Umm, Leading WITHOUT Gas Cutting ("With a Quality" Lube, Too)

[Grump]

Okay, I've isolated the keyholes of 180-gr LFRN boolits from the Glock (which shoot much better at 4-inch groups and all pointy-side first from a USP) to some marginal casts I decided to looby-size and throw into bags for short-range blasting ammo...

Full-sideways headshot hits at 13 yards just make you feel like your shooting is right even if the projectiles are about to make a left turn!!!

Anyway, curious that the effective but smelly RCBS lube I used on these things was being sabotaged by bad boolit fit, I decided to investigate those barrel-length lead streaks that typically shot up within the first 20 shots. Slug the barrel with a sized and lubed slug! Okay, totally tight seal! No room for gas cutting, the polygon grooves are more than fully filled. If anything, the boolits are oversized for even the groove diameter.

And besides no room for gas cutting, turns out those lead streaks are on the flat "lands" of the Glock barrel, not in the larger-diameter groove areas.

So what's the mechanism of lands-only leading when there is very tight boolit fit that should eliminate any chance of gas cutting? The lands also do not come anywhere close to "bottoming out" in the lube groove either.

So what gives here? My pet theory of 18 years ago that nitrided steel barrels are "sticky" to lead doesn't appear to fit either--if that were true I would expect leading in the grooves too, especially by the time 100 or more shots have gone downrange.

[Tatume]

Are you sure you're seeing lead? I'll bet it's not.

[Sasquatch-1]

How fast are you pushing the boolits? Are the boolits too big? What alloy?

I will probably get called down for this, but I believe you can push the lead bullet too fast for poly rifling. In my 44 Desert Eagle, a lead bullet traveling at 1200 to 1400 fps, never has a chance to grip the rifling.

[hockeynick39]

Probably not sized correctly for the bore. Should be able to go .002 caliber over actual bore size for best fit. I don't want to say that lube has no effect on leading, but it is minimal at best. Same thing with gas checks. Too bad Elmer and Skeeter aren't around, they would have fun with all of this.

[popper]

Bet that head shot would hurt no matter which way it hits. Where are the 'lands' on a poly barrel? I suspect case swaging - I get it once in awhile in 9mm.

[rsrocket1]

So you're seeing leading on the flats at 20 and still don't have a totally lead lined barrel by 100?
Like Tatume said, are you sure it's lead and not just fouling from the burn products? When you take a Chore Boy wrapped bore mop and run it through the barrel, are you seeing tiny "sparkles" come out? If so, that's lead. If not it's something else.

[Cowboy_Dan]

Maybe it's just antimonial wash, from what I understand there is a different mechanism for laying that down in the bore and it doesn't tend to build up like leading.

[MtGun44]

The sideways hits would seem to be far more of an issue than any possible
leading.

[Blackwater]

I'm not the most knowledgeable guy on Glocks, but from what I've heard (not the best info), Glocks have polygonal bore rifling, and some say Glock doesn't recommend lead bullets in their guns. Some say you need a regular rifled barrel to shoot cast. Maybe someone here can give you better info on it than I can, though. Supposedly, that polygonal rifling just leads up, and the lead supposedly CAN build up, if someone doesn't notice it and keeps shooting, so that it can even be allegedly dangerous. Again, I'm not a Glock shooter. They're great guns, no doubt about that, but I've just never felt they handled well in my hands and I can't usually get used to their spongy trigger release, but a buddy has a .40 compact that's really nice, and has me wondering if my mind can't be changed for my own use. Again, seek confirmation for this because I'm just not the best man to speak on Glocks.

[MT Chambers]

Blackwater has it, there's tons of stories of problems with cast boolits in Glocks with the polygonal rifling, why do they use it, must have to do with cost.

[Cowboy_Dan]

I'm not so sure polygonal rifling is so bad for lead bullets. The Lee-Metford rifle had polygonal (A.K.A Metford) rifling and it was designed before j-words were the big craze.

[Grump]

More data for us:

1. The boolit and alloy previously with this and another lube shot nice 2-inch groups at 25 yards. BHN 8-10 is all. The other lube can't be replicated, it had green Do-All band saw lube in it. One of the tests was with an earlier batch of RCBS pistol lube.

2. Deposits are definitely lead. It curled up as elemental soft lead when I felt for which were "lands" and which were "grooves". The six lands are the flats of the polygon, the grooves are the rounded curves between them. That was a surprise, I thought the white metal streaks were in the grooves.

3. The leading is no worse and no better than the other accurate ones years ago. Same powder charge and everything. These were Winchester primers, original testing might have been CCI but I really don't remember and my notes are off-site. But I've never seen a noticeable accuracy difference with either primer in handguns.

4. Velocity is about 975 fps out of a full-size Glock with factory barrel.

5. Bore was slugged with a boolit pulled from a primerless cartridge. I make mistakes AND catch them while reloading. Inspection is king, ya know. Both bore and groove engraving are full and complete--a clear demarcation line is on the boolit nose showing all barrel surfaces are sealed by the boolit. However, this batch of boolits is ****, the mould blocks were parted by some lead spatter and I remember now just loading 'em up as short range blasting ammo. Some bases are not even clean edge to edge.

6. The size die says .401. I've never checked the final product though.

7. The "lands" flats area of the slugged boolit mikes out to .0.3924 and the rounded grooves mike out to .4014.

8. The leading seems to be only on the lands--no buildup in the throat like I see with 9mm sometimes and in revolver forcing cones.

The accuracy effects from these casting defects is surprisingly large. I will check with some better loads once I identify them...but that might require a new casting session, hehehe.

