I put together an 18" AR15 as a precision semi auto. I used a fluted 1/8 barrel I picked up at a gun show. Loading 55 grain flat based nosler match hollow points I get keyholeing at about 80 yards. 55 grain ball ammo does not keyhole. Ideas?
AR15 keyholing
- Thread starter Slim Chance
- Start date
For 1:8 twist rate on a barrel you should be using A LOT heavier than 55 grain bullets, IMO. Try 69-75 grain, and work up a load. What kind of powder and charge? Use a good .223 powder and buy heavier bullets. But at 80 yards it's most likely the powder or you are doing something wrong during reloading. Crimp/no crimp? Case lube cleaning? Sounds like powder not burning correctly / wrong powder type / not enough powder.
But I am a total noob so hopefully someone WAAAAAAYYYYY smarter and more experienced will be by shortly! (On other sites I am not necessarily a noob, on this site with the level of knowledge and experience I am noob sauce).
But I am a total noob so hopefully someone WAAAAAAYYYYY smarter and more experienced will be by shortly! (On other sites I am not necessarily a noob, on this site with the level of knowledge and experience I am noob sauce).
I think the powder is Varget. I'd have to dig out my notes as I also had some rounds loaded with H322. Not sure how powder will affect bullet stability outside of low velocity. I may try some 62 grain bullets, but I really wanted a varmint type bullet.
Possibly bad bullets coming apart but unlikely. I've shot plenty of 50gr vmax in a 1-7" ran really hot with no issues other than stellar accuracy. Twist isn't an issue and you don't have to shoot heavier bullets in that twist barrel.
Here too. The 8-twist isn't likely to the reason behind the issue. I'm shot as low as the 40gn Vmax in my 1:7 and they didn't blow up or keyhole with a moderate powder charge.
OP, any idea who made the barrel? Who chambered it? There's always a chance you got a brand new POS. Unlikely, but your barrel just may not like that Nosler bullet. I'd try several others in different weight ranges to see if you still have an issue.
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Huh, what muzzle device are you using? What's your jump to lands? What velocity are getting with those bullets? Do you have pictures of the targets?
I shot highpower for a few years and if you want to shoot magazine I'd recommend 69 or 77gr. I know they can be pushed pretty fast and know of people using 77 grain magazine length rounds through the 600 yard line competitively. I'm newer to this site and style of shooting. What is the advantage of light bullets. Other question is it possibly a smaller bullet ie 220 swift
Bad crown is my idea. Can't think of anything beyond REALLY bad bullets that would cause that.
ETA; the flat base may be more sensitive than the 55gr ball.
ETA; the flat base may be more sensitive than the 55gr ball.
220 Swift uses the same .224 bullet that the 22-250, 222, 223, etc use. Don't be fooled by the "220".
OP says 55gr ball ammo doesn't keyhole. I assume you don't have a chronograph, I'm thinking it's a velocity issue. Either low powder charge, or you need to adjust the seater to put a light crimp on them.
Being flat base bullets, are you flaring the neck to seat the bullets? Any issues with seating them (shaving the bullet, crooked rounds?)
Being flat base bullets, are you flaring the neck to seat the bullets? Any issues with seating them (shaving the bullet, crooked rounds?)
You chose a no name barrel from a gunshow to do a build?
What is your experince in building AR's?
How does Factory Ammo work?
Those 3 should narrow down why you are having issues.
What is your experince in building AR's?
How does Factory Ammo work?
Those 3 should narrow down why you are having issues.
Was it factory fluted and stress-relieved?
A flat-base benchrest bullet should outshoot mass-produced 55 Ball regardless of twist. What dies are you using and what is your technique?
Double check your twist. I suppose it's possible you're on the edge if you have a really slow twist. But even 14" should be enough with those bullets.
I suspect this is a hand loading issue, either bullets seated with too little neck tension to stay or be made concentric/on axis with cartridge case, and/or not seated deeply enough to assure bullet is concentric/on axis with case neck. With either condition severe bullet distortion will result as the bullet is forced to comply with axis of bore and upon bullet release it is too distorted to stabilize or to be stable for long.
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More info on the barrel - is it a "name brand"? Does it have markings on it? Who the hell built it? Does it actually say "1/8" on the barrel?
"Picked up at a gun show" barrel is a whole can of worms. If it does not specify 1/8 on the barrel, I'd verify it with a cleaning rod and a tight patch.
"Picked up at a gun show" barrel is a whole can of worms. If it does not specify 1/8 on the barrel, I'd verify it with a cleaning rod and a tight patch.
