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.
    tonytoshiba likes this.
    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 09:09 PM.

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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!

  7. #6
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    First what kind of shift is it.....? Is it high velocity problems or low velocity problems, because you never really explained that and what you have said is vague.

    Several things here could cause high velocity problems, carbon ring, powder temp instability(can effect high or low velocity changes), powder measurements off, doughnut in the neck/shoulder junction, cases not trimmed to spec max spec and causing a bullet crimp Several things here could cause this, carbon ring, powder temp instability, powder measurements off, doughnut in the neck/shoulder junction, cases not trimmed to max length spec and causing a bullet crimp unknowingly.
    How many reloadings are on the brass, might be hard brass, it maybe need to be annealed.

    Lots of issues could be here. Like others have said, get a chronograph as your guessing, a really nice F-class shooter told me if you don’t measure things or have measurements of things your just guessing.
    Last edited by IHFarmer07; 12-05-2019 at 11:41 AM.
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  8. #7
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    Consistancy

    Quote Originally Posted by Rparker View Post
    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?
    =============================================
    I always weigh every charge when loading high intensity rounds like the 300 Win Mag, even the weight of the empty brass. They also seem to like close to max loads the best, which is also why I weigh each load and case. In reality, all calibers would benefit from being so meticulous, but it is amplified with higher pressure cartridges. They also like longer barrels, preferably a 26" for large charges of slow burning powder. IMR 4350 has proven to produce good clean burns with 165 gr. Nosler for me.

    One thing you will also encounter with high intensity cartridges is copper buildup, especially at the throat that is often hidden from the eye, can cause erratic groups. Try soaking the bore clear to chamber for an hour or so, and running a patch to see if there is any trace of green on it. It is one of the most neglected aspects of accluracy.

  9. #8
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    With electronic scales and auto powder drops I have found that temperature variations cause measuring errors. I maintain my reloading corner at 68℉ which keeps powder variations @ 0.1g. I am filling 338 LM. My sweet wife has mentioned to me that I am a bit anal, I prefer that I am particular and try hard to remove variations.
    With chronographs I have had some crazy velocity changes. I have moved the chronograph out to 14 feet from end of barrel. With the cartridge of 338 LM the barrel exhaust was causing the incorrect data.
    As in all troubleshooting, keep removing one possibility after another until only one is left. Problem found, now the need to ensure it never returns.

    Be safe, have fun and good shooting.

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