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How do you make an AR shoot steel case ammo?







JTW_Jr

WheelGunner
#21
Don’t know, they do. Can’t recall dad ever having any issues with any of his many ARs either. Cheapest ammo available...and lots of it,
 

MET45

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#23
You could build with a piston kit like Superlative Arms. The adjustable gas block can be tuned to whatever load you are using, and they shoot cleaner. You could tune your guns to cycle with Tula, and anything else should be gtg.
 

MET45

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#26
Downside to using a piston system?
I have a piston pistol and a rifle. Been happy with both. It’s pretty much personal preference. piston is more initial cost to build, but advantage is stays cleaner, can reduce recoil and blast/blowback since excess gas is vented out.
 

MET45

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#29
Downside to using a piston system?
I have a piston pistol and a rifle. Been happy with both. It’s pretty much personal preference. piston is more initial cost to build, but advantage is stays cleaner, can reduce recoil and blast/blowback since excess gas is vented out.
 

Janizary

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#30
I build a ton of uppers (I have a problem, okay, lets move on) and usually keep a few boxes of Tula on-hand for (adverse) testing purposes. I'll often use it when setting up an upper with an adjustable gas block, testing what my LRBHO is for hotter XM193, lower pressure PMC bronze 223, even lower pressure Armscor 223, and then Tula, which usually has the lowest velocity and poor chamber seal.

PMC Bronze usually requires 1 more click open than hot XM193, Armscor +1 more click (about half the time), and Tula 1-2+ more clicks open to properly cycle and have reliable LRBHO. That is running off common BA Modern Series barrels, and often won't cycle at all on BA premium series and Hanson series barrels (those two have much smaller gas ports). (Reference block: SLR Sentry Series)
 
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wandoo

New member
#35
Use a carbine gas system.

In general, carbine gas systems have higher pressure gas from a closer gas port. This increases the bolt thrust during extraction which helps with reliability. Higher bolt thrust will, however, cause more wear on the bolt lugs. This is also the reason many people recommend a mid length gas system for bolt lug longevity and a smoother recoil impulse. The increased thrust also imparts more energy to your bolt carrier group which increases recoil slightly during the firing cycle as the buffer hits the back of the tube.

Barrels on the cheaper end tend to have slightly oversized gas ports that also help with reliability. My guess would be that companies selling cheap barrels don't want to hear back about extraction failures. You can also modify your own gas port but it's tricky. Hundredths of an inch make a big difference. Also, barrel surface treatment/plating may be compromised.

You can also play around with buffer weights. A lighter buffer for low powered ammo and a standard or heavier weight to compensate for an over gassed system is easy to swap out.

I wouldn't obsess about the durability and recoil aspects, though. The M4 platform has been proven to be extremely durable. Just get a quality bolt and learn proper shooting positions.
 
#36
I build a ton of uppers (I have a problem, okay, lets move on) and usually keep a few boxes of Tula on-hand for (adverse) testing purposes. I'll often use it when setting up an upper with an adjustable gas block, testing what my LRBHO is for hotter XM193, lower pressure PMC bronze 223, even lower pressure Armscor 223, and then Tula, which usually has the lowest velocity and poor chamber seal.

PMC Bronze usually requires 1 more click open than hot XM193, Armscor +1 more click (about half the time), and Tula 1-2+ more clicks open to properly cycle and have reliable LRBHO. That is running off common BA Modern Series barrels, and often won't cycle at all on BA premium series and Hanson series barrels (those two have much smaller gas ports). (Reference block: SLR Sentry Series)
tell me more.
 

Janizary

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#37
(first, sorry for the small book, below)

Henry, the MAC video that vegasdom linked has good info in it on general steel-cased facts and findings.

First, I am by no means an expert. I just have a thing for assembling my own stuff, tinkering, and a bit of light machining. :)

As others here have already stated, gas port sizes will (and should) vary, depending on the length of the barrel, and the length of the gas system (pistol, carbine, mid, intermediate, rifle, etc.). They will also vary from OE to OE. As already stated, some OEs are a bit more 'generous' with their gas port sizes while some barrel makers have gas ports that are just able to cycle the action by skin of their teeth with quality ammo (BA Hanson profile is pretty close to this).

As I shoot mostly suppressed, I am a bit OCD about gas and reliable cycling in my AR-pattern builds for both suppressed, unsuppressed, with good target/match ammo, and cheap range day ammo (like PMC bronze, Armscor, etc.). For me that starts with a good barrel with a proper gas port size for the application, and perfect (see, OCD) gas block alignment.

