300 Winchester Magnum load development: Sierra .308 195 gr. Tipped MatchKing (TMK) REVIEW

When I found out Sierra was introducing .308″ diameter 195 grain Tipped MatchKings (TMK) I was thrilled to get my hands on some.  The weight was an interesting choice, heavy for a 308 Winchester (Win) and light for a 300 Winchester Magnum (Win Mag).  My testing with the 308 Win showed the 195 TMK was a great alternative to the 175 SMK.  I couldn’t help but wonder if the 195 TMK would offer similar advantages in the 300 Win Mag.

195-gr-tmk 168-175-175tmk-190-195tmk-220-smkas2

The 195 TMK has a G1 ballistic coefficient (BC) of  .610 above velocities of 2,000 feet/second.  Compared to my other favorite 300 Win Mag bullets, the 190 SMK with a BC of .533, 210 SMK (not shown) with a BC of .670 above 2,500 feet/second, and 220 SMK with a BC of .629 above 2,100 feet.second, the 195 TMK offers middle of the pack performance in terms of BC.

Custom 300 Winchester Magnum equipped with 5-25 ATACR scope, Spuhr ISMS, AICS AX 2.0 and a Sierra 7 bipod.

This is the test rifle I’ll be using.  Built primarily with parts from Brownells, the rifle includes:

To learn more about how I built this rifle, please see Building a 300 Winchester Magnum Precision Rifle.

The barrel on this rifle is 24″ long, fairly short for a 300 Win Mag- especially for the heavier bullets.  To see how barrel length effects velocity in the 300 Win Mag, take a look at 300 Winchester Magnum: How Does Barrel Length Change Velocity- A 16″ 300 Win Mag? for an empirical data set we gathered on a match grade barrel.  While you are at it, if you want a good laugh, take a gander at Does size matter? Custom Remington 700 16.5″ 300 Winchester Magnum follow up– my fillings still hurt from that one.

WARNING: The loads shown are for informational purposes only.  They are only safe in the rifle shown and may not be safe in yours.  Consult appropriate load manuals prior to developing your own handloads.  Rifleshooter.com and its authors, do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.

While the 300 Win Mag is certainly popular, some attributes of the cartridge do not lend themselves to accuracy.  The belted case, short neck and long powder column are uncharacteristic of what you might find in a purpose built competition cartridge like the 6mmBR.  Despite these shortcomings the 300 Win Mag is capable of extreme accuracy with careful load development.  In the past, I’ve focused on the 210 gr SMK for this rifle and have achieved great accuracy for a gun of this type.

I selected what I felt was the best quality brass on the market for this rifle- Norma.  Primers are CCI  250 large rifle magnum primers.  In the past I’ve experiments with a number of primer options, but haven’t found one primer particularly beneficial over another in magnum cases.  I tested three different powders; Reloder 22 (RL22), Hodgdon H4831SC, and IMR 7828.

Before selecting a starting load, I scoured different sources looking at data for 190 to 200 grain projectiles to establish a baseline starting point.  This isn’t a lab tested data set, it is based on my experience and should only be considered safe in the test gun.  The loads shown below are in .5 grain increments.

I decided to use an overall length of 3.585″, allowing a .015″ jump to the lands.   The large, 300 Win Mag AICS AX magazine I am using on this rifle is fairly spacious when compared to the 308 version.

All data was recorded with a MagnetoSpeed barrel mounted ballistic chronograph.  Target distance was 100 yards.  Shooting was conducted prone, from an Atlas bipod with a rear bag.  The Nightforce ATACR scope was set at 20 power magnification.


Results are shown in the table and images below.




Velocities for the loads ranged from 2,737 to 2,983 feet/second with an average velocity of 2,845 feet/second.

Standard deviation of the loads range from 12.2 to 38.8 feet/second with an average of 19.6 feet/second.

Group size ranged from .366″ (.350 MOA) to 1.489″ (1.422 MOA) with an average of .853″ (.810 MOA).  Note: take a look at the 73.0 grain load of RL22 above, there are four rounds in the bottom hole!


The 72.5 grain load of H4831SC was impressive (above), 5 rounds in .366″ (.350 MOA) with a velocity of 2,835 feet/second and an SD of 12.9.

The 75.5 grain load of IMR 7828 showed promise in terms of balancing velocity and precision as well, 5 rounds in .702″ (.670 MOA) with a velocity of 2,953 feet/second and an SD of 21.7.

I modeled these two loads out to 1,000 yards in 200 yard increments on my ballistic calculator.  For comparison purposes, I included data for 210 SMK and 220 SMK loads as well Federal Gold Medal 190 SMK ammunition from the test gun.  These are loads that I developed for and shoot in this very rifle.  The 220 gr. MK248 MOD1 data shown in the table is generic and for comparison purposes only. All values assume a 100 yard zero, elevation at sea level, and a temperature of 59F.  The lowest drop and drift values for each range are displayed in bolt font.


You’ll note that in this particular gun, the 195 TMK loads look fantastic on paper.  Note the 2,953 feet/second load outperforms the other loads across the board.  The slower and highly precise 2,835 feet/second load matches the generic MK248 MOD1 at 1,000 yards, and performs slightly better than the 210 SMK (.1 mil less drop) and much better than the 220 SMK (.9 mils less drop, .2 mils less wind) and Fed 190 Gold Medal (.2 mils less drop, .3 mils less drift).

I’m pretty impressed with the 195 TMK in the 300 Win Mag!  If you get a chance to pick up a box, I would suggest giving them a try.  If you have a 308 Winchester with a 1:10″ twist (see:Sierra .308 195 gr. Tipped MatchKing (TMK) REVIEW and load development: 308 Winchester and IMR 4064), you could load the same bullet in both guns for component commonality.

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