Grendel vie six8 recivers

[m796rider]

Necroposting to revive this topic...

I finally found a Six8 receiver set at GrabAGun and am breaking in Magpul mags using handloaded dummy cartridges (Hornady fired brass, 100gr Match Monster bullets). A bit of filing on the internal ribs and removal of 2 turns of the mag spring allow 19 rounds in a 20 round mag and 29 rounds in a 30 round mag.

I have a flat wire action spring in my 12" setup and it's getting easier to push past the drag on the mag feed lips. Lots of hand cycling...

I'm headed to my gun club in the next couple of days to zero and function test. If all goes well I'll pick up a bunch of mags and make this my go-to Grendel semiauto.

[BluntForceTrauma]

Great experiment. Following for future reports....

[biodsl]

Subscribed.

[LRRPF52]

Another option would be to do a Hydra-style lower and modular magazine well attached to the lower.

It will be easier to make the lower receiver for the home DIYer too.

[m796rider]

Here is what I did to the mag bodies.

Left is modded, right is factory. Those 4 rear ribs need to be shaved nearly flush and the forward ribs until the rounds are not nosing inward. At this point, the modded 20rd mag with 19 rounds seats smoothly in the magwell with no binding.


Here are the lines left by the bolt carrier wearing a bit of the feed lips away, since normal bolt carriers are not relieved to fit the wider Six8 PMAGs. This does not take long.

[LRRPF52]

There was somebody making metal mags for these receivers. Does anyone remember who it was?

I just measured the internal magazine well dimensions and there is a raw length (not counting the bolt catch trip tail groove) of 2.475”.

Standard AR-15 mag well is 2.395”.

[VASCAR2]

The only metal magazine that I remember for the 6.8 SPC which was most recommended was Precision Reflex Inc. (PRI). I can’t remember if they manufactured a larger body mag for the LMT 6.8 receiver. I think ASC and CPD made the AR-15 size mags for the 6.8 SPC. Knights Armament sold the PRI mags when they were 6.8 SPC uppers. I thought Magpul was the primary go to mag for the larger receiver LMT 6.8.

[LRRPF52]

The only metal magazine that I remember for the 6.8 SPC which was most recommended was Precision Reflex Inc. (PRI). I can’t remember if they manufactured a larger body mag for the LMT 6.8 receiver. I think ASC and CPD made the AR-15 size mags for the 6.8 SPC. Knights Armament sold the PRI mags when they were 6.8 SPC uppers. I thought Magpul was the primary go to mag for the larger receiver LMT 6.8.

The PRIs fit regular AR lowers. I think it was Mad Dog Weapons Systems that was talking about a metal magazine for the larger Six8 lowers, which would allow even longer COL than the Six8 PMAGs do.