AR15 keyholing at short ranges

[esheato]

I've been practicing with the AR at distances between 3 yards and 100 for 3-gun competition. Most shots are occurring between 7 and 25 yards though.

Shooting at basic cardboard IPSC targets.

Last week, I did some training..about 200 rounds. Had one keyhole at about 10 yards. Hmmmmmm....

Today I shot another 250 rounds and had 4 rounds keyhole (two on image below, another two keyholes on another tgt). Targets were at about 10 and 15 yards.

Rifle is a home job lower and CMMG upper. Lower is on a Magpul CTR, MIAD, Giesselle trigger, ambi safety. Upper is a CMMG 16" MedCon (1-7"), mid length gas system, Larue 13.2 rail, PWS FC556 brake, and a TA31F on a Larue mount.

I'm using handloads...nothing precision, just mass produced stuff.

Mixed brass
FL sized in RCBS die
Trimmed on Giraud
Primer pockets swaged in Dillon tool
Loaded on Dillon 650
Win Small Rifle primers
22.2 H322
Wideners 62 FMJ (mil spec, lead core, no cannelure)
OAL is book length

My goal was to load to M855 specs so that the BDC in the ACOG would be usable...I can't seem to get to the velocity I need without popping primers but that's a separate issue now that bullets are hitting paper sideways. :banghead:

Take a look at the tgt.........what am I doing wrong?

Bullet weight matches twist rate, gun is cleaned on a regular basis, I'm stumped.

 

[Jim Watson]

Two clear keyholes and it looks like some of the other holes are a bit oval.
Your twist and bullet are compatible.

Check that your muzzle appliance is on straight and that the bullets are not grazing it.

I'd give it some name brand bullets and see if they did better.

 

[esheato]

Brake is on straight...looking a bit beat up (~5,000 rounds), but it's only been on for about 8 months.

Loading some quality bullets is already on my list of things to do.

Most of that shooting was on the move and some shots were at a fairly oblique angle...could account for some of the oval holes.

 

[243winxb]

We'd only select a 1:7" or faster twist barrel if we had a need to shoot the 90gr VLDs.

http://www.6mmbr.com/223Rem.html Take the brake off and shoot rifle. Clean the brake.

 

[esheato]

Target 2.

Another 2 keyholes.




http://www.shootingtimes.com/ammunition/st223_120606/index1.html
The first M16 rifles built by Colt many years ago had barrels with a rifling twist rate of 1:14 inches. While that was quick enough to stabilize 55-grain bullets at what we consider normal ambient temperatures, bullets became unstable when the mercury plummeted well below 32 degrees Fahrenheit. This prompted the Army to switch to a slightly faster 1:12-inch twist, and then later when the 62-grain SS109/M855 bullet was adopted the specified twist became an even faster 1:7 inches.

 

[243winxb]

m16a1 is 1-12

(~5,000 rounds),

New barrel time. Other reasons for tumbling, oversize bore, undersized bullets, bad crown on muzzle.

 

[243winxb]

I can't seem to get to the velocity I need without popping primers but that's a separate issue

May just be your problem. Mixed brass, over pressure, to hot?

My goal was to load to M855 specs

http://www.inetres.com/gp/military/infantry/rifle/556mm_ammo.html

The M855 cartridge has a 62-grain, gilded metal-jacketed, lead alloy core bullet with a steel penetrator.

The steel penetrator makes a longer bullet, needing more twist than my 1-12.

 

[esheato]

Since I was popping primers, I backed it down to 22.2 grains of H322. Max loads in several manuals are showing a full grain over my load.

Velocity of my current load is approx 2860 fps. Even if I was popping primers, that has nothing to do with the bullets keyholing.

As far as my bullet selection, I needed M855 type bullets without steel penetrators. The club I shoot at won't let me shoot steel core bullets at their steel targets. So I needed M855 to match the ACOG BDC and without the core to satisfy the range requirements.

Closest bullet to my requirements I could find was the Wideners mil spec without the steel penetrator. One other personal requirement was the ability to buy in bulk...Wideners sell the 62 grn in bags of 5k. I'm sure as heck not buying Sierra 500 packs to plink at 15 yards.

 

[Rail Driver]

The problem with your idea as I see it is that the bullet you're using is going to have different ballistic performance than the steel core M855. The weight might be the same, but you're going to have a shorter bullet, which will affect the flight characteristics of the bullet, most likely enough to make your BDC pretty much useless for your purposes. Would they let you shoot all copper bullets? You may be able to find one of those with a similar enough ballistic profile to use with your BDC.

 

[Double Naught Spy]

I would go with taking the brake off and cleaning it as well as well as making sure the crown is free of any buildup.

I had a Colt 16" HBAR (not lined), 1:9, that became shot out at about 19000 rounds, a lot of which was rapid fire. So the barrel was run hard. At 25 yards, the one place I was almost certain the bullets would not hit was where I was aiming. I could miss 28 out of 30 rounds that would be outside my 4" target circle. Virtually all the shots would keyhole.

 

[Jim Watson]

When I was trying to push 90 grain SMKs to 1000 yards through a 6.5 twist, I lost a lot of bullets on the way to the target. I finally caught a couple of keyholes like the lower right hit on your second target in post #5. Looks like the bullet was bent, doesn't it?

How far are you shooting? M193 and M855 trajectory are not THAT different for 300 yards.

