I'll give my brothers here a sneak peek at the latest MAC video.  It hasn't been publicly posted yet.






 

As always... great review MAC

Awesome, Awesome video man!  this gets me so damn excited to get mine built!!!

Great video!

After you sent it off to Rifle Dynamics, did they use a US barrel to replace the shortened AK-74 barrel? Any details about this particular barrel? Also, it sounds like your rifle is Bulgarian, but you also seemed to intersperse some language that made it sound like yours was Russian (Tula kit?). The journals on the barrel, length, etc. are slightly different between the two countries.

actually that's interesting, is there a link that shows the difference between the two Krinkovs?

I didn't know that bit about the krinkov. Thanks for the partial history lesson.

What left side charging handle are you using on your regular AK that you compare your AK74u to? Thanks!

It's the LINCH.

Davis Tactical Solutions.

Mine is a Bulgarian.  I did mention that you could find Tula kits at RGUNS and the barrel is a about 8.2" long.



It's a long story on the barrel and I honestly don't know what the brand is.  When I got the rifle from the seller I was pretty upset that it was in such bad shape.  I went back and forth with him on getting a refund.  He wouldn't send me the money unless I sent him the rifle first... so I settled on him sending me a new proper 1:6 barrel and $100.  I didn't mention this in the video, but the barrel wasn't pinned –– it was JB Welded.  I sent the barrel to Jim and he took a look and said it looked solid.  If he thought it was going to be a problem I was going to have him install one of his barrels.
 

I subscribed, so with losing 550 FPS what does that make the fragmentation range of the ammo? From what I understand it doesnt fragment reliably with full velocity

If using 7N6 surplus, it should tumble (not fragment) reliably given the bullet design even out of the 8" barrel.



 

The barrel is made from blue prints from the real suchka barrel and made from a close friend of Rifle Dynamics.  The barrel is the right twist and chrome lined. I see the stock is nicely placed as it is a hidden signature plus a few others of Jim Fuller and Rifle Dynamics.  I can tell you personally, that you are supporting a handful of selected individuals that Jim has picked to fit his standards filled with different walks of life and are in fact, veterans, including me.

You are thinking of 5.56x45. The 5.45x39 round relies on tumbling, not fragmentation. The tumbling is not velocity dependent like fragmentation is.

These rifles can run reliably without a booster.

Bulgarian and Russian "suchka" rifles (not even sure they call it that in Bulgaria) have subtle differences in the barrel, so your statement may not even apply in this case. I would also ask you to explain your statement about the "hidden signatures".

I have not been able to stall mine when using a regular AK74 brake no matter how fast I pull the trigger or bump fire






Z

The Tula I built also runs just fine without any brake or anything. I've put a few mags through it like that. It still flings the casings into orbit.

A friend's Tula with nothing on it runs excellent, and a bit different, but my 107 runs flawlessly with a naked muzzle as well.

The OP obviously just didn't know any better. I'm interested in whether or not his will run Silver Bear or something similar with nothing on the muzzle.

"hidden signatures of what made it a Rifle Dynamics rifle  Either way, nice video and back to orinal topic, MAC.

FAC - thanks for producing this video.  I wonder if you feel this platform is less accurate due to sight radius, or some other disadvantage?  








 

Did you read the text in the video at 2:35?  It was posted well before I posted this thread was so you must have missed it.  It reads, "The muzzle device is intended to increase reliable function by increasing gas pressure, it will fire without the device installed."  Mine will fire without the device installed too.  However, it is a booster designed to trap gasses to maintain the gas pressure longer for reliable function –– that's the intent of the device anyway.



 

It's also an excellent flash hider. Dare I say, those "boosters" are flash hiders first, and gas traps second.

Isn't the keyholing from a cut down barrel expectation a bit overblown? There are plenty of folks running cut down barrels in 5.45 that have no issues whatsoever. It should also be pointed out that every SBR'd 107UR and 106UR started out with a 16" barrel... I don't believe I've ever heard of any keyholing with those.

5.45 seems to be more sensitive to barrel twist and length when it comes to keyholing.  The krinks with 16 inch barrels may also have a twist rate that is more favorable to cutting the barrel down instead of the standard twist rate for a 16 inch barrel.

Its a guessing game whether a cutdown AK74 barrel will keyhole or not.  Its worth mentioning so people are aware of the possibility.

Great video and sweet AKSU.

Mine keyholed every round at 30 yards.  

The bullet was tumbling the moment it left the barrel it would seem.  At 100 yards it would only hit a IDPA sized target occasionally and that was out of pure chance.  Many rounds wouldn't hit paper, and of those that did it wasn't anything resembling a group.
 

Yeah there doesn't seem to be any middle ground with this. If it works it works, if it keyholes then it's all over the place. Luck of the draw I guess...

Still, with 5.45 and 5.56 being so similar ballistically, you'd think this would happen with the 106s if not the 107s.

I just got off the phone with Jim (for something unrelated) but we did discuss the keyholing issues.





He confirms that it's a problem with most cut down barrels that are 1:8.   I'm sure some folks have cut down 1:8 barrels and don't see any issues, but I would imagine they're right on the cusp of the bullet being properly stabilized.



 

This is common knowledge among many of us.  This was really funny when people tried to use 1:9 barrels.

