(The following is reprinted from the Lakeville Arms Company brochure from the early 1950's.)
"In simple terms, the bullet requirements desired by every handgun shooter are: accuracy, maximum killing power per grain of weight, highest possible velocities within acceptable pressures, minimum wear and the absence of leading. Those are a lot of qualifications to pack into so small a package as a bullet. Countless metals and alloys have been tried for bullets with varying success but no single metal has fulfilled all of the above requirements.
Pure lead is one of the best bullet metals but prior to the advent of Prot-X-Bore, it had to be kept at low velocities and it had to be lubricated to prevent fouling even at moderate speeds. Alloying lead with tin or antimony to harden it reduces leading but hardening also reduces mushrooming and consequently killing power. Alloying with tin lowers the melting point of the metal making it easier for the hot gases to cut around the base of the bullet, spoiling accuracy and creating some leading. The cup gas check was designed to protect the bullet base but it does not obviate the necessity for lubrication. Ill-fitting cups can drop off into the powder charge and cause serious complications. Jacketing the soft lead core with gilding metal comes the nearest to fulfilling all qualifications, the drawbacks being cost and excessive barrel wear in some guns.
Zinc and certain zinc alloys will produce a virtually self-lubricating bullet. Such bullets are capable of top hand gun velocities and are accurate and deep penetrating at close range. Unfortunately, zinc does not possess sufficient density to sustain velocities and it will not mushroom against flesh and bone.
If we could combine lead and zinc in an alloy and retain the desirable features of each, we might produce a superior bullet. Alas, these two metals are incompatible and will not alloy. Matter of fact, this antithesis is so marked that even lead base paint is prohibited in a Klaksite manufacturing plant. Jim Harvey, inventor of the Prot-X-Bore Bullet, decided that this very characteristic of lead and zinc might be put to advantage if the two metals could be put together "cold" and hence, his now famous zinc base bullet. In this way, each bullet leaves a minute layer of zinc in the barrel upon which the next bullet "rides." And so we have a super accurate pure lead bullet that can be shot at better than magnum hand gun velocities without leading the barrel, and with a gas check that cannot fall off.
The secret of accuracy in Prot-X-Bore Bullets is the precision machined base, always uniform in all dimensions and completely reliable. These zinc bases, which resemble washers, are held on to the bullet by an integral conical rivet head of lead which is formed by extruding the lead through the base on swaged bullets. On cast bullets the moulds have a groove for holding the zinc base, to be cast directly on to the bullet.
Prot-X-Bore bullets shoot without leading at highest pistol and revolver speeds, provided only simple precautions are taken.
Revolver and pistol barrels vary in smoothness of bore and bore coatings, according to their age and the kind of alloys previously shot through them. If your bore is smooth and clean, it may not require any the the following precautionary measures.
A revolver barrel whose pores are filled with a tin lead alloy or copper alloy such as gilding metal are susceptible to mild leading from the first few Prot-X-Bore bullets that are shot through them. In many cases bores will be found that will take full velocity loads with no signs of lead smooches from the first bullet on. We have found that in some handguns it is entirely possible to switch from jacketed bullets or tin alloy bullets to Prot-X-Bore bullets without the slightest sign of leading.
However, we advise thoroughly cleaning your barrel before starting to shoot Prot-X-Bore bullets.
A thorough cleaning and low velocity initial loads are all that ninety percent of handguns require. They quickly acquire a bright, hard, coating of zinc. The barrel is then said to be SHERARDIZED. Initial rounds may show dark streaks after one shot and disappear after the next. Therefore, we advise that you watch the bore closely for the first fifty to one hundred rounds, brushing out the lead smooches as they occur.
Every serious pistol and revolver shooter should avail himself of a low powered jeweler's eye glass for inspection of his handgun bores. By proper manipulation of the eye glass, the entire length of these short barrels can be minutely inspected. The naked eye, no matter how good, is not capable of doing a thorough inspection job.
