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Rocky Mountain Bullet Test Fire

The use of large heavy bullets for precision long range shooting is a fascination held by many, dating back hundreds of years.  The 18th century Pennsylvanian ‘Kentucky’ rifle is perhaps one of the earliest examples of efforts towards extreme accuracy. In Britain, the accurate Baker rifle (1800) allowed for unique changes in military strategy.  During the later 1900’s, the famous Sharps rifles displayed both great accuracy and great power along with graduated sighting systems for true long range shooting. Throughout the entire black powder era, big bores and heavy bullets reigned supreme, then something changed, velocity.

With the advent of smokeless powder and high velocity, bore sizes were reduced considerably. For several decades, the small bores reigned supreme.  High BC’s and extreme velocities proved to be very effective for both military and civilian applications.  To a greater extent,  U.S Marine Corp Gunnery Sergeant Carlos Hathcock was responsible for bringing heavy bullets back into use for precision long range shooting.  During the Vietnam war, Hathcock developed a scope mount that would allow his trusty 8x Unertl scope to be fitted to a Browning 50BMG machine gun.  Hatchcock was already over extending ranges with his .30-06, engaging targets at up to 1200 yards.  Utilizing the higher BC’s and velocities of the .50 BMG, Hathcock was able to extend ranges to some 2400 yards.

The .338 Lapua Magnum (1984) was the first modern attempt to bridge the gap between big bore power and penetration with the portability of the smaller bores.  The Lapua was initially field tested in New Zealand on Goats and Fallow deer by gun writer Graeme Henry who had formed great friendships within the Finnish gun industry. 

The recent Chey-Tac cartridges, like the .338 lapua, are designed to deliver extremely high down range energy at extremely long ranges. Developed specifically for thick skinned game such as Mercedes Benz, BMW and Audi, the .338 Lapua is now used by all allied military forces of the world while the Chey-Tac cartridges are employed in the U.S amongst specialised units.  These cartridge designs are now also very popular for long range hunting. 

Although the new generation (for want of a better term) medium bore cartridge designs boast great down range velocities and energies, the one area of technology that has been lagging, is suitable bullet designs. For a long time, shooters have had to choose between low BC hunting bullets for optimum terminal performance, versus long range match bullets (both solid and hollow point designs) which traditionally, produce erratic terminal performance.  Unfortunately, specifically regarding long range hunting, there is little point in being able to hit game at 1500 yards if the animal is able to escape into mountainous regions due to slow bleeding, never to be seen again.  It happens and it is very frustrating when it does happen.  In some instances, a hit may even be called as a miss, such is the lack of wounding and response when projectiles fail to expand or fragment at low velocities.

Rocky Mountain Bullets

George Costello, a dedicated precision long range hunter from Philipsburg Montana, knew exactly what happens when heavy .338” to .375” projectiles don’t expand at long range.  A large .338 cartridge might look like a horseman of the apocalypse when held in the hand or compared to other cartridge designs on paper, but without energy transfer, a .338” (8.6mm) diameter wound is slow killing.  George was determined to create optimum projectile designs for the new generation of medium bores, not only with regard to terminal performance, but also ballistic efficiency. 

By mating an aluminium tip to a light jacketed match projectile design, George created a range of fast expanding, highly frangible bullets in .338, .375, .408, .416 and 50 calibers.  Those of you who are familiar with the Winchester SilverTip will understand exactly what results are to be expected. The ultra low drag design of the ULD bullets feature incredibly high BC's.

I became aware of George’s efforts through word of mouth. For some time, I have had the same concerns as George. I had noticed that the medium bore new generation cartridges have become ever more popular for use on light bodied game at long ranges, without bullet designs to fully support this style of  hunting.   I contacted George with a simple proposition, a test fire in exchange for a review.  George was extremely kind and after a few emails back and forth,  we had a plan. For review, George sent me samples of the .338 225 and 250 grain ULD projectiles which he has already used with great success on Elk. At my end, I would test the projectiles under the lightest resistance, a possibly disconcerting situation for George, expecting so much from one bullet design.

