On one Cherry Picked load but if you read the test there was actually a pretty big jump in overall. Myself I would go with a mid-length 12.5 and there are a ton of good reasons for that. Does it make a difference to me what anyone else chooses. I still don't see why anyone would rather hve a 10 inch 223 over 300 Blackout in anywhere from 7 to 10 in.
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What is the difference between a 10.5 inch and 11.5 inch barrel AR-15 pistol in 5.56?
- Thread starter gunsnjeeps
- Start date
On one Cherry Picked load but if you read the test there was actually a pretty big jump in overall. Myself I would go with a mid-length 12.5 and there are a ton of good reasons for that. Does it make a difference to me what anyone else chooses. I still don't see why anyone would rather hve a 10 inch 223 over 300 Blackout in anywhere from 7 to 10 in.
What I said was 20-25fps/inch with just about every caliber in every rifle when the barrels are made by the same company with the same specs. I sell everything from 10.5-22" 5.56, 224 valkyrie, 6mmAR, Grendel, 6.8, 300, 30 Herrett, 270 MSR, 308, 243, 260, Creedmoor. You can't compare a 11.5" BCM and a 10.5 seekins and expect any kind of accurate results between only 2 barrels, even testing only 2 of the same brand. Shoot 10 -10.5s and 10 -11.5s both made by BCM and take the average over a large group of barrels. I've seen 100fps difference between cartridges out of the same box of factory ammo shot out of the same barrel.
I don't care what anyone else shoots either but to say a 10.5 recoils more or is less reliable because there is .000032 second less dwell time is crazy. Now if someone ports the barrel with a .010 larger port then yes it may feel different but that is because people port barrels different sizes. I port all of the 10.5" and 11.5" the same size because the calculated .001" difference does not make any difference in function. As for velocity most of the time 20-25fps, as the barrels get shorter that difference will increase especially where the bore pressure is much higher. At the muzzle of a 10.5 and 11.5 the pressure is 16-17000, on a 20" it is apx 12000. Drop to a 7" and the pressure at the muzzle is apx 27000, that is where you would lose a ton of velocity.
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maybe a 12 gauge ar pistol you can shoot a 12 gage from a sawed off why not a short barreled ar pistol .12 rounds semi auto version of devastation close up .
- Nov 3, 2010
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Adjustable gas blocks are not reliable enough for any duty/HD gun.
Dwell is still an issue, and when you start messing with gas ports you can create some other issues.
12.5 is perfect, 11.5 is as short as you want to go for 5.56.
Colt, BCM and KAC use 11.5" for a reason. Its a much better option, even with advances in gas port sizing.
And then when you throw a can on it, its just that much more overgased and you are dealing with other issues.
Gas Port is a variable. You want to run the smallest gas port you can get away with, as long as it runs your ammo type with a margin for dirty/environments. It will prolong small parts ware and result in a much smoother shooting gun.
Just changing the gas port does not fix everything. It fixes ONE issue.
Okay so what size would you port a 10.5" and what size would you port a 11.5" barrel? Lets say you are making a barrels to sell and you have 100 on the shelf what size do you port the barrels?
What size if they are running wolf instead of M193/855?
What size if they are running m193 with a Dakota Varminter can, What size with a Surefire can?
What size if they were running a 30 cal can?
Would the ports be the same size if using wolf with the same 2(Dakota /Surefire) cans?
So how many people buy a barrel off the shelf set up to run M193 with a surefire can and try to shoot Wolf that produces 8000 less PSI and instantly think the barrel is a POS and blame it on the manufacturer instead of the person feeding it cheap ass ammo?
ETA- I wish it were a perfect world I really do. In a perfect world the manufacturer would port barrels to the minimum. In a perfect world every person building ARs would understand how they work and how to port a barrel to work with their own setup taking into consideration the pressure ammo creates, back pressure created by cans, buffer spring rate and buffer weight. That would make my job a lot easier.
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Perhaps you missed the other post discussing the other variables that have to change. Also, I completely disagree with your sentiment about adjustable gas blocks being unreliable. Why on earth do you think that's true? There are tons of rifles with adjustable gas running in terrible conditions without issue. Just because there's some garbage examples with a set screw in the gas path, with "out" being the direction pressure escapes, held in by loctite doesn't meant all AGBs are designed to fail.
