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Thread: How close to book data are your Muzzle velocities?

  1. #1

    How close to book data are your Muzzle velocities?

    Managed to get out with a Chrony F1 chronograph last week to see what is what.
    Was interested to see that most of my MV's (or MV + 10ft) were all lower than I expected

    now it matters not to me as I don't dial drops and have a first hand view on what the actual drops are at reasonable stalking ranges.
    also wont have me changing loads to chase that velocity. they have all performed well on deer in the field

    but we are talking 200fps less than advertised for similar components and barrel length
    Only the WinMag is shorter in the barrel and only by 1-2"
    the .270 is entire at 23.75"
    I couldn't get a reading on the .222, must have been the light...or it is just genuinely too fast and laser like!

    Those that have chrono'd loads, how far away from your expected book data have the results been?

  2. #2
    It's hard to guarantee the data's MV and yours will be the same. Much of that is achieved in a ballistics lab under very controlled circumstances. Pressure guns can measure velocity with fixed light sources and acoustic sound boards. Both are very accurate and more so than out door lighting. As you found with your .222, sometimes the light doesn't cooperate. (I once fired 20 rounds of 5mm Remington Magnum that clocked 400 fps faster then it was supposed to due to light error.) Additionally, the chambers and the bore and groove diameters in a pressure gun barrel are exactly to SAAMI spec. Brass is new, the equivalent of Small Base Full Length Resized for reloaders. And again, a different LOT of power, primer, and bullets than the home loader used.....

    If you start adding the variables, you can see how there could be a difference.

    I'm curious: How many rounds of each did you fire??~Muir

  3. #3
    Quote Originally Posted by Muir View Post
    If you start adding the variables, you can see how there could be a difference.
    I'm curious: How many rounds of each did you fire??~Muir
    Oh I figured there would be a difference and its not some much the value but the percentage of the expected figure that surprised me.
    all old barrels on my irons
    new brass
    crimped and on the whole fairly deep seated loads

    the one that stands out is the 300wm H1000 load
    they get 2869fps
    I am getting 2670 +/- 30fps

    I would have fired more but we had to stop earlier than planned (more on that another time!)

    I was thinking that MVs from powder manufactures are a bit like Fuel Economy figures from car makers!!!
    Case: Winchester
    Twist: 1:10"
    Primer: Winchester LRM, Large Rifle Magnum
    Barrel Length: 24"
    Trim Length: 2.610"


    BULLET WEIGHT208 GR. HDY A-MAX

    Starting Loads
    Maximum Loads

    Manufacturer
    Powder
    Bullet Diam.
    C.O.L.

    Grs.
    Vel. (ft/s)

    Pressure

    Grs.

    Vel. (ft/s)

    Pressure

    Hodgdon
    H1000
    .308"
    3.420"

    71.7
    2,650
    47,800 PSI

    78.0C
    2,869
    60,200 PSI





  4. #4
    Every barrel is different so it is hard to match listed data, once I tried to avhieve the velocity nosler gives to there 85gr ballistic tips in 25 06 calibre, I went 3grs over there maxload and I was still 200fps shy, my m8 has got a remmy 308 with 26 inch barrel, ive a remmy with a 26 inch armalon barrel, we use identical components, mine launches a 155gr scenar at 2933fps on 41 grs of rs40, my mates remmy is running on 42.5grs of rs40 and he only gets 2820fps,1.5grs of more powder and over 100fps slower, listed data is only a guide really.

  5. #5
    Why did you need to stop testing early Ed?

  6. #6
    I must say the I agree with bewsher500 regarding the figures published by the powder manufactures being similar to those fuel consumption numbers from motor manufacturers, i.e. unrealistic.
    I have found that the numbers published in the Speer manuals are much closer to reality. Perhaps that is because Speer mainly (but not exclusively) use real sporting rifles for their testing ?
    A pessimist is an optimist with experience.

  7. #7
    Quote Originally Posted by swarovski View Post
    Every barrel is different so it is hard to match listed data, once I tried to avhieve the velocity nosler gives to there 85gr ballistic tips in 25 06 calibre, I went 3grs over there maxload and I was still 200fps shy, my m8 has got a remmy 308 with 26 inch barrel, ive a remmy with a 26 inch armalon barrel, we use identical components, mine launches a 155gr scenar at 2933fps on 41 grs of rs40, my mates remmy is running on 42.5grs of rs40 and he only gets 2820fps,1.5grs of more powder and over 100fps slower, listed data is only a guide really.
    wow!
    that is a big difference
    but I get the issue with trying to reach the data
    thats the bit I guess I am getting at
    people chasing the book data and running close to the limits of components and rifles

    Quote Originally Posted by Cadex View Post
    Why did you need to stop testing early Ed?
    It got...er...awfully windy...localised gusting!

  8. #8
    You are probably right about the Speer. The last time I looked, they were still using sporting rifles.

    As to the data in general, it was mentioned that the data is only a guide: What they got, on that day with their equipment. For us, our loads are what they are. The problem comes with folks wanting to plug in book-published velocities to a ballistic's APP and become a woodland sniper. The problem with that, besides the unlikelihood of the published speeds being what the reloader is getting, is that the ballistic coefficient for that bullet is bound to be somewhat different than what the manufacturer claims due to differences in velocity, temperature, barometric pressure, humidity and altitude.

    The only way to build your 'drops' table with some surety is to get a chronograph and fire 20 rounds for velocity at 15 Ft for your average, and then 20 rounds at 100 yards for velocity. Plug these numbers into the proper ballistics calculator and you've got your BC and your muzzle velocity and you're set. Once you get used to doing it this way you tend to give just a passing nod to the published velocities.~Muir

  9. #9
    I am not feeling inadequate for not reaching the published figures but it seems common that the book figures especially those of powder manufacturers are more often than not HIGHER than those

    call me a cynic.....but that makes me think it is more about the marketing than the truth

    Jaguar marketed the E-type as a 150mph car
    true. one did once hit 150mph on the M1...stripped out to the absolute minimum weight running race fuel!

  10. #10
    Quote Originally Posted by bewsher500 View Post
    I am not feeling inadequate for not reaching the published figures but it seems common that the book figures especially those of powder manufacturers are more often than not HIGHER than those

    call me a cynic.....but that makes me think it is more about the marketing than the truth

    Jaguar marketed the E-type as a 150mph car
    true. one did once hit 150mph on the M1...stripped out to the absolute minimum weight running race fuel!
    Playing with the numbers is just not that easy.
    I used to consult with a ammo maker and in the ballistics lab the data was retained as record. Pressure and velocity becomes a matter of record in case of litigation. You need to have an accurate accounting of the performance/safety of the product you're selling. When an attorney asks how you (the manufacturer) know that the ammo/data was safe you need to produce it, for each LOT marketed. Ammo was always reviewed for adherence to expected/published spec. Despite this, we would get phone calls from people complaining that the velocity they were getting was not the same as what was advertized. ~Muir

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