Polygonal rifling - any experience with it

Cherokee

Well-Known Member
What has been your experience in shooting cast bullets in semi-auto's with polygonal rifling, like the Sig X5 or the PPQ Match 5 ?
 

oscarflytyer

Well-Known Member
none. but, iirc, it is much like the Marlin micro-groove. size large and go. and no, I do not know what 'large' is for poly rifling... Micro, yes, Poly, no.
 

CZ93X62

Redlands, Kalifornistan
Glock 21 with octagonal-form rifling, .449" flats x 453" 'valleys'.......4 designs of bullets from 200-230 grains, .452" and .454" sizing, BW/Alox lube, 92/6/2 alloy........zero leading after 200 rounds of each sizing, decent to stellar accuracy. I keep meaning to try similar tests in my Glock 40s, but have't gotten around to it yet. The 45 ACP is a very lead-friendly caliber, the 40 S&W can be a little less cooperative--though my shooting of castings in conventional-rifling 40 S&W pistols has been accurate and leading-free with the same alloy and lube as used in the 45 ACP. The 40 S&W operates at almost twice the pressure level of the 45 ACP, and the Glock 40 and 10mm barrels have hexagonal-form bores. It remains to be seen if if those two variables make a difference and cause a problem. A lot of folks seem to run cast bullets in 9mm and 40 S&W Glock barrels without issues. If worse comes to worst--an aftermarket barrel might get the nod. Whitworth rifles seemed to shoot unalloyed lead elongated projectiles just fine.

Just random thoughts on the matter.
 

fiver

Well-Known Member
I think Allen's size and alloy would be a good start.
big and hard seems to be the overall theme with the poly barrels in handguns.
 

CZ93X62

Redlands, Kalifornistan
To paraphrase Buckshot, from a discussion over burritos just prior to him and Glen Dye working me over during a Tuesday Burrito Shoot some years back--"Bigger is better than smaller in multi-groove barrels. When "The Big Light" hits the bullet base, it will make itself fit." I think this was mentioned in relation to Marlin Micro-Groove abominations, but it inspired me to try the old Colt 45 diameter (.454") along with the more common .452" that Lyman et al have recommended since about forever. In the Glock, both worked just about as well.
 

Ian

Well-Known Member
Speaking of MicroGroove rifling, I maintain that it is actually the best form for cast bullets. Small bore to groove ratio means less bullet distortion, and the land engagement area is 1.5 to 2 times that of conventional rifling. The nature of broached rifling makes a uniform barrel inside with minimal burrs, so what's not to like? Stay away from "bore riding" designs and use a bullet (and alloy!) proper for the dimensions and the sky's the limit.
 

CZ93X62

Redlands, Kalifornistan
I never thought that multi-groove barrels COULD NOT shoot lead well--there were and are a TON of PPC 38 wadcutter barrels out there with that bore form that can cut small chrysanthemums in target paper at 25 and 50 yards. I have seen it done too many times to harbor any doubt about the bore form. Where the makers fall down and continue to do so is in making their 44 caliber barrels with .433"-.435" throat & groove diameters and insisting that component bullets be made in .429"-.430" diameters. Of course, SAAMI is no help at all, with their chamber and cartridge diagrams that show .433" as max acceptable throat and groove specs. Cut them to better diameters, and give them reasonable real-world twist rates, and life will be good. It just makes me shake my head to see the maker matrix get 38/357, 40/10mm, and 41 specs so good and so consistent for so long, and at the same time be so "All over the map" on 9mm, 44, and 45 Colt and 45 Rifle calibers. It makes very little sense.
 

Ian

Well-Known Member
I blame the lawyers. Ammo makers go to minimum or smaller specs, gun makers go to max tolerance or over. Never mind there's a built-in safe zone for max ammo min chambers.
 

Ian

Well-Known Member
The Bard got a lot of things right regarding the spectrum of human nature; he developed characters motivated by things just as prevalent in modern times as they were then.
 

462

California's Central Coast Amid The Insanity
Seems human nature has not changed since closely after Day One.

The Bard ought to have included politicians, too.
 

462

California's Central Coast Amid The Insanity
I have a Glock 27 -- .40 S&W -- but have decided to load plated bullets rather than cast, when I get to that point, because of the perceived/reported/mythical problems associated with Glock and cast bullets.

I would be interested in hearing anyone's experience with cast and Glock .40S&W factory barrels.
 

CZ93X62

Redlands, Kalifornistan
I can only report what I have seen on Glock 40 S&W and 10mm barrels. No shooting experience with castings in either caliber yet.