I'd make a strong argument that running a gun with with a fixed port size and non-adjustable gas block with different ammunition is far more detrimental to reliability than a well designed AGB. And running fixed maximum port size to account for the worst of the worst ammunition is absolutely detrimental to the long-term reliability of a rifle, not to mention shootability.
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This is exactly why you want an adjustable gas block! Unless you only run one type of ammunition with one loading with one pressure curve and size the gas port perfectly for it, in the worst conditions you'll shoot the rifle, you're always going to have to run overgassed. Either that, or you're taking a gamble on function depending on ammunition and condition. Add a suppressor into the mix, and you need to be able to adjust gas down unless you will ONLY run suppressed, in which case your gas port will be severely undersized when you take the suppressor off.
^^^ ya this
Where are you getting this from? Examples?
A duty gun and HD are very different also... I don't require the same the gun I used in AFG in my house lol...
There has yet to be an AGB made that is reliable for a DI AR. They all eventually lock up/fail under use. Its too close to the port where the pressure is higher and the heat is magnitudes greater than back at the bolt carrier.
They are toys, for toy guns.
If you absolutely have to have adjustable gas, you do it at the carrier with something like Bootleg or Gemtech carrier.
No one serious uses them on duty guns. Even elements who run suppressed/unsuppressed who would gain the most benefit, run fixed gas blocks which are usually pinned by the way.
Decades and billions of rounds through this platform over the years tell us what works and what doesn't.
Everywhere. They are not reliable/durable enough to stand up to use and are a weak link in many guns.
They are toys.
If you want to bet your life or your families on a known failure point of a safety system, go ahead.
Duty guns and hard use guns usually run one load. Anyone with two brain cells to rub together is going to test their duty load and stick to that. Goes for mags as well.
Some elements runs almost exlcusivley suppressed, where it makes sense to go with a smaller port to reduce blowback. Some went to the 416 to mitigate that issue, but its presented a bunch of other issues.
There are certain gas systems tuned to run reliability, under harsh conditions, dirty with underpowered to full powder loads. You can even get this gas system when you buy a SR15.
I don't drill my barrels. I buy them from a known source and check with pin gauges before the block goes on to prevent issues down the road. BCM/Colt Barrels almost exclusively. DD if either are hard to find. Don't build anything under 11.5" in 5.56. Been there, done that, paid the price, have the tshirt.
KAC has the secret sauce with their gas system. If you want to have your cake and eat it too, just buy a SR15.
Otherwise your choices are more limited and you will have to make sacrifices. You need to decide what you plan to shoot and if its going to be primary suppressed/naked if you want to find the sweet spot of soft shooting/reliable.
I am asking YOU what you would do...nothing except flap your gums about things you know little about.
My days are spent installing barrel extensions, checking headspace, drilling gas ports and filling orders.
I buy factory colt/BCM/KAC for hard use and reccomend the same to people and orgs I build for. I can't build them that good for that cheap. But people want what people want.
My friends and customers won't be on this site asking how to get their gun to run or why their agb locked up.
Too many junk companies out there full of people throwing parts together by incompetent monkeys who think becuase they can push a button on a Hass and use a torque wrench, they are on the same level as the big boys. Big boys who spend more money in ammo a year doing testing than these fly by nights gross in a year.
My friends and customers won't be on this site asking how to get their gun to run or why their agb locked up.
Too many junk companies out there full of people throwing parts together by incompetent monkeys who think becuase they can push a button on a Hass and use a torque wrench, they are on the same level as the big boys. Big boys who spend more money in ammo a year doing testing than these fly by nights gross in a year.
I feel like you are not reading what is written. Sure, a "duty" rifle, and by that I assume you mean military/police/contractor issued rifle, will be shot with whatever ammunition is currently contracted. Do you think the gas port was drilled specifically for that cartridge/loading? Do you think the loads do not change as contracts are updated/renegotiated/etc? Do you think all barrels are pulled when this happens and new barrels are issued with ports drilled to different sizes? No, that's not how this works. The barrels are ported to run the worst ammunition likely to be encountered in poor operating conditions, and just run overgassed the rest of the time. You slap H2, H3, etc buffers in them and they run and run and run. There's nothing wrong with that; "duty" rifles are generally running on a very strict schedule and service interval with scheduled part replacements. They have to always run, regardless of condition, location, ammunition, and parts are replaced before they fail (most of the time...). Great.
