freebore [leade] in the grendel

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  • first strike

    freebore [leade] in the grendel

    hello all,,been reading this forum for a year,,enlightening and entertaining..now that i have one figured i'd better join..i have a question,fired my rifle yesterday for the first time,20 rds to break in as recommended..when finished the're wasn't much of a group.i used factory 120 nbt to get a base before reloading..these rounds are about 2.242 oal,,after measuring the chamber i come up with 2.313 when touching..or .071 off with this round..then measured the 123 amax..it;s 1.769 to ogive or 2.360 oal,,loaded to mag length thats .100 off..i don't have any referance,,is this normal for this rifle or is my math screwed up?? the rifle is at the upper end costwise and i'm sure if there is a problem it'll get corrected..not sure i have a problem,,just seems a long way off..appreciate any help..

  • #2
    Originally posted by first strike View Post
    hello all,,been reading this forum for a year,,enlightening and entertaining..now that i have one figured i'd better join..i have a question,fired my rifle yesterday for the first time,20 rds to break in as recommended..when finished the're wasn't much of a group.i used factory 120 nbt to get a base before reloading..these rounds are about 2.242 oal,,after measuring the chamber i come up with 2.313 when touching..or .071 off with this round..then measured the 123 amax..it;s 1.769 to ogive or 2.360 oal,,loaded to mag length thats .100 off..i don't have any referance,,is this normal for this rifle or is my math screwed up?? the rifle is at the upper end costwise and i'm sure if there is a problem it'll get corrected..not sure i have a problem,,just seems a long way off..appreciate any help..
    first strike,
    I just finished reloading and getting very similar measurements. My reloads with a Hornady 95 VMAX is .090 under recommended COL.
    I measured my chamber with:
    Hornady 95g VMAX @ ogive-1.641, COL-2.167 The Hornady Handbook recommended COL 2.245 that's difference of .078.
    I got similar results with the Sierra 120 Pro-Hunter and Nolser 120 BT. Anyone else seeing the same thing. Or worse case, my measurements are wrong and I'll be shooting reloads with a .090 jump, could that be dangerous?

    first strike, welcome to the board
    Last edited by Guest; 01-21-2012, 09:36 PM.

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    • first strike

      #3
      whelenon..thank you for the welcome and the reply..from what i've read here others load the 123 amax at 2.250 in order to get .010 jump,if i load at that i have .110 jump.i hope others reply so i [we] know what is the norm..i don't think safety is an issue,,for a given load the longer the jump the less the pressure..accuracy is what i'm concerned about..coming from a 6br background i might be expecting too much too soon..i'll load the amax and target it next week,hope it works out as i really like the quality of this rifle as well as the folks that own the company..does your's shoot that 95 well? thats the bottom line..regards

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      • #4
        i'm completely new to this forum, not to loading, however. have just picked up a very nice upper from msserge here on site and cannot find any loaded ammo or brass in the san antonio area, so have hit sinclair for brass and have redding s type bushing dies on the way. all said, i have no experience-yet-with this round. but...in seeing the issues of leade with any round that's confined to magazine length, hence a long jump to overcome, would it not make sense that barnes or bergers, which are well known for their preference for the long leap to the lands, work better in this circumstance? again, i have nothing to bring to the table of actual experience, but in working with a noveske spr and the same issue, there might be some similarity. not certain of the answer, largely thinking out loud, wonder of other's experience. thx.

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        • Drifter
          Chieftain
          • Mar 2011
          • 1662

          #5
          FWIW, 123gr A-max seems to be the most forgiving bullet when reloading for the Grendel. While each barrel might have a slightly different preference, COL between 2.245 and 2.255 seems to often be best for accuracy (and shorter than 2.260 that's usually considered mag length). IIRC, Hornady factory loads for the 123gr A-max are ~2.245, and usually shoot quite well.

          Since Hornady brass is usually ~$70 per hundred, it's not a bad idea to buy factory ammo instead for ~$100 per hundred. It serves as a good base point for rifle function and accuracy, and obviously the brass is good for reloading. Keep a few factory rounds in reserve so if there's ever any doubt about performance of reloaded ammo, a few shots with the factory load will reveal whether a potential issue is with the ammo or the weapon itself.

          If you prefer Lapua / AA brass, it doesn't make as much sense economically to buy loaded ammo for the brass, and there doesn't seem to be much difference in results between new and once-fired Lapua, but the 123gr A-max is still a good bullet when learning to load for the Grendel.
          Drifter

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          • RangerRick

            #6
            Welcome First Strike! (did you serve in 1st of the 502d?),

            Mag length is going to be the limiting factor if you need to seat long. I can usually get about 2.27 without binding a full mag.

            RR

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            • #7
              Hi, y'all. First post, but I've been reading for awhile.

