There are actually lots and lots of grendel parts out there now, and they are no longer hard to find. The three most important parts in building an accurate Grendel (.5 MOA), so you can consistently hit a coyote out 500 - 700 yrds, are the following:
1) Upper/Lower matched set WITH tight tolerance (no wobble) and square face - I prefer the Mega Arms billet upper/lower matched set. Or if you want a side charged upper (increased functionality, especially on a hunting rig), you could get the billet lower and pair it with the Mega Arms side charged upper.
2) Quality Barrel - Lilja is now producing quality drop-in barrels for the retail market (used to be a special order). I suggest a 20" for your application. I have two Lilja Grendel barrels and they shoot LIGHTS OUT (both under .5 MOA when I do my part). They retail for around $400. Another quality manufacturer at probably 60% of the cost is Ar15Performance.com. Their 20" barrel is fluted at a cost of $275 and although currently out of stock, they get them in regularly. You can also order a "super" bolts from them at the same time ($104), which are the strongest Grendel bolts made.
The parts mentioned above are most important......PLEASE PLEASE stay away from the cheap, poor quality uppers/lowers that a lot of people claim are great........been there, done that........90% of the cheap upper/lowers will have wobble (kills accuracy) or in most cases, the upper will not have a square face. Although these cheaper parts will be accurate from 100 - 200 yrds, groups will widen out thereafter. Not worth it IMO. The absolute cheapest I would go for a budget build would be the Mega Forged Lower ($105) and billet upper ($205).
If you want even more higher end (not needed), shoot me a PM.
The other important parts for accuracy, but should be based more on feel/preference are as follows:
1) Quality Trigger - I like Geissele 2-stage triggers.......budget-end for a quality trigger is the Geissele g2s, which are $80. Middle of the road, and highly suggested given crisp-clean 3.5lb break, is the Geissele SSA-E, which are around $175.
2) Adjustable Gas Block - lots of them out there, but I would find one that is adjustable from the FRONT (not side, which is very difficult to adjust with a hand guard over the top). Syrac Ordinance is best in class.
Most other items to complete your build (hand guard, stock, etc.) are purely cosmetic for the most part, but I'm happy to provide some recommendations if you want.
Shoot me a PM if you have any questions.
