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>> Muzzleloader Fire Lapping :: By Marshall Stanton on 2004-03-12
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Firelapping Muzzleloaders For Accuracy

The process of firelapping both fixed-chamber firearms and revolvers has become a relatively commonplace procedure in recent times. The advantages of firelapping are many, not limited to enhanced accuracy, reduced projectile fouling deposits in the bore, and modest increases in velocity. Perhaps the most dramatic improvement in firearm performance is gained in those guns shooting primarily cast alloy projectiles. The process is straight forward, well established, relatively simple to perform, and an inexpensive enhancement that any handloader may easily accomplish.

A couple of years ago, I was tinkering with, and making many odd utterances to, a very stubborn muzzleloader that was destined to accompany me on a late season Idaho muzzleloader-only elk hunt. The rifle, I decided, was an incurable problematic child, to say the very least. No end of coaxing, encouraging, pampering or threatening improved the downrange performance of this front-stuffer to any appreciable gain. The rifle of interest, an early ‘70’s CVA Mountain Rifle, with a 1:72” twist in .58 caliber became an earnest stumbling block to this black powder enthusiast. I had adopted this rifle out of an abusive family, where its previous owner practiced little or no after-shooting sanitation, and an ugly reddish-brown rusted bore greeted me when it came home. Lots of scrubbing, brushing and soaking took place, investing lots of time to restore this fine old gun to shooting form. However, there still remained, even after the rust was removed, a very fine, micro-pitting of the entire bore interior.

In feeding this traditional styled smokepole, about every conceivable combination of powders was tried, FFg, FFFg black powders, Goex, Swiss and Elephant were all lovingly poured down the barrel in varying charge weights, along with a sampling of the various Pyrodex powders in their various granulations, as well as Triple-7 and even some old Black Canyon powder that was still sitting in the powder magazine. This array of propellants was combined with both pure-lead and alloy round balls of both .562” and .570” diameters, and patching material from .007” to .021” in thickness, varying in material ranging from pure cotton to pure Irish linen. Too, lubricants were varied, from a straight saliva-dampened patch, to commercial preparations ranging from traditional moose-milk and Bore-Butter, to Crisco, lard and both deer and bear tallow.

The expertise of those more experienced and more knowledgeable was solicited, and spent patches examined, whereupon some changes to the loading and feeding of the gun were made, but to no avail. Over-powder wads and patches came into use in conjunction with variances in patching thickness and lubricant application. The very best fruit of all manner of experimentation yielded about eight inch groups at best at 75 yards. In absolute frustration, I tabled the project until after elk season ( I hunted with a different muzzleloader that year), and resumed my frustrated experimentation with this rifle through the winter months. Still, no positive outcome, and yet another primitive-weapon Idaho elk season passed without this gun in attendance to the festivities.

Finally, last spring, as I was slugging the bore of this gun with an oversize oval-egg sinker of appropriate size, to once again ascertain the land-to-groove dimensional relationship, I finally became conscious of something that had always been there, but I’d never given a moment’s thought to in the least: under each and every dovetail cut into the barrel, there was a significant barrel constriction, and the soft-lead oversize sinker would slide through the bore, and stubbornly get stuck at each of the dovetail locations. When the light-bulb finally came on, I quickly dragged several more muzzleloaders out of the safe, and eagerly slugged each of them as well. EUREKA!!! Each and every one of those guns had SIGNIFICANT constrictions under each and every dovetail cut into the barrels.

This gun also had some extensive damage to the lands, within one inch of the muzzle apparently from a previous owner either driving something down the bore with a hard steel object, or perhaps trying to extract something stuck in the bore with somewhat crude means. Not only was the bore damaged there to a serious extent, but the crown on the muzzle was badly damaged as well. Rather than cut the barrel and recrown, and also recut the font sight dovetail after amputation, I decided instead to cut a false muzzle in the rifle, much as Thompson Center does to many of their current production guns, thus both preserving the aesthetics of the rifle, but alleviating the issue of the damaged bore, and the recrowning issues all at once. A quick trip to my lathe with the four-jaw chuck installed, and a boring bar made short work of this little chore, and the finished product also made loading a patched roundball a snap!

