1:9 Twist barrel keyholing.
- Thread starter OKRattler
- Start date
Austin Laughlin
Active member
I’ve shot everything from 40s to 64s in my wife’s AR. I believe it’s a 1:8? It’s a stock gun. The 53s and 55s were the best group I got.
You’ll enjoy the 40s-53s if it’ll group them. Fast and flat.
Austin Laughlin
Active member
I actually happened to be sitting here talking to my calling partner and he’s a AR guru. He said 6 out of 8 of his ARs are 1:9 twist and all of his shoot the 40-53gr bullets much much better than they do 55-80gr.
This one sure seems to like the light ones pretty good. I don't remember getting that good of a group the last time I shot that rifle. If it would pick up the next round like it ought to I'd be tickled pink about how well it shot. I just gotta figure out why it's not wanting to cycle the light weight ones.
Austin Laughlin
Active member
My partner asked if the gas block is adjusted and everything is in line? No problems there?
I’m not to savvy on the AR platforms. I’m trying to be the middleman here.
I know out of the cheap Diamondback I bought my wife, and all of his, we can shoot Factory 40gr Vmax with no issues. I wonder why yours is giving you fits.
I haven't messed with the gas block at all. I'm just confused about why it would be too because when I shot those 55 and 64 grain bullets it ejected them and grabbed another bullet and stuffed it in the chamber no problem whatsoever. Those empties landed further back than the lighter bullets did too. That's what made me think it was a gas issue as well.
Seems like it's short stroking to me. When it ejects the empties with the lighter bullets it's almost like it's not bringing the bolt back far enough to grab a new round.
Austin Laughlin
Active member
He says it almost has to be a gas block issue. Making sure everything is in line and adjusted right is where he would start.
Hidalgo
Well-known member
Several areas can cause this. Not just the block. Clogged tube. Dry action. Wrong / damaged buffer spring.
Also, if purchased as he said in 2008, any and all lube that was in the rifle is probably goo right now. It should be totally disassembled and properly cleaned before anything else is looked into.
Yes it has been cleaned. Before I put it up we cleaned the gas tube and the barrel because I really kind of planned on getting rid of it. Just never did. I probably hadn't shot it in at least 6 years and it was super clean when I put it up. The only reason I cleaned it up really good is because I really planned on selling that upper. Just never did do it. It's had problably 15 rounds through it after it was cleaned really well. Gas tube, barrel and oil on the bolt.
I sprayed Rem Oil on the bolt the other day though.
Austin Laughlin
Active member
Last edited:
I guess I can go back and clean out the gas port again just to be sure. It won't hurt anything. I've never heard of a rifle being too clean. I'll have to have someone more savvy than I am check the gas block. I'm a bolt gun guy so I gotta have someone standing there that knows what they're looking at as far as making sure everything is in place goes.
Dultimatpredator
Well-known member
I had the same issue with my bushmaster target varminter rifle I bought bsck when it was first released. Around 99’ or so. Worked up a hand load with combined technology coated Nosler ballistic tips in 40 grain. A five shot group at 100 yards was all in one little hole about the size of pencil eraser head! I definitely found a hand load for it using a max load of 27.7 grain of benchmark and it still wasn’t enough to cycle ammo. It peeved me off so I traded it for my LTR. Nobody around me shot AR at the time so I didn’t know what I was doing and if I did, I would’ve gotten adjustable gas block for it and messed with it. Im guessing my gun was “under gassed”? I would assume yous is the same and probably needs an adjustable gas block for it as well if you want to shoot light bullets. Either that or it’s leaking around the gas block tube?
An adjustable gas block may be the way to go I was thinking but I don't know enough about them to know but guess as to what the issue could be really. I know enough to just make an educated guess and that's about it.
The only reason I leaned towards it being a buffer spring issue is because the heavier bullets cycled just fine. Never had any trouble with them other than they weren't shooting accurately. But it very well could be a gas block issue. It just seemed to me if one bullet weight wouldn't cycle reliably that they all would have trouble.
Dultimatpredator
Well-known member
I’ve never messed with an adjustable gas block, either other than reading about them. Guess my POF has one because you can twist between using a suppressor or not on it. Replacing the spring I think is just an another option instead of messing with a gas block pretty much does the same thing I’m guessing.
204 AR
Well-known member
Adjustable gas blocks are great but they won't give you more gas than the current one, which is wide open by default. Adjustables are for cutting down on the gas. Most likely it's just barely under gassed, heavier (slower) bullets have more dwell time in the barrel, which means more time between the gas port and the end of the barrel for the gas to bleed through the gas port and back to the bolt carrier group. That's why the heavier bullets will work.
