ejection/extraction trouble shooting: adjustable gas blocks and powder burn rates

[georgehwbush]

44 AMP surely we both agree that "some" air ahead of the bullet enters the gas port. no? and that wasn't the point. the point was that the gas entering the port doesn't instantiously reach the bolt. there is delay, be it all so small it is there. and the more restriction the longer the delay. the fact that all the air ahead of the bullet doesn't leave the pipe uncompressed into the surrounding air, but is quite compressed as it exits due to the speed and inirtia, was just something i was mentioning to get everyone to consider the "timming" issue, which i believe is the real issue i am having.

maybe i'm wrong, if so just explain i'm not stupid and i'll catch on pretty quick if you explain. or point me at more data to investigate and maybe i'll come up to speed with the rest of you.

either way, i'm not here just to argue or make someone feel bad.

just here to learn, or teach, or share ideas. that's all.

[44 AMP]

Swipe marks mean there is hard physical contact when the movement happens and the softer metal is displaced slightly. Smeared, but not cut by a sharp edge, right??

The mystery is why this is happening, and why does it happen when it happens.

Absent a burr, nick or other sharp edge to cut/scrape the brass the answer would seem to be too high pressure.

NOT "too high" meaning over SAAMI limits, or beyond published load data, but
"too high" meaning too much pressure on the case at the moment the bolt rotates.

Chamber a round, don't fire it, extract it, look at the base. DO you see "swipe marks"?? I would expect not. IF you only see those marks on fired cases, then it must be a result of firing, and that means it was done by pressure.

Shoot some of your ammo in a different gun. Shoot some in a rifle that isn't your semi auto. Do you get the same marks on the brass??
I'm guessing you won't.

The pressure might be totally fine by the book, but wrong for your rifle's timing.

Maybe the brass you have is "soft", or not elastic enough for the rifle you are using it in. Maybe your bolt is being turned too soon. Maybe its something else, or maybe a combination of things.

Good Luck!

[georgehwbush]

("Chamber a round, don't fire it, extract it, look at the base. DO you see "swipe marks"?? I would expect not. IF you only see those marks on fired cases, then it must be a result of firing, and that means it was done by pressure. " QUOTE 44 AMP)

of course you wont see swipe marks on non-fired brass. the only way you would is if the head space wont allow for the round and something is "jamming" the brass. so yes it's a pressure/timing issue. obviously, and that is where i wnet from the beginning. would restricting the gas flow help that issue? i think it will,

also of note, i have reexamined some of the factory loaded brass, and found one or two of them that have slight swipe marks, and upon close examination it is the ejector that is making the mark and not the ejector hole. case solved as far as i am concerned. the swipe mark is made by the ejector when the bolt rotates with pressure on the chamber/case. and only when that pressure is high enough to cut the brass. other wise it only polishes it a bit. and is almost undetectable, almost i say, with magnification i can see it on all the fired round from that gun. all of them.

"Maybe your bolt is being turned too soon. Maybe its something else, or maybe a combination of things" yes i'm seeing a combo here, both too soon and an ejector that is not completely flush with the bold face. so a polish and a retuning should fix everything but the trigger nut. you agree ?

[tangolima]

Originally Posted by georgehwbush

tangolima yeah. and my extractor will not push all the way down into the hole. it protrudes like .0006 " with all the hand force i can apply. and the spring behind it is stiff. so i'm wondering if the swipe mark is the extractor and not the extractor hole... ?

Sorry I should have called that ejector, instead of extractor.

Good point. I'm check mine. Sounds like your ejector bottoms out on the spring in the hole. I don't like it sticking proud. I'd rather have it slightly under flush. It may be the reason for your premature swipe marks. Effectively the ejector button has become the bearing surface of recoil force. You may need to shorten the button a little.

The swipe mark may have something to do with the failure to extract and eject. Like a brake in a car it takes energy from the motion.

-TL

Sent from my SM-N960U using Tapatalk

[HiBC]

I'll agree that an ejector standing proud of the bolt face could put a smear mark on the case head.
That would explain the mystery.

Short of having a viable explanation, the smear was a sign to take seriously. But yeah,an ejector standing tall would explain it.

Be aware when you get scapings of brass ,they go someplace. I have seen them go into the hole with the ejector, binding it up.

Now that we are past that, minor adjustments in the "vigor" of cycling can also be achieved with variation in buffer weight.

Good luck!

[44 AMP]

From a "properly made" point of view, the ejector should be able to be pushed flush with the bolt face. Not "stand proud" when fully depressed. If it does, something isn't right. However, not being "right" may not be an issue to the maker, if it doesn't interfere with operation.

Remember as far as the maker is concerned, their responsibility is to produce a functional firearm, where ammo only has to go in, fire and come out ONCE per round. Reloader friendly is nice, but not their legal requirement.

Take down the bolt, and see if the ejector will go flush with the bolt face, without the spring in place. (polish the ejector as well, removing any sharp edges on the tip) IF the spring is too long, you should get a different spring. If the ejector itself is too long, then it ought to be replaced. Also possible the hole in the bolt isn't deep enough, and so long as the gun works, replacing the bolt is not the best option.

