Sierra 6mm 110 SMK, 6 Creedmoor and 6×47 Lapua: initial impressions/load development

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Game changer? Sierra’s new 6mm 110 grain MatchKing #1575

When Sierra Bullets introduced the new 6mm (.243″) 110 grain MatchKing (SMK) a few weeks ago the 6mm shooting community was excited. With an advertised G1 BC of .617, this bullet represents a leap forward in performance for 6mm bullets without moving into 115 grain class projectiles.

The 27 caliber ogive 110 SMK is quite a bit longer (~1.340″- above, right) than the 107 SMK (~1.230″- above, center) and 95 Tipped MatchKing (TMK) (~1.180″- above, left). Sierra recommends a 1:7″ twist barrel, unlike the more commonly encountered 1:8″.

The 110 SMK appears to be a great option for the 6BR, 6×47 Lapua, 6 Creedmoor, 6XC and 243 Winchester. I decided to test it out in my 6 Creedmoor and 6×47 Lapua, both of which have a 1:8″ twist.

Commonly encountered match cartridges, left to right: 6mm BR, 243 Winchester, 6x47 Lapua, 6 Creedmoor, 6.5x47 Lapua, 6.5 Creedmoor, 260 Remington, and 308 Winchester — Commonly encountered match cartridges, left to right: 6mm BR, 243 Winchester, 6×47 Lapua, 6 Creedmoor, 6.5×47 Lapua, 6.5 Creedmoor, 260 Remington, and 308 Winchester

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.

For all of the loads shown, target distance was 100 yards. All shooting was conducted prone, from a bipod with a rear bag. The Nightforce scope was set to 15X magnification.

Muzzle velocity data was recorded with a MagnetoSpeed barrel mounted ballistic chronograph.

6 Creedmoor 110 SMK

This is the 6 Creedmoor test rifle. Specifications are as follows:

To see more information about this rifle, click here: Ultimatum Precision U300 bolt action review: Initial impressions

In my test rifle, the 110 SMK had an overall length of 2.900″ to the lands. I decided to start my load development with a slight, .005″ jam. Note: this length exceeds the length of most detachable and blind magazine.

Since I had data for this gun with the 107 SMK and H4350, I decided to start working up from the low end of it.

Muzzle velocity ranged from 2,979 to 3,196 feet/second with an average velocity of 3,060 feet/second.

Standard deviation ranged from 6.6 to 19.8 feet/second with an average standard deviation of 12.8 feet/second.

Group size ranged from .456″ (.436 MOA) to 1.483″ (1.416 MOA) with an average group size of .865″ (.826 MOA).

If you closely examine these groups, you’ll note a few bug hole clusters with a flyer or two opening it up. In my experience, this indicates the bullet would have performed better with the 1:7″ twist recommend by Sierra.

As this was my first trip to the range with the 110 SMK, I wanted to get a rough idea of how it would perform seated at different overall lengths. I loaded a few small batches (3 and 4) of cartridges in .030″ different increments; starting with a .010″ jam and decreasing to a .080″ jump (above). Results are displayed below:

Working with a small sample size can make it difficult to draw conclusions with confidence. Given the results over the wide range of cartridge lengths shown above, I think it would be safe to assume that the 110 SMK isn’t particularly sensitive to seating depth.

This testing encouraged me to conduct further development with the 110 SMK in the 6 Creedmoor seated to a length compatible with the AICS magazine, in this case 2.860″. Results are shown below:

Muzzle velocity ranged from 3,000 to 3,103 feet/second with an average muzzle velocity of 3,057 feet/second.

Standard deviation ranged from 4.8 to 17.4 feet/second with an average standard deviation of 13.2 feet/second.

Group size ranged from .479″ (.694 MOA) to 1.088″ (1.039 MOA) with an average group size of .763″ (.729 MOA).

Note that while the cartridges loaded to 2.860″ performed slightly better than those loaded to 2.900″, weather conditions were quite different on both days.

6×47 Lapua and the 110 SMK

The 6×47 Lapua test rifle was built with the following parts from Brownells:

To read more about the 6×47 Lapua, see 6X47 Lapua (6-6.5×47 Lapua) Review.

I selected H4350 powder- the same powder I was using for my 107 SMK and 108 Berger loads in this gun.

Muzzle velocity ranged from 2,854 to 2,920 feet/second with an average muzzle velocity of 2,888 feet/second.

Standard deviation ranged from 8.9 to 18.0 feet/second with and average standard deviation of 13.1 feet/second.

Group size ranged from .508″ (.485 MOA) to 1.232″ (1.177 MOA) with an average group size of .906″ (.865 MOA).

The 110 SMK didn’t perform as well in the 6×47 Lapua as it did in the 6 Creedmoor, it still managed to hold sub MOA precision, with one four shot group below 1/2 MOA.

Discussion:

While the 110 SMK was able to consistently achieve sub MOA precision in the 6 Creedmoor and 6×47 Lapua rifles with 1:8″ twist barrels, I think greater precision would have been achieved with a 1:7″ twist specified by Sierra. While I was able to obtain at least one 5 shot, sub 1/2 MOA group in each rifle, I would think the bullet still has far greater potential.

The G1 .617 BC advertised by Sierra is impressive. While we will have to wait for real world independent testing to confirm this, in my experience Sierra is extremely conservative with their BC values. My guess is they are spot on or slightly lower than what third parties will confirm in the future.

How does it look on paper when we model it out to 1,000 yards?

This is where it gets interesting. I created the table below comparing three different 110 SMK load (3,196, 3,103 and 2,880 feet/second) against some other hand loads I’ve developed from my 6, 6.5 and 308 Winchester rifles. The lowest value for drop and drift is highlighted in each column.

At the fastest velocity I achieved, 3,196 feet/second, the 110 SMK offers impressive performance- 6.2 MRAD of drop and 1.6 MRAD of drift at 1,000 yards! This is literally half of Federal Gold Medal 308 168!

Slowing things down a bit to 3,103 feet/second, the bullet still outshines the other cartridges listed.

In fact, when you dial it back to 2,880 feet/second in the 6×47 Lapua, the 110 SMK has less wind drift than all of the other loads shown in the table!

If you are considering the 110 SMK for one of your 6mm rifles, I would strongly suggest buying a 1:7″ barrel for it. You’d still be fine with the 107 SMK and 95 TMK, plus you’d have the performance of the 110 SMK available.

Tomorrow morning I plan on calling Shilen Rifles and asking if they’ll make a #7 Select Match barrel with a 1:7″ twist. If they do, I’ll be building a 6BR!

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