My thoughts quickly turned to the reasons why we firelap barrels in cartridge guns: to eliminate barrel constrictions and smooth the barrel by lapping out imperfections. So, it stands to reason that of we could firelap the muzzleloader barrel and eliminate the constrictions in the bore, that not only would accuracy be enhanced, but perhaps fouling from the black powder residue deposited in the barrel might be reduced as well. Of course, jamming an oversize, lap-compound charged bullet down the bore is out of the question with a muzzleloader, so another solution had to be found.

I’ll outline the process below, but suffice it to say, that after a fair bit of tinkering, a method of firelapping these muzzleloaders was achieved, and the results speak for themselves. As for the .58 caliber problem child? Let’s just say it was properly disciplined, and the behavior modifications were most gratifying!!! Subsequently, I wasn’t convinced that success with lapping one gun demonstrated anything conclusive, other than it succeeded in curing one poorly performing muzzleloader. As time and weather permitted, I began an ongoing regimen of shooting five muzzleloaders for record with a number of charges and projectiles, then lapping each gun with the process outlined below, and shooting the guns using the same combination of components as prior to the lapping procedure. The results are listed in the chart at the end of this article.

The five guns employed in this investigation were as follows:

.58 Caliber CVA Mountain Rifle, this is a traditional sidelock percussion rifle, with four constrictions in a fairly rough (rusted, micro-pitted) bore. This gun has a roundball twist of 1:72” and is of a mid 1970’s production vintage, sporting a one-inch octagonal barrel with two barrel wedge pins retaining it into a maple halfstock. This rifle has rather primitive sights, the front being a simple wedge of German silver, both sights are dovetailed into the barrel. Constrictions existed. The unique history for this gun is given above.

.50 Caliber T/C Greyhawk Rifle, an all stainless steel, round barreled sidelock percussion rifle that was manufactured by Thompson Center in the mid-1980’s. The round barrel is retained by a single wedge pin into a factory synthetic halfstock. This rifle has always had a very smooth bore and shot reasonably well. Loading a tight patched roundball characteristically is punctuated by brief hesitation under the wedge-pin tenon dovetailed into the bottom of the barrel. The front bead sight is dovetailed into the top of the barrel, but this barrel sports T/C’s proprietary QL muzzle, having an integral false muzzle cut in the crown of the barrel, so there wasn’t an issue with the front sight creating a constriction in this barrel. Powder fouling in this gun necessitated wiping between each successive round for acceptable accuracy, and if loading without wiping, after three rounds it became nearly impossible to force a fourth projectile down the muzzle without several cleaning patches to sanitize the bore.

.50 Caliber T/C Renegade Hunter, a one-inch octagon blued barrel model with single trigger, also a mid-1980’s production gun. This barrel sports a blade front sight dovetailed into the top of the barrel, a screwed on click adjustable rear sight, and a single wedge pin retaining the barrel in the American walnut halfstock. This barrel is remarkably smooth, but had two nasty constrictions that really showed themselves when loading tight fitting conicals. These tight spots of course were under the dovetailed front sight, and the dovetailed barrel-wedge tenon. This rifle is a newcomer to my stable, and the only shooting it received was a cursory diet of my established regimen of powder and projectiles prior to lapping. During the initial shooting the gun showed a tendency to shoot reasonably well, and wasn’t nearly as sensitive to powder fouling as was the stainless Greyhawk.

.54 Caliber CVA Mountain Stalker, a 7/8” octagon blued barreled rifle with single trigger. The barrel of this rifle is secured by a single wedge pin into a synthetic halfstock, and is dovetailed for both a post front sight as well as the primitive rear sight. This gun also has a dubious past, and prior sanitation and moisture barrier coatings were minimal at best, thus the barrel was less than pristine, but not pitted to any significant degree either. Shooting of this rifle revealed mediocre accuracy and the barrel necessitated a ritualistic wipe of the bore between shots to facilitate cleaning. Slugging of this bore revealed the expected constrictions at both dovetail sight locations as well as the dovetailed wedge pin tenon on the underside of the barrel also.


