I shot a match at Camp Lejeune a couple of weeks ago. On Saturday I shot a load of N140 with the 88's but it didn't shoot very well, but I didn't blow up any bullets. On Sunday I switched to a load of CFE223 and it shot great up to about shot 15 and I got a 6 in the lower right hand corner of the paper. The next shot the puller couldn't find. After those two it was right back in the 10 ring to finish. Next relay went to crap so I just packed it in for that match. Last weekend at Camp Butner I shot the CFE223 load again with moly bullets in a practice match on Friday with E-targets and had about 1 in 10 bullets not show up. Finally a Marine shooter behind me said he saw one blow up so I finished the day with the .223 and then went to the .308 for the weekend. You are correct that if a bullet doesn't show on the computer and there are no crossfires then you get to shoot again. If someone sees them blow up.....well then you're just SOL. I think E-targets are the future and we'll just have to work through the problems and find solutions.
90 SMK vs 88 Hornady ELD loading
- Thread starter Albany Mountain
- Start date
I think barrel length plays a more significant role in blow ups while generally being glossed over in favor of rpm/twist/mv discussions. Rpm determines the stress on the jacket but the strength of the jacket has everything to do with how much the jacket is distorted and how long it is abraded against rifling lands.
Twist comes back in here also because a 6.5tw will have a longer “path” for the land/jacket abrasion to occur than a 7tw would. In a 28” tube, the 7tw adds four bore circumferences to the distance of that path of abrasive contact. That’s about 2.75” more “barrel”. The 6.5 twist adds about 8% more, up to 3” or so. I suspect that this matters also— it’s not purely a case of jacket torque due to twist/mv.
Twist comes back in here also because a 6.5tw will have a longer “path” for the land/jacket abrasion to occur than a 7tw would. In a 28” tube, the 7tw adds four bore circumferences to the distance of that path of abrasive contact. That’s about 2.75” more “barrel”. The 6.5 twist adds about 8% more, up to 3” or so. I suspect that this matters also— it’s not purely a case of jacket torque due to twist/mv.
I used to shoot into a huge backstop faced with multiple layers of old railroad ties at 615 yds. Soon there is a pile of wood and bullets below the target, typically bent but otherwise in decent shape. Even after a winding very long and indirect drive to the backstop, bullets were still hot, sometimes scaldingly so. It’s clear that they picked up carbon, less clear that they leave any copper behind.
I think we soften the jacket and core significantly from friction, and probably there is a formula that says the tiny projectile and large heat sink barrel heat up each other exactly equally in total from frictional contact, with subsequent string bullets getting the detriment of higher ambient temps, direct heat transfer and frictional coefficient from prior shots. Then we load them at their weakest, centrifugally. (There are very good videos online of rotational forces ripping things apart, an indirect credit to our bullets).
Agree that any blowups are too many in competition. The rules permit but don’t require witness paper behind the targets, but I personally don’t think one match director in the country would want to go change that out every string as it backtracks on the benefits of etargets. Once we go for record, no one goes forward of the line unless there’s a real problem.
I think we soften the jacket and core significantly from friction, and probably there is a formula that says the tiny projectile and large heat sink barrel heat up each other exactly equally in total from frictional contact, with subsequent string bullets getting the detriment of higher ambient temps, direct heat transfer and frictional coefficient from prior shots. Then we load them at their weakest, centrifugally. (There are very good videos online of rotational forces ripping things apart, an indirect credit to our bullets).
Agree that any blowups are too many in competition. The rules permit but don’t require witness paper behind the targets, but I personally don’t think one match director in the country would want to go change that out every string as it backtracks on the benefits of etargets. Once we go for record, no one goes forward of the line unless there’s a real problem.
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Ned Ludd
Silver $$ Contributor
The primary cause of jacket failure is friction. The contact surface of the lands heats the bearing surface to a point where it becomes white-hot and the lead core underneath can actually melt and vaporize. This was discussed in some detail in a thread a while back about "comet-tails" on the target face, which was actually molten or vaporized lead spraying out of a crack or hole in the bullet jacket:
High speed videos/images taken with thermal imaging can also be found that clearly show white-hot strips running the length of the bearing surface as the bullet emerges from the bore where the lands engraved. That is all about friction, so barrel length is a big contributor to bullet jacket failure, as has been mentioned. It also goes some way toward explaining why using a less tight bore diameter (i.e. going to a 0.219" bore from a 0.218" bore) might be beneficial.
Comet tails
What the hell are those and why do they happen? Testing a load for a 1913 M96(all matching serial#’s) Trying to replicate the original 140gr load. Powder:43.7gr of RL-22 Bullet: 142gr SMK Primer: S&B LR Case: Win 3rd firing That target is at 50yds. Don’t know what that little smear is...
forum.accurateshooter.com
High speed videos/images taken with thermal imaging can also be found that clearly show white-hot strips running the length of the bearing surface as the bullet emerges from the bore where the lands engraved. That is all about friction, so barrel length is a big contributor to bullet jacket failure, as has been mentioned. It also goes some way toward explaining why using a less tight bore diameter (i.e. going to a 0.219" bore from a 0.218" bore) might be beneficial.
