Photos & Story
by Toby Bridges
Contributing Editor

You have to feel kind of sorry for today's modern muzzleloading rifle makers and saboted bullet suppliers. They work hard to bring us rifles and recommended loads that will deliver great accuracy at 2,100 to 2,200 feet-per-second (fps), and before you know it there's a group of shooters screaming . . . "We want to shoot at 2,300 fps!" But, that's just the price of being in the muzzleloading business these days.

The muzzleloading market is driven by satisfying modern-day big game hunters, and they now seek all the speed, range and knockdown power that is absolutely possible from a muzzleloaded rifle. Now, it hasn't been that long since velocities of 1,900 fps were considered "fast" for a modern .50-caliber in-line muzzleloader stuffed with a hot 150-grain charge of Pyrodex Pellets and a saboted 200- to 250-grain bullet. Today, if a rifle and load can't top 2,000 fps, it isn't worth talking about!

Back in 1984, when Del Ramsey of Harrison, AR, introduced the sabot system to muzzleloading shooters, the polymer used in his early Muzzleload Magnum Products (MMP) sabots did good to stand up to enough pressure to get a 250-grain bullet out of the muzzle at more than 1,700 fps.

Fortunately, the polymer composition has gotten tougher and tougher over the years. Still, it is not uncommon to hear shooters still exclaim that the sabots simply won't hold up to today's hotter charges. And, that's probably true since we're a never satisfied lot, continually trying to get our modern in-line muzzleloading rifles to shoot faster and farther than any muzzleloaded hunting rifle of the past.

Shooters ask an awful lot of the tiny plastic cup that must serve two purposes. First, the sabot actually grips the bullet tight enough in order to transfer the spin of the rifling to the projectile. Secondly, it must seal off the rapidly expanding gases caused by the burning (exploding) powder charge that propels the sabot and bullet down the bore. If the polymer sabot fails even slightly in either regard, accuracy will suffer.

More and more, shooters are loading with hot 150-grain compressed pellet charges (Pyrodex and Triple Seven) to attain 2,000+ fps velocities from a No. 209 primer ignited in-line rifle like the Thompson/Center Arms "Omega" or the new Knight "Revolution." Some are even loading massive amounts of loose grain FFFg Triple Seven to get light 200-to 220-grain bullets out of the muzzle at 2,200 to 2,300 fps-and faster.

I know of one major sabot bullet supplier that has done extensive pressure testing with 150-grain Triple Seven Pellet charges and has found such loads with a 250-grain bullet do produce internal barrel pressures right at 29,500 psi. That's about twice the amount of pressure the sabots of the early 1990s could withstand.

And even as good as today's sabots have become, there is still a limit to how much pressure the polymer material can hold back. And when the sabot lets go, all hopes of maintaining any degree of accuracy goes with it.

If your favorite muzzleloading hunting rifle is not grouping saboted bullets well, or at all, take a few minutes to look for the sabots that you're loading. What you find can tell you a lot about what your rifle and load are doing . . . or not doing.

Sabot Failure
A major problem with loading and shooting heavy 150+ grain charges of Pyrodex or Triple Seven, in pellet form or loose grain, is that such charges tend to heat up the barrel quickly. And the warmer the outside temperatures, the faster that barrel becomes "hot." Once inside a hot barrel, the plastic (polymer) material of the sabot becomes softer and less resilient the longer it is left in the bore. And when it does, it also becomes more prone to being "blown" by the higher pressures generated by these hotter loads.

So, if you find that the first couple of shots out of your rifle print relatively close to one another, and the third suddenly jumps four . . . five . . . six or more inches from the first two, there is more than a good chance that you've just experienced "sabot failure."

Take a few minutes to look for and recover your sabots. This can be tough at a public range where lots of muzzleloading shooters do considerable shooting. For that reason, I spend a great deal of time shooting on private property, where I've established a 50- and 100-yard range . . . and where I can police my sabots after every couple of shots.

