it is to spend a couple ten or hundred thousand replacing or modifying their array of dies... and also, depending on how those dies and the machinery that automates them is made, the third alteration may introduce problems where the new material is in the way of the release path for the casting (i.e it'd stick in the die) or worse, the extra material would require changing the sprue and relief setup on the die if the extra space couldn't fill without cooling or getting blocked (i.e the new smooth-slided P22 slide ends up not having serrations, but ends up with a much greater rate of rejected castings due to casting voids or thermally stressed areas).

Basically then, they may simply have hosed themselves into the iffy POJ that the P22 has become, because they didn't properly do their homework in the run-up to production.

Other zamak guns, if you'll notice, don't have sections in their structure that are less than 1/16" thick and bear a series of notches with 90 degree corners in the dead middle of the section that takes the highest shocked tension load *and* inertial bending moment. Of all the things keeping me away from a .40 caliber Hi-point, worried about slide failure isn't one of them.

I've also seen enough of the hi-point to remember that the slide is retained by a thick-ish steel cross pin at the rear... if the slide were to break, it shouldn't be able to leave the frame, or if it does, it shouldn't be straight back or with enough speed to cause injury.

Roberta X said...

The Docbeat me to it. I was going to come to the defense of zamak as a superior casting metal -- and to go on the offensive against plain cast gun parts. Or plain cast anything, really, other than toys (includes some .22s, IMO) and decorative elements. Casting is cheap and fast, especially white metal, but strength and freedom from defects are issues.

(Tam may point out that parts milled from billets or forgings are themselves cast to begin with; it is true and my preference for a part that's been machined, preferably after being whacked by a huge hammer while superhot, is as much superstition as science. Stubbornly, it feels to me that they've been given more chances to fail under stress.... YMMV; IANAM. Or an M.E.).

Dr. StrangeGun said...

Whack-a-frame.

Anyhow, if you want to pick grievously upon materials selection in a firearm that would otherwise have no issues at all... Skyy's pistols take the cake.

Steel slide. Aluminum frame. Polymer lower shell. Browning style short recoil lockup in a 9mm package. Hard to go wrong?

All you need to do to go wrong in the worst way possible is choose an aluminum alloy for the frame that so soft that it begins flowing under the impact from the slide. The rental Skyy at CCA... rather, both of them, failed exactly the same way: the frame material around the slide lock/recoil pin, and there was plenty of it, began to flow... until it egged the hole severely and ate up the clearance between the slide and frame so completely that the slide would, if fired warm, stick about halfway back and freeze solid as everything cooled off. I later took the pistol and from a non-critical (and hidden) corner of the frame, shaved a long, thick sliver of metal off the frame with a DULL POCKETKNIFE.

IIRC we cajoled T to include in the warranty letter something about the frame being made of Edam cheese. Or maybe it was gouda, don't recall.

Tam said...

Y'all had SKYYS in the rental case?!?!?!?

CTone said...

My P22 slide has not shattered, so I don't have any gripes with Zamak as of yet. I do have a gripe with the crappy magazines that came with it, the endless feeding problems with ammo other than CCI mini mags, and the issue of the gun no longer firing in DA because of horrible engineering. That there are threads called "How I made my P22 not suck," outlining in detail how ordinary folks who probably did not spend years in school learning to be engineers have fixed obvious problems in the P22 design, should be the indicator to Walther and S&W that they should get back on the ball and fix what they have done.

The P22 is the second of such products that I have purchased that were an outcome of the Walther/S&W venture, and both were beyond horrible.

Mad Saint Jack said...

Would CCI Mini Mags be classified as "zippy" ammunition?

joannahurley said...

So, what WOULD you recommend, then, for small hands, .22 and/or really low recoil, and inexpensive, which are all the reasons I own a P22? I didn't want to spend a lot on a new hobby until I was sure I would stick with it, but now that I know I will, yeah, I want to upgrade. I'm definitely open to suggestions.

Dave_H said...

@ Noah D

It must be cheaper and easier to work with judging by the low dealer prices I have seen on those guns in the catalogs.
If they used steel in the slides, they would price themselves out of the niche they are in. The tuck it in the night stand crowd is probably better off with Hi Point being in the business of meeting that low end demand than say, Lorcin, Talon, or Sedco. However, judging by that picture, I'd stay with my where there is smoke there might be fire approach to their handguns, or at least the .40 S&W, but I'll admit to an interest in the Hi Point throwdown. I own a couple of their carbines so I'm sort of a well wisher towards their handguns. If someone could make a cheap 9mm pistol that actually works well, I think that would be a good thing.

http://en.wordpress.com/tag/hi-point-throwdown/

Firehand said...

Roberta, the way I always looked at it is that a forged part has fewer ways to fail than one made by casting. A forging either makes it through (proper) shaping and heat-treating, or it doesn't; a casting can have a bubble or something hidden deep inside just waiting...

WV='multi', as in 'multi ways to break'

Butch_S said...

@joannahurley: Browning Buckmark, or a Ruger Mk II/III.

My personal preference would be a basic Mk II with a 4.75" tapered barrel.

Ed Foster said...

I used to have fun casting Zamak (pot metal) bullets in .45acp. If I remember correctly, the 230 grain roundnose mold threw a Zamak bullet that weighed about 145 or 150 grains, and they shattered really nicely when they hit the plate.