.54 Caliber Knight BK85 blued inline rifle with synthetic sporter stock. I won this rifle in the mid-1990’s in a big-buck contest, and it has seen very little use. The bore is very smooth, loading easily without the slightest hint of barrel constriction. The barreled action is attached via an allen-head screw through the stock into the forward part of the action itself, thus there are no wedge-pin tenons, and since both front and rear sights are screwed to the action there are no dovetails whatsoever cut into the barrel. As such, there are no perceptible constriction points in the barrel. While this has always been an amazing shooter, it’s predisposition to powder fouling previously demanded wiping the bore between shots.

The described points of description are identified in this photo”

The process for lapping a muzzleloader follows exactly that of preparing a cartridge gun for the same procedure. The bore must be squeaky clean as a first pre-requisite. Preparation of the lapping bullets is precisely the same as that described in the Beartooth Bullets Technical Guide and key to the success of the lapping project is the proper projectile. The heart of the matter is the bullet design, and harness as well as the choice of lapping compounds. The bullet employed for firelapping the muzzleloader is a hollow-based mini, with a thick skirt, but here, not any cast mini will function for a firelapping projectile. The bullet MUST be of a BHN (Brinell Hardness Number) 11-12. No harder, and no softer. A softer bullet allows the lapping compound and it’s abrasive to totally imbed into the soft bullet, thus negating the effective lapping action of the compound. A harder bullet will not expand the skirt of the bullet properly with the pressures generated by the comparatively low pressures generated by black powder.

The reasoning behind the hollow-based mini is that the bullet expands to entirely fill the bore upon ignition of the black powder loaded under it. Thus the lapping bullet, carrying its abrasive compound, is forced fully into the bottoms of the grooves of the rifling in the muzzleloader bore, and consequently both the tops of the lands and the bottoms of the grooves are unilaterally lapped at nearly the same rate. As the firelapping bullet encounters barrel constrictions during its passage through the bore, those tight spots will receive a more aggressive lapping action than will the remainder of the barrel. Since muzzleloading barrels are not the same harness as those of centerfire cartridge guns, the constrictions are removed quite readily, and in each case of these test guns lapped no more than twenty lap loads were required, even for the tightest of constricted barrels.

Preparation of the lapping bullets is made by imbedding a 320 grit silicone carbide lapping compound mixed in a high lubricity carrying agent (Beartooth Bullets Lapping Compound), into the surface of the lapping bullet, by rolling the bullet between two steel plates that are coated with the lapping compound. Very firm downward pressure must be exerted on the bullet when rolling between the plates to ensure the lapping compound is embedded into the BHN 11 bullet. Roll the bullet until the surface, when wiped off with a paper towel is a dark charcoal grey color. It is immediately apparent where the lapping compound is embedded into the lead, and if all bearing surfaces are not a uniform charcoal grey color, continue rolling the bullet between the steel plates, and adding lapping compound as necessary until the desired appearance is attained. The time required to prepare each bullet in this manner will be somewhere between three and seven minutes with aggressive rolling of the lapping projectile.

The reader will notice that BLACK POWDER has been specified for firelapping muzzleloaders. The reason is this: the black powder substitutes, while generating the same basic pressures as that of original black powder, do so with a pressure curve that more closely resembles modern smokeless powders, where the pressure rises in an exaggerated bell-type curve, and doesn’t reach peak pressure until the projectile is well on its way down the bore. Consequently, the black powder substitutes do not expand the skirt of that lapping bullet until it is partly traversed the barrel, thus no effective lapping action takes place in the barrel for that portion up until the skirt expands when full pressure finally hits the bullet. Contrast that with the quick “swat” that real black powder develops, where pressure is almost instantly spiked upon ignition, and the skirt of the hollow based lapping bullet is immediately expanded, fully engaging the barrel and lapping the bore uniformly throughout its entire length.

Powder charges for lapping purposes, using the hollow-based minis that Beartooth Bullets supplies, in BHN 11, optimally perform when loaded using 40-60 grains of FFFg black powder. The specification of the FFFg granulation too is purposeful. The finer granulation of FFFg powder will spike pressure more quickly than FFg, and underscores the same reasons as why black powder over any of the many substitutes that are currently available. The reasons are the same. Too, the powder charge needs be sufficient to reliably expand the skirt, but develop no more velocity than absolutely necessary. It is a very fine line, and the charges necessary will vary depending upon the caliber of gun, the twist rate of the barrel, and the dimensional tightness of the bore. Loading of the BHN 11 lap-charged projectiles will be slightly difficult, requiring an abnormal amount of pressure on the ramrod to seat them due to their hardness, and the resistance encountered due to the embedded lapping compound. Although it is somewhat difficult seating the lapping bullet, be absolutely positive that the bullet is resting firmly upon the powder charge before capping the nipple. The slightest space between the projectile and powder can be not only detrimental to the bore, but potentially hazardous as well.

