1:9 Twist barrel keyholing.

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OKRattler

Well-known member
I bought a DPMS Sportical in about 2008 or so. Never really have shot it much. Before now I hadn't shot any bullet over 50 grains through it. I tried some 64 and 55 grain bullets over the weekend and actually found out those bullets were hitting the target sideways. I had it sighted in with 40 grain Nosler Ballistic Tips before and got about 1" groups with them at 100 yards. I find it odd that a 1:9 twist won't stabilize any bullet over 50 grains. I shot some 45's just to see what they were doing and the bullet holes looked like you'd expect on paper. The 55's and 64's on the other hand were apparently tumbling through the air before striking the target. Has anyone dealt with this with a 1:9 twist barrel? The gun is what I'd call new considering I haven't shot but maybe 100 rounds through it since I got it. I've cleaned it a few times over the years so I know the barrel isn't dirty. I just can't figure out why it's not shooting the heavier bullets but shoots 40 grain bullets fairly decent. Should I get a different barrel or what would y'all suggest?
 
I have 3 DPMS uppers and they all shoot excellent. Mine are 1:8 twist heavy barrels and shoot 60 VMax into cloverleafs.

More info if reloads: What bullets are you having trouble with? Brand & model? Powder? OAL?

If this is factory ammunition, what is it exactly?

If there a muzzle device on the barrel? If so, what is it?

That barrel should shoot all the way to 70 grain bullets easily (or perhaps even heavier depending on the bullet design).

You can verify the twist rate by running a very tight patch through the barrel and counting the turns on the cleaning rod as it passes through. See how many inches it takes to make a complete turn.
 
I tried Sierra 64 grain factory ammo and 55 grain. FMJ, unknown brand. Probably reloads of some kind. I bought them in bulk a long time ago. I also shot Winchester white box 45 grain JHP's. The 45 grain bullets didn't keyhole. The other two did.

I'll have to confirm twist rate because I'm starting to think it's not really a 1:9.
 
OKRattler said:
I tried Sierra 64 grain factory ammo and 55 grain. FMJ, unknown brand. Probably reloads of some kind. I bought them in bulk a long time ago. I also shot Winchester white box 45 grain JHP's. The 45 grain bullets didn't keyhole. The other two did.

I'll have to confirm twist rate because I'm starting to think it's not really a 1:9.
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Not trying to be a smartazz, but trying to diagnose a problem like this with unknown ammunition is chasing your tail. Go grab a box of factory ammunition with 55 to 64 grain bullets and see what happens.

Did you buy this rifle new or used?
 
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The bullets could be undersized. I had a box of Speer .358 180 grain hot cores that were oversized a few years back and wouldn't seat unless they crush the cases necks. Sent them to Speer and they were replaced. So manufactures do screw up on bullet diameter. My guess is your projectiles are rejects or undersized. Did you crimp them or are they factory crimped and the crimp distorted and undersized the bullets?
 
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Hidalgo said:
Not trying to be a smartazz, but trying to diagnose a problem like this with unknown ammunition is chasing your tail. Go grab a box of factory ammunition with 55 to 64 grain bullets and see what happens.

Did you buy this rifle new or used?
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The 64's are factory Sierra Total Game Changer. I just shot the 55 grain bullets to get on the target so I wasn't burning up my huntin ammo. I've shot those for years and never had that problem with my bolt guns and they're surprisingly accurate. Of course I don't hunt with them though because they're Full Metal Jacket.

I bought the rifle new. I'd still consider it fairly new because I haven't shot it very much.
 
Dultimatpredator said:
The bullets could be undersized. I had a box of Speer .358 180 grain hot cores that were oversized a few years back and wouldn't seat unless they crush the cases necks. Sent them to Speer and they were replaced. So manufactures do screw up on bullet diameter. My guess is your projectiles are rejects or undersized. Did you crimp them or are they factory crimped and the crimp distorted and undersized the bullets?
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I'm not sure on that end of it. I just know the FMJ's have been super accurate out of every bolt gun I've shot them in. The Sierra 64 grain Total Game Changer ammo is new to me. I've never used it before. I bought like 100 rounds of it a while back and just now decided to test them out on some coyotes.
 
Really the only reloads I've used in this gun were some my grandpa loaded up which were the 40 grain Nosler BT's. Which shoot the best out of it by far. Reloads that I can find any data on I mean. The FMJ's are reloads but I couldn't say for sure what powder was used or anything like that.
 
If it is a Sportical and the barrel is stamped incorrectly it will be the first one I have heard of. And there are literally hundreds of them out there. But as a favorite personality of mine always says ......... "The only thing that will surprise me today, is if nothing happens that surprises me". ;)
 
Shoot some of the heavier bullets at 25 yards, compare to your 100 yard targets. Target should be good card stock. Or at least paper firmly attached to cardboard that doesn't move. Way easier to "read" bullet holes. Coloring the bullets also can show wobble. I won't find it unusual that hand loads are better performing than factory. I don't recall DPMS ever marketing a slow twist barrel. Also check where the brass is being ejected to, if there is a difference between light ammo/heavy bullet ejection timing that could indicate you need an adjustable gas block for tuning.
 
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Well, that was pretty uneventful. I ran a cleaning patch through it and the tape made 0 turns so either my cleaning rod doesn't turn that well because it's older than I am. Or I just don't even know what I'm doing. Or my rifle is a smooth bore. So there's three options. Good news is the patch picked up some powder residue so it's super clean now.

I'm gonna say it just prefers light bullets for whatever reason. It's weird to me but I don't know what else to do besides shoot the light ones. Measuring twist rate was a complete fail. I basically just dry cleaned the bore. I'm not too upset really if I can't shoot the heavier bullets. I just got it back then because Democrats hate AR-15's and I love everything they hate. So I'm cool with shooting 40 grainers through it if I have to. It's crazy to think about how high prices on AR's were back then. Now you can build one for $400. Now it's bolt guns I can barely afford to buy. Crazy times.
 
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