Just Got My JP Ent. "Tactical" Bolt Carrier Today.

[Strykervet]

And man, is it something!

I'm building a Grendel rifle, planned on doing it using the cheapest milspec parts I could find except the 20" barrel and the FF tube (Satern and Knights Arm. respectively). The 2 stage worked RRA trigger came from another rifle, most of the small milspec parts are DPMS, an AR Stoner buttstock, and Aero Precision receivers that I got a REAL good deal on. It'll get a 7.62 ACOG from another rifle. This will be the SDM rifle I always wanted when I was an SDM. The configuration is a semi M16A4 with a FF rain instead of the M5. But I ran into a few extra dollars and decided to scrap the Daniel Defense carrier group in lieu of the JP Ent. carrier assy. only. I didn't need the bolt because the Satern bbl. came with a bolt.

The Daniel Defense looked like a very fine milspec part, much more attention to detail than the Oly I have in my M4. But the JP part is just awesome. It is stainless, but coated or treated with something that makes it dark. The part is so smooth and slick, real attention to detail was done here, it oozes quality. No machine marks at all. None at all. Everything looks highly polished. For $30 more than the DD part -the bolt that it came with makes this an awesome deal I feel, especially for me since I didn't need the bolt.

For anyone building an AR, I highly recommend taking a look at this part. I really don't know of any bolt carrier out there that even comes close.

I got the "tactical" version, that is the one most like a milspec one and works with the regular recoil assy. They make a very light version, but you need the appropriate recoil assembly to go with it. Sort of costly there. They make some very fine products, but don't get much lip here. They even make .308 AR rifles, costly, but less than some talked about here, and I bet they rock.

 

[taliv]

cool. i agree they're pretty nice, but i haven't seen that model yet. (at least, outside a JP rifle)

btw, hopefully you already know this, but if you got the Knights URX rail, you need a special wrench for it

 

[68wj]

Those are some good looking carriers. Sounds like a nice build.

 

[madcratebuilder]

Have you lapped the upper? Many of the Grendel shooters have found that lapping the upper reduces the possibility of bolt breakage that happens with the Grendels.

Midway sells the lapping tool fairly cheap, it's a good investment.

http://www.midwayusa.com/viewProduct/?productNumber=810457


I've done a half dozen uppers now and found my A Arms upper was out of spec to most of any I have done.

 

[Robert]

JP makes very high quality parts and amazing rifles.

 

[Tirod]

I own and have used that lapping tool. All it does is square the nose of the upper to get the barrel shoulder to sit a bit more at a true 90 degrees. And that usually translates to not using up as much windage setting zero on the sights.

What it won't do is guarantee the shoulder on the barrel extension is at 90, although machined on a lathe, it should be. What complicates it are the threads inside the extension that screw onto the barrel - are both exactly 90 degrees? Likely, but now consider that the tolerance stack of the threads can allow a slight misalignment. Anyone who's started a bolt in a tapped hole knows it has some looseness, it's required or we'd have to torque them in from the start. And added to this multipart joint is the barrel nut clamping the extension shoulder from the other side as it screws onto the receiver nose. If the inside shoulder on it is misaligned, plus the thread fit tilts the shoulder at all, more deviation occurs.

Many custom AR builders don't do the operation on their standard offerings, it's an extra charge. Nobody has much documented any accuracy increase at all, just anecdotally noted that their windage was more centered.

Alternate caliber bolts have one issue that 5.56 doesn't. The original bolt was designed to have sufficient material to support the cartridge case head. Alternate calibers use larger case head diameters which weaken the bolt face, and ITS 9310 bolts in a stronger alloy are recommended as a result - or the bolt could fail. That's the specific reason for it, not the slight misalignment of the barrel on the nose of the upper. There is actually a lot of looseness in the upper to tolerate it without breaking the bolt. "Tight tolerances" in the AR are just a myth, rattle that BCG around in there yourself and you'll see it.