Swab the bore of the barrel thoroughly between each and every lapping bullet sent downrange! This is critical to effective lapping action in the bore, as you don’t want to be lapping against, or over fouling remaining in the bore from a previous shot. Too, use a tight-fitting bore brush to thoroughly brush the bore to loosen any stubborn debris that a damp patch might leave behind. Repeat this process of loading/shooting and cleaning for twenty sequences, and any constrictions in the bore of the muzzleloader will be totally lapped out, and any anomalies in the barrel smoothed and eased.

Finally, after all twenty lapping bullets are fired, and the barrel once again cleaned thoroughly, make a polishing bob for the barrel out of an undersized bore-brush tightly wrapped with a loose weave cotton cloth (Tee Shirt material works well here), then totally soak and impregnate the cotton bob with the same lapping compound used on the firelapping bullets. Then, using a bore-guide muzzle protector run that lap compound saturated polishing bob up and down the bore one hundred strokes, where an up-and-down cycle counts as one stroke. This is critically important, and not a step to overlook or to skip, as it is an absolutely essential step to the finishing process. Briskly run the polishing bob in and out of the barrel, and occasionally the cotton cloth will need replacement as it will literally disintegrate from the friction and heat generated, and from the abrasive action of the lapping compound. When replacing the cotton cloth, follow the earlier steps for preparation, and then resume the polishing task.

Once the polishing phase of this project is complete, thoroughly clean the barrel. First, by using some brake and clutch cleaner in the barrel, following with a tight patch, repeating this sequence until such time that the patches begin coming out pretty much clean. Then, use a traditional hot water cleaning technique with the addition of a grease cutting dishwashing liquid pumped in and out of the barrel using a tight fitting patch on a jag, while the breach end of the barrel is in a can or bucket of the hot sudsy water. Follow this with a clean, hot water rinse using the same technique. Dry the barrel with clean patches, then protect with a good quality moisture barrier, whether that be petroleum or natural based, just make sure the bore is protected.

This process was performed on the five test subject muzzleloaders, without variation. The shooting results listed below in the table are the composite sum of all the data collected. The information for this article was a project that evolved over quite a long period, due to the extreme time consuming nature of this kind of work, and the pace inherent with shooting black powder arms in general. Consequently, the data here wasn’t all fired under the same atmospheric conditions, temperature, lighting conditions or humidity. Some these loads were fired in snowstorms, rainstorms, days below zero and days that were nearly a hundred degrees in temperature. However, due to the positioning of our company rifle range, which sits in a natural draw, we rarely, if ever have any wind to contend with, even on very blustery days, so wind was never an issue in firing this data. This information is presented so that the reader may better interpret the findings here, that they are not absolutely conclusive, but are rather the representative culmination of much time spent in testing under many varied conditions, any one of which could have altered final outcomes of groups fired from any given gun.

This group fired from the .58 Caliber CVA Mountain Rifle which spawned this whole exploration (after firelapping). Distance was 75 yards.

In this photo is an interesting composite group fired from the post-lapping T/C Greyhawk. It is ten shots, with loads of 70 grains, 80 grains and 90 grains of FFFg black powder, behind a .015” pure linen patch, lubed with deer tallow, and a .490” BHN 11 round ball. After lapping all three loads basically shot into the same group. The coarse bead front sight on this rifle makes fine shooting difficult. Fired at 75 yards.

A neat little cluster created at 75 yards using 120 grains of FFFg black powder and a Knight MML Magnum sabot and Beartooth .430”-325g LFNSSBB ML bullet. This is a post-lapping group fired with the receiver sight pictured on this rifle.

The data in the table below was developed using pure lead round balls, of the specified diameters listed, and employing .015” pure linen patches lubed with deer tallow. Powder was FFFg Goex, all percussion caps were CCI No. 11 magnum except for those loads in the T/C Greyhawk which used RWS #1018FL musket caps. Nipples were all HotShot nipples, except for the T/C Greyhawk which utilized a T/C ¼”-28 tpi musket nipple.