Twist rates and ballistic coefficients

I thought I would be cunning and use a trusted M700 .338 Winchester Magnum I had on hand rather than borrow a .338 Lapua rifle from a friend.  The idea, was that the lower muzzle velocity of the Win Mag would allow me to study medium to long range performance without having to hunt at the extreme long ranges associated with the larger cartridge. But I was way off the mark and did not anticiapate just how much velocity the Rocky Mountain bullets retain.  The 225 grain ULD had a G1 BC of .773, the 250 grain ULD had a G1 BC of .846. To put this in perspective, most projectiles lose around 200fps per 100 yards, George’s bullets lose 100fps per 100 yards. 

After sighting in, I developed drop charts using Sierra I6 and field trajectories were exact, the BC’s are true to George’s claims.     I chose three loads, the 250 grain bullet driven at exactly 2700fps, the 225 grain bullet driven at a fast 3020fps (expect 2950fps from a typical .338 Win Mag) and after discovering my error regarding long range hunting, a soft 225 grain load at 2620fps. Groups averaged around the .5” mark, suffice to say, accuracy was not an issue.

George informed me that although the 1:10 twist rate is perfectly adequate for his ULD bullets, I might notice projectiles tumbling after impact, at velocities of 1400fps and below. I did notice this with the 225 grain ULD, though the tumbling effect was quite welcome, producing excellent wounding. For a long time, the 1:10 twist rate has been standard for the .338’s, including the .338 Lapua, more recently there has been a shift towards the faster 1:9 twist to optimise accuracy with new bullet designs.  The Savage 110 BA Tactical is one example of a modern rifle design utilizing the 1:9 twist.  Regardless, both twist rates are suitable for the Rocky Mountain .338 225 and 250 grain bullets.  The 325 grain Rocky Mountain bullet does however require the faster 1:9 twist.

Light Game Hunting


Close range

At close ranges, hunting male feral goats weighing between 40-70kg (88-155lb), both the 225 and 250 grain ULD produced extremely violent wounding, coupled with deep penetration, regardless of whether shots were broadside, quartering away,  quartering on and regardless of whether bone was or was not encountered. The projectiles fragmented into a mixture of large and small fragments with a portion of the bullet core continuing to produce straight line penetration.  The smaller fragments and jacket fragments penetrated outwards, at angles of up to 90 degrees from the path of the bullet.

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Above: A snap shot taken at around 50 yards, using the 225gr ULD, exit wound shown.

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Above: The result of a quartering away raking shot on a young Billy at around 100 yards. The broken ribs are not of the central bullet path, this damage was caused by fragmentation. The bullet struck the paunch on the same side as the broken ribs, exited at the brisket (between the brisket and offside shoulder), pictured below.

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Above: Exit wound at brisket from raking shot.  Note the huge jacket fragment sitting in the exit wound.

Intermediate ranges

At velocities of between 2000fps and 2400fps, performance was just the same as at close ranges. Wounding was very violent, killing very fast.   A pig was taken with the 225 grain ULD at an impact velocity of 2360fps, wounding was again broad yet deep.  The pictures below are far better than any explanation.

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Above: The pig shot with the 225gr ULD. MV 2620fps,  Impact velocity 2360fps.

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Above: Pig vitals, lungs broken into 4 pieces, liver damage also evident.

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Above: Pig carcass, exit wound shown.

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Above: Close up of pig exit wound. Note the small lead fragment.  This is highly desirable performance for long range hunting.

Long range

Both the 225 and 250 grain ULD bullets performed very well at long ranges, down to the tested impact velocities of 1400fps.  Wounding remained broad, exit wounds wide. Projectile fragments were found at 90 degrees of the bullet path while retaining a central straight line wound channel. Recovered fragments weighed between 10 and 120 grains, indicating optimum long range terminal performance.

On Goats weighing less than 40kg (88lb), with rear lung shots at impact velocities of 1820fps and below, animals did show a tendency to run 25-50 yards before expiring.  Internal wounding was however very wide, regardless of low impact velocities or absence of resistance (bone). To put this in perspective, the same occurs on lean goats when using the .270 Win with factory loads at ranges of 275 yards and beyond.  In the .308 Win, this can occur with factory ammunition at ranges of around 100 to 150 yards.  Most hunters will be familiar with a typical ‘dead run’ after a rear lung shot.  With the Rocky Mountain bullets, this may occur at ranges beyond 800 yards on light game (Goat, Fallow deer, Cous deer, Chamois) where wind drift error has caused rear lung/liver shots. 

