Sierra .308 155 Grain Bullet Explanation
A little unsure about which Sierra 155 we are talking about? This could be why.
There are three Sierra .308 155 Bullets
At the time of this writing, there are three different .308 155 grain bullets available from Sierra. First, the ‘legacy’ 2155. This was the original bullet introduced in 1992 for Palma Matches. The Sierra 2155 Palma MatchKing as it was labelled, quickly developed a very good reputation for accuracy all around the world and is still popular today.
The Sierra 2155 is loaded in GGG issue ammunition as used at the Imperial Meeting. The Sierra 2155 will work in many different chambers as the bullet ogive is of tangent design and is thus not as sensitive to ‘jump’ as many more recently designed bullets are. This is one significant reason why the NRA here in the UK specify it for use in their Imperial Meeting issue ammunition. In addition, the Sierra 2155 does not require a barrel with a twist faster than 1 in 13″ to be accurate. The Sierra 2155 is now just a MatchKing, Sierra having moved the ‘Palma’ designation to the 2156 when it was first introduced.
In 2008, as other major bullet manufacturers were offering bullets with high ballistic coefficients, Sierra had to keep up and introduced the Sierra 2156 .308 155 Palma MatchKing to satisfy and retain their customers, not least of which consisted of some high profile US Shooting Teams. To achieve a higher BC, the Sierra 2156 was given a sharp ‘point’ or meplat, as well as a different ogive and boat tail as compared to the 2155. It is also longer. All of these factors contributed to making this bullet less forgiving than the beloved Sierra 2155 as far as seating depth and barrel twist rate go, but made the Sierra 2156 a valid, affordable option for long range target shooters with the patience to do a little load development and testing.
Introduced in 2015, the Sierra 7755 was the .308 155 grain offering as part of the ‘Tipped MatchKing’ , or TMK product line added to the Sierra Brand. The TMK line extends across many different calibres and is not restricted to .308 only. Sierra marketing even gave this produce range its own ‘purple’ version of the Sierra MatchKing Logo. The 7755 is not a 2156 with a tip on it, it is a completely new design. The 7755 is longer than the 2156. The boat tail has been lengthened. The bearing band (full diameter bit) to ogive transition point is more visible than on the 2156. The Sierra 7755 looks more like a VLD bullet in appearance than the Sierra 2156. These factors all make this a rather unique animal, not to mention the green tip.
Information on this bullet is scarce to say the least. I do not know a single shooter at Bisley who has had any experience with this bullet. Yesterday (11/05/2021), I and a friend were testing loads at Stickledown, and as part of the exercise, I included 50 7755’s test rounds, all seated 0.050″ back from the lands, using VV150 powder at charges within the guidelines provided for this bullet in their tables. At 1,000 yards, shooting from a bipod, with iron sights, the first 5 shot group had slightly under a minute of vertical dispersion. The following nine 5 shot groups could not duplicate this performance and all showed a vertical dispersion in the range of 1.5 to 2 minutes. There was a gusting tailwind on the day, which may have had an adverse effect on the group sizes as well. Velocity for all of the loads was lower than I had hoped, but the SD’s (below 12) were surprisingly good, considering I was using tired practise brass and not fresh ‘test’ brass. I will give it another go with a more formal testing regime, now that I have at least a base point.
I have reached out to Sierra Technical support for seating depth recommendations and will share what I am able to find out. The bullet appears to look upon first glance to be of VLD type, but slightly softer at the ogive/bearing band transition so is it supposed to be sort of a ‘hybrid’?
*** 13/05/2021 Update. Today, after a telephone call with a Sierra Technician I learned more about the 7755. The Technician had access to a ballistics program and created a model that took my barrel twist and test velocity into consideration. He stated that my 1-12.5″ twist was fast enough to stabilize the 7755. He also verified that the relatively low velocity of my lightest test load was still sufficient to shoot the 7755 supersonic out to 1100 yards. He suggested that I perform seating depth tests starting with .010″ and working upwards, as the 7755 is a VLD type bullet and would perform better with a smaller ‘jump’. He also reminded me that developing a load starting with a small jump is beneficial as it defers further jump testing and load development as a barrel wears. The individual I spoke with had personal experience with the 7755 in a personally owned .308 Winchester. He also mentioned that Sierra had done extensive testing with the 7755 using VV140 powder with good results. Based on my conversation with the Sierra Technician, it seems that Sierra are quite confident, and enthusiastic with the performance potential of the 7755.
Brian Litz has independently tested the 7755 bullet and found the actual BC to be identical to the Sierra 2156, but if it is more consistent from bullet to bullet due to some production process optimization, then it could provide a benefit to shooters. It was a very uplifting experience to speak with someone qualified to objectively review test results for their product and was in a position to make constructive recommendations. Thank you Sierra Bullets.
Conclusion
Sierra has positioned its offerings to be a balance of price and performance, as well as trying to retain the belief by many shooters that Sierra products work well in a wide variety of factory produced firearms.
Their .308 155 bullets are used in a multitude of disciplines around the world which involve different distances from short through to long ranges and shot with different rifles. Many of these bullets are consumed in semi-auto’s and loaded into magazine rifles. Some are shot in rapid fire events, and others used in Palma Matches. Most of the Sierra .308 155 bullets are not shot at 1,000 yards, but at much closer distances. The Imperial Meeting is an example of this.
One other point to mention is the ‘C’ designation after the Sierra Bullet number. The ‘C’ denotes a box of 500 rather than box of 100. You therefore have the 2155, the 2155C,the 2156, the 2156C, 7755, and the 7755C . Back in the day, there was also the 2156M, which was a box of 500 moly-coated 2156 available over the counter. Anyone remember moly?
With other manufacturers offering a multitude of different .308 155 grain bullet types and styles, I cannot see a reason why Sierra will not maintain all three of their offerings into the future as well.
