Pulled block. Mic on hole was showing .076 best I can tell. I then got a thing piece of plastic stock and worked it circularly into the hole, then mic’ed it and got .077. The gas ring around the port is exactly centered.
AR Tuning question
- Thread starter brutus1776
- Start date
Gas rings are only half of the bolt's gas system seal. The other half is the tail of the bolt and the corresponding bore of the carrier. It's a very tight tolerance fit, and I wouldn't be surprised to see it out of spec on a 25k round count BCG/bolt/carrier. The only way to check is with specialty pin and ring gauges.
The internal specs of your bcg are f'ed up. The rings are only a part of the system. Swap the carrier that works with the bolt that does not. That will tell you everything you need to know about what is going on. If it works then your newer carrier is the problem. If not then it is your bolt causing it.
And to just prove it, swap the bolt that does work into the carrier that does not right now.
Just make sure which parts go where they need to.
And to just prove it, swap the bolt that does work into the carrier that does not right now.
Just make sure which parts go where they need to.
Yes, did this Sunday and got lock back with noticeably more gas/recoil, and was able to tune the gas block a bunch of clicks before no more lock back
Whoa there. Are you proposing that he drill the gas port out by 15 or 20 thou?! No, no, no. Even if that is the problem, we are at the fine tuning stage. .003 at the most. If you put another zero in there after the decimal, it makes more sense.
Update:
Installed JP LMOS bcg. Full gas, instant lock back. (18 clicks.) tuned it down to about 6 clicks, got bolt action. Got lock back around 8 or 9, Then settled around 12 clicks to try it out. Got lock back on 5 1-rd mags, then shot a full mag of bill drills and got lock back. Plan to do a full practice session this weekend.
Ejection is almost exactly at 3 o clock. Do I need to put the weight back in the h1 buffer that I took out? I’m still running standard spring
Installed JP LMOS bcg. Full gas, instant lock back. (18 clicks.) tuned it down to about 6 clicks, got bolt action. Got lock back around 8 or 9, Then settled around 12 clicks to try it out. Got lock back on 5 1-rd mags, then shot a full mag of bill drills and got lock back. Plan to do a full practice session this weekend.
Ejection is almost exactly at 3 o clock. Do I need to put the weight back in the h1 buffer that I took out? I’m still running standard spring
Sounds like you already have it set up/tuned to your current weight. If you add back in the H1 buffer weight you will likely have to play around with the AGB clicks again so it’s up to you I guess.
I don’t run adjustable gas blocks, so I will usually tune the buffer weights to be as heavy as possible without getting any short stroking.
He's not "fine tuning" with the gas port - he has an adjustable gas block for that. If you look to an earlier post he measured the gas port at .076" so .015-.020" bigger is a .091-.096" gas port. This gives plenty of gas to the adjustable gas block to adjust for a full range of propellant charge, bullet weight, bolt weight, buffer weight, buffer spring tension etc etc. This is a good place to be particularly if you run with a heavy buffer.
Cool. Is there any benefit to the recoil impulse or anything with going heavier on buffer or spring? Is it more optimal to have a more closer to 4 o clock ejection?
Yes. From Grok:
A heavier buffer weight (e.g., H2 or H3) and a stiffer buffer spring (e.g., Sprinco Blue) in an AR-15 can reduce recoil impulse by slowing the bolt carrier group’s cycling, creating a smoother, less snappy shooting experience, particularly in over-gassed systems like carbine-length setups or when using suppressors. These upgrades can also improve reliability by reducing bolt bounce and managing excess gas pressure, but they come with trade-offs: too heavy a buffer or spring can cause short-stroking or feeding issues with weaker ammo, increase forward recoil, or stress components. The benefits depend on your specific setup (gas system, barrel length, ammo, and suppressor use), and pairing with an adjustable gas block can optimize performance. Testing incrementally is key to ensuring reliability.
If he has a 14.5" barrel with a mid length gas system with a port diameter of .076, odds are that it is properly gassed to run a standard spring with an H2 buffer or there about. You're telling him to blow the gas port out by 20 thou to accommodate an adjustable gas block that he likely doesn't need. If he gets rid of it and goes with a standard gas block, it will likely run right.
Is this is a gaming rifle that you are trying to tune to shoot softly or do you want reliability? You dont want to be running on the ragged edge of having too long of a closed bolt lock time. If you tune using the ejection pattern on a clean rifle, once you get to about 300 to 500 rounds, the rig is gonna start to choke unless you stop what you're doing and apply lube.