If all you can find are bits and pieces of sabot, or a stringy blob that was once your sabot, your powder or charge is creating way too much pressure. As already pointed out, as often as not, this is compounded by a barrel that's too warm.

Allowing the barrel to cool down sufficiently between shots sometimes remedies the problem. And barrels tend to cool a lot quicker when it's in the 30s and 40s than when the temperatures are above 70 degrees. In really hot weather, it can mean letting the rifle sit for 15 or more minutes, in the shade, between shots.

A heavier bullet will also create higher pressures. A maximum or near maximum load that shoots well with a 250-grain bullet may blow the sabot every time if a shooter switches to a 300-grain bullet. I've found this especially true with many of the smokeless loads that can now be shot out of the Savage Model 10ML II.

Get into the habit of picking up your sabots whenever you can. Even if they appear to be fully intact and relatively clean, closely study the inside of the gas-seal cup at the base of the sabot. Be sure to check the edges of the skirt. Rifling that is too deep will show up as tiny gas cuts between the marks left in the plastic by the lands of the rifling.

Likewise, when a powder charge is pushing the limits of the plastic sabot, stress cracks or breaks will begin to show around the edges of the skirt where the plastic is thinnest. The smart shooter will then do one of two things . . . either back off of the powder charge slightly-or load a sub-base between the powder charge and sabot/bullet combination. The latter provides added protection for the sabot from excessive pressures of hotter powder charges. Either of these approaches will help to eliminate those unexplainable fliers.

Finding a suitable sub-base for the popular .50 caliber is relatively easy. For the past couple of years, a number of Savage Model 10ML II shooters have simply been cutting the gas seal from the rear of a 28-gauge Winchester "AA" plastic shotgun wad, then loading just this cup over the powder charge. The sabot and bullet are then seated right down on top of this. The arrangement works very well, allowing these shooters to maintain great accuracy even when the weather turns hot.

New Sub-Base
Muzzleload Magnum Products, who brought us the muzzleloading sabot system in the first place, has taken the idea to the next level, developing the Ballistic Bridge Sub-Base. The rear of this sub-base looks somewhat like a deep sabot base, while the top area features a slight dome that fits right up inside the base of the sabot that holds the bullet.

The MMP sub-base works so well that it becomes the primary seal, and the sabot simply becomes the bullet carrier. The base of a recovered sabot that was pushed down the bore by one of the new sub-bases usually looks as if it has not even been shot.

With most of today's loads, a sub-base is not needed. Regardless of the type of powder recommended for a rifle, recovered sabots should have most, if not all, of the petals intact (unless pushed from the muzzle at more than 2,300 fps) and the cup at the rear of the sabot should be slightly flared. Minimal burning or gas erosion should be evident along the thin lip of the skirt.

If your sabots look good, but accuracy is still far less than desirable, maybe it's time to weigh your bullets to check for significant weight variation from bullet to bullet. If you are shooting Pyrodex Pellets or Triple Seven Pellets, run these across the scales as well. I've found as much as a 7-grain variation with 150-grain pellet charges, which can and will affect accuracy.

Higher Velocities
With today's higher velocity loads (upper 2,100 to 2,300+ fps) the petals or sleeves of a sabot are often torn off due to how rapidly they peel back once the bullet and sabot exit the bore. Occasionally, this does affect accuracy, but this happens after the sabot and bullet have already exited the muzzle. Still, if just one or two petals/sleeves separate from the base the very instant the bullet and sabot leave the bore, it is possible that the tipping of the sabot could make slight contact with the projectile, affecting bullet flight.

Trying to get upper end velocities with saboted soft lead projectiles often creates a new problem for the muzzleloading shooter. When the sabot and bullet are suddenly hit in the rear by all of the pressure created by magnum charges of Pyrodex or Triple Seven (and especially the smokeless loads shot in the Savage Model 10ML II), an all-lead bullet not only obturates more freely than a copper jacketed bullet, it also tends to bell slightly at the base.

