Massive velocity problems. Please help.

Massive velocity problems. Please help.

This is a discussion on Massive velocity problems. Please help. within the Reloading forums, part of the Sniping Related category; I have a remington sendaro II/ 300 win mag. The load is Sierra match-king HPBT 175gr. Powder- 72.5 gr of IMR 4831. Norma brass. Federal ...

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Thread: Massive velocity problems. Please help.

  1. #1
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    Massive velocity problems. Please help.

    I have a remington sendaro II/ 300 win mag.

    The load is Sierra match-king HPBT 175gr. Powder- 72.5 gr of IMR 4831. Norma brass. Federal 215M primers.

    I have seen massive velocity shifts with this round and I just canít figure out what the problem is. At 600 yards I have a 1.7 mil shift at a 40 degree temperature change. At 1000 yards itís a massive 5.2 mil shift at only a 60 degrees in temperature change.

    When I put this data into a calculator itís says I have an almost 700 FPS change in velocity. I doubt thatís right though.

    The rounds are exposed to outside temperature but are kept in a box so no sun. There are some elevation shift when I collect data but I doubt that the problem.

    Iím using a RCBS charge master 1500 the powder is the same every time.

    Is this normal? Has anyone had this problem before? If so what where some solutions? Can you predict velocity changes with change is powder temp?

  2. #2
    Member lathoto's Avatar
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    I would check the repeatability of the chargemaster.
    See you at the range.

  3. #3
    Senior Member Gunguy308's Avatar
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    Here is some info from the Hodgdon website. It is a comparison of their Extreme powders (known to be some of the most temp insensitive) with other commercial powders. Question, how does that load group at 100 yards? Are you picking up your powder pan as soon as you hear the BEEP, or waiting to confirm the correct load on the display? What barrel profile? How many shot at a time? Is your barrel getting really hot? What scope? Have you checked the scope and mounts? Tracking test at 100 yards? Action screws checked for proper torque? Have you chronographed your ammo to ensure its an ammo issue and not something else? These are just some of the standard things to check.


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    Last edited by Gunguy308; 11-30-2019 at 10:09 PM.
    straightshooter1 likes this.

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  5. #4
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    Get a chronograph. Right now you're guessing that you're having velocity problems. It could be (no insult here, we all screw up) a shooter issue or a rifle issue or an optic issue or a mounting system issue.

    Now, if you're trusting a Chargemaster to be dead on every time, you're kidding yourself in a dangerous way. Electronic scales and automatic dispensing systems are temperamental and sensitive to electromagnetic interference, creep and all kinds of other bugaboos that have lead to more broken guns than I can count. I have seen this size of issue crop up with large (75gr+ capacity) cases and auto-dispensing of powder charges. Frequent tare-ing, lifting the pan and setting it back down after the charge dispenses, checking for verification on a high quality beam scale and other methods.

    IMR 4831 is has a normal MV variation in the size case you're using of >1fps per degree F like most of the older IMR powders. That said, going all the way to 2fps per degree... that's saying something about the powder itself.

    So, get a chronograph so you can be sure, try verifying your powder weights on a beam scale, get another can of 4831 from a different lot and test that alongside what you have on hand. Might just be a screwy lot. Report back with single variable elimination results and we'll pick it apart.

  6. #5
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    My guess is it is either charge master inconsistency or action bolt torque is off or loose.

    Good luck!

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