5.45 AR keyholing

[Junkie]

I just put together a 5.45 AR.

I bought a barrel that had been drilled for the gas tube at the wrong angle, and drilled my own port (at the same distance).

It's marked: ST LW-19 CMV 5.45X38 1/8 QPQ MP

I took it to the range this morning to sight it in and every single round was keyholing at 25yd. Group size was maybe 3", not as bad as I'd expect for the rounds hitting sideways. This was using 7N6 surplus.

Is there something I'm doing wrong, or do I need a new barrel?

edit: it's not the same bore as a PSA 5.56 barrel I have - rounds, both 5.56 and 5.45, fit farther into the muzzle of the 5.56.

[gun toting monkeyboy]

Yes, it is the bore. Just because you can fit the much-longer-ogive 7N6 bullets farther down the barrel that the shorter 5.56 bullets doesn't mean anything. Keyholing at that range means your bullets aren't being stabilized. If it truly has a 1/8 twist with a correctly-sized bore, it would work. Since it obviously is not working, something is wrong. Since there is a history of companies making barrels for this caliber using .223 diameter bores, and those barrels exhibit exactly the same problem you are describing, I would guess that it what happened here. Get a new barrel.

-Mb

[Junkie]

A 5.45 round doesn't go into the 5.45 barrel as far as it goes into the 5.56 barrel, so there is a difference in bore size. Using the same bullet for two different bores seems like a reasonable test.

[w210838]

It's not a 5.45 barrel sounds out of spec .

[valley82]

Barrel out of spec. +1

[klewan]

OP, slug the barrel. There were a bunch that were drilled to 5.56 and sold as 5.45. It was one of the f*ckups that got US 74 barrels a foul rep...

[Junkie]

What tools are required to slug a barrel? It's Melonite if it matters.

[klewan]

Originally Posted by Junkie

What tools are required to slug a barrel? It's Melonite if it matters.

You need a lead slug a little bigger than .214. Fishing sinker, or some pure lead sheeting rolled into a ball. 3/16" wood dowel to drive it down the barrel.

What you are trying to accomplish is driving a lead ball down the barrel with the dowel. Then measure how big the ball is with a micrometer or caliper. The lead slug will be as big as the smallest part of the bore. If it's .223 instead of .214, you'll know where the problem is. .223 marked as .214 were a problem a couple of years ago.

[Junkie]

Any suggestions on where to order said lead ball? I don't fish and don't have any lead sheeting around. I have a set of calipers and even a mic that I can use to measure.

As I said, it IS smaller bore than the 5.56 barrel, but I suppose it likely isn't small enough.

[d0wnShifT]

Originally Posted by Junkie

Any suggestions on where to order said lead ball? I don't fish and don't have any lead sheeting around. I have a set of calipers and even a mic that I can use to measure.

As I said, it IS smaller bore than the 5.56 barrel, but I suppose it likely isn't small enough.

Go to Walmart and locate a lead sinker in the fishing department. They have plenty. Pretty sure 1/2 oz will do ya.

[klewan]

Originally Posted by d0wnShifT

Go to Walmart and locate a lead sinker in the fishing department. They have plenty. Pretty sure 1/2 oz will do ya.

Thank you for that. It's hard to inform the young'ins.

[vincewarde]

What is the usual/recommended twist rate for a 5.45 barrel? If it requires a much faster twist rate, it could be engaging the rifling and simply not being spun fast enough.

While I certainly agree with everyone who is suggesting that the bore is over sized, there are other causes of keyholing. Damage to the crown is a classic cause, and a bent barrel (even slightly) can also cause bullets to tumble.

[Junkie]

1/8 is pretty typical from what I've read, it's what Saigas run.

The crown looks good. I suppose I could toss the barrel in the lathe and check for runout to see if it's bent.

[gun toting monkeyboy]

Why would the barrel being bent cause keyholing? It is not stabilizing the bullets. That means there is a problem. Since the twist is in the correct range, it has to be the bore diameter.

[G-Man WC]

Here a guide for a larger diameter slug, but you'll get the picture / process. -g
http://7.62x54r.net/MosinID/MosinSlug.htm

[ar15barrels]

Originally Posted by Junkie

As I said, it IS smaller bore than the 5.56 barrel, but I suppose it likely isn't small enough.

The groove diameter is what really matters more than the bore diameter.
Slugging the barrel will let you measure the groove diameter.
Your bullet test is measuring bore diameter...

[Junkie]

The lands on the bullet (groove in the barrel) measure about .218"

[w210838]

Too big should be .214 I know some East German barrels where .218 but I never shot them, I sold them all before I could but other barrels I have are .214

[Junkie]

After finding my mic it's more like .219, so certainly too big.

[Junkie]

Another question:

I bought the barrel from someone here. He told me that it was a 5.45 barrel. It appears to be a 5.56 barrel with a 5.45 chamber.

What's a reasonable solution? Is he supposed to pay me back? Am I supposed to eat the cost of a barrel that doesn't work?


