first round fired, need a bit of guidance

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  • first round fired, need a bit of guidance

    So after many weeks of anticipation, finally got all my loading gear in one place, assembled three loads to function test, get scope lined up, etc. 107 Sierra over 29.0 of 8208, old Nosler 120 BT's and 123 Amax over 28.0 TAC. All went better than I'd expected, having depended on wisdom and experience gleaned from this site-thank you.

    Do have a question related to attached photo-every piece of brass has a similar dent in neck, regardless of load. This is from 24" Satern 8.75 twist barrel upper sitting on Noveske lower. Run a Tubb flat wound spring and Spikes T2 buffer, which functions perfectly with 75-77gr reloads in 18" SPR upper, and truthfully, both 120-123 loads throws brass in a nice small pile, locked bolt open, no function issues, but did dent Lapua brass. Any comments as to source of dents or way to alleviate condition?

    Very impressed with Grendel for first outing, took some chrono results and appears my barrel may be 'fast', based on some results I've seen and no readily evident signs of pressure. Pretty good day at the range, already have another pass loaded to go today if the weather will cooperate. Thanks for any assistance with above. First time uploading photos, as well. This from Iphone, but have also set up Flickr account.

    Last edited by Guest; 02-12-2012, 01:20 PM.
  • leopard6.5

    #2
    bobke: I couldn't view your picture but from the same description on this forum and the old forum the cause was usually from the brass hitting the deflector on the upper.

    A few times people have found it happening from the brass hitting a hard surface like concrete, etc., but it is usually from hitting the deflector.

    Most people just put a piece of the velcro( the softer side) on the deflector and it seems to solve the problem.

    Hopefully this helps and good shooting.

    Lee

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    • #3
      i'm heading to the hardware store for some velcro, for a temp fix. Could there be more to do with the timing at which brass is ejected? I'm just thinking out loud here, but with flat spring and T2 buffer and UBR stock, would rifle length buffer/spring make any difference in this-have a PRS that I could reinstall, as required. Also have a Tubb carrier weight if I needed to slow down bolt further. Upper also has an adjustable gas block, and since this upper is new to me, haven't had opportunity to adjust in any direction. Again, brass is ejected into a pretty neat pile at about 4 o'clock, 8-9 feet from bench, so something is right in the setup.

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      • #4
        Ditto on the deflector diagnosis: and how fast the brass is rotating from the ejector spring, how fast it's traveling straight back just before release, and when it's clearing the front cutout.

        See here: http://www.youtube.com/watch?v=gduok...feature=relmfu

        If it's really bothersome (or destructively severe) I'd just cut a 1/8-3/16" thick piece of a dry sink sponge about a 1/2" square and glue it to the deflector face and forget about it.
        Last edited by Guest; 02-15-2012, 03:22 AM.

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        • txgunner00
          Chieftain
          • Mar 2011
          • 2070

          #5
          I had the same denting issue when I was running a standard upper. I tried several things to "fix" the timing but in the end, a fuzzy side velcro pad was the solution. I now run a billet upper w/o a deflector. No dents.
          NRA life, GOA life, SAF, and TSRA

          "I ask, Sir, what is the militia? It is the whole people, except for a few public officials. To disarm the people is the best and most effectual way to enslave them."

          George Mason, co-author, 2nd Amendment.

          Comment


          • #6
            did the velcro patch on deflector, which did reduce neck denting by about 50%. but...in looking in the tech threads here, the ejector spring tension and degree of gas turned on/off with adjustable gas block may be the real answer. won't know til this weekend, but have the springs on the way from Brownell's and will know immediately thereafter. czeck this thread out.

            Finding dents on my ejected case main body (my Satern Spartan home build, see first picture). I don't get this dent on my AA built Entry upper. The middle picture shows lack of denting on neck with my home build, while the third picture is the dented neck from AA Entry. What would cause the dented main body? Will this affect

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            • txgunner00
              Chieftain
              • Mar 2011
              • 2070

              #7
              Originally posted by bobke View Post
              did the velcro patch on deflector, which did reduce neck denting by about 50%. but...in looking in the tech threads here, the ejector spring tension and degree of gas turned on/off with adjustable gas block may be the real answer. won't know til this weekend, but have the springs on the way from Brownell's and will know immediately thereafter. czeck this thread out.

              http://www.65grendel.com/forum/showt...se-on-ejection
              Tuning the gas and springs is the real answer. Just be aware that it could vary for different loads. I could get it to stop for my 123 match loads but 100 gr loads wouldn't cycle reliably.
              NRA life, GOA life, SAF, and TSRA

              "I ask, Sir, what is the militia? It is the whole people, except for a few public officials. To disarm the people is the best and most effectual way to enslave them."

              George Mason, co-author, 2nd Amendment.

              Comment


              • #8
                I feel pretty sure I can get this tuned in properly, but have spent most of my AR time with 75-77gr loads in 223, and have that dialed, but gaining experience by the weekends only with Grendel right now. Have 8.75 twist Satern and haven't arrived at loads that shoot best yet, but will likely work with a setup that will accomodate both 107's and 123's, if possible. Wouldn't think this would have to be that specific, as 223 if pretty flexible, but will do what's necessary for it to work. Appreciate the assist from those here on forum-very useful/helpful info.

                Comment


                • #9
                  You should be able to find an ejector spring tension that will reliably eject the range of bullets you are wanting to use without damaging your brass. I have done so for several Grendels. After a while you get a feel for the proper spring tension and it is no big deal. Rather than clip mine I grind them with a bench grinder and trial fit the ejector and feel the pressure with my finger or by placing a case under the extrator and pivoting it to comperss the ejector. You just want enough tension that it will resist compressin but is easily accomplished. I shoot all the way from 81.5 to 142 grain bullets out of mine with no issues.

                  I also use the Hornady 75 grain BTHP and Sierra 77 grain Match King out of my .223 with excellent results, they are both great bullets and very insenistive to jump length. I think you will find the Hornady 123 grain A-Max and the Sierra 120 grain Match King in the Grendel to be very similar to your .223 experience but other bullets will require more fiddleing.
                  Bob

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                  • #10
                    Another good day at the range. Did the ejector spring mod, starting by reducing the length of same by .050, from .910 to .860, and shot 40 rounds of mixed bullet weights from 100 BT's to 123 AMAX , all with TAC and RP 7 1/2 primers for a constant of sorts. Also have the velcro on deflector and while not absolutely perfect, has substantially and almost entirely eliminated the dented necks of two weeks ago. Running Tubb flat spring, T2 buffer and Tubb carrier weight insert to delay ejection as long as possible and the combination seems to be working. Actions stays open on last shot, spent cases in a fairly small area and hasn't missed a beat as yet. Haven't adjusted the gas just yet and will work with that next pass at the range, but I'm starting to feel pretty optimistic about possibilities with this round. Thanks for the heads up on this one, I'm going to try same mod on my 223 bolt next and see how that functions. Picked up a few extra springs, but seems measure twice, cut once is in order on this fix.

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