Effects of barrel length on muzzle velocity – rifleshooter.com

Effects of barrel length on muzzle velocity – rifleshooter.com



The 6 Creedmoor offers shooters softer recoil and quicker follow up shots than the 6.5 Creedmoor. Back in January 2017, I wrote 6 Creedmoor barrel length versus muzzle velocity (31 to 17 inches), in which I used a new barrel to gather a data set for varying barrel lengths with 3 different loads. In this post, we’ll look at how a well worn barrel performs.

I swapped out the tube on my friend Matt Hornback’s well worn 6 Creedmoor. Before I took the barrel off, I went ahead and shot it to see how much the barrel length affects accuracy.

This is the gun, it’s one of Matt’s match rifles. The gun uses a Howa 1500 action, Proof Stainless-Steel 1:8 twist 24″ M24 profile barrel and sits in an excellent MDT ACC competition chassis. If I remember our conversation correctly, Matt told me this barrel has about 1,800 rounds through it!

Before we get to the good stuff, let’s take a few minutes to read the following disclaimer:

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.

I loaded the Hornady 108 ELD Match over 41.5 grains of Hodgdon H4350 with a CCI 200 primer in new Starline brass (shown after it was fired above).

To increase the precision of my handloads, I’ve upgraded my powder thrower to a combination of a ONEZERO Auto-Trickler and Auto-Throw combo kit and an A&D FX120i scale. These tools allow charges that are within .002 grains of your target amount (both are available through Brownells)!

The test protocol is the same as my previous barrel length posts. At each barrel length I fire 5 rounds of the test load, record the muzzle velocity data with a MagnetoSpeed V3 barrel mounted ballistic chronograph, cut one inch off of the barrel and repeat the test. You’ll note the MK machining MagnetoSpeed mount in the image above. This is a great upgrade that prevents the chronograph from impacting the performance of the rifle. I simply mounted it to a short section of Picatinny rail I attached to the MDT ACC’s M-LOK slots.

Technology keeps advancing here at rifleshooter.com. We used a Sawzall and hacksaw for our first barrel length and velocity post, graduated to an inverter generator and cold saw, moved onto a grinder with a cut off wheel, and now we have a DeWALT cordless metal circular saw with a stainless steel cutting blade to make the cuts! This makes the entire process much easier.

To prevent the saw from impacting the chronograph, I removed the barreled action from the MDT ACC chassis . This was as simple as removing two socket-head cap screws. This kind of ease of installation makes chassis a great choice over traditional stocks.

Muzzle velocities ranged from 2,893 ft/sec at 24″ to 2,598 ft/sec at 16″ for a decrease in muzzle velocity of 295 ft/sec. Muzzle velocity changes per inch of barrel length ranged from 6 ft/sec/inch between 20 and 19 inches to 63 ft/sec/inch between 19 and 18 inches. Average velocity change per inch of barrel length was 37.9 ft/sec.

I also took the time to plot the barrel length (inches) against standard deviation (ft/sec) and didn’t notice any trends.

While some barrel length reductions resulted in larger velocity drops than others, an average drop of 37.9 ft/sec/inch of barrel is fairly significant and what would be expected with a fast moving 6mm cartridge like the 6 Creedmoor. While I’m used to seeing 6 Creedmoors with slightly longer barrel lengths than 24″, when coupled with a sound suppressor the additional length can make moving the rifle quickly a more difficult task. I’d suggest staying with longer barrel lengths wherever possible with this cartridge; at shorter lengths, it does give up more performance that its big brother the 6.5 Creedmoor.

The MDT ACC chassis coupled with the MDT vertical pistol grip was an absolute pleasure to shoot. With the ACC adjusted to fit me perfectly, recoil was mitigated, and the gun tracked very well. To learn more about the ACC, click here.





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