I am trying to figure out if Spikes will replace the barrel, that would be my first choice. I just don't know if I can get that to happen.

[CRTguns]

5.45 rusian ammo is designed to keyhole and tumble.
Establishes an "area of effect" on and around your target.

[Bangzoom]

Originally Posted by CRTguns

5.45 rusian ammo is designed to keyhole and tumble.
Establishes an "area of effect" on and around your target.

Huh???

Mine never key holes

[kel-tec-innovations]

Sounds like the barrel was incorrectly stamped or a definite manufacturer defect.

[Bhobbs]

Originally Posted by CRTguns

5.45 rusian ammo is designed to keyhole and tumble.
Establishes an "area of effect" on and around your target.

It was designed to tumble INSIDE the body, not on the way down range.

[russ69]

Originally Posted by Junkie

...I am trying to figure out if Spikes will replace the barrel, that would be my first choice. I just don't know if I can get that to happen.

Give them a call.

[hermosabeach]

Originally Posted by CRTguns

5.45 rusian ammo is designed to keyhole and tumble.
Establishes an "area of effect" on and around your target.

The 5.45 is designed to fly true. Upon impact the bullet will flip as the base of the bullet is heavier than the tip. This creates a huge wound cavity

Bullets cannot tumble in the air. They can rotate 180 degrees and have the heavier rear fly forward.

A 5.45 is similar to a dart being thrown backwards. It naturally wants to flip 180 degrees and have the heaviest part forward. The spin keeps it stabilized in flight.


This is true of many rifle rounds.

Back to the OP

I shot a WASR that was a 5.56 diameter with a 5.45x39 chamber
(Thanks century)

You could still keep them on steel at 100 yards.

So even with the keyhole issue, how does it hit at 100 yards?

Consider keeping it as a solid shooter and rebarreling as it is further shot out.

[Junkie]

Originally Posted by russ69

Give them a call.

I got an email reply from them this morning and didn't have a chance to send one back until after 5pm Eastern time. I'll call if they don't get back to me.

[Junkie]

Originally Posted by hermosabeach

The 5.45 is designed to fly true. Upon impact the bullet will flip as the base of the bullet is heavier than the tip. This creates a huge wound cavity

Bullets cannot tumble in the air. They can rotate 180 degrees and have the heavier rear fly forward.

A 5.45 is similar to a dart being thrown backwards. It naturally wants to flip 180 degrees and have the heaviest part forward. The spin keeps it stabilized in flight.


This is true of many rifle rounds.

Back to the OP

I shot a WASR that was a 5.56 diameter with a 5.45x39 chamber
(Thanks century)

You could still keep them on steel at 100 yards.

So even with the keyhole issue, how does it hit at 100 yards?

Consider keeping it as a solid shooter and rebarreling as it is further shot out.

After seeing that it was keyholing at 25yd I didn't try anything farther than that. Groups were around 3" at 25yd, which is pretty bad.

It's a melonite barrel, it should take a LONG time to shoot it out.

If I end up having to buy another barrel it'll probably be a Ballistic Advantage.

[gwgn02]

5.45 in addition to tumbling, was designed also to do cartwheels, jumping jacks, and ribbon twirls. Duh.

[w210838]

OP you could always cut off the chamber and re chamber it and make it a pistol barrel? Just an option

[cruddymutt]

Im just spit balling here as I have zero experience with 5.45 but could ammo be handloaded for this barrel?

[w210838]

You could but it wouldn't make a difference , you would need 222 brass , dies and a resizer for 223 to 221 . Yes I've done it but it's a pain.

[Pryde]

Originally Posted by w210838

OP you could always cut off the chamber and re chamber it and make it a pistol barrel? Just an option

You can't recut a chamber on a melonite barrel..........

[MrPlink]

^ why?
not doubting you. Just not that familiar with melonite

[w210838]

Um you can it's just a coating

[ar15barrels]

Originally Posted by w210838

Um you can it's just a coating

Have fun with that.

[ar15barrels]

Originally Posted by MrPlink

^ why?
not doubting you. Just not that familiar with melonite

It produces a surface hardness around 60C.
That's about the same as most chambering reamers.
You want the material you are machining to be at least 10-20 points softer than your cutter in order for your cutter to survive.

[RobGR]

Can you just send it back to the manufacturer, at least exchange it? Don't even deal with this, as stated above, give them a call. When S&W came out with their 5.45 uppers, they had a lot of returns and they honored the returns with excellent customer service. Good luck, OP.

[w210838]

I understand that ar 15 but it can be done. Just like when guys shoot the crap out of 41v50 it hardens but it can be cut is it hell to do yes but can be done.

[Pryde]

Originally Posted by w210838

I understand that ar 15 but it can be done. Just like when guys shoot the crap out of 41v50 it hardens but it can be cut is it hell to do yes but can be done.

So is it worth ruining your $100+ chamber reamer to recut and salvage a production grade barrel? Good luck finding a smith willing to do that. Also you don't seem to understand the distinction between work hardened steel and an extremely hard surface finish.