It is relatively easy to eyeball gas block fitment and get a AR running. That said, I've found after doing way too many builds (my own, family, friends, friends of friends, random guy that drops parts off at my doorstep...heh) with a stupidly-mixed bag of parts (see "bag of parts dropped off at doorstep" with note "Russ, please make something with this" :) ), that all gas journals, barrel shoulders, and gas blocks are not made with the same measurement specifications in mind. Some blocks you can just line up, jam up to the shoulder, and its good-to-go (mostly), some gas block makers account for the thickness of the hand-guard retainer, thus, jamming that block back against the shoulder will get you a poorly-gassed rifle (or worse, almost no gas) as it will be aligned too far 'back', relative to the gas port. Some gas block makers will give you a spacing spec (Adams Arms, for instance), but most you just have to figure it out.

Since I'm building on my own time, I can take the time to measure all my distances (calipers/micrometer). With an adjustable block like the SLR Sentry, I know I need to be a bit forward to get a perfect alignment. Incidentally, the SLR adjustable blocks have a smaller intake 'hole' than a normal gas block. Found that out the hard way once on a shorty 7.62x39 build where the barrel's gas port was bigger than the intake hole on the block, and the upper would not cycle due to under gassing. Even perfectly aligned it would not cycle. Needed more gas. Pulled the block off, and could tell by eyeballing that the hole was far smaller than the hole on a 'normal' gas block (Spikes, Aero on hand at the time to compare to). Cycled fine with a normal gas block, but so overgassed running a can that the carrier now outran the magazine lift (which is a whole other story and how to mitigate).

Once I know my measurements, I can quickly see if anything looks odd (do it enough and it jumps out pretty quickly). Then make some pencil marks for the alignment points (front-to-rear, a couple of index marks for side-to-side alignment, etc.) and mount the block. As you can see, I put way more work into this than is specifically needed, but when I pull a block I can see the gas port is perfectly aligned in the center of the carbon ring that is formed where the gas block intake hole sits. Too much? Maybe, but I don't have gas issues due to alignment, ever :) (And having to 'fix' a handful of other people's home builds...and a factory build or two, where malfunctions can be traced to poor gas block alignment/indexing, it sinks in pretty quickly, heh)

I also look at the alignment of the gas tube as it sits inside of the upper receiver. Is the gas tube biased to one side or the other? (Generally it is a tiny bit). That said, if it is biased substantially, your gas block could be out of side-to-side alignment, or, in in a few rare cases that I've run into the gas port is not aligned perfectly with the barrel extension (which throws everything off). Its fun to explain that one to the OE, argue about it, send measurements, then have them finally cough up to it once it is in their hands. Anyway, with enough bias you'll find increased resistance between the carrier key and the gas tube. You can feel a smooth, aligned engagement, vs the initial 'click' and resistance you'll feel with a biased tube. Again, a small amount of bias (thousandths) is normal due to the vagaries of the receiver to barrel extension fitment, barrel extension to barrel fitment, gas port alignment to extension, etc.), however, generally if it is visibly biased it can be traced to poor side-to-side (rotational) alignment of the gas block.

Another thing to consider is the chamber. Barrels makers that ream 'match' chambers (or close to match chambers) may also give you issues with steel-cased ammo. It will generally chamber and fire, but may be likely to 'stick' in the chamber due to the tighter tolerances of the match chamber. Faxon's early 308 barrels had very tight match chambers, and a few that I assembled with would not extract (brass) 7.62x51 surplus/M80 ball, often tearing off a chunk of the case rim when the bolt cycled leaving the round jammed in the chamber. Faxon eventually put a memo out about it so many folks were running in to that issue. I never ran any steel Wolf 308 in those, however, anecdotal forum reports (from other sites) showed a number of folks that were having definite extraction issues with that as well.

Generally, with good components that are known or tested to work well with your other component selection (including a good, quality BCG), well-spec'd gas port size for barrel length, gas length and caliber, good gas block alignment, and proper lubrication, I do not run into gas issues. Only when I get the 'grab bag' of parts dropped off by a friend, run in to something that is out of spec/defective, or get a barrel with a purposefully-small gas port, do I generally run in to gas issues with 'underpowered' ammo. I've built a lot of shorties and (excluding the caveats, above) have no issues cycling Tula in my adverse test cycle when I first take them to the range to test for proper cycling and LRBHO. (Exception: Adams Arms piston kits are the only ones that I've ever had on-and-off issues possibly cycling Tula at full gas. Call it 50/50 in the 8 or so I've assembled. They like a bit more 'oomph'.)

Again, I am sure others have their own experience, and caveats, and have good advice that they can also share. It is a great group here for helping others through their build issues and recommendations.

Please excuse my wordiness.
 
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VGM837

Future Gun Toting Grandpa
#38
I have an AR pistol in 7.62x39 I run mostly Tula in. After swapping out the firing pin and one quick to break extractor. It runs great with no light strikes.
 

Kinoons

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#40
Sam and joe beat me to it - if you want to run steel and be dead nuts reliable without fiddling with it, get an AK.