My 5.45x39 Key Holes! Why?

[crossgun]

Ok I can’t figure this out and really need your guys input. I have spent the winter trying to bring reliability to the 5.45x39 platform. I have succeeded and feel very comfortable with the reliability now that a few things have been tweaked and worked over. In fact I was so confident that I took one of my 5.45x39 S&W uppers and cut it to 10.5 to SBR as a trainer. Here is a YouTube link that shows the reliability of not only my 5.45x39 SBR but also Dave.O’s who also decided to go the SBR route with his as well.

http://www.youtube.com/watch?v=S7zEw7Ux_Vw

While most of the testing has been firing shots either into the berm or at 50 yards for accuracy there have been no issues. The SBR rifle will hold 1.5-2 MOA if I really bare down on her and use a good two stage trigger which by the way I have had no issues with. For me the heavy hammer spring is gone! I have put over 500 rounds of the 53grain Surplus down the tube of the SBR and at least that same amount if not more from my 16” 5.45x39.

Yesterday, seeing as I am going to a Pat Rogers class I decided to refresh myself with the EAG target and to brush up on my NSR from about 5 yards. I couldn’t believe my eyes when I saw that the rounds were key holeing on the paper. The issue was the most predominant from my SBR with the KX3 but Dave.O’s 10.5 and my other 16” upper showed signs as well. What the hell can be going on?

I confirmed the zero again at 50 yards at a high rate of fire and all the holes were round as they have been in the past. All rounds were accounted for.

There is absolutely no way that the bullet is striking anything on the rifle or that it is sideways at 5 yards and then recovers to stabilize at 50 yards. Is it possible that when I “really” get on it that the KX3’s forward muzzle blast is forcing some of the rounds sideways? Is it some freaky ammo issue? I just don’t understand.

THOUGHTS PLEASE

[cptx123]

My smith keyholes every round with 60 grain, 1 out of a 50 with 53 grain. Iam not sure why and Iam to lazy to send it back. When I called smith I spoke with one of their cs reps in masshole, he said lt was an ammo issue-whatever. CAI had the same issue with their tantals. My guess is it is a chamber issue, twist rate, or bore diameter issue. All just speculation, sorry I know that does not help much.

[sdacbob]

My S&W upper keyholed with 60gr Wolff too.

[Ned Christiansen]

I've shot a few AK 74's that keyhole mildly at 10-15 yards and in, but beyond that they're OK. I've seen this before-- bullet is yawing slightly as it exits the bore and then finds it's center and 'goes to sleep" as they say. Yours is looking pretty extrememe though.....

[Ned Christiansen]

I've shot a few AK 74's that keyhole mildly at 10-15 yards and in, but beyond that they're OK. I've seen this before-- bullet is yawing slightly as it exits the bore and then finds it's center and 'goes to sleep" as they say. Yours is looking pretty extreme though.....

[crossgun]

Ned

As mentioned, the other rifles do not key hole as bad as this one. In fact the holes are just slightly out of round.

Any chance the KX3 is disrupting the bullet a little more?

[yellowcarbon]

I suggest the obvious, remove the KX3 and see if that does anything. Also try different ammo. The ammo may be undersized every so slightly. It could be why we are getting it so cheaply. I don't think S&W would undersize their bores like Century (who used 5.56 blanks for their 5.45 barrels).

[Dave.O]

I suggest the obvious, remove the KX3 and see if that does anything. Also try different ammo. The ammo may be undersized every so slightly. It could be why we are getting it so cheaply. I don't think S&W would undersize their bores like Century (who used 5.56 blanks for their 5.45 barrels).

That may not be the problem.... As Crossgun said, there were 3 weapons that exhibited the same problem.. It just happened that the SBR with the Krink seemed to be the worst... His 16" upper keyholed as well as my 10.5 SBR...

You can see by the pic that bullets are turning completely sideways.. The 16" and my 10.5 you could just see that the bullet is yawing but not turning all the way..

The surplus ammo bullet measures .223 (at the mouth of the case) without pulling the bullet...

The trouble I have is that none of the bullets keyhole at 50yds.... It is hard for me to believe that bullet can get so sideways right out of the muzzle and find it's way to the target and go in straight..

[rob_s]

Is it possible to set up a target pair such that you can shoot through one at 5 yards (or wherever you're seeing the keyholing) and still hit another at 50 yards? If you use the paper alone without the cardboard backer I don't think it would be enough to disrupt the rounds.

If you're getting perfect holes at 50 yards but keyholes at 5 yards, it would seem that Ned's answer is correct. No idea what to do, if anything, to correct it though.

[USSA-1]

Seeing how both of the barrels were cut down 16's, I would re-examine the muzzle crowns. Make sure the crowns are concentric with no burrs.

Next would be the ammo. I've never seen or heard of Romanian 5.45 ammo being recently available, just Russian and Bulgarian. Do you have another 5.45 upper with a 16" barrel to test the ammo?

You also might have a barrel twist/ bullet weight incompatability issue, but I think that might be stretching it.

Check the crowns and ammo and see what you can find out.

USSA-1