Prot-X-Bore bullets do not require lubrications in a properly sherardized barrel. A small amount of lubricant during the "breaking in" period is helpful in certain barrels. If you want to lubricate during the sherardization period, it may be applied to cast bullets during sizing. To lubricate swaged bullets, point the inside of the case neck with a little "Rig" or other bullet lubricant. Use grease wads only with light loads. Due to fast twist and roughness of new bores, the Super 38 ACP and the 9MM Luger are the most difficult bores to sherardize, sometimes requiring up to a hundred lubricated Prot-X-Bore bullets.
We have yet to see an "offender" that could not be sherardized and once conquered (coated) the gun will shoot thousands of rounds without more than an occasional swabbing and cleaning. Furthermore, a zinc coating is a excellent protection against moisture corrosion."
(The above is reprinted from the Lakeville Arms Company brochure from the early 1950's.)
Here at Hawk we are always intrigued with the current and past work in the field of bullets. For years Hawk founder, Bob Fulton, used the Prot-X-Bore bullets in an array of firearms. He enjoyed them and liked the results he attained. After Jim Harvey passed, a change was made to the zinc base (they were made just under bore diameter). This negated the advantages of the base and allowed gas to cut the sides of the lead bullet and left lead fouling.
Despite correcting the problems subsequent companies serviced the old Lakeville Arms Company customers and never really promoted the bullets to a growing reloading population. Hawk has improved on Jim Harvey's original concept and plans to publicly offer the Prot-X-Bore bullets to hand loaders again.
While the Prot-X-Bore bullets aren't the answer to every shooting situation they are very unique and highly advantageous under some situations.
Extensive research has identified basic rules for the Prot-X-Bore bullets:
Zinc will only sherardize to steel with a maximum build up of a 1-3 mil coating. This will not harm your firearm's performance from build-up.
To Quote Marks Mechanical Engineers' Handbook "The most effective lubricants for non-fluid lubrication are generally those which react chemically with the surface and form an adhering film that is attached to the surface with a bond."
The coefficients of friction for dry surfaces depend on the materials sliding over each other and on the finished condition of the surfaces. Next we must consider the rubbing speed relating to the coefficient of sliding friction. The coefficient of friction is approximately independent of the rubbing speed, when the speed is sufficiently low so as to not affect temperature of the surface; at higher velocities, the coefficient of friction decreases as the velocity increases. Zinc, sherardized in a bore is one of the few metals that impart an improved lubricity in a bore. The friction coefficient of zinc is the lowest metal at just .21.
Zinc material is produced with varying percentages of lead, iron, and cadmium. Subtle differences between grades of zinc can produce greatly different results. Further investigation reveals one grade, the purest, most refined stands out for the production of the zinc gas checks in the Prot-X-Bore bullet. This grade possesses a high ductility factor, chemically bonds to the bore (like a good lubrication should) and remains on the bore, bright and shiny. One of Harvey's predecessors used the cheapest composition of zinc material (least refined having high iron) to lower production cost but the zinc base became considerably harder to sherardize a bore and actually became brittle in low temperatures, the attained sherardization would lift from the bore with each shot taken at below freezing temperatures.
A bore that is properly sherardized will shoot all bullets more accurately (cast bullets, jacketed, 1/2 jackets, etc).
The Prot-X-Bore's zinc base must make contact with the bore to seal the gas behind while scraping the bore clean and running the length of a barrel.
Prot-X-Bore bullets usually give best performance when they are at least .0005" larger than groove diameter. This assures a snug fit in which the zinc base gives "piston ring efficiency". Bullets made up to .002" larger than bore grove diameter still give good results without undue pressures.
Increasing barrel length eventually reaches a point that the zinc base has eroded and no longer protects the bullet from gas or scrapes the bore clean. Pistols and revolvers have barrel lengths that work fine. Some rifles may perform well with the Prot-X-Bore bullets but it's a case by case proposition.
Shorter bullets may work in a barrel when longer bullets won't. If you are shooting the Prot-X-Bore just to treat your bore the shorter bullets are your best choice.
Adding an additional zinc base can sometimes improve your bullet's performance in a particular bore.
Using certain nose punches it is possible to make a Prot-X-Bore bullet having a zinc base and a zinc disc on the forward shoulder.