All groups measured with a stainless steel dial caliper.


CVA .58 Caliber Mountain Rifle 1:72" Twist

Projectile

FFFg Black Powder Charge

Group Size Before Lapping

Group Size After Lapping

Yardage

.562" RB

80.0g

8.79"

2.73"

75

.562" RB

90.0g

7.96"

2.83"

75

.562" RB

100.0g

8.84"

2.64"

75

.562" RB

110.0g

9.26"

2.77"

75

T/C .50 Caliber Greyhawk Rifle 1:48" Twist

.490" RB

70.0g

4.98"

2.14"

75

.490" RB

80.0g

5.17"

1.96"

75

.490" RB

90.0g

5.64"

2.28"

75

.490" RB

100.0g

5.56"

2.31"

75

370g Maxi

80.0g

4.22"

2.04"

75

370g Maxi

90.0g

4.24"

2.38"

75

370g Maxi

100.0g

3.86"

1.73"

75

370g Maxi

110.0g

3.55"

1.52"

75

T/C .50 Caliber Renegade Hunter 1:48" Twist

.490" RB

70.0g

3.97"

2.24"

75

.490" RB

80.0g

4.06"

2.21"

75

.490" RB

90.0g

4.42"

2.28"

75

.490" RB

100.0g

4.38"

2.78"

75

370g Maxi

80.0g

4.21"

1.97"

75

370g Maxi

90.0g

4.43"

1.83"

75

370g Maxi

100.0g

3.39"

1.62"

75

370g Maxi

110.0g

2.87"

1.55"

75

CVA .54 Caliber Mountain Stalker 1:48" Twist

.530" RB

70.0g

3.42"

2.89"

75

.530" RB

80.0g

3.36"

2.74"

75

.530" RB

90.0g

3.42"

2.52"

75

.530" RB

100.0g

3.77"

3.12"

75

430g Maxi

90.0g

4.19"

3.87"

75

430g Maxi

100.0g

3.87"

3.24"

75

430g Maxi

110.0g

3.15"

2.74"

75

430g Maxi

120.0g

2.89"

2.26"

75

Knight .54 Caliber BK85 1:28" Twist

.530" RB

60.0g

2.42"

2.26"

75

.530" RB

70.0g

2.89"

2.64"

75

.530" RB

80.0g

3.54"

2.94"

75

.530" RB

90.0g

4.57"

3.49"

75

430g Maxi

90.0g

2.49"

1.86"

75

430g Maxi

100.0g

2.18"

1.74"

75

430g Maxi

110.0g

2.49"

1.56"

75

430g Maxi

120.0g

2.09"

1.42"

75

280gWFN/Sabot

100.0g

2.16"

1.18"

75

280gWFN/Sabot

110.0g

1.87"

1.24"

75

280gWFN/Sabot

120.0.g

1.74"

1.18"

75

280gWFN/Sabot

130.0g

1.78"

1.12"

75

325gLFN/Sabot

100.0g

1.98"

1.78"

75

325gLFN/Sabot

110.0g

2.10"

1.68"

75

325gLFN/Sabot

120.0g

1.87"

1.22"

75

325gLFN/Sabot

130.0g

1.79"

.94"

75

Interestingly, as a side benefit to the fire-lapping of these muzzleloaders, each and every one of them, except for the Knight BK85, showed a remarkable change in the amount of powder fouling deposited in the bore of the guns. Those muzzleloaders which required mandatory cleaning between each shot fired, or between every three shots in order to maintain accuracy and facilitate loading became much more user-friendly. The .58 Caliber CVA Mountain Rifle can virtually be fired all day without cleaning between shots, something not possible before lapping. The two T/C .50 caliber rifles may be fired with patched round balls multiple times before fouling necessitates swabbing the bore, and the Traditions .54 caliber rifle, while not an all-day shooter without cleaning, it too exhibited marked improvement, and now, under field conditions doesn't require cleaning between shots for those number of rounds likely required in a hunting scenario.

Although the lapping of these guns resulted in solid gains in accuracy after lapping, the process is entirely worth the expended effort just for the gained attributes of ease-of-loading, and the reduction in blackpowder fouling.

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