I built my dad a 243 AR out and he had some issues firing it today. He’s running an adjustable gas block. During firing some of his round were not ejecting and staying in the chamber and then trying to double load the next round. The problem is he lives very far so I’m unable to troubleshot it. I thought maybe he needed to open his gas block more but with the rounds not extracting at all it sounds more like an extractor problem? Some guesses would be greatly appreciated
243 AR cycling issues
- Thread starter wyattgtx
- Start date
More gas or less buffer, gas is easier to fix by phone.
That doesn't matter. The powder burn rate makes the difference. I have some powders operate the system better than others using the same bullet. I also doubt it is an extractor issue. As mentioned, there's not enough gas through the tube to function properly. If gas is at max setting, then drop buffer weight. If gas tube is not proper length, as I experienced, there can be problems. Does the gas tube extend 1/2 way into the cam pin cutout area of the receiver?
THIS for sure. Inside the BCG where the gas rings are. I'd suggest synthetic engine oil.
The problem could use a better description if you want good answers. But, given that you said it's trying to load a fresh round while the empty case is still in the chamber, that means the BCG has enough gas to fully cycle and either the extractor is not catching the rim and extracting, or the extractor is ripping through the rim. First problem is an extractor problem, second problem is an overgassed problem.
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Who's BCG? Low end LFAR extractors can have very shallow claws. This was a known issue 10 years ago. Today's BCG'S are better but you still run into it.
I missed that it was trying to load a fresh round. Yeah, this smells of extraction issues.
We need a detailed breakdown on parts and how they were assembled.
If it was a BCA barrel, I’m out.
If it was a BCA barrel, I’m out.
Pulled the BCG apart, noticed that the extractor is missing the rubber o ring I have seen on others?
So .243 Winchester AR-10 is a different animal from an engineering standpoint, compared with .308 Win. Might as well be different rifles.
Bore volume is dramatically smaller, so port pressure tends to be a lot higher. Case volume is the same, but propellant burn rates are slower in .243, otherwise you would hit peak pressure way too early before case fill.
When you have less bore volume and higher port pressure, cyclic rate tends to be faster if you can’t control the gas flow.
Too fast of a cyclic rate can leave the case in the chamber, because it hasn’t de-obturated yet.
So you will see extractor slip-off if the case is still obturated.
You need to dial down the gas flow with some type of adjustable gas, or metered port.
Bootleg now makes carriers for the large frame guns in DPMS pattern, so if it was mine, I would probably get that or a RIfleSpeed AGB.
I would not mess with a set screw adjustable gas block.
Bore volume is dramatically smaller, so port pressure tends to be a lot higher. Case volume is the same, but propellant burn rates are slower in .243, otherwise you would hit peak pressure way too early before case fill.
When you have less bore volume and higher port pressure, cyclic rate tends to be faster if you can’t control the gas flow.
Too fast of a cyclic rate can leave the case in the chamber, because it hasn’t de-obturated yet.
So you will see extractor slip-off if the case is still obturated.
You need to dial down the gas flow with some type of adjustable gas, or metered port.
Bootleg now makes carriers for the large frame guns in DPMS pattern, so if it was mine, I would probably get that or a RIfleSpeed AGB.
I would not mess with a set screw adjustable gas block.
I would put a RifleSpeed gas block on the .243 Win AR-10, or any other caliber for that matter.
Smaller bore volume relative to case capacity = finicky with load and temperature changes, especially with the slower-burning powders used by .243 Win.
Smaller bore volume relative to case capacity = finicky with load and temperature changes, especially with the slower-burning powders used by .243 Win.
If your extractor is correct it will rip the rims off before it lets go. Maybe the gun is gassed incorrectly and maybe it isn't, there is still an extraction issue. If this was a gas issue he'd be posting pictures of extracted cases with heavy extractor marks.
OP, post a picture of the extractor claw.
I'll post some pictures tonight with some extractor comparisons.
OP, post a picture of the extractor claw.
I'll post some pictures tonight with some extractor comparisons.
243 is a finicky dog, i ended up opening the gas hole in the barrel, gas block wide open, 2.9 oz buffer, standard spring, and shoot 2900 plus fps ammo (70 grn bullet) and havnt had any issues since. Tosses brass slightly forward of 90 degrees. Its expensive but tis a PRS hammer.
#1 is shallow and slides off rims.
#2 is Toolcraft.
#3 and #5 are JP.
#4 is Toolcraft and works as well as JP.
I have a DPMS G2 extractor but can't find it. Those were excellent replacements 10 years ago.
#2 is Toolcraft.
#3 and #5 are JP.
#4 is Toolcraft and works as well as JP.
I have a DPMS G2 extractor but can't find it. Those were excellent replacements 10 years ago.
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I would be concerned about the APF BCG. Good ejection and extraction is an interplay between being dwell time, appropriate gassing, and extractor geometry, and extractor spring tension. Get any of those wrong and it isn't going to work.
Would recommend trying a different BCG if it is verified to be gassed appropriately and this is not cured.
Would recommend trying a different BCG if it is verified to be gassed appropriately and this is not cured.
Dang. My 17.6” Lilja 6.5 Grendel spits 90gr out at 2900fps with factory Federal 90 TNT.
22”-24” 6.5 Grendel does 100gr ELD-VT at 2850-2900fps with CFE223, with way lower chamber pressure than .243 Win and barrel life that lasts forever.
One of the reasons why I never messed with .243 Win in AR-10s.
ETA
I just ran my numbers through a Grendel-specific internal ballistics engine.
My 12” 6.5 Grendel would spit a 70gr bullet out at 2998fps (between 2949-3048fps) if a 70gr existed for 6.5mm.
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