June 3rd, 2020

0.8 MOA for 500 Shots at 300 Meters — Sierra Test Tunnel Result

Sierra Bullets 500 round tunnel test

For load development, some guys shoot 3-shot groups. Other guys shoot 5-shot groups, or even 10-shot strings. But for testing its projectiles, Sierra Bullets takes it to another level entirely. A while back Sierra was testing its .30-Caliber 175gr HPBT MatchKing in the Sierra underground tunnel. The results appear above — a FIVE HUNDRED Round group!

500 Shots Form 0.82 MOA Group at 300m (328 yards)
The photo above shows the result of 500 shots taken in a 300 meter test tunnel. Sierra’s trigger-pullers sent five full boxes of bullets down-range at a single target. The raw group size, edge to edge of the farthest shots, is about 3.13 inches, as shown on the calipers’ metal linear scale. Subtract a .308″ nominal bullet diameter* to get the 2.823″ on the digital readout. So you’re seeing a 2.823″ group at 300 meters (328 yards). One MOA at this distance is 3.435″ so this 500-round group is 2.823 divided by 3.435 or 0.82 MOA (0.8218 MOA to be precise).

This 500-round group was shoot as part of a pressure/velocity test for a commercial customer. The cartridge was .308 Winchester, loaded at 2.800″. The powder was Reloder 15. A 26″ barrel was shot from a return to battery rest. The gun was cleaned every 125 rounds and two foulers shot.

What do you think — could you beat this group from a bench for 500 rounds?

One Facebook poster joked: “500-round group? Everyone knows anything less than 1000-round groups are a waste of time and statistically irrelevant.”

Test Tunnel Sierra

Sierra Bullets Test Tunnel Barrels

Sierra’s 300 Meter Testing Tunnel
Ever wonder how (and where) Sierra tests its bullets? The answer is underground, in a 300-meter test tunnel located under Sierra’s factory in Sedalia, Missouri. The photo above shows the construction of the tunnel back in May, 1990. Like most bullet manufacturers, Sierra does live-fire bullet testing of its projectiles. Sierra’s 300-meter test range is the longest, manufacturer-owned underground bullet test facility in the world. Sierra offers free tours of the test tunnel as part of Sierra’s Factory Tour Program.

* Normally, to get an exact group size, you should subtract the TRUE bullet hole size, which is usually smaller than the nominal bullet diameter. E.g. a .308 bullet hole may show on paper as .298 or so. But here, for simplicity, we are subtracting .308″ because we do not have the original target to measure.

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May 7th, 2016

A Look Inside Sierra’s 300m Underground Test Tunnel

Sierra Bullets Test Tunnel Barrels

Ever wonder how (and where) Sierra tests its bullets? The answer is underground, in a 300-meter test tunnel located under Sierra’s factory in Sedalia, Missouri. The photo above shows the construction of the tunnel back in May, 1990. Like most bullet manufacturers, Sierra does live-fire bullet testing to ensure that Sierra projectiles perform as promised, with repeatable accuracy. Sierra’s 300-meter test range is the longest, privately-owned underground bullet test facility in the world. Sierra offers free tours of the test tunnel as part of Sierra’s Factory Tour Program.

Sierra Bullets indoors testing barrels

Sierra Bullets tests every new bullet design and each lot of bullets. Sierra tells us: “When [we] change to a new bullet they are continually shooting them until they get the bullet properly set up and running and the range releases them to run (meaning the bullets shoot to spec). [Testers] are required to shoot at any lot change and periodically throughout the lot … even if it is just a press operator change. Lot sizes can vary from 5,000 to over 100,000 thousand. If anything changes — it is a new lot. When a new operator comes on — it is a new lot.”

Bevy of Barreled Actions for Bullet Testing
Sierra Bullets uses dozens of barreled actions for testing bullets. These barreled actions are clamped in stout, return-to-battery test fixtures. These heavy test fixtures provide near-perfect repeatability (with no human-induced holding or aiming errors). Each barrel has its own logbook to track the barrel’s usage. Interestingly, Sierra does not have a specific round count for barrel life. When a barrel starts “opening up”, i.e. showing a decline in accuracy, then the barrel is replaced, whether it has 800 rounds through it or 5,000.

Sierra Bullets indoors testing barrels
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Sierra Bullets 10-Shot Groups at 200 yards
What kind of 200-yard accuracy can you get in an enclosed, underground test range? Would you believe 0.162 MOA at 200 yards with a .338? Check out these 10-shot test groups shot at the Sierra Test Range at 200 yards. Note that the numbers listed on each sample are actual measurements in inches. To convert to MOA, cut those numbers in half (to be more precise, divide by 2.094, which is 1 MOA at 200 yards). For example, the 0.340″ middle group works out to 0.162 MOA at 200 yards.

Sierra Bullets indoors testing barrels

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