Tinker with it till you get it right, or live with it like it is, since it does work, your call.

[tangolima]

Just checked my ar-10. It is good. The ejector button is about 0.005" below flush.

-TL

Sent from my SM-N960U using Tapatalk

[Nathan]

are ejecting all over the place from 1:00 to 5:00 and have rotation/ejector marks, the last cartridge will not lock the bolt back.

These 2 points are a bit contradictory. I’d start with does it function. It feeds, it extracts….it sounds like. Is that true? If so, I’d go after doesn’t lock back. That may be not enough port pressure, but to confirm, I would try closing the port all the way, then open in increments until it locks back.

If that doesn’t improve things, I might try another powder.

How long is port length from chamber to port and port to muzzle?

[bfoosh006]

Sorry if I misunderstood, but is your upper a OEM factory upper or was it assm.d by yourself ?

I would double check the gas block is aligned with the gas port first.

I would also look for possible signs of gas leakage at the gas key or the gas block and gas tube.

What buffer setup are you using ? A .308 length rifle setup ? Carbine setup ? ( and which pattern ? )
Just trying to make sure the right combo of parts are being used.
What buffer length's and weight ?

I find it kinda hard to believe a .243 isn't producing enough gas to routinely cycle a LFAR. Not saying yours isn't, just there should be plenty of gas being produced.

[44 AMP]

handloads (nosler 90g spr, H-4350 42.0gr, cci200 primers, winchester brass)

I find it kinda hard to believe a .243 isn't producing enough gas to routinely cycle a LFAR.

The load is burning over 40gr of powder, enough gas is being produced. The bullet is zipping out of the barrel, enough gas is being produced.

The problem is tapping the needed amount and getting it where it needs to go, when it needs to be there. Everything in the system that affects rearward movement of the bolt carrier is a factor. Figuring out which factor(s) are responsible for the undesired quality of operation is the trick.

When empties land in different places, it is usually a sign that the bolt is not moving at the same speed, shot to shot. But not exclusively, an inconsistent ejector or extractor tension might also have the same effect.

Or it could be a combination of those. Test other loads, use factory loads as your reference. See if the rifle's performance is the same with those as with the handloads you used.

Do you get swipe marks with other ammo? does the brass land somewhere in a 160 degree arc or is it consistently all in a bout the same place??

Before you go swapping parts to "see what works" decide which is the priority, tuning your rifle to shoot a certain load, or tuning your ammo to run well in your rifle??

[georgehwbush]

44 AMP [Before you go swapping parts to "see what works" decide which is the priority, tuning your rifle to shoot a certain load, or tuning your ammo to run well in your rifle??]

if all loads act differently, then the latter of the two is a moot point. i will develop a load that i like, then tune the gun to shoot it.

or at least that is the plan.

[44 AMP]

You've got a plan, go with it and let us know how it goes.

Just keep in mind that semi auto rifles are not good "multifuel engines".

The Deuce and a halfs that we had in the Army back in the 70s when I was there were "multifuel engines". They were normally run on diesel, but would run on gasoline. We discovered that, in an emergency they would also run on rifle bore cleaner, or high proof booze, if fueled while running, but wouldn't start on those fuels. One poor fellow discovered they would run on jet fuel, for about 30 seconds or so, then explode...
Semi auto rifles rarely have that much of an operating range built in, in stock configuration.

Point here is that you can, carefully with patience and experimentation probably tune your rifle to run well on the load you want, BUT doing so MAY render other loads unsuitable for use in that tuned gun.

Good luck, be safe!!

[Scorch]

For troubleshooting or adjusting the gas bloack on a large frame AR, open the gas block wide open and fire factory loads. Trying to start somewhere in the middle with handloads that are all over the place is a recipe for frustration. Once it's adjusted to run reliably with factory loads you should be able to run anything with minor adjustments.

Make sure the buffer sping is lubed. Make sure the bolt is lubed.

[georgehwbush]

update: was able to run another ladder test today, with an even slower powder, but also found a heaver bullet that i like. anyway seven shot groups are down to 1.011 in. at 100 yds, that's an even one minute of angle and i think i can do even better with some fine tuning, the shells are ejecting at 3 to 4 o'clock but the bolt doesn't always lock back on the last shot, would reducing the buffer weight help that ?

anyway; everything looks very promising to me. and thanks guys for all the input.

[georgehwbush]

some more testing done: with 43.1 grs of reloader 19 and the 107 gr, sierra match king, they are clocking 2922 ft/s 15 ft from the muzzel and grouping at 0.785 in. cycling well but not always locking back on empty mag. so that's where we stand right now.

[44 AMP]

Have you have tried more than just one mag??

[jetinteriorguy]

One of my rifles quit locking back when empty once, I pulled apart the bolt catch and somehow the spring got messed up. It’s been quite a while and I don’t remember how the spring got messed up but I put in a new one and it’s been 100% ever since.

[georgehwbush]

amp 44: different mags? errr no.

