Parts Reveiw

[kcheung2]

On my x39 AR the only thing I changed to "tune" it was an aftermarket firing pin from Black Rifle Arms. It still has occasional trouble with Golden Tiger but works fine with Tula & Wolf.

[pokesdeadthings]

Update

Hey just an update on the assembled rifle. I have canned the APOC armory adjustable gas block and replaced it with a YHM gas block/front sight combo. After some debate with some friends we came to the question: If some AK Gas block/Front sight combo blocks by very reputable manufacturer are held on with pinch screws, why not an AR? I have yet to see how the rifle's gas system takes it but report on it when tested.
I emailed Bear creek arsenal asking to purchase spare extractors, after a few days and asking me to make an account to add them to my order summary they informed me that they are short handed on extractors and will not be selling them separately at this time (FEB13). This does not inspire confidence due to fact that if mine had broken I might have a useless bolt.
After researching and asking other companies (Troy, blackriflearms, aimsurplus) it seems that others may not fit the 7.62x39 bolt that BCA sells. May buy, probably from KAK after my experiences with the barrel. I will ask BCA again in about another 2 months time.
Otherwise on the test bed for the next range trip will be a sig romeo 5, vortex scope and strike industries J-comp.

[pokesdeadthings]

Parts Review Update

Well, the last range trip was a disappointment. The gas tube roll pin on the built rifle with the YHM gasblock/front sight combo walked out. The 20-30 or so shots it fired before hand were enough to zero the scope and Iron sights. It was cycling and ejecting well but felt as though it had far more gas/recoil than the BCA upper. Both lowers are using the exact same parts. The Vortex 1-4 works great and is easy to pick up in daylight. The strike industries j-comp break works very well. The blast is to the sides, and makes it a lot easier to stand over and help spot for a friend as opposed to other brakes that direct the gas upward.
The Sig Romeo on the BCA was easy to zero and works well, even in bright daylight. With the provided mount it co-witnessed zero well with the Iron sights. I am continuing to have an issue with the BCA upper not detonating rounds fired, and failing to extract. The rounds that fail to fire have what seem to be healthy primer strikes within them, and fire when put in the Russian counterpart. That said, the same ammo is being used in the Russian counterpart with no issues, ever. I have cleaned the chamber and even gone so far as to swap the lower receivers out to see if one may be the culprit. I am at a loss, as both lowers are built exactly the same. I have now since installed Wolf XP hammer springs to try and see if the issue will be resolved. This has in turn made the trigger pull quite a bit harder, not uncomfortable but noticeable.
To this date, I like the BCA upper alot, but can't seem to get either rifle working to where I would trust them. More to follow...

[pokesdeadthings]

Final Update

Everything is working like a champ. The extra power hammer springs allowed me to fire approx. 600 rnds this last weekend in the BCA rifle with 1 malfunction, a heavily dented primer. I tried firing it multiple times, never went off. At one point I fired 8 10rnd strings as fast as i could load and got the rifle too hot to touch, and started melting the magpul sl hand guard, and it kept running. At this point the only think I'm going to experiment with is if the extended pin is necessary, or if I can run a standard firing pin and extra power spring. The trigger pull is short with eh S.I. trigger group, but stiff with the hammer spring, its usable but nothing special now. The sig romeo has been on for a few weeks straight now, and after the many rounds fired worked loose, not enough to fall off but enough to affect zeroing. The torx style fastener is a pain to tighten. Otherwise, I'm very satisfied after all this.

The Built KAK barreled rifle is still having problems with the gas system, the barrel parred with the vortex 1-4x has been working great, with very good repeatable accuracy. It's a proven to be a great soft shooting rifle, and the YHM front sight block stay out of the way but allows great iron sight use for when we choose. However, The gas tube roll pin walked out again after approx. 100 rounds turing the rifle into a single shot. The inside of the hand guards and the gas tube itself show signs of excessive gas leakage. This was present with the APOC armory tuneable gas block and now with the YHM block. I have since removed the gas tube and am changing it to a more reputable brand, as well as trying a standard roll pin and if that fails again the spring type pins.
B.C.A. still does not have 7.62x39 extractors in stock, seeing this now over a period of time (Several Months) I think I will go with KAK in the future. It is to be noted I have had no issues with the BCA extractors, but have now seen 2 Aim Surplus extractors break and a third bought from midway. All breakages were while using steel cased ammo, if it may be relevant. Will update with relevant news IE parts breakages and round counts.

[ar15barrels]

If the new gas tube still has gas tube pin problems, it could be that the hole in the gas block is not drilled in the center of the gas tube bore.
When I run into that, I drill through both the gas block and gas tube (while assembled/aligned) with a 0.078" drill bit to clean out the misalignment.
Then install a new roll pin.