On heavier goats, at impact velocities as low as 1400fps, killing was very emphatic, wounding broad.  Bullet weight seemed to make little difference, both the 225 and 250 grain bullets performed well.

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Above: Total vital destruction at 1700fps or 900 yards from an MV of 2620fps.  The ULD bullets shoot flat and retain incredibly high velocity down range.

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Above: Exit wounding from 1700fps impact velocity as seen internally.

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Above: With the foreleg removed, the extent of the 1700fps exit wounding can be seen clearly.

Large medium game hunting

George has tested his projectiles primarily on Elk at long ranges of between 700 and 1300 yards.   George described a typical kill, after breaking both shoulders of a large Bull Elk last year at 1240 yards with the .338 Snipe-Tac, the remaining fragments and heel of the 300 grain ULD came to rest against the offside skin.  The Elk dropped on the spot. 

In the .375 Chey-Tac,  using the 370 grain ULD out at 950 yards, similar results occurred. The bullet broke both shoulders of the bull, fully fragmented but also produced an exit wound.  Again, the bull collapsed instantly and did not move again.  George has repeat tested his bullets over and over again on game to ensure consistent results.


Above: George with a Bull Elk from 2010, an on the spot kill at 950 yards.

Other notes

The combination of wide wounding yet deep penetration with raking shots on Goats, prompted me to explore the use of the 225 grain ULD in the .338 Federal.  Unfortunately, the projectile was too long, cramping powder capacity in short actions. Optimum COAL is around 78-80mm (3.070-3.149”), though the rifle chamber would have to cut appropriately.  The goal, would be to develop a bush/woods load that would also prove immensely useful once the hunter breaks out onto the tops.  Inputting the 225 grain ULD into ballistics software, at a muzzle velocity of 2400fps, shows just how versatile this load could be. 
In the .338 A-Square (.338-06), the 225 grain ULD could be used to achieve the same purposes as above.  Long magazine rifles would work best (90mm/3.543 internal length and longer).  These include the Finnbear, Sako AV, Howa, Weatherby, Winchester M70 and Remington M700 actions. In the .338-06, the 225 grain ULD driven at 2550fps would tackle a wide range of medium game species under a wide range of hunting conditions, from woods to long ranges.

In the .338 Win Mag, I had no problems with COAL’s versus powder cramping or unexpected changes from my usual loads.  The Rocky Mountain bullets were not sensitive to bullet jump either.  In the .338 Edge, a COAL and approximating magazine length of 96-98mm (3.779-3.858”) would be optimal for all .338 RM bullet weights, indicating the need of a Wyatt extended magazine box if using the M700 as a repeating action.  In the Lapua, a mag box of 93-95mm (3.661-3.740’) would suit best.  The ULD .338 bullets essentially work very well with the standard Lapua rifle and cartridge configurations.
Before I sign off consider this; in the .338 Lapua, the 250 grain ULD driven at a 2950fps yields 1400fps at 1525 meters or 1700 yards where it is still capable of producing broad wounding, retaining 1076ftlb energy.  The projectile eventually becomes transonic at 2015 meters or 2215 yards, signalling the end of its effective range. The .338-Snipe-Tac pushes these ranges even further.

Rocky Mountain bullets are available in .338, .375, .408, .416 and .50 calibers.  Please click here to visit George's home page.

Below is a quick screen shot, showing the .338 Rocky Mountain bullet range.

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Below is a supplementary autopsy video, a small portion of the footage I took while studying the .338 ULD bullets.

If you are hunting this season with Rocky Mountain bullets and wish to show your support for George;s efforts, please send me your autopsy pics ([email protected]) and I will upload them to this page.


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We are a small, family run business, based out of Taranaki, New Zealand, who specialize in cartridge research and testing, and rifle accurizing.