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| Copyright © Eugene Nielsen | ||
Tac OPS Tango 51:
Shorter
Barrel Defies Conventional Wisdom
by Eugene Nielson
Most precision rifles today are manufactured with 24- to 26-inch barrels. Conventional wisdom has been that it’s necessary to sacrifice maneuverability to gain a more complete powder burn and significantly reduced flash signature. As is so often the case, conventional wisdom may be wrong.
Internal ballistics is a very complex subject. Many things affect the internal performance of a given cartridge and bullet. These include the powder chamber capacity, load density, amount and burning characteristics of the propellant powder; temperature of the propellant prior to ignition; uniformity and speed of ignition; diameter, weight and bearing length of the bullet; and the length of the barrel and its interior dimensions.
Longer barrels give the powder more time to work on propelling the bullet. For this reason longer barrels generally provide higher velocities, everything else being equal. As the bullet moves down the bore, the gas pressure behind it diminishes. Given a long enough barrel, there will eventually be a point at which the bore friction and air pressure in front of the bullet will equal the gas pressure behind it. At this point the velocity of the bullet will start to decrease. There isn’t any clear-cut answer as to how much velocity will be lost per inch of barrel length reduction. The amount of loss is closely tied to the expansion ratio. As previously noted the type and amount of powder, as well as the weight and bearing length of the bullet, also play a major part. Rifles with high expansion ratios (smaller calibers) tend to lose less velocity than rifles with low expansion ratios (larger calibers).
Tactical Operation’s new .308 Winchester (7.62x51mm NATO) caliber Tango 51 rifles typify the new thinking on the subject. Tac Ops considers 18 to 20 inches to be the optimal barrel length for the urban environment , with 18 inches preferred .
During the development of the Tango 51, Tac Ops took a standard 26-inch barrel and chopped it down it to 18 inches in one-inch increments. Between 10 to 20 rounds we re fired from each increment. They found that a 20-inch barrel provides for a complete propellant burn and no velocity loss when using Federal Match 168- grain BTHP, a cartridge that has become something of an industry standard. Going to an 18-inch barrel only results in a loss of 32 feet per second (fps).
Shorter barelled rifles are more versatile, being equally suitable for both urban and rural operations. According to Tac Ops, there isn’t any need to go to the 26-inch barrel unless you want to use a heavier bullet or push the round to higher velocity using more powder. The Los Angeles County Sheriff’s Department’s Special Enforcement Bureau performed similar tests and came to similar conclusions.
Tommy Lambrecht, SEB armorer and special weapons team long rifle expert, re c e n t l y chronographed the Federal Match 168-grain BTHP rounds. Lambrecht said that with the 20-inch Tango 51 that Tac Ops delivered to him, the muzzle velocity was averaging around 2,660 to 2,670 fps.
Tango
51 Rifle with Tac Ops 30 sound suppressor.
M
A N E U V E R A B I L I T Y
Many agencies prefer the 18-inch barrel
for its added maneuverability. You’re still shooting around 2,630 fps
with Federal Match. The target isn’t going to know if he’s being
hit with a bullet traveling 2,660 fps or 2,630 fps. Going to an 18-inch barrel
doesn’t affect the accuracy.
Tac Ops has achieved incredible accuracy with the shorter barrels. The 18-inch barreled Tango 51 rifles will still shoot sub-1/4 MOA . The performance is just as good with the 18-inch barrel as it is with the 20-inch barrel out to a distance of 600 yards. After initially going with the 20-inch barreled Tango 51s, the Los Angeles County Sheriff’s Department has decided to go with the 18-inch barrel and Tac Ops 30 suppressor on all new Tango 51s that they purchase.
Shorter barrels are actually often more accurate than their longer counterparts. A rifle barrel is a cantilevered beam and as such they sag. Barrel sag induces longitudinal stress. More sag results in more whip and vibration as the bullet travels down the bore. Using a shorter, heavier barrel minimizes accuracy robbing barrel vibration, because a shorter barrel is stiffer and vibrates less.
Barrel length and contour determines the relative “stiffness” of a barrel, i.e., how much a barrel will tend to vibrate. Shorter barrels generally have oscillations of smaller amplitude than longer barrels. Thicker barrels generally have fewer vibration nodes than slimmer barrels. The ringing frequency of a thicker barrel is higher and the oscillations are of a smaller amplitude and of a shorter duration. This equates to less barrel motion at the muzzle.