              First-strike, I have a .264 LBC barrel and my measurements are almost exactly like yours: 1.784 to ogive / 2.360 oal for 123 grain Scenars, and 1.773" to ogive / 2.356" oal for 123 grain AMAXs, and 1.777" to ogive / 2.288" oal for 123 grain Nosler Custom Competitions. The Noslers have a less agressive tangent ogive than the others, and I suspect that they're built like the SMKs. Other than flyers, which I'm convinced are the 1st round coming off the magazine when I drop the bolt, I've gotten the AMAXs to shoot tight into basically one hole with XBR at 100 yards with consistency. Working the seating depth, it was obvious that they like 2.265" oal in my gun, with new or fired cases. I just started working the Noslers, and I'm walking a different path with those using Benchmark and Federal match primers.

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              • #8
                Hi First Strike, Welcome.

                Your measurements are correct and I agree that the Hornady 123 A-Max is the most forgiving bullet, accepting a fairly wide range of jump lengths while still delivering excellent accuracy. It is a very good place to start your accuracy evaluation. Bill Alexander advises that his compound throat makes jump measurements null and void and not to do it. I'm not sure what he knows that I don't but I've found measurements to be very revealing. Things like some of the bullets if seated at mag length are jammed into the throat significantly and others have huge jumps. What you do with that knowledge is up to you.

                In general VLD (secant ogive) designed bullets are the most sensitive to jump length, some require that the bullets be jammed into the rifling hard to shoot their best, but these same bullets will often have nodes at other jump distances that shoot just as well such as 0.030" off or 0.080" off or some times even greater. While other bullets shoot well at almost any jump length, these are typically tangent ogive designs. The 123 A-Max is of this design as is the 120 grain SMK. Those are two bullets well suited to the Grendel. The 123 Sceenar and 123 SMK are examples of bullets that are of VLD design and typically show a strong preference for a very specific jump distance. They are more desirable for their ability to cut through the air with greater efficiency but plagued by accuracy problems. Even if you are successful finding a jump length that works well, you will have to chase the lands as your throat wears and change seating depth from lot to lot of bullets as required by the ogive variance.
                For magazine length loads I generally stay away from VLD designed bullets. I do use VLD designs in single load applications and some long range hunting applications where wind doping is a strong factor. But even then I'm not convinced it is worth the hassle of maintaining the accuracy. Luckily I have a few rifles that the mag length loads match up with VLD bullets preferred jump length and I happily shoot them until the throat erodes away from this sweet spot. None of these are Grendel AR's though.
                I hope this helps and doesn't confuse.
                Bob
                Last edited by Guest; 01-22-2012, 02:31 PM.

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                • 6BRshooter

                  #9
                  I have a 264LBC barrel and with 123 NCC, my JAM figure from the ogive is 1.700". That is an ave from 5 measurements. The barrel was brand new and sometimes that figure will lengthen .005 thou as the burr on the rifling from chamber reamer is smoothed out. I need to remeasure tonight. I know with my very short throat that my 123NCC are crunching good in the 29.0 varg at 1.690"

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                  • first strike

                    #10
                    thanks all for taking the time to reply..builder asked if i used a hornady or lapua modified case to measure but i haven't heard from since,,after measuring both i don't know the difference..ranger rick..not in the 502nd,,2nd mar.div..in country 67-68..but we were all brothers and thats a fact..

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                    • RangerRick

                      #11
                      Originally posted by first strike View Post
                      thanks all for taking the time to reply..builder asked if i used a hornady or lapua modified case to measure but i haven't heard from since,,after measuring both i don't know the difference..ranger rick..not in the 502nd,,2nd mar.div..in country 67-68..but we were all brothers and thats a fact..
                      The reason I ask is that the motto of the first batt of the five oh deuce is "First Strike." I was in later, but amen to the "we are all brothers."

                      Welcome to the forum, thank you for your service during a rough time, and Welcome Home!

                      RR

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                      • BjornF16
                        Chieftain
                        • Jun 2011
                        • 1825

                        #12
                        builder asked if i used a hornady or lapua modified case to measure but i haven't heard from since,,after measuring both i don't know the difference
                        Never occurred to me...will it make a difference if I use Hornady modified case versus making one from lapua brass?
                        LIFE member: NRA, TSRA, SAF, GOA
                        Defend the Constitution and our 2A Rights!

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                        • txgunner00
                          Chieftain
                          • Mar 2011
                          • 2070

                          #13
                          Originally posted by BjornF16 View Post
                          Never occurred to me...will it make a difference if I use Hornady modified case versus making one from lapua brass?
                          Shouldn't matter if it was fire formed in your gun. I used fire-formed IMI 7.62x39 brass to make mine.
                          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.

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                          • first strike

                            #14
                            i used a once fired lapua case today to measure and it actually came out .010 more than the hornady modified case for both the 123 amax and 120 nbt..i guess what i'm really trying to find out is if .100 jump w/123amax normal? shot to break in barrel last week,,will shoot for groups this friday..if it shoots well then i wasted everybodys time over a moot point..[actually i hope that happens then all i have to do is apoligize]regards. f/s
                            Last edited by Guest; 01-26-2012, 06:48 PM.

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                            • BjornF16
                              Chieftain
                              • Jun 2011
                              • 1825

                              #15
                              I have a once fired Lapua cartidge that I used first, then got the Hornady "commercial" modified case (never been fired).
                              LIFE member: NRA, TSRA, SAF, GOA
                              Defend the Constitution and our 2A Rights!

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