Why are my bullets suddenly tumbling?

[nikdanja]

I use 2 different bullets and always have for the last 2 years. 

 

The first bullet is a molly Coates bullet that i use for loacal matches and practice sessions. I’ve used this bullet for years and I’ve shot at least 30k rounds and they all have flown great. Diameter is .401

 

the second bullet is a plated bullet that I use for major matches and the diameter is .400.  Once again I’ve shot thousands of these bullets and they have always worked fine. 

 

Now all of a sudden I’m having tumbling issues. 1 out of 150 with the molly bullets will tumble and 1 out of 20 of the played bullets will tumble. WTF? I checked my crimp and it’s barley vizable. You can tell a small distinct ring around the bullet so it’s not due to over crimping. 

 

I havent changed my powder charge and everything has staged has stayed the same for years. I’m just now having this problem. 

 

Its a KKM barrel with around 30k rounds. 

[Hi-Power Jack]

Could the barrel be either leaded up or shot out ?

 

Who makes the plated bullet ?   Many plated bullets are known for causing accuracy problems.

[mont1120]

If you have not changed the crimp, I would look next to the brass. Some brass will be thicker, depending on manufacturer, and that could be causing a tighter crimp pressure then you think you are applying. I have seen some brass from foreign companies that are noticeably thicker and I found loading 147 grain bullets in them was useless. During you loading process if you notice a round that seemed fairly restrictive to taking a crimp, set it aside and shoot it at the range, then see if that brand could be the source of the tumbling.

[Furrly]

I'm with hi-power jack.. Barrel!! 

[nikdanja]

5 hours ago, Hi-Power Jack said:

Could the barrel be either leaded up or shot out ?

 

Who makes the plated bullet ?   Many plated bullets are known for causing accuracy problems.

I’m using xtreme bullets for plating. I just talked to Adam from Atlas where I bought the gun from and he seems to think it’s a barrel issue also if I get top quality bullets and it still tumbling.  Really disappointed in the barrel but maybe I got one from a bad batch. Of course it’s gojng to happen right as the season gets going! 

[sfinney]

Look I know some people say they get unreal large amounts of round count from their barrel. Its possible.

30K rounds over "years" of shooting is not a bad barrel in my opinion. Its a "wear" part. I have had a well used STI that probably had over 100K rounds though it, but at least 2 or 3 barrels.

[zzt]

It is possible that you have a little bit of crud on the barrel crown.

Edited May 21, 2018 by zzt

[rishii]

Something changed, the 1st thing to do is isolate the cause

I would buy factory ammo and run that thru the gun, if they tumble then check the barrel

if they don’t then check your press, are your dies tight, you checked the crimp, did you check that belling die is opening the case mouth wide enough not to scrape or cut the coating and plating

[Jeremyc_1999]

   I'd read this thread and it will give you some ideas.  When I had tumbling I was shooting Berry's bullets in my glock. I switched to xtreme and haven't had problems since.  

[sfinney]

On a stainless barrel use a 50/50 mix of hydrogen peroxide and white vinegar - maybe 15 minutes at a time - submerge whole barrel and let sit. Then Run a brush - might have built up moly. Hard to get out otherwise.

[drexotic]

On a stainless barrel use a 50/50 mix of hydrogen peroxide and white vinegar - maybe 15 minutes at a time - submerge whole barrel and let sit. Then Run a brush - might have built up moly. Hard to get out otherwise.

Hmmm . . . Weak acid then a weak base. What's your thinking here as far as removing the moly fouling?

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[sfinney]

I didn't make it up. Some moly manufacturers like Master Blaster Bullets, etc used to publish this and recommend it. It works. It breaks down the moly in the grooves into a dark goo that can be wiped out with patches.

 

Just running a wire brush or patches through moly usually just polishes the moly, rather than fully removing it. If you use this on a moly barrel, or one with bluing, it can take the finish off. Use at your own risk, and don't leave the barrel in to long.

[Bkreutz]

You should be able to see if your barrel is fouled. If you have bad close vision, have some young whippersnapper look at it. Shiny bore with sharp edges to the lands is what you're looking for. In my experience, every case of bullet tumbling was from one of 2 causes. The most common is over crimping, you shouldn't be able to see a line on a plated bullet, back it off a bit and see what happens. (you could always measure the thickness of your case, multiply that by 2 and then add it to the bullet diameter to get the exact crimp measurement) The other case of keyholing was from crummy bullets (not actually crummy, but I was pushing plated 9mm way past 1500 fps for major PF, switched to FMJ and problem disappeared). Good luck.

[noylj]

Pushing coated and plated bullets in the same barrel is a bad idea, unless you have thoroughly cleaned the barrel when switching.

Next, are you getting a sideways imprint of the bullet on the target paper or is the occasional shot simply a flier that could be operator error? True key holing is generally due to use of plated bullets, generally in 9x19, where the bullet diameter is too small. Other leading cause is damage to the muzzle.

Both coated and plated can be inconsistent in dimensions and you might want to check them with a micrometer and slug your barrel.

Really, if we were to diagnose the problem, pictures and better descriptions would help.

If nothing else, scrub that barrel completely clean and run one or two thousand Precision Delta jacketed bullets through it. 

[TrackCage]

On 5/21/2018 at 8:13 AM, nikdanja said:

I’m using xtreme bullets for plating. I just talked to Adam from Atlas where I bought the gun from and he seems to think it’s a barrel issue also if I get top quality bullets and it still tumbling.  Really disappointed in the barrel but maybe I got one from a bad batch. Of course it’s gojng to happen right as the season gets going! 

It's  the Xtreme bullets. I had this issue early last year on a barrel with ~5k rounds or less. Something changed with Xtreme in recent years and they now seem to ship undersized bullets more than usual. I even reached out and asked them to send me new ones. Still undersized. Have you put a set of calipers on the bullets to see if this is a problem for you? Also have you slugged the barrel?

 

I know you said you're also having an occasional issue with your coated bullets, but I'd ditch the Xtremes if I were you. Also what's your concern about running the coated bullets for larger matches? They certainly aren't lower quality than plated.

[Aric]

Check the diameter of the projectiles. A few years ago I got a batch that had .399 bullets.  I contacted the manufacturer and they said it’s was within spec.  They were not accurate and had about the same tumble rate as yours.