functioning of 30 cal. AR's

[RU shooter]

I have always wanted a 30 cal AR, and have been looking at the 7.62x40 since its slower 1:12 twist would seem to be better for me with cast bullets at usable speeds,never really wanted to stay subsonic so never really warmed up to the whisper or blackout ctg. Question now is with the standard port size these barrels have I believe .090? Does anyone see any issues getting proper functioning with say a 150-160 gr cast bullet at 17-18K fps. with a standard setup like full length gas system or would I need to go to a mid length /carbine gas system or bigger port /adj block ect. ??? Just not sure how much gas it takes to make a black gun run properly, I assume using fast rifle powders would be the best route?

Thanks,Tim

[madsenshooter]

I can't completely answer your question. I have an AR in 6x45. I have a standard size gas port and a rifle length tube. The rifle will not quite function with a max charge of 4198 under a 55gr jacketed bullet. Even going from .223 to .243 bore, there's a 16% increase in the volume of the bore to the gas port, so there is also a reduction in pressure at the port. Going up to 30 cal, I'd go with a carbine length system that's adjustable, and I think I'd prefer a piston set up. Guys with more experience with them will chime in, but I think if I were going to 30cal, I'd also opt for more case capacity than the .223, just in case I needed it. When you get to the amount of powder needed to get a 30 cal bullet going the speed you want, you're going to be up there in the pressure department with the 223 case, but it will be quick pressure that will leave you lacking at the the gas port. Get with 82nd Airborne, he's had some hands on experience.

[dk17hmr]

I shoot alot of 200gr Cast in my 300 whisper with H110 at about 1400fps

[HARRYMPOPE]

I have been playing with a 308 Russian "Saiga"(ugly AK thing) with a 21" barrel in 308(1-12" twist) this last month.I know the gas systems are not the same but i have two loads that are working well.The first is 29-31g of IMR 3031 and 155-180g bullets and 30g of IMR 4895 both with CCI 200 primers.The 3031 load chronograph between 1850 and 1975.I haven't chronographed the 4895 load yet but it appears to cycle and eject the same and have the same point of impact as the 3031 load.Functioning is not perfect with the lighter 3031 load(a stovepipe about every 40-50 rounds but it groups a bit better than 31g) but with the 31g and the 4895 load has shot 250 so far without a hitch.Accuracy seems pretty good for an AK with a crappy trigger and dark 6X Russian scope.I use the RCBS 180sp and NEI #72 both sized .311 of range scrap water quenched to 20-24 BHN.Groups run best @ 1" at 100 yards(5 shots) to 2-1/2"Occasionally at 200 yard i can shoot under 3" but 3"-4" is closer to average.

No fillers used over powder by the way.Oh yea,i haven't cleaned the rifle for the last 400 rounds and all seems well.

Here are groups from today and were a bit better than average(7/8" to 1-9/16" @ 100 and 3-1/4" @ 200).Right side are at 200 yards and left side @ 100.Both with 30g of 4895.I l also gave a close up of two of the small groups on the target i feel are lucky but i will take them!

I imagine an AR in 308 would be a very nice 30 cal.cast gun and use common easy to scrounge brass.

HMP

[Diegokid]

Not a good idea to shoot lead in a gas gun like an AR type. The lube and other debris will stop up the tube. I haven't shot AR types with cast but have known others that have. They ALL reccommend gas piston types like the M1A, 30 carbine FN-FAL ect.

[redneckdan]

I had a 16" 300 whisper for a while with a carbine gas port position. This is my advice. Get the gas port drilled at .125" and use an adjustable gas tube to get the desired function of the action. Go with a tube over a gas block because it is easier to clean any leading out of the mechanism. Take a 10-32 tap and grind it off so that full diameter threads go all the way to the end. This will scrap the gunk out of the screw adjuster threads.

http://www.midwayusa.com/viewproduct/?productnumber=396319



Contrary to what numb nuts in the product reviews said, you don't need to remove the front sight to install it. Pull the roll pin and slide the tube all the way into the upper receiver, then slowly and gently pull it out while applying just enough side pressure to work it around the front sight. You can kink the tube doing this but you have to apply a lot more pressure then is required to work it around the sight.


There is no problem with gas building up in the gas tube. Any leading will build up in places where the gas velocity pressure drops and stagnates, ie the crevices in the adjustable gas tube, the expansion chamber on the bolt carrier. Both of these places are easily cleaned. You may notice heavier fouling due to the bullet lube but this cleans up easily with pretty much every solvent I have ever tried. Gas pistons systems get gas build up when the piston reaches the end of the cycle and pressure drops, the leading settles in the cylinder and gets scraped up and deposited on the piston face when the rifle returns to battery.

[Johnch]

http://www.midwayusa.com/viewproduct/?productnumber=396319






Thanks
I was just starting to research a ajustable gas port for the AR
So I could turn it off , like I do with the FAL

John

[Larry Gibson]

Not a good idea to shoot lead in a gas gun like an AR type. The lube and other debris will stop up the tube. I haven't shot AR types with cast but have known others that have. They ALL reccommend gas piston types like the M1A, 30 carbine FN-FAL ect.

