My 5.45x39 Key Holes! Why?

[Dave.O]

. Do you have another 5.45 upper with a 16" barrel to test the ammo?
USSA-1

We had all 3 at the range.. 2 SBR's and 1 16".. And all 3 keyholed.. The SBR with the krink seemed to be worse.

I believe that both crowns are fine and were done by the same smith..

As far as Romanian or Bulgarian.... It is surplus ammo from over there.. Maybe it is ammo...

[TOrrock]

Rate of twist has a lot to do with it. You need a 1/7" twist, a lot of the US barrel mfg's use a 1/9" twist.

As far as the "Krink", I'll need more info on it.

Russian 7N6 is a 53 gr. bullet with a sliding steel core. The bullets are very long, as you can see, and require a tight twist.

It gets even worse with some commercial 70 gr. loads, that use the same bullet jacket but instead of a steel core and hollow cavity under the nose of the bullet, just fill the jacket up with lead.

[crossgun]

According to Smith&Wesson the twist rate on the barrel is 1 in 8. I will try to get out this evening or next to try some different ammo.

Still cant understand why the rifle with the KX3 causes such a large key hole as compared to the others.

[Littlelebowski]

I'd like to hear more about your reliability enhancements.

[steve-oh]

This is weird. I just put 200 rounds of Silver Bear and 350 of Wolf military classic through mine on paper on Monday. I didn't see one keyhole.

Mine is bone stock, for what it's worth.

[steve-oh]

This is weird. I just put 200 rounds of Silver Bear and 350 of Wolf military classic through mine on paper on Monday. I didn't see one keyhole.

My 5.45 is bone stock, for what it's worth.

[crossgun]

At this point I am prepared to right it off to an ammunition problem. I just finished shooting another 1200 plus rounds through it this weekend at a Pat Rogers EAG carbine school. Weapon ran fine and I only noticed two key holes the whole time and all rounds were accounted for. Accuracy was there as well as I shot 98 out of 100 with the 5.45x39 during the MEUSOC qual.

Templar, now that I understand the construction of the ammo thanks to you and the article by Ned in Aprils S.W.A.T. magazine I believe that the possibility for the core to slide at times can and will be a big issue.

I also shot some of the WOLF 70 and 60 grain bullets and noticed that the heavier bullets will do the same as mentioned.

After this weekend’s carbine class I guess it’s just not that big of a deal and the cost savings is well worth it.

10.5" Smith 5.45x39 upper with LaRue 9.0, Vltor LP gas block and Noveske KX3 on a Rock River lower with two stage trigger. Magpul CTR and MIAD, Aimpoint Comp C3 2MOA and Troy front and rear flip ups.

[TOrrock]

Glad to hear it wasn't an issue with the weapon, that gets expensive.

[WS6]

The answer, I think, is found in the construction of the round. There is a LARGE cavity of air in the tip, followed by a not-so uniform core. What all this really means is that it is going to take a minute for the rotation of the projectile imparted by the rifling to overcome the horrid imbalance of the projectile (think about if you have ever played with a top, if you dropped it from a few feet it would jitter a minute before stabalizing vs. if you dropped it from a few inches when it almost immediately "went to sleep").

This phenomina has been observed with .30AP ammunition in the past as it has been shown to penetrate A LOT better at 200 yards than at 20.

Maybe also why my groups with M855 at 200 yards are under 2 MOA for 10 shots while at 100 yards they are over 2.5 MOA for the same.

The russian bullet is just an extreme example.

[03humpalot]

Been hearing a lot about this as of late. My Bulgarian AK does the same to about 20 to 22 meters with bulgarian surplus(only ammo i have put through it yet). Round seems to stabalize after that and im not having any problems hitting Steel IPSC's to 300 meters with it.

Weird. Like others far more versed in this round than me have said..it seems to be an ammo problem.