I don't even know what you're referring to with magazines or how this related to this discussion, at all.
Running suppressed and reducing port sizing isn't about reducing blowback, that's a side effect of the primary goal, which is ensuring the BCG and bolt are moving/unlocking at the appropriate time in the firing cycle, then crossing the magazine and giving enough time for the next round based on spring pressure to move into position before moving forward and stripping the round from the magazine into the chamber while locking up again. This timing is VERY important. When you suppress without an adjustable gas block, with a gas port drilled large to run in adverse conditions with poor ammunition, then fire full power ammunition with the suppressor attached, the severe excess gas can cause malfunctions, in addition to beating up the rifle and shooter. Many will slap in heavier buffers to offset this, but you'll feel this as a shooter, and the bolt will definitely be exposed to significantly more forces and wear.
I've never heard of "elements" running barrels with smaller port sizes for suppressed-only usage. What's your source on this? I find it hard to believe anyone is running rifles ported to only run suppressed in any "duty" capacity.
KAC has some good stuff, but seriously, lay off the koolaid. There are a lot of different platforms, AR15 and otherwise, that have adjustable gas systems. To claim an adjustable gas block is a reliability issue is insane. Go look up Ol' Dirty from FAL Files sometime. I've got a SCAR17 on a second barrel already without a single issue. Go look at all the military issued piston firearms which are almost all adjustable gas systems, and tell us how unreliable they all are. Just install an AGB, and stop worrying about all of these issues with "dwell time" and just focus on your needed velocity with your bullet of choice and the barrel length necessary to get there. That's all that matters - the rest can be tuned to work. If 10.5" doesn't cut it for whatever needs you have, do what you need to - but don't be hung up on 11.5" as the cutoff for a functional firearm; that is patently false.
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Yet you say you check every port with a pin gauge, why? I mean you buy from those guys that do all of that testing what are you worried about? If you check every port of every barrel you use you should know every port size of every length barrel without looking at a list and should have been able to answer the questions I asked in a minute.
You just said you use stock barrels from those guys with whatever port they put in them. You mean you don't change them if someone wants to use Wolf ammo or if someone is running a Dakota 22 cal varminter or YHM can? I mean if the barrels are ported where they work with Wolf they will be over-gassed if using M855, way way over-gassed if 855 and a can like that. What do you tell your customers when they ask you questions like that?
Pretty easy to make a rifle run perfectly when they are all built the same and use the same ammo producing the same pressure. My Surefire cans don't cause much backpressure so the ports don't need to be changed most of the time.
It's no surprise you can't beat mass manufactures on cost. If you can't beat them in performance, you're doing it wrong.
I would hope your friends and customers aren't here asking for assistance with "locked up" AGBs. I wouldn't suggest people purchase AGBs that lock up. I'd also like to remind you than a locked up AGB is just a gas port that is no longer adjustable.
I completely agree on companies in the game that don't know what they are doing. Some of the product I've seen is absolutely shameful.
I do want to point out something, however - many of the beloved brands are using HAAS machinery. This is an entirely different discussion, but if you go talk to serious CNC machine shops like those in aerospace, they won't even touch HAAS machines. It's not because they're bad, just not suited for the task. You want to talk about "big boys"? Firearms manufacturers are small potatoes when it comes to tolerances of aerospace and beyond. KAC uses Mazak last I checked which is actually quite impressive, but again - the design tolerances are entirely different. You can set up some of the larger HAAS machines and hold the tolerances KAC is at the rate they produce. I suspect KAC is saving a boatload of money in repairs, though. Those Mazak machines are hard to beat except in up-front cost - but that's a nonissue for KAC.
Pressing a button on a HAAS shouldn't be seen as a bad thing - I think many underestimate just how much work goes into CAD/CAM to even get to the 'button pressing' stage. It's a hell of a lot harder to run a CNC at any reasonable rate than a manual mill, and your setup, fixturing, and cut planning mean a lot more. A table crash is VERY expensive.
