6 Arc

alf said:
Exactly, not locking back on the last round is way down the list of things to worry about in a hunting rig...
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That may be true, but if it really is under-gassed, as soon as it starts to get a bit dirty or the weather turns super cold, the extra drag on the BCG may cause the BCG to not move rearward enough to pick up the next round from the mag. Now your AR is intermittently a single shot...
 
@MPFD
Yeah I'm at four now, and always looking at adding another 4 or more. Although all of mine are centerfire currently, I need a rimfire or two first. It is a addiction.
while many would view our comments as thread drift, it "might" actually be a easier solution for the OP. A 30 caliber can could be chosen (which should serve for many). The good side is the OP could use it on a differing host even if he tires of the current system. Thus not a wasted use of funds. But some shy away for differing reasons from the suppressors.
 
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Well, I drilled the gas port this morning. It was close to the .0935 because my drill had little to no effort to open it up. Heck it may have just been carbon build up, but its opened up now. I'm figuring worse case is an adjustable gas block and a new tube.
 
I'm learning, but seems lessons cost money. The rain let up enough for me to make a trip to the club for a test run. Results were the same but I am learning. To back up a little, the first and only time I have shot this rifle, I used a brass catcher so I had no idea where the brass was going. Today I didn't use a catcher and even after opening up the gas port in the barrel, the bolt doesn't stay open and according to the chart Sgt. Mike posted, I'm over gassed. (Hulls were going at 1 o'clock. I didn't know this until today.) So, I bought an adjustable block and tube today to see if I can regulate the gas better. The guy at the store mentioned my mags and also my buffer spring. I have extra mags to try, but I have no idea if its a spring issue or how to check it. Hopefully the new gas block will solve this issue. If weather permits I'll make another range trip. Kinda wishing I had left it alone but that's not me. Being an old retired maintenance man I won't stop till its right.
 
Yhm sells a “Suppressor” gas block that has a tighter port and no adjustability for $18, Midway carries it. It sounds really over gassed. That shouldn’t keep it from locking back. I’d look at your bolt catch and make sure it’s not bound up or tight. If it’s fine I’d try a new magazine.
 
I have three mags. I plan on trying all three next time out. I've already replaced the gas block and tube today. Found a good one locally. Wasn't cheap so I hope it works. Bolt latch seems OK. It works smooth or so it seems.

Don't hate on me, but I read that an over gas issue can cause the bolt not to latch. All I have is you guys and the internet for information. That and trial and error. I'm almost hoping it isn't the mag after spending the $$ on the new gas block. I'll feel really stupid if the mag is the issue but the was it was ejecting spent rounds I feel there was a gas issue also.
 
William Suter said:
That and trial and error.
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believe it, or not we all do that more than we care to admit.
measure your buffer spring as preventative measure in the future, if carbine it should be 10.0625 (10 5/8") to 11.25 inches Rifle is 12" to 16" if less than the nominal suggested length a new spring will help to keep the rifle running properly.
It's not uncommon to have to change the settings on the block to match a differing load with differing powder bullet combos.
(personally I usually put a adjustable gas block on all mine, exception is the factory Colt and the Ar-15 9mm blowback no gas)
Have fun Bill
Best regards
Mike
 
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@hunt0168 again thank you Sir.
Pointed out a error when I attempted to turn a decimal measurement to fraction for ease. the carbine spring length should be 10 1/16" not 10 5/8"
I must have looked at the value incorrectly as .625 would be 5/8" and .0625 as 1/16"
again thanks for pointing that out as I do know that 10.0625" is the min spec in free length.
 
I haven't shot my 6 ARC since adjusting the new gas block and then I shot for function, not accuracy. I've been ready a few posts here and there and some are moving away from the 6 ARC because POI keeps shifting. One guy said it did the same thing with two different barrels and one barrel was a premium barrel makers. Anyone here have similar issues? I plan to shoot my rifle this week-end just to see for myself.
 
Over gassed will cause the bolt to move too fast and the catch won't work. Sometimes will over-run the next case (jam). Solution CAN be a heavier buffer weight. My guess. Won't hold open on last rnd? Bolt is moving fast but the mag spring force/weight is less and the mag MOVES. Try pushing UP on the mag on the next to last shot.
Be careful cleaning the tail of the bolt - that is the rear gas seal in the BCG. Don't scrape it. All the ARs I have never did have a problem with stock gas rings.
 
William Suter said:
I haven't shot my 6 ARC since adjusting the new gas block and then I shot for function, not accuracy. I've been ready a few posts here and there and some are moving away from the 6 ARC because POI keeps shifting. One guy said it did the same thing with two different barrels and one barrel was a premium barrel makers. Anyone here have similar issues? I plan to shoot my rifle this week-end just to see for myself.
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If POI is shifting, it's NOT a cartridge problem. Could be a number of things, including poor / inconsistent shooting technique, bad scope, loose scope fasteners, loose barrel nut, something touching the barrel (not free-floating), not enough clearance between hand guard and gas block, etc, but it's NOT because it's a 6 ARC.

In an AR especially, there can be a POI difference depending on if you're shooting off a bipod located near the muzzle vs a bag or tripod near the mag well. I believe it's related to the differing amount of stress applied to the barrel nut, and therefore the barrel. Unless you have a special get-up where the hand guard attaches directly to the upper receiver, you'll probably experience some amount of this problem.
Reference: AR Positional POI Shift Test
 
Kinda the reason I was asking. I've not seen a certain cartridge be a POI issue. (LOL, unless I'm shooting it.) One guy claimed he was shooting 600yds and his first barrel would throw the POI so he had a custom barrel made and it did the same thing. This dog don't hunt!! Sounds like shooter error to me. Maybe he should get closer.
 
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