65 Receiver Set with Polymer mags from PF (HOPEFULLY)

[Variable]

Heh, heh. Well, if only Variable was a bit more adventuresome, he'd have bought a Six8 receiver set and Pmags, and we'd know for sure if a "Six5" rifle would work!

If they weren't 700 bucks a pop I probably would have tried. http://www.onpointsupply.com/cart.ph...054&substring=

They were a hundred bucks cheaper in the group buy they had, but it passed before I even knew about it. Regardless, that's too much scratch to make it a worthwhile gamble to me. If it didn't pan out I'd end up with a very expensive 6.8SPC that I wasn't really interested in. Nothing against 6.8, but when I already have 3 Grendels and am in the process of building number 4, I don't need to be complicating the cartridge pool without a darned good reason.

[LRRPF52]

I looked at this years ago, and here is where I am at with it conceptually:

* Building a specific receiver set for the Grendel is probably a custom job only for all the reasons stated here already.

* There are no practical performance advantages to be had, especially considering powder development.

* If polymer magazine option is the main driving point, then why are the Six8 guys already talking about making new mags specifically for the Six8 receiver set other than PMAGs, with less capacity, but longer COL? Because they want BC that we already have. They want performance, and don't really care about 30rd PMAGs as much as the Saudi's do.

* If you want performance enhancement, you need to step up to a new case with more powder capacity, and a COL of ~2.5". Set your on-target performance requirements, then determine what bullets and speeds will achieve that. Set the desired pressures you want to run, then build engineer the dimensions around that with the desired FOS. Eventually, a pressure containment system and receiver set will begin to form.

* Set aside a pile of cash equal to a decent residential home cost for RDT&E.

* See if you can get one of the brass manufacturers to add yet another cartridge to their production schedule.

Another way around this, which is the conclusion we came to years ago, is to make a Lancer-style magazine with metal body and feed lips in the mag well, and a polymer mag body outside of the gun. There is your 30rd or higher capacity magazine that will stack correctly.

And I think this is a legitimate discussion because more and more people are going to want little 6.5 Grendel blasters with the availability of cheap plinking ammo now with the steel case. All of this is doable with a hybrid Lancer-style magazine, to include pushing the OAL out more if you really want for hand loaders, but QC will have to be more stringent on increased COL requirements, leading to expectations of cost increases if they are to hold the tooling and inspections to a much tighter standard than existing mags.

[PrecisionFirearms]

I finally was aware of this discussion. Here is my take to date.

Machining a wider mag body with a billet is not very hard to do. Setup to run that will require about 25 units. Cost around 225. I don't think much would need to be done with the upper, but I would need more research to verify this.

As to the 68 mag working - I again would need to more research. I personally run the 6.8 SPC PRI mags loaded to 25 rounds and have had no issues. Our customers are buying them from us and none have complained of feeding issues. They are $47.

I have asked Lancer to work with us in making a dedicated 6.5 cal mag and they aren't much interested unless I commit to 10,000 mags. You do the math. That is a lot of money.

Mark Hostetter

[Variable]

I agree with LRRPF52 about the Lancers being pretty desireable. I also see where Mark having to commit to 10,000 of them up front would be a major buzzkill.

I like the idea of a $225 lower to fit the mags, and I'd place my first order with 10 mags. Selling the other 9,990 of them might take a while though, even if I loved them and placed some follow-up orders.

It'd be a mighty big hurdle to get over.

[LRRPF52]

You do need a new upper if you want to fit the wider polymer magazine into it. Then you have to machine a different bolt carrier with enlarged cartridge cutaways on the bottom, just like you have to do with 7.62x39 and the LWRC. That's another reason why the Six8 receiver set approach is probably a non-starter.

As to Lancer mags, 10k units would break down like this if we did a group go fund them project:

100 forum members would have to pay for 100 mags each.

250 forum members would have to pay for 40 mags each.

