How many rounds till you noticed key holing in .223?

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CanadianBaconPancakes

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When i was new and shooting allot of 7.62 I noticed somthing i didnt recognize at the time, Key holing rounds on paper. This would always happen with cheap corrosive surplus after like 4,000 -5,000 rounds at longer distances over 100 yards. Super prominant at or over 200 yards.

When do you notice it in .223? Dose the range ur shooting effect chance?
 
It would most likely be from out of spec ammo than anything else. Some batches Norinco 223 were known for having undersized projectiles and that caused keyholing.
Most 223 semi auto rifles (chrome lined or nitrided) should be good for at least 20,000 rounds before any noticeable decrease in accuracy and around 30,000 when the barrel would be replaced due to accuracy loss. I doubt you would see keyholing till over 50,000 rounds as long as the ammunition was decent.

If you were seeing it with a 7.62x39 I'd say it's just a cheap barrel combined with cheap surplus ammo that's causing it. Not something you normally have to worry about though till you have a lot of rounds down the pipe.
 
Horse96 said:
Key hole-ing is the projectile losing its stability. Either from an inadequate twist rate or from velocity loss, or both.
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It doesn't work that way. Stability is lowest at the muzzle (highest velocity) and increases as the velocity drops because the spin rate hardly decays at all compared to the forward velocity. If a bullet stays stable in the first bit out of the muzzle it will be stable all the way to its target. If it's going to keyhole you will see it at very close ranges.


Mark
 
How many rounds till you noticed key holing in .223?

Usually after seven or eight pints,,,.
:runaway:
No seriously, it is more dependant on out of spec ammo.
Most shooters will not cause enough wear on a barrel in their life time.
Especially between five round mags, ammo prices and people at the range making faces of great consternation and constipation if you should firre more than six rounds a minute.
 
mmattockx said:
It doesn't work that way. Stability is lowest at the muzzle (highest velocity) and increases as the velocity drops because the spin rate hardly decays at all compared to the forward velocity. If a bullet stays stable in the first bit out of the muzzle it will be stable all the way to its target. If it's going to keyhole you will see it at very close ranges.


Mark
Click to expand...

Why at closer range?
 
Only .223 keyholing I have observed was when the bullet was too long for the rifling twist.
Have observed bullets destabilize and keyhole at long range when they went subsonic. Some bullets can go transonic without destabilizing, others can't.
 
I had a minimum of 18 000 rounds through my 223 factory Remington barrel before I changed it out because of accuracy loss but I never saw any keyholing. Probably closer to 20 000 but I use it as a dirt rat gun and overheated the barrel a few times and should have got more life from that barrel.

I had a 30 06 that threw bullets sideways if they weighed more than 165g but that was due to twist rate.

I have heard of keyholing from a barrel that was fishmouthed ( the muzzle was worn out like the description) but I never verified it.
 
I have had a little 7.62x39 key holing as well, seems to happen randomly with good barrels and surplus ammo.
Have had lots of key holing with my attempts at reloading various other cartridges. Seems to be about ammo problems: gas cutting, twist and speed.
 
CanadianBaconPancakes said:
Why at closer range?
Click to expand...

Because the bullet gets more stable as velocity drops off, assuming it stays supersonic (see below).


tiriaq said:
Only .223 keyholing I have observed was when the bullet was too long for the rifling twist.
Have observed bullets destabilize and keyhole at long range when they went subsonic. Some bullets can go transonic without destabilizing, others can't.
Click to expand...

Fair enough, I was assuming we were talking only about supersonic flight since OP was mentioning 200yds as the range he saw keyholing. The transition to subsonic does cause all sorts of problems for some bullet designs.


Mark
 
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