The problem with any metal containing zinc is zinc creep. The stuff doesn't alloy well with most other metals when at room temperature. The stuff is slippery and wants to be on the outside, which is why it gets used for plating so much (Galvanizing).Copper does alloy well, and zinc does hold on to copper reasonably well, which is why most Zamak "alloys" (really mixtures) run about 4% copper.

It's like the relationship of lead to antimony in a cast bullet. Lead and antimony alloy at high temperatures, but seperate at room temps. However, lead and antimony both alloy with tin at typical temperatures, so you end up with the antimony crystals stiffening the bullet, and the crystals held to the lead by their coating of tin.

Zinc content is the reason you can't weld 7075 aluminum, the wonder material used for everything from pistol frames and M-16 recievers to armored personnel carriers and light tanks. The zinc content creeps out of the weld over time and results in work hardening, something that also happens with Zamak. It always becomes more brittle with time.

It's used mostly in the sheetmetal industry for short run forming dies in low stress applications, then remelted and used again, until "the color goes funny" and they throw it out.

Or it sluffs, spalls, splits and shatters, which happens a lot. I used to see it all the time as a teenager, working in the sheetmetal shops down in Durham CT. In all fairness, the stuff that busted almost certainly had been reused a few times, but still....

I just had a chuckle. We're offering the .400 CorBon as an option in the 1911's in a few weeks. That cartridge kicks some savage kiester, and it shoots freakishly good.

I was running acceleration and deceleration curves for it a few days ago, trying to see what my options were vis-a-vis spring rates and possible buffers (I hate the little bastards, but that's another story).

If I can find some numbers for Zamak in the Machinery's Handbook, I'll ballpark about how safe the stuff is in a pistol slide.

Given the lack of hardness and propensity to spall, how do the breech faces hold up? I've never looked at one of the pieces of cow flop, so I really don't know.

I mean, damn, if I ran a 10-1-1 linotype mix and cold water quenched it, it would be almost as tough and hard, and it's still mostly frigging lead.

Tam said...

Ed,

"Given the lack of hardness and propensity to spall, how do the breech faces hold up?"

They use a steel breechface insert.

The nines actually hold up pretty well. The recent change to the forties has seen some issues with bbls coming loose. (I believe they ditched one of the pins.)

reflectoscope said...

Tam,

Sorry if I had my Steve Buscemi on yesterday. Ask Roberta what I do for a living, particularly in the context of this one. That'd probably explain things.

Jim, who is shy.

Will said...

Ed,
if you use a reverse spring plug with a wide flange, the buffer doesn't get shredded like normal. I run them in my Officers size .45's, but it would help if they had a lower durometer, due to the greatly increased surface area of the flat flange. I avoid the fiber filled ones, as that's not needed since there is no cutting action. They last a looong time. I change them out of habit, rather than need.

If you are concerned about loose buffers in the gun, I've got a couple ideas about that.

Jeff the Baptist said...

"There are 5-10 different formulations of zamak, it's not 'pot metal', and is actually stronger than aluminum though it is always going to be a little more brittle. "

Not entirely true. Whether it is stronger than aluminum is highly dependent on the Zamak alloy, the aluminum alloy and the aluminum's heat treatment. A good aircraft aluminum like 7075-T6 is a fair bit stronger than any zamak grade. And those are the grades used in firearms.

VA Dave said...

I thought the reason for using zinc in the p22 slides was primarily weight and not cost. (although cost probably has something to do with it.) A little .22 round doesn't have the same recoil as a larger cartridge. The slide needs to be light enough to cycle from a .22. I could be wrong but this was my understanding. I've also heard there are more slide cracks occuring with the longer barrelled versions. The ones with the extra chunk of gun at the end of the standard barrel. The slide cycles and bangs into that material at the front causing additional stress.

markm said...

Roberta X: Your preference for forgings is not superstition. Unless the casting process is exquisitely well-controlled, dissolved gases will undissolve as the metal cools, forming bubbles ("voids"). Forging crushes the voids and pressure welds them so they will stay closed. It also smears out other inclusions so they are less likely to cause failures, and finally it work hardens the metal.

The reason for using castings is always cost. Forging and then milling to final shape is expensive. Casting costs considerably less, and with alloys like Zamak that don't contract when they freeze, there will be considerably less final milling. But there's good reason to be leery of castings where strength is critical.

One example: A motorcycle company once decided to save a buck or so on it's brake levers by changing from forged aluminum to cast aluminum. They also contracted the castings to the low bidder. The result was voids in the castings and a series of usually fatal accidents where the levers broke just when the rider was braking harder than ever before.

Now, selecting a casting wasn't the whole problem. There are foundries that could cast that aluminum alloy with no voids, but purchasing selected a foundry with experience mainly in decorative castings. Secondly, nowadays it doesn't cost that much to x-ray every casting. You don't have to have someone standing there studying the picture, either, automated inspection computer programs can do the job.

And then there's the second issue: with castings, good performance in casting becomes a more important criteria in selecting the alloy than the final mechanical properties. A steel slide with the same design defects might fail at the same spot, but with the right alloy the slide would deform and jam so you could not fire the gun again before it cracked all the way through and sent pieces flying. With firearms in particular, the failure mode matters!