If we could get a few 6.5 Grendel companies on board to up front initial outlay, we could share it all across the board, spec out a mag, and fork out the investment.

[cory]

You do need a new upper if you want to fit the wider polymer magazine into it. Then you have to machine a different bolt carrier with enlarged cartridge cutaways on the bottom, just like you have to do with 7.62x39 and the LWRC. That's another reason why the Six8 receiver set approach is probably a non-starter.

As to Lancer mags, 10k units would break down like this if we did a group go fund them project:

100 forum members would have to pay for 100 mags each.

250 forum members would have to pay for 40 mags each.

If we could get a few 6.5 Grendel companies on board to up front initial outlay, we could share it all across the board, spec out a mag, and fork out the investment.

I agree that you'd want a new upper designed for the wider lower, but I don't think you'd need it. I completely disagree on needing a new carrier, that could potentially limit how wide you went. Or it might not be a bad idea to design the mag to single stack the last round, like the XD/XDm pistol mag.

I've been thinking about it. It seems like if we did this we should lengthen the magwell 0.15" to 0.20". If the buffer retaining pin location was moved equal distance, it'd allow us to keep the same carrier.

[stanc]

If polymer magazine option is the main driving point, then why are the Six8 guys already talking about making new mags specifically for the Six8 receiver set other than PMAGs, with less capacity, but longer COL? Because they want BC that we already have. They want performance...

There are a couple of different things going on. There are the performance guys who want to take advantage of the Six8's bigger mag well, to get steel mags that would permit cartridge OAL of 2.40" or more. Then there are the hunters and bench shooters who want low-capacity Pmags for compliance with hunting regs and handiness when firing from a bench rest.

Another way around this, which is the conclusion we came to years ago, is to make a Lancer-style magazine with metal body and feed lips in the mag well, and a polymer mag body outside of the gun. There is your 30rd or higher capacity magazine that will stack correctly.

Except that is not a polymer mag. It is half steel, and half polymer. Why not just stick with an all-steel mag?

[stanc]

I agree that you'd want a new upper designed for the wider lower, but I don't think you'd need it. I completely disagree on needing a new carrier, that could potentially limit how wide you went. Or it might not be a bad idea to design the mag to single stack the last round, like the XD/XDm pistol mag.

How many people would want a high-capacity, single-feed, rifle mag? I sure wouldn't.

[bwaites]

How many people would want a high-capacity, single-feed, rifle mag? I sure wouldn't.

Has anyone ever made one work? My understanding was that the increased length of rifle rounds created problems that aren't an issue with short pistol rounds.

[cory]

How many people would want a high-capacity, single-feed, rifle mag? I sure wouldn't.

No, the mag would be a double stack. However, at the top, the mag converges into a single feed mag.

[cory]

Has anyone ever made one work? My understanding was that the increased length of rifle rounds created problems that aren't an issue with short pistol rounds.

Honestly, I have no idea.

[stanc]

Has anyone ever made one work? My understanding was that the increased length of rifle rounds created problems that aren't an issue with short pistol rounds.

I don't know whether or not there are technical/mechanical issues that would prevent it from working. I just can't imagine why anyone would even bother trying to make one.

[stanc]

No, the mag would be a double stack. However, at the top, the mag converges into a single feed mag.

Yes, I understood that you were talking about a double-column, single-feed mag. It'd be much more tedious to load than a double-column, double-feed mag, due to the manner in which the rounds would have to be inserted into the mag. Compare:

https://www.youtube.com/watch?v=XbZJt2P50K4

https://www.youtube.com/watch?v=Yta8TjCkVGU

https://www.youtube.com/watch?v=9dujUDYn-18

[stanc]

P.S. Many years ago I briefly owned a Remington M788, which had a single-feed magazine. It was a real pain to load the mag, even though capacity was only 4 or 5 rounds. I shudder at the mere thought of having to load six or more high-capacity, single-feed rifle mags.

[PrecisionFirearms]

Single stack mag will require a redesign to the barrel extension due to feed ramps.