During the initial sherardization process lube may be applied to the side of the bullet using your fingers or rolling them on a lube pad to lightly coat them.
The addition of a grease wad can aid a stubborn bore.
If a crimp is desired the Prot-X-Bore bullets should be seated and then crimped in a separate operation to avoid expanding the soft lead shoulder of the bullet. Seating and crimping in one operation can allow the exposed shoulder of the bullet to expand three to five thousandths. (Using two seating dies in a progressive press greatly speeds up this operation)
If one chooses to make a zinc base bullet having an alloy of tin or antimony the bullet should be sized to .0005" larger than groove diameter. We would use this as a last resort if you wanted to shoot a long rifle barrel.
Hunting with the Prot-X-Bore bullets can be rewarding. For varmints the hollow points loaded to high velocities are particularly destructive. On deer the solid nose having pure lead to insure a proper mushroom is ideal. Those loading for deer in bear country should make Prot-X-Bore bullets of heavier weights. Among the shooters we spoke with that make Prot-X-Bore bullets and hunt with them, many have at one time or another taken bear with them seeing good terminal performance, usually a treed or baited scenario. For many applications we cannot recommend a better bullet for hunting. It's tough to beat a pure lead bullet at pistol velocities on light game.
Pope barrels (those having a subtle choke in them) have the greatest chance of desirable results.
By swaging the Prot-X-Bore bullets yourself you determine the weight bullet you'd like to make. We have found good results with 106-156 grain 38 caliber bullets, 158-220 grain 44 caliber bullets (170 hollow points being top's in accuracy), and liked the 190 grain Prot-X-Bore best in the 45 caliber.
Testing the Prot-X-Bore bullets in a number of guns proved interesting.
1. A 44 Mag that never really shot great was tested. By 30 shots both ends had a beautiful mirror-like zinc coating. The middle however, had a grey oblong spot on one side. Accuracy was nothing to marvel over. Inspection revealed the barrel had a minute bend in it that was never detected before.
2. A 38 Special was sherardized by the 15th shot and gave 2" groups at 25 yards.
3. Sherardizing a 444 Marlin carbine proved difficult with a 300 grain Prot-X-Bore bullet, but using 240 grain Prot-X-Bore bullets worked fine.
4. A 30 caliber Contender barrel of 16" length would only sherardize the first 12" of the bore. When a second zinc Base was added to the forward shoulder the complete barrel was treated.
5. A 45 caliber pistol was not cleaned prior to using the Prot-X-Bore bullet and refused to sherardize until existing lead fouling (heavy fouling) was cleaned.
6. Another 45 caliber pistol shot over 1000 190 grain Prot-X-Bore just splendid with no cleaning. This bore required 30-35 shots to fully coat the bore with the shiny zinc that now gives superb accuracy. Half-jacketed bullets were next made from the same die being slightly over .452"; they, too, shot better than 2" groups.
7. Good results were attained from a 44-40 with 185 grain Prot-X-Bore bullets.
8. 2" groups @ 25 yards from a 44 Special that was sherardized in 12 shots. Additional loads using the 220 grain bullets proved even tighter groups could be found.
9. A 30 Remington rifle was shooting 3" groups with a hand loaded jacketed bullet. It was completely sherardized using 110 grain bullets and zinc washers on the base and forward shoulder. Switching back to the jacketed bullets, they now grouped 1 1/4".
10. Sherardizing a 32 ACP proved easy with Prot-X-Bore bullets miked at .310".
11. On the tenth shot you could see the beginning of sherardization at the breech of a 30 Luger. Twenty shots covered the lands and 70-75% of the grooves. Complete 100% coverage was visible on the 40th shot. Bullet used measured just over .309".
We are aware of many guns that were sherardized years ago and have fired thousands of bullets through those bores and today the sherardization looks like a mirror.
Many older Lyman molds were made to cast the zinc gas checks onto the bullet as cast and are still being used today. The press and tooling used by Hawk is the same tooling Jim Harvey used and will produce applicable gas checks for these molds. Additionally many swaging dies have a special base punch to add a rivet that will fasten the gas checks to the bullet's base. Such dies will make splendid bullets with our pure zinc gas checks.
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