Brent0331 review of the AR-RPK by Klein Machining


Brent0331 review of the AR-RPK by Klein Machining

In this video were going to take a look at the new AR-RPK uppers made by my friend Mike Klein at Klein Machining. If your interested in obtaining one of these uppers please check out the pinned comment by me in the comment section.

Specs:
Chambered in .223 wylde (so .223 or 5.56mm is good to go in it!)
24 inch nitride bull barrel
1/8 twist
.875 gas block and nitride coated gas tube.
12.5 m-lok hand guard (small section cut out of the bottom towards the front to accommodate the bi-pod legs)
7075 forged upper.

**For those that are interested, here is what Mike told me in regards to velocity in a 24 inch barrel:**

“So there is conflicting data out there in regards to velocity loss over 20″ in 5.56

Barrel Length Studies in 5.56mm NATO Weapons


Is the most damning report against barrels over 20″ in length. But if you look at the data, the case being made is don’t do a 20.1 – 22.9″ barrel for m855. But if you look at 23″ and 24″ the velocity picks back up and is darn close to 20″ maybe 20-30 fps shy.

but if you look at this fellas’ report on it

223 Remington/5.56 NATO, velocity versus barrel length: A man, his chop box and his friend’s rifle

Velocity over 20″ keeps increasing for all ammunition. With the exception of UMC .223 ammo which falls on its face at 26″

There is also this fella

Using M193 he was getting ~170 fps More velocity with the 24″ over the 20″ barrel
Using M855 he was getting ~120 fps More velocity with the 24″ over the 20″ barrel

So from the data I have, worst case scenario is the 24″ barrel is about the same velocity as the 20″, but more than likely the 24″ barrel is at least 100 fps faster. I’d say the 24″ is a great choice.

Coupled with all the extra selling points for the 24″ over the 20″ barrel:
1) Larger moment arm, to go all physics on you. (bipod at muzzle equates to a fulcrum further away 24″ vs 20″ which, gives you a enhanced force multiplier which increases control of the muzzle)
2) More real estate on the forearm when the bipod is folded
3) ~1000psi lower bore pressure at bullet exit than a 20″ barrel which leads to
a) Less Blast
b) Less Flash
4) Its cool, Its like an RPK Bro! ( well technically RPK’s barrel is 23.2″, but MERICA ! )
I’d say the 24″ is a great choice. I could make 20″ shorties if folks want that though.”

-Mike Klein

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