I agree. I have a 224 Grendel in 1:7 Twist Four groove that pushes the 88's at 3000fps with Zero jacket failures. This barrel is only 24" and i believe this is large part of that equation like you point out. Certainly seems to trend that way.
Hi all I am considering chambering a new barrel for F-Class TR and using the 88 ELD-M, would there be any progressions with the 88 ELD-M anyone would care to share.
Thank You
George
Thank You
George
Speaking only from a sling shooter's perspective here (not the pure accuracy requirement of F class). Ive been using N135 and 88's seated 0.010" off the lands this year in my. 223 Palma rifle. 31" 5R Bartlein, .110" freebore reamer. 23.5ish or maybe a bit higher is where it seems happy, which is a pretty stout load of N135. It's a very good combo for sling. Single digit SD's at 1000 on our Silver Mountain targets.
No reason Varget, R15, R15.5, N140, or Shooters World Precision wouldn't work just as well.
Ned Ludd
Silver $$ Contributor
George - if you read through this thread, it pretty much runs the whole gamut. To summarize most of it: if you are planning on using a 30"+ length barrel, I would suggest using a Bartlein 5R in 0.219"/0.224" (bore/groove) configuration. I'd have it chambered with something like 0.250" freebore. I'd order the barrel in 6.7-6.8 twist. If you do all of these things, developing a load that shoots like a laser but still allows all the bullets to actually reach the target with their jackets intact and doesn't kill the brass in 2-3 firings should be relatively straightforward. If I were currently building another F-TR .223 Rem rifle, or having one of my current rifles re-barreled, this is exactly what I would do.
Ned Ludd
Silver $$ Contributor
Just out of curiosity, what kind of muzzle velocity are you getting with that load/setup, and do you have any idea what the bore/groove dimensions of the barrel are? As I mentioned previously in this thread and elsewhere, I have never yet lost a bullet jacket in a 30" 5R 7.0-twist barrel with 0.218"/0.219" bore/groove configuration. However, I will only use 0.219" bore barrels in the future. I suspect I may have been close to jacket failures in the past in matches on hot summer days. Even though I've yet to lose one in that specific barrel setup, I'd rather not push the envelope quite as much in the future.
I'm honestly not sure. I've never shot them across a chronograph. Back calculated from on-target velocities using Hornady's app, it says I'm 2760 fps at the muzzle.
Ive never lost a bullet to my knowledge, either. I have had some not show up at 1000 if its high 40's, low 50's, or if the wind is blowing from 6 o'clock, but thats not uncommon using a .223 at 1000. I've never had any mysteriously dissappear at 900 yards and in, so I'm confident its a target issue, not a bullet poofing issue.
Both myself and a friend shoot the same rifle prone, Shilen barrel 7 twist, and chambered with .220 freebore. My load is 25.0g RL-15, he shoots 25.0g varget. We're both 20k off the lands with 88g ELDM. Neither of us have ever lost a bullet from blowing up. I shot my rifle "just for fun" FTR and was surprised how well the vertical was at 600 yds. (about 2 inches)
Been shooting 223 prone since 2006. My first barrel was a 6.5 twist Pac Nor 3 groove. I lost bullets (90g bergers) as the barrel aged. I'm guessing, from the firecracking and the overspining, jackets failed. 5 barrels later (2 Shilen and 3 Krieger) I've always used 7 twist. Any faster is too much. I live at sea level and shoot in temps in the 40's and 50's at times and have never lost a bullet (any brand or weight) and have never had issues with stabilizing a bullet. Currently using Lapua brass but I have used LC and frankly can't tell the difference on target. LC might even hold up better (primer pockets) Hope this helps............
Should mention I do shoot 90 VLD's at times too. 24.8g RL-15 jammed 20k shoots very well. And, my friend shooting 88g ELDM using the load mentioned above shot a 200-19x prone during a practice string.
Been shooting 223 prone since 2006. My first barrel was a 6.5 twist Pac Nor 3 groove. I lost bullets (90g bergers) as the barrel aged. I'm guessing, from the firecracking and the overspining, jackets failed. 5 barrels later (2 Shilen and 3 Krieger) I've always used 7 twist. Any faster is too much. I live at sea level and shoot in temps in the 40's and 50's at times and have never lost a bullet (any brand or weight) and have never had issues with stabilizing a bullet. Currently using Lapua brass but I have used LC and frankly can't tell the difference on target. LC might even hold up better (primer pockets) Hope this helps............
Should mention I do shoot 90 VLD's at times too. 24.8g RL-15 jammed 20k shoots very well. And, my friend shooting 88g ELDM using the load mentioned above shot a 200-19x prone during a practice string.
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