An HK USP fullsize with original lands and grooves barrel shot these same loads MUCH better but as lousy as I expected for the boolit quality--8 inches at 25 yards. The Glock at the same distance put 3 out of 6 shots on the paper--the backer was 24 inches wide and I think at least one went low and another went right. The three hits were scattered so far I didn't bother to measure, but I remember it looking like something close to 14 inches from the two furthest from each other.

[sigep1764]

if you're sizing to .401 and your bore is .4014, size the boolits larger. Size them at .402-.403 and tell us what happens.

[35remington]

While gacutting may not be the issue, the only way to determine a lack of gascutting is to examine fired bullets. Slugging a barrel is an invalid way of doing so.

Always has been.

[rsrocket1]

When you slugged your barrel, did you slug it with a lubed *** booit?
I wonder if the *** boolits were so fat that the bottom of the lube groove was > 0.3924" and you weren't getting any lube on the flats of the barrel which caused the leading.

Anyway, since this was an anomaly with a limited run of junk boolits, you probably won't run into this problem again. Personally, I would have simply thrown the whole batch into the "remelt" pile for another day's casting session. I did that with about 150 PC boolits where some of them slumped because I bumped the oven knob and set the temp to "broil" instead of 400 degrees. It wasn't worth sorting, I just dumped them into the pot for the next castings.

[Grump]

You make me laugh, rsrocket1. I have tossed quite a few into the melt pile myself. Loaded these up when one of the kids loved to pour rounds through the thing at cans 10-20 yards away. Not really that much of a false economy if you REMEMBER the limits of the product.

This particular gun has been hard to get better than 4-inch groups out of at 25 yards anyway. The USP is barely better, it can be counted on to do 3 inches or better. Both will do 2 inches with the finest jaxteded loads, and that's about it. I was spoiled by revolvers doing that at 50 yards when I started out...

What did you type that got starred out? I thought I was gentle using the C word for po op, but I guess even that one gets a bad rap here. Like over at one forum I used to play in far too much, gotta keep it friendly for Art's Grandmaw...

Yes, I used a lubed boolit for the slugging, and sent it in from the chamber end and pounded it through. I'm reasonably sure to the point of "prove otherwise" that the nose/shank junction engraving is valid and unaffected by pushing it from the rear.

I'm out of town right now and cannot mike the sized finished product...will dig around when I get back to see if I have any in all those boxes...

They are RCBS 180-gr boolits, BTW. Don't remember if we're sizing them in the Star or the Lyman, but I don't really believe that makes a difference except for how you toss 'em in the box when done.

Oh, rsrocket1, I did report that the lands are NOT bottoming out in the lube groove.

I suspect that the coefficient of friction of nitrided steel is pretty high with lead, lower with copper, and way low with any reasonably hard steel, as compared to the usual barrel steels. Tried to Google up some answers to that more than 10 years ago, including online correspondence with the guy [formerly?] known on either TFL or the old Gun Zone as MarCo or something similar, but found nothing that appeared reliable then. But because of that suspicion, I also suspect that any nitrided bore will perform better with boolits lubed over the whole shank to the ogive, like outside-lubed .22 RFs are. Maybe I'll test that someday...

[gloob]

The six lands are the flats of the polygon, the grooves are the rounded curves between them. That was a surprise, I thought the white metal streaks were in the grooves.
On all my glock barrels, the grooves are the wider flatter areas, and the lands are seemingly narrower and rounded. And I have them in all of the calibers.

My definition of the "land" is the part with the smallest diameter. Grooves, the largest diameter. You're on the same page with me, from your post, yet your description is totally foreign to me. I don't see these smaller diameter lands as being flat, whatsoever. Just a small rounded triangular profile, protruding in from the rest of the bore.

FWIW, I get some fine fouling or maybe antimony wash with my Glock bores on the leading side of the lands when using commercial lube-grooved bullets. Tumble-lubed, I can shoot about a thousand before seeing much, if any. I think you might be onto something with your theory. If I seat a commercial MBC 180 grain bullet into a brand new Starline case, it can't be pulled with a kinetic puller.

[rsrocket1]

What did you type that got starred out? I thought I was gentle using the C word for po op, but I guess even that one gets a bad rap here. Like over at one forum I used to play in far too much, gotta keep it friendly for Art's Grandmaw...

Yes, I used a lubed boolit for the slugging, and sent it in from the chamber end and pounded it through. I'm reasonably sure to the point of "prove otherwise" that the nose/shank junction engraving is valid and unaffected by pushing it from the rear.


Thanks for the info. One more hypothesis eliminated.

Oh, and I didn't type anything wrong that got starred out, I simply quoted your stars. :bigsmyl2:

[Wayne Smith]

Thanks for the info. One more hypothesis eliminated.

Oh, and I didn't type anything wrong that got starred out, I simply quoted your stars. :bigsmyl2:

Nope, not eliminated. You 'slugged' your bore with a hardened boolit, which will spring back and give you a smaller reading. You need to slug with pure lead, it does not spring back.

[Grump]

Nope, not eliminated. You 'slugged' your bore with a hardened boolit, which will spring back and give you a smaller reading. You need to slug with pure lead, it does not spring back.

True as far as the dimensions measured, I believe.

But I do not believe this changes the observed signs that the boolit is NOT under-sized. Don't see much discussion of what happens if the boolit is oversized for the bore by .001, .002, on up to .010 or so.

And so I don't have to say it again, no, the bottom of the lube groove is NOT contacting the lands. Nowhere close to doing that.

[44man]

Need to recover boolits to look for "SKID". I don't know the "BITE" of your rifling. But it must grab the boolit to spin it. How about a much harder boolit?