Buffer weight, not spring rate, controls closed bolt lock time. Yes, spring rate will slow the bolt velocity and you can tune your ejection pattern with spring rate, but doing that can leave you with an over gassed rig with a good ejection pattern. What heavier springs really help with is reliable feeding when the rifle gets dirty.
Assuming that your ejector and extractor are in good working order, tuning your rifle to eject at about 3:00 to 3:30 when its clean, while running an H or H2 buffer should net you a rig that will power through most adverse conditions.
PEOPLE!!!!!!! Stop with the AI stuff. It never gives the correct answer. It is just repeating everything people say. Kind of like how people just repeat what others say about everything. No one knows how to actually work on things or have the knowledge or problem solving instincts to solve anything.
OP, leave it the way you have it.
OP, leave it the way you have it.
Right on, thanks.
Yes. It’s a gamer rig 100%, however I need it to survive, say a high round count training day or multi day class without playing around with anything besides keeping it lubed.
No, haven’t had time. I plan to this weekend if at all possible, I’m curious as to whether it’s the bolt or carrier as well
OK, then this changes things. The addition of the low mass carrier is a much better idea than an under powered spring. That should allow you to run a standard weight buffer at around 3 oz.
When you changed the weight in that buffer, did you replace the tungsten weight with something else? Like a standard steel weight or one made of aluminum? I wouldn't run it with just two weights and too much extra space between weights. The spacers could orient themselves parallel to the body of the buffer and keep the weights from moving as they should. The weights reciprocating in the buffer is what stops bolt bounce.
If I recall, 18 clicks out on the adjustable gas block you're using is wide open. Less than 18 clicks puts the gas block in restrictive mode. More than 18 clicks puts it in bleed off mode. If you're running in restrictive mode, keep an eye on the adjustment screw and keep it lubed or put some carbon solvent on it. Those gas blocks carbon lock pretty quickly when used in restrictive mode.
I don't think I'd go lower than 3 oz. on the buffer weight. Less reciprocating mass can get you less felt recoil, but too little and you're gonna affect reliability.
Good deal. I put a wooden dowel the same length as in the h1 to take up the space of the weight I took out… I did all this hastily to just try to get the gun to lock back right… quickly.
Agreed on keeping the agb lubed. I had to put one on my suppresses 308 gun with the orange spring to keep it from being over gassed. I got to where I move the screws on them after every range session with a dab of lube.
Agreed on keeping the agb lubed. I had to put one on my suppresses 308 gun with the orange spring to keep it from being over gassed. I got to where I move the screws on them after every range session with a dab of lube.
Yeah, I wouldn't think that wooden dowel would last long, but good thinking in a pinch.
I just re-read this thread because I had some time to kill and it occurred to me that things could have gotten conflated and there could be some confusion.
If you're putting together a gaming gun that only needs to run a few hundred rounds between cleanings or, at least, some measure of maintenence, then you want something that shoots flat with the least amount of recoil.
The best way to do this is to use an aggressive muzzle brake and tune the rifle to run on as little reciprocating mass as possible. On a carbine buffer system, this usually means a system running a standard spring, with a standard 3 oz. buffer and some sort of reduced mass bolt carrier group.
This isn't hard to do, but there are always trade offs. Generally speaking, systems running little reciprocating mass are more sensitive to changes in gas volume and conditions, whether due to the rifle getting dirty, a change in the ammunition or even a 20 degree change in temperature. To put it simply, tuning for light reciprocating mass makes for a rig with a pretty narrow operational window.
Conversely, a rifle tuned to run with a full weight bolt carrier group, springco white hot spring and H2 or H3 buffer will be much less sensitive to environmental changes and will therefor, have a much wider operational window and will be more reliable.
I won't go so far as to say that having a gaming gun that will survive a 1500 round weekend shoot is impossible, but there are always trade-offs.
Many old schoolers are adverse to adjustable gas blocks and to a degree, I agree with them. An adjustable gas block is something that you don't go to, unless you know you need it or made accommodations for one in your assembly. They all leak. Some to a point where adding one to a properly gassed rifle will cause the rifle to malfunction.
If you're putting together a gaming gun that only needs to run a few hundred rounds between cleanings or, at least, some measure of maintenence, then you want something that shoots flat with the least amount of recoil.