[44 AMP]

When a magazine feeds ammo, but fails to lock open on the last shot, it is unlikely that short stroking is the reason.

What is more likely is that the magazine spring is just slightly underpowered.
OR, possibly the follower is dragging just enough to not lift into position to activate the bolt catch, in time.

The "in time" part is what matters.

Check for wear or damage where the follower and bolt catch engage. There probably isn't any, but check.

The empty magazine operates the bolt hold open properly when you open the action by hand, right?

It feeds ammo properly, right??

Since the mag feeds, that proves the bolt is coming back far enough to pick up the next round. Is it possible the bolt is coming back enough to pick up the next round, but not far enough to allow the bolt catch to activate after the last round? Yes, it is possible, but I think it is more likely to be an issue with the magazine, or the bolt catch. Testing with a different magazine will rule out some factors.

Good Luck.

[tangolima]

Originally Posted by georgehwbush

some more testing done: with 43.1 grs of reloader 19 and the 107 gr, sierra match king, they are clocking 2922 ft/s 15 ft from the muzzel and grouping at 0.785 in. cycling well but not always locking back on empty mag. so that's where we stand right now.

Good shooting.

The cycling has improved with this slower powder, has it not? I think you are in the right direction. Gas block fully open now? I would give it another half turn if not.

Not my first choice to correct cycling issues, but it has worked for me. I would cut coils off the recoil spring, half coil at a time. It enables the BCG travel back a bit further with same energy.

I also went shooting my ar-10 in .243 win yesterday. 10-shot group of 0.8" at 100yd. I have 38.2gr Ramshot hunter behind 100gr speer spbt bullet. MV is around 2850fps. Good enough for me. Will take it to 200/300yd next week.

I'm new to this caliber. A bit disappointed when I started with cheap 75gr flat base varmint bullet. Ballistically it was slightly better than 5.56 NATO. The 100gr spbt makes huge difference. It is a keeper.

-TL

Sent from my SM-N960U using Tapatalk

[georgehwbush]

tangolima; "gas block fully open now?"

in fact no. with it full open, it doesn't eject properly and leaves swipe marks on the case heads, it is a bleed off type adjustment, and i'm bleeding some of the presure to get it to cycle correctly. the gas-block instructions says open four complete turns for full open and open more to bleed off. they do not reccomend closing to reduce pressure but opening more... up to 16 turns total. i am at six and an half right now, it is cycling perfectly. but just doesn't "always" lock back.

amp44: i will try another mag and see what happens. also have a buffer weight set ordered, just in case.

[georgehwbush]

tangolima: i have no doubt now that with a little testing, you can get half MoA out of these, the 243win is an accurate round, and the ai version is even better, it has been my experance that, (at least with bolt guns) most 243win's like the 2950 to 3050 ft/s range, that seems to find a node on 22 - 24 inch tubes. also the heaver '90gr +' pills work best, assuming you have enough twist of course.
But, i have never gotten good accuracy out of cheeper factory loads,
if all you want is proper cycling in an ar platform they seem to do that very well. but the 1.7~2.2 MoA is only good for..... nothing really.

thanks guys "and gals" for all the feed-back it helps to hear what others think about what one is doing, (one doesn't have to agree) but it helps to hear it... enjoy your freedom and your health while you have it.

[tangolima]

I meant to put a bit more gas to cycle the action, however your gas block works.

I am currently loading with 100gr spbt bullet. It is long but not terribly long. It seems stabilized ok. 2850 - 2900fps is the end of the push as the primer starts having shallow cratering. I will try 85gr bullet next, where I can go a bit faster. Flat base varmint bullets are cheap. But they have much more drag. Speed drops to subsonic pretty soon and they are sensitive to cross wind. I probably can do better with better bullets. But I'm on budget. 0.8moa is mighty good enough for me. I think I can consistently hit a letter paper sized target out 750yd with it.

I found it quite easy to convert .308 brass into .243. It is a plus for me.

-TL

Sent from my SM-N960U using Tapatalk

[georgehwbush]

indeed quite easy to resize 308 > 243. just lube and shove it in the full length die... but, i prefer to keep the head stamp correct. unless you are using something like mil/spec/surplus where the headstamp is caliberless .
tangolima, i know that it may sound obtuse but, i always prefer the heaver higher B.C. pills, what they lack in initial speed they more than make up for in long range performance. but that's just me.

i'm surprised that you are seeing preasure signs at 2900 ft/s with 100gr pills. it might be the powder. ? i find slower powders generally yield higher speeds with lower presures and usually only start seeing signs at around 3025 with 100gr 3000 with 103gr,

i'm sure you know what you are doing and i need to just leave it alone, just thinking out loud !

cheers

[tangolima]

The load is mid point between min and max. I could have pushed it closer to 3000fps, but I had a couple of pierced primers. I feel more comfortable with where I'm at.

Other than cost, I use varmint bullets with lower BC quite often for "emulated long range training". A lousy bullet at closer distance emulates a better bullet at farther distance, so that I can practice wind reading without going to a real long-range range.

-TL

Sent from my SM-N960U using Tapatalk