Myth

Many of have shot thousands of cast bullets through ARs without any problems of the gas tube "stopping up" from the lube and debri. Consider if there is enough psi to function the action there is more than enough to keep the gas tube blown free of lube and debri. Also, many of us have shot thousands upon thousands of .22LR through ARs with subcal devices such as the m261 I have. The gas tube doesn't get clogged. Many bajillion .22LRs were fired through M16A1s for many years by the military with the M261 device. The TM states to fire 1 or 2 M193 cartridges through the rifle to clear any debri still in the tube. At the SF Armory I worked in we had 2 dedicated M16A1s for use with the M261 devices shooting .22LR on the indoor range. I traked one of them for 10,000 rounds of issue Winchester .22LR without cleaning the gas tube. I then took it to R12 at Fort Lewis and fired 9 shots of M193 to confirm the zero and then ran 40 hits for 40 shots on pop up targets to 300 meters without a single malfunction.

Shooting cast bullets in the AR will clog up the gas tube is nice in theory but a myth in reality.

To answer the OP's question; I would go with the standard length gas port and look at the adjustable gas tube that Brownell's sells. That should be a very decent cast bullet AR with cas bullets in the 1800 - 2200 fps range depending on weight of the cast bullet.

Larry Gibson

[rays308]

My ARs are 308 but, I run Lee C309-160-Rs through them daily. My first one is a 20in bought in 1999. has had countless thousands of 160gr cast boolits through it.
Actually its not the fast powders that work the best for me. Its the medium to slow like 4895, 4064, Varget, 335, 4350 and 4831. They have higher pressure at the gas port than fast powders.

The leading of the gas port has a little truth to it. Heres how to do it.
Take a heavy for cailber boolit. 180 to 200gr in a 308
Size it too small. Right at bore size or smaller. Gas check optional at this point though mine were wearing them.
load it to maximum jacketed velocity.
Rapid fire 20rnds as fast as you can.

I can almost garantee you leading on your spent cartridge heads, bolt assembly and in your gas tube. It may take a couple hundred rounds to clog it though. I didn't go that far. I sought the help of an experienced cast shooter. God love him, he still laughs about it and won't let me forget it when he thinks I need some humble pie.


Instead of doin that, come here and ask questions like you did and you will already be smarter than most(me included).

[JeffinNZ]

Rays308 is on the money. I had a SKS I used to run reduced loads in. 180gr Jword. It would cycle brilliantly over 23gr W748 for 1600fps. Faster powder would not cycle. It's a factor of generating a pressure curve in the cyclic range that extends far enough down the barrel to or beyond the gas port.

[scb]

I just got a 7.62x40 barrel and set of dies from Wilson. Using what I would consider max loads (primers flattened right out to the edge of the primer pocket) of H110 I could not get it to function. The gas port was .096" dia. measured with pin gages. I had set it up with an Adams Arms piston system which works great on my 5.56. When it didn't work I changed it over to a direct impingement system. It still wouldn't work - short cycled. I opened up the gas port to .104" and it works about 95% of the time (w/di). I'm going to open it up some more and see if the reliability improves.

[Larry Gibson]

Sheesh....Rays, I guess that's what those of us get for doin' it right - no clogged gas port or such and nothin' but good shooting with cast bullets. My SKS purrs like a kitten and doesn't lead with cast either........:)

To get reliable functioning I sure be trying a slower buring powder to increase gas port pressure before altering the rifle.

Larry Gibson

[RU shooter]

I just got a 7.62x40 barrel and set of dies from Wilson. Using what I would consider max loads (primers flattened right out to the edge of the primer pocket) of H110 I could not get it to function. The gas port was .096" dia. measured with pin gages. I had set it up with an Adams Arms piston system which works great on my 5.56. When it didn't work I changed it over to a direct impingement system. It still wouldn't work - short cycled. I opened up the gas port to .104" and it works about 95% of the time (w/di). I'm going to open it up some more and see if the reliability improves.
Were you shooting cast or jacketed loads?

[scb]

Jacketed. Yes I know, heresy. There is a method to my madness however. I have always found it easier to get a gun (rifle, revolver, or pistol) to shoot well with jacketed bullets. So I use my jacketed data as a base line. If it won't shoot 2" group @ 100 yds with jacketed stuff I won't waste a lot of time trying to do better than that with cast.




To get reliable functioning I sure be trying a slower buring powder to increase gas port pressure before altering the rifle.

Larry Gibson

I'm not too concerned about that. I have an adjustable gas port (block) on it.


BTW this is a 16" bbl. with a carbine length gas system.