Lots of questions. The ammo was loaded for a bolt gun, but was grabbed for this range trip. I have been building AR type rifles for several years. The ammo was loaded on Redding dies and I should be around 3100 to 3200fps, but I have not chronographed them. Bullets strike from just slightly tipped (oval holes) to completely sideways. I think I need to run a few through the Remington 700 and try a different bullet in the AR.
I needed a barrel and just happened to spot a fluted barrel at a show. It is marked 1/8, but I have not checked this. I appreciate the answers and advice. I may pull a couple down and see if there is any damage to the base. I may also weigh a few.
I needed a barrel and just happened to spot a fluted barrel at a show. It is marked 1/8, but I have not checked this. I appreciate the answers and advice. I may pull a couple down and see if there is any damage to the base. I may also weigh a few.
I looked earlier at Nosler's offerings and noticed that their match bullets are not available in 55gr, you either have 52gr Custom Comp or 55gr Varmageddon (they're available with and without the polymer tip). I ran a quick search online for "varmageddon keyholing" and saw a couple mentions of it but one stood out. A shooter listed group sizes from a ladder test and with a hotter charge of varget under the 55gr varmageddon he had keyholing, lighter charges he did not. Look here, maybe they're just going too fast (not sure why that matters, thin jacket I suppose?)
.223/5.56 Test results [Archive] - The Firing Line Forums
I'll paste the info here, not mine, it's from the link above
I went out and shot my RRA AR-15, 1:9 twist 16" chrome lined. I have loaded up 7 different loads with 2 different powders. All bullets are Nosler Varmageddon 55gr .224
Varget, LC Brass, CCI 41 primers
23.4gr 1.25" group
23.9gr 2" group
24.3gr 3"group (the rounds keyholed on this one)
IMR4064, LC Brass, CCI 41 primers
23.0gr 1.7" group
23.6gr 1.5" group
24.0gr 1.5" group
24.5gr 1.1" group (this grouping had 1 round not touching the other holes)
Target was 100 yds
.223/5.56 Test results [Archive] - The Firing Line Forums
I'll paste the info here, not mine, it's from the link above
I went out and shot my RRA AR-15, 1:9 twist 16" chrome lined. I have loaded up 7 different loads with 2 different powders. All bullets are Nosler Varmageddon 55gr .224
Varget, LC Brass, CCI 41 primers
23.4gr 1.25" group
23.9gr 2" group
24.3gr 3"group (the rounds keyholed on this one)
IMR4064, LC Brass, CCI 41 primers
23.0gr 1.7" group
23.6gr 1.5" group
24.0gr 1.5" group
24.5gr 1.1" group (this grouping had 1 round not touching the other holes)
Target was 100 yds
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GrantA,
I bought these as an overrun from Nosler a few years ago. Looks like I need another trip to the range with a variety of loads. I will take the chrono as well.
I bought these as an overrun from Nosler a few years ago. Looks like I need another trip to the range with a variety of loads. I will take the chrono as well.
The twist is not the issue. I shoot 50 gr V-Max out of four 1:8 twist rifles with no issues. FYI: The 220 Swift is a.224 diam. bullet also.
I think you're on to something here. The neck tension, or lack thereof, would produce much less pressure and ultimately velocity. But wouldn't there be at least a bigger difference, if not blatantly obvious difference in group placement on the target? I presume we need to see a target. I think at 80 yards it might be too close to tell stability issues without noticing something very wrong with the cartridges?
OH, maybe the bullet just hasn't woken up yet!! Lol, just kidding, let's not get into that one
With the expanded info given by the OP, stating he bought "overrun", I'd add defective bullets to what I suspect. Buying another lot off the shelf somewhere might prove it out.
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I doubt Nosler would sell defective bullets. I weighed 8 of them all but one weighed 54.7 grains and the last was 54.8. I believe these were an overrun for an Australian contract. It strikes me as odd that a flat base bullet would tumble and the longer boat tail bullet is stable. I will have to get to the range and try a few things to get to the bottom of this. I do appreciate everyone who has chimed in.
We have to keep in mind you're only shooting 80 yards. Do you have a marked difference in group location relative to the center of the target? I think Sterling is on to something with velocity. If it were my problem, my flow-chart (so to speak) would quickly rule out twist and flat based vs. boat tail as well as bullet distortion specifically at 80 yards.
I think everyone is assuming a twist of 1/8. Perhaps the OP could check (cleaning rod and close pins would be close enough)? 1/18 barrels are made (rimfire, but still .224), so it is at least possible, someone screwed up and grabbed the wrong twist blank....
