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6.5 Creedmoor Barrel Length & Muzzle Velocity

16 Jul

One of my closest friends has two 6.5 Creedmoor rifles made by Surgeon Rifles that he has tried a couple different barrel sizes on.  He started with a 26″ barrel, because that is what Surgeon typically used but lately we’ve been shooting in more practical/tactical long-range competitions where you have to carry the rifle for miles every day … so he wanted to lighten the load.  He was also planning to add a suppressor to his rifle, and a 26″ barrel + 9″ suppressor makes for a pretty long and cumbersome rifle.  He eventually rebarrelled to a 22″ barrel, which he loves.  Both of the barrels were big, heavy, Krieger #10 contours with 1:8 twists (and both rifles could shoot 10 shot groups under 1/2″ … mostly in one ragged hole).

6.5 Creedmoor Surgeon Rifle Schmidt & Bender Scope AICS Stock with Viperskins ThunderBeast 30P 1 Suppressor

6.5 Creedmoor Excerpt from Berger Bullets Reloading ManualHe mentioned that he’d searched online to see what barrel lengths people were using for the 6.5 Creedmoor cartridge and get an idea for what kind of velocity he would be sacrificing, and saw a lot of debate … but not a lot of helpful information.  The new Berger Bullets Reloading Manual said you could expect a change of about 25 fps per inch (see excerpt image).  So he was expecting 100 fps loss, but that is not what happened.  So we thought it’d be helpful to share what he found.  He regularly shot each barrel length over an Oehler 35P chronograph, which is a professional grade chronograph and one of the most accurate ones made.  He kept really good documentation on the velocities, and here is what he found.

6.5 Creedmoor Barrel Length and Muzzle Velocity Diagram

6.5 Creedmoor with 26″ Barrel

This is the original configuration he tried, because it was the one Surgeon typically makes.  Here are the velocities he found:

  • 2805 fps – This was his muzzle velocity was out of a brand new barrel (without a suppressor attached)
  • 2860 fps – His barrel sped up a little as the barrel broke in, and this is what his muzzle velocity was after 1,200 rounds out of the 26″ barrel (again, this was without a suppressor attached).  This is the point where he rebarrelled, but he inspected the the barrel guys with a borescope with a professional gunsmith at Surgeon and based on the barrel wear they estimated this was about 1/2 way of the accurate barrel life.

6.5 Creedmoor with 22″ Barrel

  • 2760 fps – This was the 1st velocities recorded with the brand new 22″ barrel (without a suppressor attached).  He was ecstatic to see this, because he was expected more than 100 fps of velocity loss with 4″ less barrel, based on the estimates in Berger’s new reloading manual.
  • 2805 fps – This is what he is now getting after 800 rounds, with the barrel completely broken in and no suppressor attached.
  • 2833 fps – He has since started using a Thunder Beast 30P-1 suppressor with his 22″ barrel, and the added 9″ of length the suppressor adds has helped his muzzle velocity a little as well.

So ultimately, after he added the suppressor he only lost 27 fps with 4″ less barrel.  That essentially means he only has 2/10 more vertical adjustment of a mil at 1,000 yards, and wind drift is virtually identical.  In return he has a lighter, more maneuverable rifle … and he couldn’t be more happy with that trade.

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10 responses to “6.5 Creedmoor Barrel Length & Muzzle Velocity

  1. Chris

    September 13, 2013 at 4:00 am

    What barrel twist does your friend have on his surgeons?

     
    • calz

      September 13, 2013 at 1:08 pm

      He uses a 1:8 twist on all of his 6.5 Creedmoors. He honestly might go with a faster twist if Krieger offered one. One of the guys we really pay attention to is Todd Hodnett with Accuracy 1st, and he thinks overstabalization is a ridiculous concept. Here is a quote from Todd on the topic:

      “I am a fan of fast twist rates, so let’s look at this very important component. Here are some considerations: barrel length and twist rate, long VLD-type bullets, heavier VLD-type bullets and shorter barrels may require a faster twist. I have tested this on several occasions and found the same answer with each test. In my opinion, the Greenhill Formula is a little outdated. Even though it may work for some types of bullets and some types of shooting, I believe we need much faster twist rates for extended long-range shots. This gives us better-retained gyroscopic stability as the bullet is reaching transonic flight and into subsonic flight, thus, better grouping capabilities as well as less loss of BC due to loss of stability. I even had a 1:7.8-inch twist on a .308.” – Todd Hodnett (Sniper Magazine, May 2012)

      The only downside I’m aware of with going to a faster twist rate is that you will have more spin drift. “Faster spin rates will produce more gyroscopic drift because the nose ends up pointing farther to the side.” (View Source) However, the difference is usually very slight. For example, I ran the ballistics for a 6.5 Creedmoor with a 1:8 twist rate and the spin drift at 1200 yards was 10.5″. I changed the twist to 1:9 and the spin drift was 9.1″ at 1200 yards. If someone can shoot between those numbers at 1200 yards, I’d like to see it. So my thought process these days is to buy the fastest twist rate Krieger offers and go with it … especially if you are really pushing your gun beyond its supersonic range.

       
  2. Chris

    September 13, 2013 at 4:47 pm

    Thanks for your reply. I’m planning on having a surgeon scalpel built over the winter and was wondering if I should go with a 8″ twist or a 8.5″. or if it even matters. I thinking has been to go with the 8, and after reading your post, I’m thinking of sticking with a 8″ twist over an 8.5. How much do tighter twists affect muzzle velocity? Any insight on that? How much slower will an 8 be over an 8.5″. Thanks.

     
    • calz

      September 13, 2013 at 5:28 pm

      I really don’t know if twist has a measurable impact on velocity. Although theoretically its possible, it seems unlikely. But honestly that’s just my opinion. Sorry I couldn’t be more help.

      If someone else has some insight on this, please chime in.

       
  3. CR Rains

    October 4, 2014 at 11:22 pm

    I recently gave my wife [ who has won 1st place at the Texas Trophy Hunters Extravaganza ] a Lady Savage 6.5 Creedmore and I worried about the shorter barrel. I think I will have a suppressor installed and see if that doesn’t help her MV.
    CRaTXn cratxn@me.com

     
    • Cal

      October 6, 2014 at 1:30 pm

      You should try it out. You’ll probably recover a little muzzle velocity. It is effectively extending the barrel, although most suppressors are 30 caliber and not 6.5mm … so it isn’t exactly the same as a longer barrel.

      From what I’ve heard the 6.5 Creedmoor was originally designed for a shorter barrel. One of the lead guys on that project has even said that 22 inches is the ideal barrel length for a 6.5 Creedmoor … he was very adamant on that point. Not 24″ or even 23″ … 22.0″. My friend now has a few 6.5 Creedmoor barrels. He has two rifles chambered on Surgeon Actions (one pictured here and the other in a McMillan A5, but he prefers the AICS). He also has a few barrels in his safe that are already chambered. All of them are 22″ … he couldn’t be more happy with his choice to go shorter.

       

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