I would first make sure the block is centered up on the port hole. If it's a set screw type of block, or one with tapered cross pins, chances are it's aligned correctly already. If it's a clamp on, it could be twisted a little, or it could be too far back. I'll explain that further if need be.
Also a good clue is where the brass is landing. Further back is usually less gas, forward is too much as the case is bouncing off the deflector and then forward. You said the light bullets went straight out but not very far at all, a couple feet iirc. You're really close to just right imo. Just needs tweaked a little bit.
I suspect you'll end up needing to open the gas port a tiny amount, which is pretty easy if you have access to a comprehensive drill bit set. We have a pretty good hardware store that sells individual bits, I would take the barrel or whole upper in with the gas block removed, and use their bits to gauge the hole that's there, then buy the next two bigger sizes. I'm talking a few thousandths of an inch so numbered and lettered bits come into play here. Run an old cleaning rod in the barrel to stop the bit from touching the opposite side of the bore and drill it out and test. It won't take much.
If you want to experiment more before messing with all that, and you have multiple powders to try, powder selection can make a difference for sure. Think slower burning powders. I've specifically had issues with 4198 cycling ar's back in the day. Something along the lines of h335, varget, or 8208 should work ok.
The last thing I've had issues with was hammer drag, specifically with a certain lot of RRA two stage triggers. Unless you have that specific trigger group it's probably not your problem.
HTH
I would first make sure the block is centered up on the port hole. If it's a set screw type of block, or one with tapered cross pins, chances are it's aligned correctly already. If it's a clamp on, it could be twisted a little, or it could be too far back. I'll explain that further if need be.
Also a good clue is where the brass is landing. Further back is usually less gas, forward is too much as the case is bouncing off the deflector and then forward. You said the light bullets went straight out but not very far at all, a couple feet iirc. You're really close to just right imo. Just needs tweaked a little bit.
I suspect you'll end up needing to open the gas port a tiny amount, which is pretty easy if you have access to a comprehensive drill bit set. We have a pretty good hardware store that sells individual bits, I would take the barrel or whole upper in with the gas block removed, and use their bits to gauge the hole that's there, then buy the next two bigger sizes. I'm talking a few thousandths of an inch so numbered and lettered bits come into play here. Run an old cleaning rod in the barrel to stop the bit from touching the opposite side of the bore and drill it out and test. It won't take much.
If you want to experiment more before messing with all that, and you have multiple powders to try, powder selection can make a difference for sure. Think slower burning powders. I've specifically had issues with 4198 cycling ar's back in the day. Something along the lines of h335, varget, or 8208 should work ok.
The last thing I've had issues with was hammer drag, specifically with a certain lot of RRA two stage triggers. Unless you have that specific trigger group it's probably not your problem.
HTH
I think I'm gonna clean it up real good and then test it again before I dive too deep into messing with the gas block situation. I can load more with different powders if that don't work. I just can't get past the heavier bullets functioning flawlessly and once I switch to the bullets it actually likes it starts acting up. Just doesn't make sense to me. I mean it's about par for the course. Something dumb like that always happens. The gun can't just work like it's supposed to. That'd be way too simple.
Dultimatpredator
Well-known member
I can say I was super paranoid when I bought the Bear Creek arsenal in 243s and wanted to shoot 55 grain light bullets out of them thinking I was gonna have the same issue. Happy to say every ladder test that I tried in 55 and 60 grain light projectiles from starting loads to max loads kicked out every one of my shells. The heavy barrel 22” stainless fluted upper really upper launches them. The 20” SOCOM version one throws them out about 3 to 4 feet away from me In a nice little pile. I put some female sided Velcro on the outside of the ejection port, because the brass was getting banged up pretty good when ejecting it fixed that issue. In one of them I also had the end of my cases, getting torn up pretty good and scratched. I polished up the inside of the bolt lugs, and my brass looks really nice now when it ejects. Little things learning along the way with ARs. Have them on and off for about 25 years but just don’t mess with them enough to care.
I would break it down to all parts and pieces. Clean everything really well. Double check that the gas block matches up with holes in barrel. Make sure all screws are still tight.
My wife bought an AR off of a friend. He "cut her a deal". The thing was one problem after another until I took time to dissect the whole gun. Screws were loose letting the gases seep by instead of functioning the bolt. Bolt was nasty inside. Looked clean from outside.
Many new guns are "greased" from the factory to prevent rust.
JB Bore paste in the blue can can work wonders to clean the bore out.
My wife bought an AR off of a friend. He "cut her a deal". The thing was one problem after another until I took time to dissect the whole gun. Screws were loose letting the gases seep by instead of functioning the bolt. Bolt was nasty inside. Looked clean from outside.
Many new guns are "greased" from the factory to prevent rust.
JB Bore paste in the blue can can work wonders to clean the bore out.