The use of a shorter barrel also allow s the use of a heavier contour without making the rifle unwieldy. The use of a heavier contour tends to provide less variation between a cold shot and any subsequent follow-up shots. Barrels expand as they heat up. As the barrel expands any stress on or in the barrel will cause stringing of the shots. Bore expansion results in an increase in group size. Heavier barrels tend to be more consistent because they take longer to heat up. Shorter barrels do increase the muzzle blast and muzzle flash somewhat. However, from a practical standpoint, the differences between a 24- or 26-inch barrel and an 18- or 20-inch barrel are negligible, unless slower burning powders are employed.
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Manufacturer : Tactical
Operations, Inc., |
SOUND SUPPRESSOR The Tac Ops 30 sound suppressor is extremely compact, measuring approximately 8 inches in length with an diameter of approximately 1.5 inches. The suppressor utilizes a conical baffling system that’s virtually maintenance free and will easily last the life of the rifle. All that’s necessary to maintain the suppressor is an occasional dunking in cleaning solvent or hot, soapy water. Despite its compact size, the Tac Ops suppressor is surprisingly efficient at reducing the sound signature of the rifle. Although I haven’t had the instrumentation to actually measure the decibel reduction, I would estimate the sound signature to fall somewhere between that of a .22 LR and a .22 Magnum. Tac Ops rifles shoot extremely well, consistently producing three - round groups of 1/4 M OA or better with Federal Match, providing the shooter does his or her part. While at the range with the author and San Fernando Police Department SWAT sniper Chris Colelli, Tac Ops owner Mike Rescigno fired a three-shot group at 100 yards that measure d just under 1/1 6ths of an inch. Chris Colelli once fired a three-shot sub- 1/4-inch group at 200 yards with his department’s Tango 51. The target is now framed and hanging in his lieutenant’s office. Colelli also recently fired a three-shot group at 700 yards that measured a hair under 2 inches center to center. The group, which was witnessed by several credible spotters, was shot off a bipod with one small sandbag. |
A C C U R A C Y
I recently spoke with Max Maven, Tac Op s gunsmith, to find out how they have
accomplished this level of accuracy in their rifles. Maven, who has a considerable
background in military - related “black projects” for the
U.S. government, was quite forthright in his answers, discussing the construction
of the Tango 51 in considerable detail. According to Maven, most of the ideas
that Tac Ops has on building rifles came from the questions that they asked.
They discovered that building an accurate rifle was really an engineering
problem . One thing that Tac Ops noticed was that many sporting rifles that
we re made of old, loose military Mausers still shot extremely well. When
Tac Ops investigated, they found out that the more accurate rifles all had
snug, on-axis chambers with minimum head space. This confirmed that cartridge
alignment was critical and even more important than having a close fitting,
expensive action. Later on, while re viewing the gun literature, Tac Op s
found that the whole cartridge alignment and bullet fit issue was really
resolved by the cast lead rifle bullet crowd. They proved that a long, correctly
shaped throat and lead we re critical to accuracy. The answer to accuracy
is to get the cartridge to correctly fit the barrel and correctly fit in
the throat and keep from moving while it’s fired. Be yond that, everything
else besides the barrel is just support. For this reason, it’s really
important to remove as much of the receiver’s influence on the cartridge
as possible.
For customers with special needs, a takedown version of the Tango 51, the Charlie 51, is also available. Tac Ops is also coming out with an Alpha series rifle, similar to the Tango 51 but in .300 Winchester Magnum. A great deal of time, workmanship and know - how goes into building a precision rifle of this quality. With tight budgets, some may question the need for this level of workmanship and accuracy. A 1 MOA capability has been considered to be adequate in the police sniper community. Certainly, 1 MOA is perfectly adequate for making reliable head shots at the ranges and under the conditions commonly encountered by the police sniper. According to FBI statistics, most police sniper engagements take place at distances less than 100 yards. The average distance is around 77 yards.
Falling victim to the “1 MOA is adequate” mentality is in reality no different than that of the rookie cop making a “routine” traffic stop. In law enforcement nothing is routine. The police sniper must be prepared for all possibilities, not just probabilities. The lives of innocent civilians and fellow law enforcement may depend on it. In the real life-and-death world, only the best tools for the job will do and no price can be put on confidence.
Tactical
Operations, Inc.
433
North Camden Dr. 4th Fl. #239
Beverly Hills, Ca 90210
Phone 310 275-8797
Fax 323 933-3521
Email: blackops2@earthlink.net