But 55gr ball ammo shoots fine, just the handloads are tumbling. The velocity is just off, that has to be it. The info I found and pasted earlier is strange, showing too much powder caused tumbling with these bullets
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GrantA,
Yes, I understood the OP's statement, and it is a good point. However, ball ammo runs a lot faster than 3100-3200 fps (his handloads). As you are probably aware, bullet stability is a factor of twist ratio (spin) and velocity. It may be that the 55gr ball ammo is fine (or appears to be at 100yds), but the handloads are going just slow enough to see instability at that range. It'd be interesting to see his group sizes with the ball ammo, as when you're on the hairy edge of stability and velocity, as range increases, groups sizes open up in a non-linear graph slope. I've seen this same thing before that left me and a business partner scratching our heads when testing prototype ammo for a manufacturer/client. It turned out the bullet was just short enough to stabilize at one range, but add another 50 yds, and then another 50yds, and then another 50yds; and you could see the instability increase dramatically up to the point where bullets keyholed into the targets.
Hence my suggestion: Have the OP physically verify the twist rate. This sounds like a 55gr bullet in a slightly too slow twist barrel...like a 16 or 18 twist. With the number of rimfire uppers around these days for AR's, I wouldn't be surprised if the OP bought a "gunshow special" that was really special...
Yes, I understood the OP's statement, and it is a good point. However, ball ammo runs a lot faster than 3100-3200 fps (his handloads). As you are probably aware, bullet stability is a factor of twist ratio (spin) and velocity. It may be that the 55gr ball ammo is fine (or appears to be at 100yds), but the handloads are going just slow enough to see instability at that range. It'd be interesting to see his group sizes with the ball ammo, as when you're on the hairy edge of stability and velocity, as range increases, groups sizes open up in a non-linear graph slope. I've seen this same thing before that left me and a business partner scratching our heads when testing prototype ammo for a manufacturer/client. It turned out the bullet was just short enough to stabilize at one range, but add another 50 yds, and then another 50yds, and then another 50yds; and you could see the instability increase dramatically up to the point where bullets keyholed into the targets.
Hence my suggestion: Have the OP physically verify the twist rate. This sounds like a 55gr bullet in a slightly too slow twist barrel...like a 16 or 18 twist. With the number of rimfire uppers around these days for AR's, I wouldn't be surprised if the OP bought a "gunshow special" that was really special...
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Uh...no, not always (.22 Mag barrels are often .224) and even if .223, a mildly loaded .223Rem will still fire with no apparent signs...and with a 5.56mm or Wylde chamber it probably wouldn't even show a difference with hot, ball ammo.
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Good points [MENTION=39164]MarinePMI[/MENTION] I hadn't thought about the popularity of rimfire uppers either, I'll stay tuned for an update
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Umm....
the weight of the bullet is perfectly acceptable.While a 1/8 will also shot those 69-75gn bullets the 55gn will work just fine.
The limitations or affect on longer distances is the primary concern.
Most likely the handload specifications of this particular load need to be examined but relegating it to simple bullet weight would be an error in this case.
To be clear, I am not saying this has to be the issue, only that I haven't seen it ruled out. This (IMHO) may be an Occam's Razor thing; plain and simply the wrong twist barrel. If that is not the case, I have no impact, no idea as to what would cause this (aside from what has already been mentioned).
For the OP: If it is the barrel twist, and you're looking for an inexpensive, but reputable barrel, try Green Mountain. Their contract over runs are often quite good and fairly inexpensive.
http://www.gmriflebarrel.com/ar-15-m16-m4-rifle-barrels/
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[MENTION=39164]MarinePMI[/MENTION], so you're saying that we will be able to actually see completely sideways keyholes at 80 yards due 55gr ammo through a 1/8 barrel? But before that you say that it could be a "slightly" slower twist at 16 or 18? Maybe my paradigm is off, but that is a little incongruent. I'm not particularly versed in this line of specifics, but I'm reasonably sure that is too short of a yardage and too minor of a difference to even make it worthy of comment. I don't think we should be even considering twists at all much less until we get these chronographed, no?
OP, if you lack the means of a chronograph, do you remember noticing a marked recoil difference in the two types of rounds? Or like I said earlier, different group placing on the target?
OP, if you lack the means of a chronograph, do you remember noticing a marked recoil difference in the two types of rounds? Or like I said earlier, different group placing on the target?
[MENTION=45229]0311 Hesco[/MENTION],
No, what I'm saying is that he has not definitively proven it's actually a 1/8 twist barrel, only that that is what is stamped on it. What I'm saying is that he may have a mis-marked barrel, and that someone may have grabbed a 1/18 barrel (rimfire barrel possibly). If that is so, the 55gr bullet may not stabilize, even at 3100-3200fps.