Op, great video!!!  Very well done.  

When I was buying the parts to complete my build, Troy from inrange told me that it was a 50/50 on it keyholing if I used a cut down barell.

I was thinking what I had read was it tumbled and broke apart.

I sat on a bulgy kit for 2 years before getting around to sending in the form 1 and having Troy at Inrange build it. As mentioned the most surprising thing about these guns are how light they are, reminds me of a M1 carbine.

I am glad that mine came with the original barrel so that I did not have to hunt down a new one with the proper twist.







I have since refinished the forearm to a blonde.


 

Mine will be ready later this week from Jim, 7 month wait on the ATF stamp for some reason.

7 months is about right.  I'm 5 months into an expected 8 month wait on another suppressor.



 

Damn, I need to get off my ass and send in the paper work for the receiver I have for my Tula kit.  I've only been sitting on it for 9 months now.. lol  Being a broke student gets in the way of things

Is your Suchka significantly louder than your SGL-31?

Oh yeah.  My old one had a fake can, and it was still considerably louder.

Yes, and launches fantastic fireballs without the booster!

I was too preoccupied with the oral presentation (visual/audio, video) to read the text. You said, "These rifles will not operate properly without that device on the muzzle". Why say it if it isn't accurate? No offense intended, but there is more than enough misinformation about these weapons as it is. Just trying to cut some of it off early, that's all. People come into the shop and drive me nuts with this stuff. I appreciate the contribution. I would love a low light video of you really raising some hell with that thing (like you are trying to break it). Very little talking, no text, just lots of fireballs and the sound of steel crying for mercy. Bring that....

ETA: The 5.45 round will sometimes tend to keyhole at close ranges, but stabilize further out. The bullet 'yaws' when it leaves the barrel. The design of the projectile is the main reason for this (heavy rear, light nose).

Try public speaking that's totally unscripted and without the aid of teleprompters (dig on the President) and see if you say things perfectly every time.  In editing I realized my comments weren't clear and was faced with two options.  Taking another day to drive out 20 miles to my rrange and reshoot or putting clarifying text in.  I opted for the later.  

 







 

I don't buy that theory. It seems like if the bullet was even a little crooked near the muzzle, your accuracy would be crazy off even if it did 'stabilize'.

Try it?
Spur of the moment, I rewrote and gave my youngest daughter and wife's eulogy in front of well over 1500 people in the largest church in the city when no one else could hold themselves together well enough to do it, while my oldest daughter was still in pediatric intensive care from a head on collision with a semi with a broken spine, internal injuries, a brain injury, and a host of other injuries. My family thought I had a screw loose because I wanted to do it. Damn it, no one else could. All while I wonder how I will speak one-on-one with my daughter to tell her that her mother and sister are dead, if she even lives or ever comes out of a coma. That one-on-one was harder than any public speaking ever. Someone saw me speak (still don't know who it was) and I went on to speak on behalf of the Children's Miracle Network at fundraisers to some of the wealthiest people in our community as an effort to benefit people whom I will never meet who might later be in the same position as myself, a parent who could only hope that their child could outshine the face of tragedy and become a miracle. The odds are extremely slim. I've done it from the heart, no script, no pep talks, no nothing, just me and banquet halls full of people. I've done it on live TV. I've done it in front of an NFL team. Now, every time someone in my family dies, people want me to write and speak, so I do it as one of the last nice things that will be done for them on this planet. Try it? I feel like I am the undertaker. I sincerely hope none of you experience what I have. Those who have, I sincerely feel your pain and offer my deepest sympathy. Point being, public speaking on a gun video is Romper Room compared to what I have done, really. I shoot gun videos for fun. Sorry, just wanted to snap some of you guys out of the trance of regular life ;) Carry on.... hug your wife and kids.  

I've wasted plenty of money and time going back and forth to the range over and over to make a single contribution that I hope will inspire at least one person. Whatever it takes to make that happen. If all of that effort puts a smile on one person's face, mission accomplished. Whatever, bring that low light naked muzzle video and I'll be the happy camper. Save me and put a smile on my face, bro. I use this passion and interest as a means of trying to temporarily forget the things in life that I do not like or can't find it in me to understand, but have to live with. Drive that 20 miles and bring that video.... hopefully gas won't $5 a gallon by the weekend .... bring those fireballs! I love this stuff

The end of the nose stays in the center of the bullet path while the rear rotates around it (yaw). Research it or just don't buy it. Just trying educate here.

I've heard people say this, but it's physically impossible.  Once a bullet starts tumbling due to instability, it's not going to suddenly stabilize itself.  



 

Why would the bullet rotate about tip, rather than the center of mass?

You think once the bullet turns 30 degrees sideways while traveling at hypersonic speeds, even if the bullet could stabilize, that it's not going to be wildly in accurate?

I would be glad to research it, but all I can find on the subject is Internet forum hearsay. If you have a solid peer-reviewed technical article or something, I would be glad to be enlightened.

Wow...I'm sorry for your loss. But are you sure you want to spill your life story on the internet? Some late night alcohol may have loosened your tongue there a little bit.

No alcohol. Just saying that this stuff is elementary in the grand scheme of things, that's all. Maybe it can give a few people some perspective on what can be handed to them in life. Will they step up when called from within? You never know until it is your reality.