73gr. ELD-M in 1-9 twist ?
- Thread starter jotrot
- Start date
I’ve shot a bunch of them through the same hole in a 9 twist at 100 yards and 5 inch groups at 700 yards in a factory Remington barrel. Mine liked 25 grains of TAC and 0.050 off the lands. I throated the barrel to get them out to 2.545 COL. 2900 fps was the ticket.
The 73 grain ELD-M Bullet has been shortened a Bit, as it's, a "Downsized", 75 grain, ELD-M to Fit, in AR Magazines with, the desired, COAL's required, by them. Since "Shorter", they DO work, in 1-9 Twists so, the 1-8 twist, is NOT needed. Some 1-9's, won't stabilize, the 75 gr., M's very "well" ( Elev and Temp, dependent ).
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Thanks, may grab some, shot the new 22cm barrel today 18" 1:9 with 69 tmk and got them going pretty good, think my starline brass was thick necked, hornady brass was ok.
Will work on my neck thickness and then try 73's
Ned Ludd
Silver $$ Contributor
This type of question has been coming up often here of late. Hornady recommends a minimum 1:8 twist barrel. They aren't making that recommendation just to hear themselves think out loud. There is a reason for it. Here's the reason: when the gyroscopic stability coefficient (Sg) starts getting down into the mid 1.3s down to about 1.1 or so, the bullet may fly with sufficient stability that one might not ever notice obvious signs of gyroscopic instability such as oblong holes in the target, keyholing, or even tumbling at longer distances. However, that does not mean the bullet's trajectory is unaffected by the insufficient twist rate. Within that sub-optimal Sg range, the predominant effect is loss of intrinsic BC rather than more obvious signs of gyroscopic instability. In other words, the bullet will behave as though the BC is much lower than it actually is, thereby increasing wind deflection. As the Sg value goes even lower, groups may start to open up noticeably, and generate oblong holes in the target, or even keyholes.
Does that matter to everyone? Obviously not. For those that just wish to shoot with reasonable precision and are not overly concerned with BC, such sub-optimal twist rate scenarios of ~1.25-1.3 Sg and higher may work just fine and may never even be noticed. For those that use a specific bullet with the intent of getting the very most out of the advertised BC, maybe this approach doesn't work so well. If one wishes to try a specific bullet in a sub-optimal twist barrel setup, have at it. As long as the predicted Sg values fall somewhere in the range of let's say maybe about 1.20 to 1.49, the bullet will likely fly reasonably well (FWIW - I'm making a total SWAG with these Sg values, but that range is probably not too far off the mark). I once had a .223 Rem rifle with a validated 10-twist barrel that would shoot 77 gr Sierra Matchking commercial ammunition just fine, even though on paper it really shouldn't have worked very well. One simply has to run a prediction at an online stability calculator such as JBM (https://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi). If the predicted Sg is greater than about 1.2 or so, then it's probably worth a try. At that point the best thing to do is load/shoot the bullet and see how it behaves in the specific rifle setup. Then you'll know.
To the OP, the 73 ELDM is only about 7% longer than the 69 TMK. They may not behave all that differently from a 9-twist barrel. Further, several posters herein have claimed success running the 73 ELDMs out of 9-twist barrels. As long as you are not overly concerned with some loss of intrinsic BC for your specific application, that should be sufficient evidence to give them a try in your rifle. I'd suggest buying one box to load and test, which should be more than enough for that purpose, but won't break the bank if they don't shoot as well as you'd like. Please let us know how they work out for you.
Does that matter to everyone? Obviously not. For those that just wish to shoot with reasonable precision and are not overly concerned with BC, such sub-optimal twist rate scenarios of ~1.25-1.3 Sg and higher may work just fine and may never even be noticed. For those that use a specific bullet with the intent of getting the very most out of the advertised BC, maybe this approach doesn't work so well. If one wishes to try a specific bullet in a sub-optimal twist barrel setup, have at it. As long as the predicted Sg values fall somewhere in the range of let's say maybe about 1.20 to 1.49, the bullet will likely fly reasonably well (FWIW - I'm making a total SWAG with these Sg values, but that range is probably not too far off the mark). I once had a .223 Rem rifle with a validated 10-twist barrel that would shoot 77 gr Sierra Matchking commercial ammunition just fine, even though on paper it really shouldn't have worked very well. One simply has to run a prediction at an online stability calculator such as JBM (https://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi). If the predicted Sg is greater than about 1.2 or so, then it's probably worth a try. At that point the best thing to do is load/shoot the bullet and see how it behaves in the specific rifle setup. Then you'll know.
To the OP, the 73 ELDM is only about 7% longer than the 69 TMK. They may not behave all that differently from a 9-twist barrel. Further, several posters herein have claimed success running the 73 ELDMs out of 9-twist barrels. As long as you are not overly concerned with some loss of intrinsic BC for your specific application, that should be sufficient evidence to give them a try in your rifle. I'd suggest buying one box to load and test, which should be more than enough for that purpose, but won't break the bank if they don't shoot as well as you'd like. Please let us know how they work out for you.
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I don't want to be the cat turd in the sand box but don't get your expectations too high. They don't always stabilize well in a 9 twist rifle. Higher elevations help alot and pushing them above 3000 fps helps a tiny bit as well. Good luck. My 9 twist 223 doesn't stabilize them at 780' elevation.
I've never shot any bullets heavier than a 70 gn VLD in my Savage LRPV 9 twist 26" 223 Rem CBI barrel UNTIL this morning.
No load development and probably such low velocity it shouldn't have shot well at all, but...
This barrel has been a very accurate barrel for the past few thousand rounds, but had started to become somewhat finicky lately. I bought the David Tubb throat maintenance system which comes with 50 Sierra 77gn match bullets impregnated with a very fine abrasive to lap the throat with. I loaded up 6 bullets in virgin Starline brass with CCI primers and 20.5 gns of Benchmark. (Instructions say to use a fast powder with a minimum charge). I have always been told the absolute max weight bullet that will stabilize from a 9 twist barrel is a 75 gn but you had to really push it hard to do it. These 77s grouped VERY tight at around .350" c to c @ 100 yds. all with no load development and at the lowest velocity possible. I can't wait to get hold of a box of those 73ELDs you ask about to try those as I'm sure they too will shoot.
No load development and probably such low velocity it shouldn't have shot well at all, but...
This barrel has been a very accurate barrel for the past few thousand rounds, but had started to become somewhat finicky lately. I bought the David Tubb throat maintenance system which comes with 50 Sierra 77gn match bullets impregnated with a very fine abrasive to lap the throat with. I loaded up 6 bullets in virgin Starline brass with CCI primers and 20.5 gns of Benchmark. (Instructions say to use a fast powder with a minimum charge). I have always been told the absolute max weight bullet that will stabilize from a 9 twist barrel is a 75 gn but you had to really push it hard to do it. These 77s grouped VERY tight at around .350" c to c @ 100 yds. all with no load development and at the lowest velocity possible. I can't wait to get hold of a box of those 73ELDs you ask about to try those as I'm sure they too will shoot.
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