IMR 4198 short stroking

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  • Jgloveracob

    IMR 4198 short stroking

    Im shooting 95g V-max. With 25.2g of IMR 4198 (max/Compressed load) It wont eject spent brass. But with 24.8 IMR 4198 it will eject brass but will not strip an new round out of the magazine.

    What is the problem? 28g of benchmark runs just fine. H335 works as well.

    Hornady brass, federal match primers, 95 vmax.
  • Drifter
    Chieftain
    • Mar 2011
    • 1662

    #2
    Short-stroking in a setup that normally runs fine is usually tied to fast burning powders, light bullets, or a combination of the two.

    4198 is a relatively fast burning powder for the Grendel, and the 95gr V-max is a relatively light bullet. If you insist on using this recipe, you'll need to modify your setup for reliable operation. Lighter BCG, lighter buffer, and / or weaker buffer spring might help.

    You might consider a slower burning powder instead of modifying your setup.

    Glancing at AA's load data, 4198 is faster than any powder on the chart. Perhaps 4198's absence is for good reason...
    Drifter

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    • rasp65
      Warrior
      • Mar 2011
      • 660

      #3
      JGlove IMR 4198 is just not a good choice for the Grendel. Like Drifter says something slower would be a good choice. Stick with 335 or or benchmark with the 95 V-Max. And if you go to heavier bullets you will want powders in the 2520 range. Search the reloading section here there is a wealth of knowledge and some excellent contributers, or better yet readall the posts and you can save yourself time in finding a good load for your rifle.

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      • #4
        Originally posted by Jgloveracob View Post
        Im shooting 95g V-max. With 25.2g of IMR 4198 (max/Compressed load) It wont eject spent brass. But with 24.8 IMR 4198 it will eject brass but will not strip an new round out of the magazine.
        .
        I think you have a couple things going on here.
        First, when a powder burns it produces gas, this gas travels down the bore and some of it enters the gas port and cycles the action. This is called "Port Pressure". The faster the burn rate of the powder the less gas traveling down the bore thus the less port pressure, the slower the burn, the more gas and the more port pressure. IMR 4198 is on the fast side and is not producing enough port pressure to cycle the action. This is common and not the fault of the rifle or the gas system. Switching to a slower burning powder will increase the port pressure and cycle the action.

        Second, your 24.8gr load will eject the spent round. Increasing the charge to 25.2gr would not eject the spent round. Why? Why would 24.8gr eject and 25.2 not eject? Answer, Pressure, Chamber Pressure, not port pressure. Your 25.2gr is over pressure and the case is sticking in the chamber, this is akin to a stiff bolt lift in a bolt action. Couple the over pressure load with the weak port pressure and the spent round stays put.

        Switch to a slower burning powder, start low and work up and look for them there high pressure signs.
        Last edited by Guest; 12-24-2011, 01:42 PM.

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        • Jgloveracob

          #5
          Alright thanks guys, I found a good load with H335. I wish I could use the 4198 as it shot great. but oh well

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