The best way to do this is to use an aggressive muzzle brake and tune the rifle to run on as little reciprocating mass as possible. On a carbine buffer system, this usually means a system running a standard spring, with a standard 3 oz. buffer and some sort of reduced mass bolt carrier group.
This isn't hard to do, but there are always trade offs. Generally speaking, systems running little reciprocating mass are more sensitive to changes in gas volume and conditions, whether due to the rifle getting dirty, a change in the ammunition or even a 20 degree change in temperature. To put it simply, tuning for light reciprocating mass makes for a rig with a pretty narrow operational window.
Conversely, a rifle tuned to run with a full weight bolt carrier group, springco white hot spring and H2 or H3 buffer will be much less sensitive to environmental changes and will therefor, have a much wider operational window and will be more reliable.
I won't go so far as to say that having a gaming gun that will survive a 1500 round weekend shoot is impossible, but there are always trade-offs.
Many old schoolers are adverse to adjustable gas blocks and to a degree, I agree with them. An adjustable gas block is something that you don't go to, unless you know you need it or made accommodations for one in your assembly. They all leak. Some to a point where adding one to a properly gassed rifle will cause the rifle to malfunction.
Assuming no leaks in gas block/system, If you had to choose between using a low mass carrier or drilling out the gas port 2-3 thou which would you recommend (assuming both would be paired with standard spring & 3oz buffer)?
Im kinda at this cross roads now with one of my builds failing to feed/lock back with std spring/3oz weight. Im guessing low mass carrier bc its less involved and less likely to get messed up?
if your gun will not lock back on a standard buffer and spring you have a problem. I would never drill a port unless it it a last resort thing. There is also no need for a low mass bcg. You have things out of spec if it will not run with the standard stuff. The H,H1,H2 buffers are not really needed unless you are running suppressed. Same with the agb.
Buy quality parts and not off ebay or the gun shows. That crap is all china junk. Most barrels nowadays are way over gassed so no need to drill them out. If your brass is throwing from 3-5 oclock then you have a properly tuned system. The farther forward your brass is thrown the more out of tune the system is. You can use a heavier buffer to delay the bolt from unlocking to soon. But you can also go way too far and then you get what you were having with no lock back. With the lightweight parts you can go way too far also. Then you get brass throwing way forward and still can have no lock back as the bcg is cycling too fast for the bolt catch to catch the bolt to lock.
Buy quality parts and not off ebay or the gun shows. That crap is all china junk. Most barrels nowadays are way over gassed so no need to drill them out. If your brass is throwing from 3-5 oclock then you have a properly tuned system. The farther forward your brass is thrown the more out of tune the system is. You can use a heavier buffer to delay the bolt from unlocking to soon. But you can also go way too far and then you get what you were having with no lock back. With the lightweight parts you can go way too far also. Then you get brass throwing way forward and still can have no lock back as the bcg is cycling too fast for the bolt catch to catch the bolt to lock.
I don't know. In theory I agree with this. But I've spent the last decade assembling gaming rifles tuned to the max for the sole reason that people on the internet say they won't work.
In practice I can't prove any of the unreliability, finicky when dirty, temp sensitive etc. things that are always said about gamer guns.
I understand that the operational window of my primary match rifle with its 16" RLGS barrel, titanium carrier, low powered spring and .3oz delrin "buffer" and gas turned down to just lock back should be small. But well over 30k rounds in all temperatures, at ranges that are basically constant dust storms, with cleaning intervals well over 2k rounds shouldn't work great, but it does.
I'm sure the fact that I have two loads I shoot, a light 55gr load and a hot 69gr load (used to be a hot 77gr) the guns are tuned for that ammo and I never shoot anything else, must help.
But I've also loaned it out at matches and watched people throw all sorts of cheap ammo through it and it just keeps running.
Again, in theory I understand it is "less reliable" than anything closer to mil spec, but I can't seem to find out where that failure point exists.
I have even weirder configurations of rifles that also refuse to fail, but they don't have the round count on them for me to definitively say they are absolutely rock solid.
Ok, I want to preface my response first. I usually get stuff from vendors/manufacturers that have a good track record and I start out assuming that all is right, until I have a reason to think it isn't.
If I put a rig together and it's short stroking, I always go with what's simple first. Put a different bolt carrier group in it and see what happens. If it runs, then its something in the BCG.
