SBR Grendel

[BjornF16]

Having missed the opportunity to get an AA 10.5" upper, I'm finally at the point where I'm looking to build a Grendel SBR.

1. What would be a good length for the Grendel with carbine gas system? 10.5 as done by AA, or some other slightly longer length?

2. Who would be a good source for a Grendel SBR barrel or upper?

3. What size gas port?

Thanks,

[Variable]

1.) Well, the carbine gas system already runs the 10.5" fine as-is, so that length is arguably "long enough". If you went longer like maybe 12.5" or so, you 'd pick up some velocity while still being relatively handy in length. I dunno, I'm pretty happy with the 10.5" as it is.

2.) That is a good question, and I have no idea right now. PSA was going to have some Grendel barrels done for them (by FN I'm fairly sure) before everything went apecrap crazy. I was really hoping they'd come through with a cold hammer forged and heavy chrome lined tube in any length between 10.5--12.5". I'm still hoping someone does it someday within my lifetime.LOL


3.) Bill A. Can hopefully chime in on the port size. I'm too lazy to disassemble mine to measure it for now. If it becomes a stickler later I'll do it, but I'd druther not if possible. I have a superstition about not monkeying with things that work.

You could have a longer barrel cut down, but I'd much rather have a chromed barrel already made that way-- like Sabre did for AA on the old tubes. It'd be great if Bill Alexander could get some cold hammer forged tubes from FN in 6.5 (and already heavy chrome lined--- SAW style). I imagine he's too hopelessly buried in other more popular ventures at the moment though-- if he even was amenable to such a thing.

I'll be watching too though, as I'd like to pick up another one. As crazy as things are these days I need to stash an extra barrel at least, but I'd grab a spare upper or two if the price was right.

The more I think about it, it'd be fun for me to get a 12.5" tube just so I could do side by side comparos in identical conditions on ammo. It'd be more water instead of fuel for the barrel length arguments. I could post up actual measurements of side by side tubes at the same altitude, temperature, etc., etc., etc.

Bottom line is that Bill Alexander could make it happen, but I'm skeptical he would during the current craziness. I'm betting you'd have to chop a longer barrel to get anythng right now.


One additional thought---- If you want to run subsonic loads through a suppressor.... To date I haven't been able to get anything subsonic to cycle in a 10.5" tube. The gas just simply isn't there for the dwell time and port size used on the old AA upper. You could possibly get away with subs using a pistol length gas tube, but that's another can of worms I personally wouldn't want to have to contend with. Bill A. Left the port smallish on his 10.5" tubes, as he knew they'd likely be run suppressed. Upping the port diameter and using a switchable block might help. Doing so on a 12.5" barrel might be even better since you'd have more dwell time.

To me the holy grail was always that I wanted a subsonic load with enough pressure to cycle the stock 10.5", since if you could cycle that one all of the others would be very easy to do. I'm still holding out hope for an eventual 175 grainer from a custom bullet maker (Tex got us some 160's from Hawk) that might make it possible.