"Hard cast" bullets and Polygonal/glock barrels good to go.

[Unimakpass]

Kind of new around here so this might be old news but I just read this on Buffalo Bores website.

https://www.buffalobore.com/index.php?l=product_list&c=54


Differences Between 'Lead' & 'Hard Cast' Bullets
THE DIFFERENCES BETWEEN 'LEAD' BULLETS AND 'HARD CAST' BULLETS
Many gun owners refer to hard cast bullets as 'lead' bullets. In most cases, they do not understand the drastic differences or they would not use such an inaccurate generalization. This generalization is as inaccurate a generalization as referring to all motorized vehicles as Volkswagens.

Hard cast bullets may contain some lead and be grey in color, but that is where the similarities stop. Hard cast bullets can be formulated of numerous alloy mixes (antimony, silver, tin, etc) containing some lead, but the alloys make the bullet much harder than pure lead. Pure lead has a Brinell hardness # of about 4. Most hard cast bullets will have a Brinell hardness # of 11 to 30 and as such are several times harder than lead.

Generally speaking, a properly designed, sized and lubed hard cast bullet will not leave lead alloy deposits in a rifled barrel, but pure lead bullets will almost always foul a barrel to the point of a total loss of accuracy (with very few rounds fired) and perhaps to the point that the barrel will split or worse. ( see my essay on 'Dangerous Pure Lead Cowboy Ammunition' ) I am employing many abstractions here, as there are a number of ways to make a hard cast bullet foul your barrel and make a pure lead bullet not foul, but on the whole, what I have written in this paragraph is accurate.

Depending on certain variables, in many instances and for many uses, hard cast bullets will not deform or 'mushroom' when they impact living mammal tissues, but lead bullets will deform or 'mushroom' at very low impact speeds. Lead bullets will deform and have much less penetration while hard cast bullets will maintain their shape and penetrate deeply however, this requires using sufficiently hard alloy mixes, matched with intended impact speeds on the intended medium.

Hard cast bullets can be alloyed and designed for hunting large and dangerous game where deep penetration is needed - a lead bullet cannot be used this way. I shudder every time a customer refers to our beautiful hard cast hunting bullets as 'lead' bullets. It happens almost daily.

This short essay could not cover all the variables of/and the differences between hard cast and lead bullets - it would take a large book to do that, but hopefully it sheds some light on the on the general/gross differences.

[The_Shadow]

Unimakpass, Welcome to the forum, thanks for linking the article and the article is correct.  One of the best references to bullet casting and alloys can be found at this website; http://www.lasc.us/Fryxell_Book_Contents.htm  It covers everything in the 16 chapters relating to the subject.

There needs to be a good balance of lead or alloy to its size to fill the bore and proper lube to enhance the properties to prevent leading or fouling. 

I am by no means an expert, but I do well casting my own bullets, from older wheel weights for my pistol needs.  I also have a small supply of linotype alloy to add to my wheel weight or even pure lead supply that can help with enrichment of the properties as needed for rifle velocities.

As for 10mm and even 9x25 Dillon velocities, the wheel weight alloy has been just fine with the White Label Carnuba Red lube even those seeing 1800 fps.

That being said, some of the powder paint coatings, when baked on, are providing a fantastic properties for eliminating lead and alloy fouling.  There are several methods of application to produce results.

Best regards.

[Unimakpass]

Shadow, thanks on that. Was thinking I was going to have to get a different barrel for the glock, seeing how it's supposed to be the most reliable barrel available this is good news. Upgrading to 6" on the the glock 20 so will just order from  glock. Like simple. 

[The_Shadow]

The polygonal bore on Glock's factory barrels have been measured by some at about 0.4020"!  What does this mean for cast bullets?
Usually cast bullets need to be 0.00"1 to 0.002" over bore size to properly seal and prevent the combustion gasses from cutting the bullet along its sides which can be a cause of fouling.  However obturation (bumping up the bullet size to fill the bore by the pressure) can help seal the bores to prevent deposits.

I size my 10mm/40 cal cast bullets at 0.4015" when applying the lube and they are a medium BHN around 12 air cooled, this seems to work well in all of my 10mm guns including the Glocks.  I run them 1100 to 1400 fps depending on the bullet weighs used.

[Unimakpass]

Ah, I knew I would Learn something on this site. Might star rating reloading 10mm so will file info away. Thanks again.

[sqlbullet]

Fit is king.  Issues with Glock and lead, as Shadow mentioned, are the groove diameters are big.  Mine all measure .402 or a bit bigger.  Shooting any metal with a melting point under 1200° that doesn't fit is going to be an issue, hard cast or pure lead.  You are going to have plasma jet cutting and it will cause problems.  It even effects steel, which is why barrel erosion is a problem at the throat and muzzle, but not the mid point of the barrel.

I agree technically with the article, reality is a curious beast.  Most bullet casters definitely mean an alloy that is predominantly lead when they say "lead bullets".  In forums a true lead bullet is denoted by the keyword "pure".  Otherwise it is assumed to be a lead/antimony/tin alloy.

It is also interesting to note that to most modern shooters, lead means today what "hard cast" meant in Elmer Keith's heyday.  "Pure lead" today means what "lead" used to mean.  And today "hard cast" means what Linotype meant 30-40 years ago.

Thanks for the great post.  Load large lead/hardcast for Glock and they run just fine.

[DM1906]

Also consider, Buffalo Bore's statement in regards to the differences is from a retailer, with a product to sell. I don't but much weight in their statement, and their base statement is misleading, if not outright untruthful. The reference to their hard cast containing "some" lead is not reality. Fact is, hard cast, by anyone's definition, including yours, mine and theirs, contains mostly lead, almost exclusively 90%+. Very (very!) rarely will a lead alloy used for casting bullets contain less than about 90% lead. The BHN variation between 4 and 12 requires less than 5% "other than lead" (antimony/tin), while 18-21 requires about 7%.

That said, most hand-casters don't know, really, what lead alloy they are using. On a rare occasion, one may have a source that is more predictable than others. SQL, for example, has a source that is probably more predictable than any other, short of sourcing a specific order from a smelting supplier. Even then, it isn't certain, as most all lead "alloys" are made from recycled lead, and are certified at a specific "pour weight", rather than a specific alloy content, with only a "range" specified as to content. "Pure", virgin lead is costly, and becoming more difficult to source outside the corporate world in other than finished retail products (such as a component bullet). Purified lead, which is recycled lead with much of the alloyed metals removed, is only slightly less costly, but can be done by the consumer. I do it with very close temperature monitoring and pine pitch. Still, my pure lead isn't "pure" (such as virgin lead), but it's close enough for my needs (about 5-6 BHN). For example, a Minie-ball BHN over about 7-8 will cause some leading in my rifles, while less does not (at all). Higher BHN = more leading. It's only that simple. Of course, this doesn't translate exactly from a muzzle loader to a breach loader, but it is relevant. A breach loader has the advantage of free-bore, which offers greater projectile-to-bore diameter differentials, which is what we are talking about, after all.

The bottom line.....
Firing bare-lead bullets from your polygonal barrel is possible, and safe. All the same rules apply as for traditionally rifled barrels. The problem is knowing exactly what you have, in order to follow those rules. Slug the leade and bore, then size the bullets accordingly. It can be complicated, but it doesn't have to be.