If that doesn't do it, I'd pull the gas block and get a gauge on the gas port diameter. If you don't have pin gauges, get some drill bits in wire sizes from the hardware store. They're pretty cheap. For an 11.5" barrel, it should be about .070 and for a 14.5/16" something around .076.
Honestly, although I've seen it and I wouldn't call it unusual, having to drill out the gas port isn't the norm.
Still, in answer to your question, I'd drill the gas port. It will make for a more reliable setup. Just remember that you can always remove more material, but you can't put it back on.
If you truly have an under sized gas port, a lightweight carrier is just a band aid.
Oh, and make sure your bolt catch is working right. I once had a guy bring me his AR saying it was under gassed because it wouldn't lock back on an empty mag, although it would when cycling manually. Shooting the rifle made it clear that it was not under gassed. Upon inspection, it turned out that there was an incompatibility between the BAD lever he was running and curves on his billet receiver.
What I'm saying is to make sure it needs drilling before you drill it or you will need an adjustable gas block.
I don't agree with this. I don't of many, if any, ARs being issued with a 3 oz. Buffer. Not ones that run reliably in adverse conditions anyway. On the other hand, I can see gassing a rifle to run on a 3 oz buffer, just in case the end user decides to go suppressed so you have some tuning over head.
Thanks for the feedback Tony. This is my next step. I was using a mix and match bolt and carrier bc the barrel came with a headspaced bolt. The fit between the bolt and carrier was so tight that after shooting only 50 rounds when I went to take the bolt out of the carrier it was almost carbon locked. Pretty sure this may have been the root cause of the short stroking (bolt drag due to tolerance stacking or whatever you wanna call it).
My next move is to put the bolt into a matching carrier (I also put a JP enhanced one piece ring on the bolt to help reduce drag even further) then will test again for short stroking. If that still doesn’t work I will reach out to the manufacturer and see what they recommend for next steps/troubleshooting.
I've never met anyone that is. And I even live fairly close to JP, on the outskirts of JP fanboi land.
I tried one because every other JP part I've used is top tier. To this day it lives on my little shelf displaying all my mistakes, catastrophic failures and money wasted.
Thanks I will keep it on a short leash and have a complete bcg with std rings with me to swap in if Im still short stroking. Pretty sure I have narrowed down the issue to the mix and match bolt and carrier.
Haha I like the idea of a little mistake shelf for reminders of time/money wasted, great move!
I haven't followed this thread or your issue very closely, but seriously, seeing that one piece gas ring I know exactly what the very next diagnostic move would be if I were you.
I don't doubt this at all and it's a testament to what I've been saying for years. An AR doesn't need to be clean to run right. How often do you apply lube? Many configurations will continue to run if you keep the action wet.
I suppose the definition of "adverse conditions" can differ. My definition of adverse conditions go far beyond a range setting wherein the worst you have to deal with is dust in the air.
The goal of the way I put my ARs together is to allow the use of the rifle without the need for field maintenence and applying lube more because I should rather than needing to because the rifle stopped running. Dust is an adverse factor, what is worse is sand, which I encounter a good bit of. Worse than sand is rain and mud. I've had my action to a point where cycling the action was downright crunchy and peeling that first round off of a topped off metal mag required the use of the forward assist. Simply put, I want to be able to run my rig without having to worry about it.
I've tried going light mass, low gas, and it just doesn't work for me.
I agree with this. Those one piece rings don't work like they should. Just order a bunch of standard rings from a reputable vendor. Contrary to the rest of their menu, the maintenence items from Forward Controls Designs are very reasonable priced.
Dudes:
Thanks for all the input on this thread. Hope to get a good session in tomorrow and swap bcg parts to get a proper diagnosis on the non working bcg just to put closure to this thread.
TonytheTiger, enjoyed your post and lets me know there is hope in this gamer stuff lol.
Thanks for all the input on this thread. Hope to get a good session in tomorrow and swap bcg parts to get a proper diagnosis on the non working bcg just to put closure to this thread.
TonytheTiger, enjoyed your post and lets me know there is hope in this gamer stuff lol.
Yep this thread has some good discussion & info. Especially toward the end here, on the 1 piece gas ring from JP, who otherwise make awesome stuff.
Shot 300 rounds in pouring rain today. Gun ran flawless, I’m not tuning anything else on it unless something breaks. I will replace the wooden dowel in the buffer or switch to an h. I didn’t have time to mess with swapping bolts/bcg’s due to the rain. Will report back on it when I get the chance.
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