All the signs he has, points to too slow a twist. All I'm saying is everyone is assuming its a 1/8 twist barrel because that is what is stamped on it.
No, what I'm saying is that he has not definitively proven it's actually a 1/8 twist barrel, only that that is what is stamped on it. What I'm saying is that he may have a mis-marked barrel, and that someone may have grabbed a 1/18 barrel (rimfire barrel possibly). If that is so, the 55gr bullet may not stabilize, even at 3100-3200fps.
All the signs he has, points to too slow a twist. All I'm saying is everyone is assuming its a 1/8 twist barrel because that is what is stamped on it.
Yes, but a 16 twist or slower is marginal at 3200-3100fps (assuming .665" length of the bullet per the website, though they measure .715" when I run a caliper against one), meaning it may or may not stabilize.
If you run the numbers with the length being .715", then they are marginal in a 14 twist and completely unstable in a 16 twist.
Oh, BTW; I forgot to mention, I shoot these same factory second bullets from Nosler. They function fine in a 1-9 twist bolt action Savage (hence my suspicion of the barrel twist itself) and work well enough for my daughter to shoot a metal wire holding her prairie dog flipper target from a 100yds. That sounds accurate enough to me to rule out the "factory seconds" IMHO.
If you run the numbers with the length being .715", then they are marginal in a 14 twist and completely unstable in a 16 twist.
Oh, BTW; I forgot to mention, I shoot these same factory second bullets from Nosler. They function fine in a 1-9 twist bolt action Savage (hence my suspicion of the barrel twist itself) and work well enough for my daughter to shoot a metal wire holding her prairie dog flipper target from a 100yds. That sounds accurate enough to me to rule out the "factory seconds" IMHO.
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Either the bore diameter is off, too large or the only time I have seen keyholes is shooting 1000 yards and the bullets went subsonic and tumbled......
But he has stabilized 55gr factory rounds thru the same barrel. So the main issue is looking like it's in the rounds, not the barrel.
Shoots 55gr factory ammo? Hand loads tumble? OP never said what his load was? Maybe his scale is way off? Just weigh a 55gr bullet and see if the scale is close?
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My bet is you might see some witness marks on any type of muzzle device you've got installed on that AR. But, one other possibility: Have you checked the feed ramp in the barrel extension? Do you see any type of witness mark there? Are the points of these projectiles getting beat up as they head up into battery?
Is there any physical evidence of a "traumatic birth" loading-from-magazine-to-chamber, or any evidence of muzzle-brake strike?
If neither of those, then: What's the melting temperature of the core material inside those bullets? Are you darn sure it's lead? Or are you just assuming it's lead?
Maybe I shouldn't have said that...
Is there any physical evidence of a "traumatic birth" loading-from-magazine-to-chamber, or any evidence of muzzle-brake strike?
If neither of those, then: What's the melting temperature of the core material inside those bullets? Are you darn sure it's lead? Or are you just assuming it's lead?
Maybe I shouldn't have said that...
Folks, I like a good mystery, but this is not a mystery at all. Logic indicates hand loaded cartridges and/or bullets are not concentric. Bullets may have excessive run out. Any of this would cause the bullet to fly erratically upon clearing the bore as the bullet transitions from the bore axis to its own. Excessive yaw eats up so much energy that the bullet does not right itself and begins to tumble The effect is much like what you'd get from a burnt out barrel. I suspect the Nosler bullets are not over runs but just defective. After all, the problem is associated with a particular hand loaded bullet.
I'm not saying it's not possible, but I highly doubt it the Nosler bullets are that badly deformed. I've ran countless projectiles from Nosler that were overruns or blems of different mass and calibers. I've never shot this bullet but I've never seen a tumble like this.
I think it's much more likely a no name barrel from a gun show.
I suspect it was something in the reloading process and he wasn't getting nearly the velocity he thought he was with those projectiles.
**Keep in mind guys, the target picture is NOT from the OP, it was someone else asking if OP's looked like that
A flat-based benchrest or varmint bullet is designed for precision at 100, 200, and (a stretch, but many use them) 300 yards. Precision enthusiasts around the country try to shoot the smallest bug-hole five and ten-shot groups for bragging points every weekend.
Pushing them to extreme velocities to where they vaporize or group paper-plate size dimensions is a waste of powder and rifling.
Pushing them to extreme velocities to where they vaporize or group paper-plate size dimensions is a waste of powder and rifling.