This puts excessive pressure against the bottom edge of each sabot sleeve. And by the time the sabot and bullet reach the muzzle end of the barrel, the sleeves are very often no longer attached to the base. They have melted through due to the high friction heat caused by the added pressure where the soft lead bullet belled out at the bottom.

Sleeves or petals that are no longer attached to the sabot base will not fly too far from the muzzle. Look for them laying on the ground just four or five yards from the shooting bench. If the bottom edge of the sleeve/petal is cleanly sheared, the separation happened outside of the bore. If the plastic of the sleeve appears to be stretched, then it most likely happened inside the bore.

MMP Sabots
MMP is the leading producer of muzzleloader sabots today. Most of the company's designs intend for the sleeves to open up . . . form an airfoil . . . and pull back from the bullet. This all takes place within just inches of the muzzle, allowing the bullet and sabot to part company with as little interference as possible.

However, MMP has recently produced several different sabots in which the sleeves are supposed to break away! And these are generally sabots that allow a bullet of significantly smaller diameter to be shot out of a larger bore, such as shooting a .400-inch diameter bullet out of a .50-caliber rifle. The break-away sleeves eliminate the problem of too much plastic refusing to relinquish its grip on the bullet.

Another problem with such radical sabots is that heavier plastic isn't as strong as a thinner plastic gasket around a bullet that's closer to actual bore size. And with some of the .50x.40-caliber/bullet combinations, many shooters find that a hot powder charge (again especially smokeless loads out of the Savage Model 10ML II) often tends to blow the bottom right out of the sabot. So, if you are finding sabots with a hole blown right through the bottom, either cut back on your dose of powder or begin using a sub-base between the powder and sabot.

While pure lead bullets tend to over-obturate and bell out at the bottom, all-copper bullets can also cause problems by not obturating at all. Recently, I have done extensive testing with the new Barnes all-copper spire-point "Spit-Fire" Expander MZ hollowpoint bullets.

Blowing Sabots
With hot 130-grain charges of FFFg Triple Seven, I got the bullets and special sabots for the boat-tail design to shoot well without having to load a sub-base. But when I tried to push the velocity of the 245-grain "Spit-Fire" up over 2,400 fps with a 45-grain charge of Vihtavuori N110 out of a Savage Model 10ML II, I was blowing the sabot every time.

Since all-copper bullets fail to obturate at all, there is no sideways pressure against the sabot sleeves. And with hotter charges, this secondary seal often plays an important role.

Now, the load I was shooting generates around 40,000 psi in the Savage muzzleloader, and without the added seal of bullet obturation, the sabot base alone could not contain this kind of pressure. However, when I started loading with an MMP Ballistic Bridge Sub-Base under the "Spit-Fire" sabot, I got the velocity and accuracy I was hoping to get. The rifle and load was good for 2,420 fps, often printing three shots right at 1- inch at 100 yards.

When looking for fired sabots, most can usually be found 10 to 15 yards from the muzzle. With a slight breeze, they have a tendency to propeller off to the side now and then. Have someone watch over your shoulder to see where they land and finding them is much easier.

If you load with a homemade sub-base fashioned from the gas seal cut from a 28-gauge wad, these tend to fly out to about 25 yards. However, due to the bullet shape of the MMP sub-base, you'll have to walk out to 40 or 50 yards if you want to recover any for inspection. These should be imbedded with rifling marks and flared at the rear, but otherwise very much intact.

If you are happy with velocities of 1,600 to 1,700 fps with a saboted bullet, today's sabots are more than capable of standing up to the heat and pressure. However, if you're looking to get 2,000+ fps out of your modern in-line muzzleloader with accuracy, the sabots alone may not be able to handle the task. But by paying attention to what's happening to the plastic sabots and providing a little assistance with a sub-base, hot high-velocity loads can be tamed.