Barrel velocity

Discussion in 'Reloading' started by jeffro, Dec 21, 2010.

  1. jeffro

    jeffro Well-Known Member

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    What have you noticed with your barrels. As the barrel gets more rounds through it have you notice an increase or decrease in your velocity? The barrel on my Edge seems to have slowed down a bit since it was brand new. A load that was going 2842fps is now going 2800fps. These were shot in similar temps so I can rule that out. H-1000 is suposed to be less temp sensitive anyways. Would shooting on a sunny day verse an overcast day make that big of a difference. I just talked to CED, and he made it sound like if you have enough light to get good readings then you should have good numbers. When I was working up a load for speed I never had speeds that were down in the 2800fps range once I got the powder charge past 91gr. My load Im using is 93gr H-1000, and a 300SMK.
     
  2. Kevin Thomas

    Kevin Thomas Well-Known Member

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    Jeffro,

    a decrease in velocity as the barrel wears is the norm, and not at all unusual to see. Varies with different chamberings, bore sizes etc., but after the first shot, any barrel is on its way downhill.
     

  3. jeffro

    jeffro Well-Known Member

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    I only have 60rnds through the barrel. Im trying to figure out if the slow down is due to the barrel being broke in, or it may be due to the change in lighting condition while using the chrony. Overcast vs sunny day.
     
  4. RT2506

    RT2506 Well-Known Member

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    Is everything EXACTLY the same in your loads? Same lot of everything and did you use the very same cases you used before to get your velocity. Even seating the bullet 1 or 2 thousands away from the lands could change things. 42 FPS is splitting hairs. Like had been said from the first shot barrel wear starts. Probably just a slicker barrel and the bullet slides better with less resistance which will lower pressure and thus velocity.
     
  5. jeffro

    jeffro Well-Known Member

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    Everything is the same. The ES have been 8fps over 18rnds. Shooting between .260-.320 at 100yrds. It has held under .4 MOA out to 553yrds. I will take it out farther later this week. The load shoots great, im just wondering what the real speed of the load is. I can allways shoot it and see what it does at one speed compaired to what the chart says it needs.
     
  6. Kevin Thomas

    Kevin Thomas Well-Known Member

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    Jeffro,

    At 60 rounds, you're not seeing an issue with barrel wear. What I was refering to was once the throat has begun to be roughened by erosion, and we're talking hundreds of (or even well over a thousand) rounds. Sounds to me like you're getting a bit too concerned over a very limited amount of shooting thus far. Give it some time, and several different trips to the range before deciding there's a trend here. In the meantime, sounds like it's shooting right well. Enjoy!
     
  7. jwp475

    jwp475 Well-Known Member

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    According to Ken Ohler an overcast days are the best to chronrgraph on and will give more accurate readings. A very bright sunny day can give faster readings than what you are acctualy doing
     
  8. Bravo 4

    Bravo 4 Well-Known Member

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    How many rounds do you have down the barrel?

    If the answer to my first question is well past a thorough break in, then I would say this is your culprit. Unless you have always used the same lot. I have a 100fps decrease in velocity from a year ago with the same load and H1000.
     
  9. nheninge

    nheninge Well-Known Member

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    The chrony is your culprit. They can be finicky even on the best of days.
     
  10. jeffro

    jeffro Well-Known Member

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    I chronyed my load on a very overcast day. The vel came out to 2795fps 300SMK. ES 8 fps 50deg F

    Groups at 100yrds were .260-.320

    I put the data into the balistic program, and shot at 1000yrds. groups were 4.7in, and the groups centers were 2 in low. Not too bad, and I guess the data I got is quite accurate. I was just trying to figure out why the vel has dropped from where it was when the barrel was brand new. Its probably the chrony data from very bright days.

    The barrel now has 70rnds through it.