Pushing a button on a HAAS is likely all most of the manufacturers are doing nowadays based on FEA run in simulations on a PC. Live fire is just a formality, and the more years that pass, the more true that becomes. When you can run 100,000 stress cycles on a part in a few minutes, it's hard to beat. The firearms industry probably isn't there yet - but it's coming. Don't count out the new guys.
Apologies on derail. AGBs aren't reliability issues, try some that don't suck sometime - your customers will be a lot happier.
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If its a bare barrel I will check because its easy, quick and I have the tools. Have only had one port that was undersized and it was easy to ream out. If its a complete upper from the factory, I don't bother. Not worth driving pins when there is a 99.99% chance it is good to go.
No one ever said they plan to shoot wolf exclusively, and there are not my clientele. I tell people strait. If they can buy something better/cheaper elsewhere, I will recommend that. A properly built barrel will run on wolf to full power 5.56. The issues are when its dirty, or cold or running on the ragged edge. IMO .073-076 is the sweet spot for running reliably will full power loads. Some manufactures will run .08+ to ensure a wide range of ammo will run, usually to make up for other issues with their builds. They will also have a harsher recoil impulse and you may have issues if you throw a can on it. .072 is a good estimate for a suppressed only gun, but will be ammo dependent. You can go smaller, but I don't feel comfortable with duty guns. Rather have to deal with a little more gas and recoil than have it choke under adverse conditions, especially the way many of these guns get abused and treated.
Rule of thumb is the shittier the product, the bigger the GP they will use. Covers up alot of other issues.
I will never put an AGB on a gun destined for duty, until someone can create one that is reliable/durable enough to ensure function across the spectrum. To each their own.
Another good point - many military contracts are for poorly performing (relative) suppressors. There's an excellent reason - they are low back-pressure designs. Function first, then port volume/at-ear for shooter is the primary concern. They are poorly performing in traditional at the muzzle tests, but at the gas ports in an ar15, they tend to be fine. With supersonic ammunition, muzzle amplitude isn't a huge deal. Why run a high backpressure design with good at the muzzle numbers, but worse at-ear numbers for the shooter? Surefire has the contracts locked down, but the low backpressure suppressors are really the way to go on the AR platform. Surefire figured this out years ago which is why they are in rotation. The gas port is right by your ear!
Feel free to name ones that will not lock up or fail. So far we have numerous issues and complete failures with Superlative , SLR, JP, Seekins, Odin and a few others i forget. They will all lock up or have a small parts failure under hard use. You can mitigate this by tearing down the unit and doing PM at regular intervals (1000rnds or less) but fuck that noise and it still won't solve the issues of set screws, plugs or detents failing.It's no surprise you can't beat mass manufactures on cost. If you can't beat them in performance, you're doing it wrong.
I would hope your friends and customers aren't here asking for assistance with "locked up" AGBs. I wouldn't suggest people purchase AGBs that lock up. I'd also like to remind you than a locked up AGB is just a gas port that is no longer adjustable.
I completely agree on companies in the game that don't know what they are doing. Some of the product I've seen is absolutely shameful.
I do want to point out something, however - many of the beloved brands are using HAAS machinery. This is an entirely different discussion, but if you go talk to serious CNC machine shops like those in aerospace, they won't even touch HAAS machines. You want to talk about "big boys"? Firearms manufacturers are small potatoes when it comes to tolerances of aerospace and beyond. KAC uses Mazak last I checked which is actually quite impressive, but again - the design tolerances are entirely different. You can probably set up some of the larger HAAS machines and hold the tolerances KAC is at the rate they produce. I suspect KAC is saving a boatload of money in repairs, though. Those Mazak machines are hard to beat except in up-front cost - but that's a nonissue for KAC.
Pushing a button on a HAAS is likely all most of the manufacturers are doing nowadays based on FEA run in simulations on a PC. Live fire is just a formality, and the more years that pass, the more true that becomes. When you can run 100,000 stress cycles on a part in a few minutes, it's hard to beat. The firearms industry probably isn't there yet - but it's coming. Don't count out the new guys.
Apologies on derail. AGBs aren't reliability issues, try some that don't suck sometime - your customers will be a lot happier.
