Keyholing in my new rifle

montoya32 · Aug 25, 2014

Just a feeler about keyholing. I was shooting my brand new Mossberg MVP Predator(5.56 w/threaded 18.5" medium bull barrel) yesterday. After I zeroed it in at 75 yrds( I plan on stretching it out, just didn't have time), I noticed the shots were leaving oblong holes in the paper(keyholing). I was shooting 55gr FMJ ammo. I see a number of XM193l on the box.

Any ideas?

BradMacc82 · Aug 25, 2014

IIRC, the MVP is a 1:9 twist, so it SHOULD have been stabilizing those rounds just fine.

Pull the bolt and look thru the barrel (from the breech end obviously) at a light source and see if you can see a broken land in the rifling or some other type of manufacturing defect.

Jimbob2.0 · Aug 25, 2014

Thats odd, I have the exact same gun and it drives tacks with no issues. Regularly run 55 and 62 grain and bullets. Havent tried the heavier stuff yet.

Inigoes · Aug 25, 2014

Could try 62 grain ammo till you get the gun broken in.

clandestine · Aug 25, 2014

Check the bore for damage and the crown for damage. Try different ammo and report back.

montoya32 · Aug 25, 2014

clandestine said:
Check the bore for damage and the crown for damage. Try different ammo and report back.

No bore or crown damage. I will try some different brands and weights this weekend.

Boss94 · Aug 25, 2014

Normally tumbling is a crown issue. But it could be the Dia of bullets .

lx1x · Aug 25, 2014

Boss94 said:
Normally tumbling is a crown issue. But it could be the Dia of bullets .

Not all... Could be powder charge also...

BradMacc82 · Aug 25, 2014

Boss94 said:
Normally tumbling is a crown issue. But it could be the Dia of bullets .

I've witnessed firsthand a broken land in a AR barrel cause keyholing at 25 yards - big burr on the back edge of the gas port, and a broken land. Left perfect bullet profiles in the target.

Not saying that's what is going on with Tim's rifle, but it's one more thing to check/rule out.

pwoolford · Aug 26, 2014

I had a cheapo flash hider that must have been drilled crooked causing that for me once.

Semper Noctem · Aug 26, 2014

Not to derail this thread, and I know it is a safety issue - so I'm not advising or recommending anything here. But, I'm curious...

Has there been any research into what type of damage a tumbling bullet would do to a target as compared to one that exhibits a normal flight pattern? I imaging that a bullet impacting a target sideways would dump a significant amount of kinetic energy and splash a lot.

montoya32 · Aug 26, 2014

lx1x said:
Not all... Could be powder charge also...

That was my first thought too. This rifle has no crown and I was shooting 5.56 ammo.

I picked up a few different types of .223 ammo to test.

outrider58 · Aug 26, 2014

Is that rifle chambered in .223 or 5.56? could be problem but I don't know if tumbling would result from shooting 5.56 through a .223 chamber. Prob. a muzzle issue.

:shrug:

BigDaddy · Aug 26, 2014

Semper Noctem said:
Not to derail this thread, and I know it is a safety issue - so I'm not advising or recommending anything here. But, I'm curious...

Has there been any research into what type of damage a tumbling bullet would do to a target as compared to one that exhibits a normal flight pattern? I imaging that a bullet impacting a target sideways would dump a significant amount of kinetic energy and splash a lot.

Yes, google 5.45x39 or 7.65x32 and tumbling.
It's not supposed to tumble before it gets to the target, or it's a knuckle ball.

Pinecone · Aug 26, 2014

Semper Noctem said:
Not to derail this thread, and I know it is a safety issue - so I'm not advising or recommending anything here. But, I'm curious...

Has there been any research into what type of damage a tumbling bullet would do to a target as compared to one that exhibits a normal flight pattern? I imaging that a bullet impacting a target sideways would dump a significant amount of kinetic energy and splash a lot.

Not much penetration though.

Pinecone · Aug 26, 2014

montoya32 said:
This rifle has no crown

How can it have NO crown??????

The crown is the end of the barrel where the bullet comes out. It could be a horrible crown, but it HAS to have one.

montoya32 · Aug 26, 2014

Pinecone said:
How can it have NO crown??????

The crown is the end of the barrel where the bullet comes out. It could be a horrible crown, but it HAS to have one.

Completely flat. No crown. Even checked another rifle at the shop and no crown.

Sent from my SCH-I545 using Tapatalk

Ifdot · Aug 26, 2014

You've got a bad crown. I'd take it back or take it to a gunsmith.

Ifdot · Aug 26, 2014

montoya32 said:
Completely flat. No crown. Even checked another rifle at the shop and no crown.

Sent from my SCH-I545 using Tapatalk

This is the problem, it has a crown its just not recessed to protect the lands. There is more than likely a small burr on the crown you can't see!

BigDaddy · Aug 26, 2014

montoya32 said:
Completely flat. No crown. Even checked another rifle at the shop and no crown.

Most people think of as the crown, is a location, and while it could be various shapes, the important part is at the end of the rifling end at the end of the barrel.

It's called a crown but it doesn't look like the Queen of England's crown. It can have various profiles: flat, recessed, rounded or 15 degrees, but the important part is it at the end of the rifling.

The guru's may argue about which profile is more beneficial, but none of them cause bullets to tumble, unless there is an abnormality with how they are done.

Keyholing in my new rifle

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