Not long after I got my first Gen 3 Glock 23, I compared the chamber support areas near the case head between my barrel and the earlier-version Glock 22 and 23 barrels we had as armory guns at the old shop. The Gen 3 chamber area showed dramatically more support than did the earlier barrels.

I drew a couple of the armory guns, and ran some of my CCW carry ammo (WWB 180 JHP) through it. All of that fired brass showed the famous "Glock Smiley" expansion. Same ammo/same lot number run through my Gen 3 Glock 23 (and all succeeding Gen 3 40 S&Ws and 10mms) shows no such expansion behavior. FWIW, the Glock 21's fired brass did not differ in expansion characteristics significantly from my Colt- or SIG-Sauer-fired ammunition.

My usual load in 40 S&W is meant to duplicate my carry load (the above WWB 180 HP) that delivers 915-925 FPS from the Glock 23 barrel; in the Glock 22 this load gives about 955-970 FPS. Powder weight is 4.7 grains of WW-231, lit by CCI SP primers and packaged in W-W brass. This load produces no swell-outs either, and brass life has been very good.

FYI only.
 

CZ93X62

Redlands, Kalifornistan
As for the "Glock kaBOOM" stories--they are true, but less frequent than their constant repetition would indicate and FAR less frequent since the intro of the Gen 3 Glock 40 S&W variants. Lots of theories "out there" concerning the wherefores and the whys, my own is that expansion areas of 40 S&W brass got worked over and over in sequential reloading cycles, and--since Murphy's law gets no plea bargains--one of those worked over and over areas got work-hardened and weakened to the point of failure. As luck would have it, that weakened portion chambered right over the unsupported chamber area and when The Big Light hit the propellant the case head failed and 35K PSI went to work in areas of the pistol not meant to contain it. I don't think that "cast/lead bullets' had any direct effect on these outcomes, other than that cast/lead bullets were always found in reloaded ammunition. Lots of jacketed loads created kBs too, but that got lost in the scrum of mall ninjas and exspurts rushing to analyze unwitnessed events. And I am in the same position as those 2nd-hand critics--I have yet to see a kB in person. But after almost 50 years of reloading and shooting and 20+ years of forensic firearms examinations and assessments, I might have a bit of insight into how these events took place. HTH.
 

Pistolero

Well-Known Member
Al,
The early guns were prone to BOOMS. I had the opportunity to read a letter from the head of our
Federal Security Force to the President of Glock, asking why so many .40 cal Glocks were exploding
when they were ONLY fired with factory ammo. Apparently the better chamber support was a response
to this issue. Our security force, with something on the order of 75 officers had two or three BOOMs that I was
aware of. Other Fed Sec Force groups had similar issues, prompting the letter.

Bill
 
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CZ93X62

Redlands, Kalifornistan
With factory ammo, eh? The kBs I am familiar with--albeit all 2nd hand info--all involved reloaded ammo in Gen 2 40 S&W pistols. I have yet to try castings in a Glock 40 S&W or 10mm barrel, but I have run thousands of reloaded rounds with j-words through Glock 40s and 10s without issues or even "guppied" brass.
 

Pistolero

Well-Known Member
Yes, I had heard all sorts of rumors about .40 BOOMs with handloads, including one friend who destroyed
a gun, but I was a bit surprised when my friend, Chief RO and trainer on our security force showed me
a copy of the letter. He said there had been "a couple" in our force, I never went into exact ammo brand,
but the letter clearly stated factory new ammunition. I really think the early chambers were quite 'generous'
and apparently the feed ramp cutout was larger than really prudent.
A whole new product was created to "deGlock" brass which had the base so swollen that it couldn't fit into
other brand .40s with ordinary sizing. As it was explained to me, this is a push through sizer like the Lee
bullet sizer, sizes all the way down the head. IMO, if the head of a factory round is swelling at all, this is
a very bad sign.

Clearly, the overwhelming majority of the time, 99.9999 or something, all is well. But with literally billions
of rounds made and fired, even exceptionally rare events happen.

Bill
 
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CZ93X62

Redlands, Kalifornistan
I guess that the crux of my argument has always been that cast bullets played no direct role in the onset of Glock kBs, as was believed in many quarters. That cast bullets were the exclusive province of handloaded ammo in 40 S&W didn't seem to register with folks at first.

My favorite 40 S&W pistol is the one I have owned for the longest time--the CZ-75B. It has excellent chamber support, is very lead-friendly, and has one of very few OEM 40 S&W barrels with a realistic twist rate (1-16") instead of the insanely-fast 1-10" or 4 turns/meter usually found in 40 S&W. I have never understood that twist rate in 9mm Luger of 40 S&W barrels, given the short squatty bullets usually fired through them.