[pokesdeadthings]

Up and Running 100%

Thank you for the tip ar15barrels, I picked up a Wilson combat gas tube and the drill bits. The WC gas tube didn't need it but the gas block needed it. The fit was tight, and the drill bit allowed me to install the roll pin without any damage. I am now convinced it was a QC issue on the orignial gas tube and won't ever be buying on the cheap, it really just ends up costing more in the end. The original gas tube was 9 and some change from APOC, the Wilson as 18 not on sale from midway and fit perfectly.
I have also since changed the lower on the KAK barreled rifle to a Luther Rifle Buffer tube as an experiment to see if the rifle buffer over carbine would have any difference on recoil impulse. I nor several other shooters can tell a difference, but the rifle itself feels better balanced. It is also functioning without malfunctions and has for several hundred rounds. An interesting observation is when the uppers are swapped, the carbine gas on the rifle buffered lower seems to have significantly more recoil impulse. Both Uppers interchanged and functioned 100%, but the combination was particularly noted for being recoil heavy. Maybe it's just me but I would have thought the carbine upper on the rifle lower would have lent itself to greater felt recoil than a carbine on carbine setup, or the prevision mid length to carbine. Any ideas, thoughts?

Otherwise the builds are now as follows-
1. BCA complete H BAR 7.62x39 barreled upper with A2 front sight post.
Apoc Armory extended firing pin
Strike industries latch less charging handle
Strike industries poly dust cover

2. Aero precision upper receiver,
KAK value line 18inch mid length 7.62x39 barrel
BCA complete 7.62x39 BCG
YHM combo folding front sight/Gas block
Apoc Armory extended firing pin
Wilson combat mid length gas tube
Strike industries latch less charging handle
Strike industries poly dust cover

Both Lowers are LMT with the complete Strike industries LPK and wolf extra power hammer springs and YHM extended take down pins. One lower is fitted with an Anderson carbine buffer kit and the other is a LUTH arms complete rifle buffer kit.

Both setups are now working 100% for several hundred rounds in between cleanings. I am only running c-products magazines which have not been modified in any way. The rifles are running with reliable firing with the crappiest steel cased and nicest brass I can find with the exception of lacquer cased ammunition, neither will cycle the stuff. Hope this helps someone else on the 7.62x39 Ar quest, I know I'm happy with it.

[kcheung2]

Problems with lacquer-cased ammo rules out GT & some Wolf.

On Mosins, they likely have decades of accumulated lacquer stuck in the chamber, and after about 40 firings it starts to melt & cause sticky bolt. The solution is to take a lubed chamber brush and really get in there to scrub it out. Like chucking the brush handle to a drill and just spinning for a minute. Taking care to only clean the chamber, not the bore! I suspect that your problem & solution is the same.

[ar15barrels]

An interesting observation is when the uppers are swapped, the carbine gas on the rifle buffered lower seems to have significantly more recoil impulse.
Maybe it's just me but I would have thought the carbine upper on the rifle lower would have lent itself to greater felt recoil than a carbine on carbine setup, or the prevision mid length to carbine. Any ideas, thoughts?

Carbine gas systems run the bolt carrier much faster than longer gas systems.
You are feeling the weight of the operating system bottom out.
The rifle buffer is much heavier than a standard carbine buffer.

More reading here:

http://www.ar15barrels.com/prod/operation.shtml

[pokesdeadthings]

Wow

kcheung2, I wish there had been some acumulation but these barrels are fresh and don;t have any build up. The polycoat is fine, but any of the brownish laquered ammo, from any of the makes I have tried do not work in either barrel. The barrels being from KAK and BCA. I was reading up on chamber polishing, but am hesitant as I don't see a inexpensive way to do it without possibly inducing wear on the lugs.

Ar15barrels, If your up in the LA area, we may know some of the same people, specifically if you offer in house (Or literally garage) A2 front sight pinning. I hope so, as the work was excellent but in either case thanks for the read. It has honestly opened more questions than it has answered. If the carbine action is moving faster (More speed=inertia between the systems with the constant being the same weight BCG) why am I not experiencing the same recoil impulse with the lighter weight buffer in my carbine buffered lower? Is the carbine buffer just not carrying the same mass yet still bottoming out as the rifle system is? The lighter weight attributing to less felt recoil? It would make sense that the mid length with a heavier buffer would be "Slower" and therefore take more inertial energy (Further slowing things down) to move the rifle buffer. Applying that logic I am just not following how the carbine on carbine system is not really beating the shooter up. Input is always appreciated.

[ar15barrels]

if you offer in house (Or literally garage) A2 front sight pinning. I hope so, as the work was excellent
Is the carbine buffer just not carrying the same mass yet still bottoming out as the rifle system is?
The lighter weight attributing to less felt recoil?
It would make sense that the mid length with a heavier buffer would be "Slower" and therefore take more inertial energy (Further slowing things down) to move the rifle buffer.

Yes.