 

[taliv]

i had this happen once. couldn't figure it out. finally used a cleaning rod and piece of tape and ruler to measure the twist and it turns out... wasn't 1-7 after all. i bought a 1-7 barrel but they sent a 1-9.

 

[esheato]

The problem with your idea as I see it is that the bullet you're using is going to have different ballistic performance than the steel core M855.

Makes sense. I can get SS109 M855 steel penetrator bullets from the same establishment for only a couple cents more per round.

I would go with taking the brake off and cleaning it as well as well as making sure the crown is free of any buildup.

I'll add it to the list.

1. Good cleaning (my idea)
2. Try quality bullets.
3. Try SS109 bullets.
4. Manually measure twist rate.
5. Clean brake and crown.

How far are you shooting?

Most shots are occurring between 7 and 25 yards.

Thank you gentlemen...I'll see what I can find.

 

[Jim Watson]

Most shots are occurring between 7 and 25 yards.

Then the BDC is of no consequence. Try other bullets. After 5000 rounds, your barrel may well be too worn for cheap bullets. Might handle a flatbase better than boattail. It might be too worn for anything.

 

[esheato]

For 3-gun? No, BDC doesn't matter as the farthest shot is 100 yards. I'm trying to have my cake and eat it too. Theres no reason why I can't get the BDC to work the way it's supposed to work and use it for 3-gun on the side.

Honestly, sideways bullet holes don't matter either, it still counts as a hit. If I could only place them accurately. LOL

 

[243winxb]

Carbon Ring

A carbon ring can form in a worn barrel. I am no expert on the subject as i only had 1. This ring may increase pressure. Could it have a sizing effect on the bullet? I do not know?? When i got lazy and was not using a brush, after 40 rounds (243win.) you could feel the constriction right in front of the chamber with the cleaning patch. Not having a bore scope to have a good look, i can only guess. A good soaking & brushing with #9 removed it.

 

[wcwhitey]

Just a quick question. What is your neck tension, how tight of a crimp. I am wondering if you are not deforming the bullets over crimping. Bill

 

[loadedround]

Just did some minor research and have found that the current Speer #14 manual doesn't list H322 powder with the the 62 gr bullet. The manual lists H335, BL-C(2) and 748 as accurate powders, so I would try one or two other powders and see if it eliminates your problem. BTW, I have had excellent results with the same 62 gr bullet and Varget in my Colt Hbar with a 1/7 twist. I bought that rifle really cheap since the previous owner ciouldn't get it to group under 3'' with 55 gr bullets.

 

[esheato]

Gave her a wicked cleaning tonight. Bore was quite soiled and copper solvent put out really REALLY deep blue patches.

Removed the brake and soaked it and wiped down the crown. No damage anywhere, crown looks good, rifling at the muzzle was visible and didn't look abused.

Twist is a confirmed 1-7".

1. Good cleaning (my idea) COMPLETE
2. Try quality bullets.
3. Try SS109 bullets.
4. Manually measure twist rate. COMPLETE, 1-7"
5. Clean brake and crown. COMPLETE
6. Measure crimp. COMPLETE
7. Change propellant.

Crimp is only a couple thousandths.

Speer (#13) lists a 62 FMJ (w/ cannelure, obviously not the same bullet) with a loading range of 23.0 to 25.0 max but that's using a CCI mag primer. I'm using standard Win small rifle primers.

I'll run some Varget and those bullets and see what happens.

Thanks again,

Ed

 

[Kernel]

Anything between you and the target like tall grass, or weeds? Could some of your shots be so wild, while you're dancing around, that they hit the ground first, then deflect up into the target?

 

[sansone]

check crown and flash hider

 

[esheato]

Nothing between me and the target but air. Most shots are between 7 and 25 yards. Targets are hung with the top approximately 4-6 feet off the ground. I am willing to say that there is absolutely no way I'm bouncing them off the ground.

Already checked crown and brake.

 

[Rail Driver]

Are you rapid firing? I've found that sometimes if I'm firing rapidly the front of a bullet will sometimes get deformed from hitting the feed ramp when I'm using a newer magazine (less than 100rds fired from that mag) that will cause keyholes.

ammo could also be the issue. Is your press off square even by a tiny bit? Could you be seating the bullets even the least little bit off? Is this a load that functions properly in other guns or do you get the same problem? Is the muzzle brake timed properly (not sure if that can affect ballistics or not?)

 

[Mal H]

You should try to capture some fired bullets; maybe fire several into a pile of newspapers. The damage to the bullet nose doesn't matter. What I would like to see is what type of imprint the lands are making on the bullet. Are they deep enough? Are they spread a little circumferentially indicating that the bullet isn't following the lands and grooves as it should?

I think someone else mentioned this, but it bears repeating - you are getting more keyholing than the few really noticeable ones. In target 2, for example, the hole on the right of the target midway between the two obvious keyholes is also a keyhole shot. The bullet entered the target at a slant. There are several more with similar slants to them.

Like Jim Watson, I'm wondering how the bullet in the lower keyhole got bent like that. It might have been so wobbly that the bullet bent itself in flight since the RPM's involved are extremely high.

 

[NCsmitty]

Keyholing, especially at close up targets, often are indicative of a poor bullet to barrel fit, and/or a deflection by a bad crown or misaligned muzzle brake.
The crown has been verified as ok, so shoot it without the brake to see if there is an improvement.
If not, try some brand bullets, preferably some flat base 55gr-60gr SP or HP.
I may have missed it, but is there a round count on the barrel?



NCsmitty