[madsenshooter]

scb, is there some particular reason that you have your heart set on H110? 95% is pretty good and just a slight change in burn rate, say to 4198 or 2015, ought to get rid of the remaining 5%. I changed from 4198 to 2015, which isn't much of a spread, and went from partial function (it ejected), to 100%. If the port is too big, shaving can become a problem, even with jacketed. By the way, the Swiss made 4198 Widener's offers is pretty good stuff.

[scb]

scb, is there some particular reason that you have your heart set on H110? 95% is pretty good and just a slight change in burn rate, say to 4198 or 2015, ought to get rid of the remaining 5%. I changed from 4198 to 2015, which isn't much of a spread, and went from partial function (it ejected), to 100%. If the port is too big, shaving can become a problem, even with jacketed. By the way, the Swiss made 4198 Widener's offers is pretty good stuff.

No not at all. H110 was recommended by Wilson (along with Accurate 1680) and I've got 8# of it. I'm pretty sure I've got a little imr4198 left and I'm going to try it, probably before I open up the barrel any more.
If it improves things I'll look into that Swiss stuff. Is that the spp210?

[zomby woof]

I've got an AR in 7.62X39. I have so much Chinese ammo I'not considering casting for it.

[Lloyd Smale]

Im with larry. Maybe its the caliber i dont know but ive shot thosands through my beowulf without a bit of trouble. The fouling from bullet lube will make you need to clean a bit more often but ive yet to see any build up in my gas tube and if i did i guess id just buy a spare and toss the old one and put a new one on it as there pretty cheap.
Myth

Many of have shot thousands of cast bullets through ARs without any problems of the gas tube "stopping up" from the lube and debri. Consider if there is enough psi to function the action there is more than enough to keep the gas tube blown free of lube and debri. Also, many of us have shot thousands upon thousands of .22LR through ARs with subcal devices such as the m261 I have. The gas tube doesn't get clogged. Many bajillion .22LRs were fired through M16A1s for many years by the military with the M261 device. The TM states to fire 1 or 2 M193 cartridges through the rifle to clear any debri still in the tube. At the SF Armory I worked in we had 2 dedicated M16A1s for use with the M261 devices shooting .22LR on the indoor range. I traked one of them for 10,000 rounds of issue Winchester .22LR without cleaning the gas tube. I then took it to R12 at Fort Lewis and fired 9 shots of M193 to confirm the zero and then ran 40 hits for 40 shots on pop up targets to 300 meters without a single malfunction.

Shooting cast bullets in the AR will clog up the gas tube is nice in theory but a myth in reality.

To answer the OP's question; I would go with the standard length gas port and look at the adjustable gas tube that Brownell's sells. That should be a very decent cast bullet AR with cas bullets in the 1800 - 2200 fps range depending on weight of the cast bullet.

Larry Gibson

[Lloyd Smale]

by the way ive got a bushmaster in 762x39. Ive havent shot alot of cast through it but have shot enough to know that i can run a 130 at about 1800fps and run the action.

[madsenshooter]

No not at all. H110 was recommended by Wilson (along with Accurate 1680) and I've got 8# of it. I'm pretty sure I've got a little imr4198 left and I'm going to try it, probably before I open up the barrel any more.
If it improves things I'll look into that Swiss stuff. Is that the spp210?

Yes, the SPP210. I don't know who really made it. I get single digit SDs and great accuracy shooting it out of my Krags under the 169gr Eagan MX3-30AR. One of those Wilson barrels for my AR is tempting, but out of my reach right now.

[IridiumRed]

What I think is kind of funny / kind of ironic is that 30 cal AR's are seen as new thing / odd thing, when as far as I know, the 30 cal AR actually predates the 22 cal AR (I'm thinking the .308 AR10, which came before the 5.56 AR15).

(not trying to pick a fight with anyone, about anything, just pointing out something that makes ME chuckle a bit. I own an AR10 derivative, a POF P308, and own a CMMG AR15 lower that I'll build up someday when I have more money)

[Moonie]

Yes but the 30 cal AR-15's are much lighter than the AR-10's, and much cheaper to both build and shoot.

[scb]

Yes, the SPP210. I don't know who really made it. I get single digit SDs and great accuracy shooting it out of my Krags under the 169gr Eagan MX3-30AR. One of those Wilson barrels for my AR is tempting, but out of my reach right now.

Thanks for the tip. I didn't have any 4198 so I went out and bought a pound locally (for almost 2X what the SPP210 is selling for per pound, ouch). I loaded a bunch with charges from 18 to 21 grains. They all functioned perfectly. Even with the light loads that showed absolutely no signs of pressure. The 21 grain load which was compressed pretty good still showed just the beginning signs of increased pressure. Accuracy was just as good as the H110 loads. Next time I'll see if the chronograph still works along with some of my 311465's.

[madsenshooter]

Hmm sounds like Wilson was a bit off on their recommendation. Maybe you should drop them a line about the lack of function with that powder.

[madsenshooter]

Can't say for sure, because of all the subsidiaries and mergers involved, and with one company making powders for another company. But after much research it appears to me that SPP210 may be Vectan TU2000.