If you can find someone who makes as consistant and proven CL barrels as Colt or BCM for a similar price, let me know. DD makes good barrels but are overgased. LMT barrels can be a real bitch to source depending on time of the year and what .mil contracts they are fulfilling.
Colt will not use AGB. BCM will not use them on their factory guns/uppers. KAC will not use them. LMT does not use them on their DI guns.....starting to get the hint?
IN a perfect world where they could be made to work reliably, it would be a fantastic thing. I will agree the benefits are huge being able to tune loads In the real world, they are for toy guns.
At the moment I would rather someone run a Bootleg or Gemtech carrier with a quality bolt than an AGB. I am still getting used to the idea and have reservations, but indications are looking good with no failure yet. Maintenance is also much easier with them.
AND FYI, big HAAS fan here. Just making a point.
Funny thing about those Haas machines, they have to be programmed after the parts are engineered/drawn. The sequence and ops have to be determined also. The person programming the machine has to know every dimension, how each metal cuts with what insert, chip breaker and coating, the speed and feed rate to get a good surface without burning the insert. More than likely when it's a small company the same guy designing the parts is the same one programming the CNC and setting it up. Then the button pushers take over, stick a part in clamp it down and hit the little green button.
Bash those Haas all you want, each one will still make $4 a minute, 3 machines make about $720 an hour. None of that or anything in the last 10 posts changes the fact that a 10.5" barrel will run just as good as an 11.5 when both barrels are ported correctly. A good smith/builder knows what he needs to do to get a rifle to run even if it starts out over or under-gassed.
Bash those Haas all you want, each one will still make $4 a minute, 3 machines make about $720 an hour. None of that or anything in the last 10 posts changes the fact that a 10.5" barrel will run just as good as an 11.5 when both barrels are ported correctly. A good smith/builder knows what he needs to do to get a rifle to run even if it starts out over or under-gassed.
Let's start with this one, merely because it was the first you listed, so I assume it was the example you had the most knowledge of. I've seen (one in person, one online) two failures with these, both related to someone managing to back out the set screw completely, beyond the threading available. arfcom has a 'famous' thread with this. Both were a massive misunderstanding of instruction, 20 clicks vs. 20 revolutions. I am asking honestly, can you show me the 'numerous' issues and complete failures with a Superlative arms AGB aside from that mentioned? Again - and while I've not seen this - I'll remind you that a 'stuck' AGB is just a fixed gas port.
Right on. They make good stuff for the price point.
Back in the 80s before there were screw adjustable gas blocks we use to drill and tap the gas blocks then screw a set screw between the barrel and gas tube then drill the new correct size port through the set screw to fix over-gassed barrels. Now it's much easier to just make gas blocks and sleeves or gas blocks with a smaller port.
The OP has his barrel, if he has problems they are fixable whatever they are.
The OP has his barrel, if he has problems they are fixable whatever they are.
People discount the effort that goes into CAM. I spend a lot more time designing good toolpaths/picking tools and layout strategies for material than I do designing the initial parts. You're exactly correct, if you can machine a part with the tolerances you need in the time defined, you're making money. It's all a balancing act. Port sizing is a tiny little problem, and good smiths will determine the needs of the client, and if they are single-purpose a single port size may be selected. Same for servicing a huge contract. At the end of the day, if a port is oversized, you can run heavier buffers/sliding weight buffers/adjustable BCGs, etc. If it's undersized - there's not much you can do; add a high back-pressure suppressor?
Drill out the port. I would rather start out undersized/under-gassed and open the port to match the setup than use an adjustable gas block if those are my only 2 options.People discount the effort that goes into CAM. I spend a lot more time designing good toolpaths/picking tools and layout strategies for material than I do designing the initial parts. You're exactly correct, if you can machine a part with the tolerances you need in the time defined, you're making money. It's all a balancing act. Port sizing is a tiny little problem, and good smiths will determine the needs of the client, and if they are single-purpose a single port size may be selected. Same for servicing a huge contract. At the end of the day, if a port is oversized, you can run heavier buffers/sliding weight buffers/adjustable BCGs, etc. If it's undersized - there's not much you can do; add a high back-pressure suppressor?
Right, any gas operated auto loader. HK91s and 93s don't seem to be effected much but even after changing out the rollers to slow the carrier speed the recoil is so violent anyway I couldn't tell.
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