Grendel mags?

[stanc]

I took a PMAG and a CProducts 25rd mag, and did some measurements. A polymer mag could go thinner on the inside, but only where the Grendel case wall is...

But isn't that the area that most needs to be thick?

This seems very solvable without resorting to a different mag well, like LWRC did with the Jordanian PDW.

You may be right, but I keep thinking that if it were doable, somebody would've already dood it...and LWRC would not have taken the route they did to get polymer mags for the 6.8 SPC, which has a smaller case diameter than 6.5 Grendel.

[LRRPF52]

There has been a lot of industry resistance to supporting the Grendel, since so many companies knee-jerked onto the 6.8 SPC bandwagon. There has been a not so subtle effort to attack the Grendel, cut out products from manufacturers who were offering both 5/8x24 and 9/16x24 thread patterns in favor of the 5/8x24, and a constant barrage of disinformation on how the Grendel can only match 6.8 trajectories out of a 24" barrel, versus the 6.8's 16" barrel. I even started to believe that crap until I broke down and ran the ballistics.

What I learned was the exact opposite...the Grendel with a 16" barrel pushing 120gr Barnes TSX at 2500 fps matches 6.8 SPC 110 Barnes TSX launched at 2650 fps...both out of 16" barrels. The difference: The Grendel retains more energy SHOCKER, and has less wind drift than the 6.8 SPC with those loads.

We're even looking at guys who have been adamant and outspoken opponents of the Grendel announcing that they will now be offering Grendels, because they're tired of turning customers away. There are hordes of new shooters who are maturing into hunting with the AR, and they look at the different caliber options that have actual industry support (not some developmental wildcat), and are naturally leaning in .264" projectiles with their superior Sectional Density and BC's. They could care less how many guys walked around the floor of SHOT 7 years ago telling everyone about Special Forces' new, uber-secret cartridge.

As this industry trend continues, demand and support for the Grendel will continue to grow, even though most shooters will not realize any practical difference in 6.8 SPC ballistics vs. 6.5 Grendel ballistics within 300yds! I could even make a point for how the 75gr AMAX is a better choice than both of them out of your regular AR15, but perception is reality, and since "everyone knows a .223 is only good for varmints", people will naturally look for some other caliber solution in their trusty AR15 platform.

That demand will bring more magazine offerings to market. The width of the magazine doesn't need to be the same over the entire height...hint hint. We will have a polymer mag for the Grendel within the near future. It's just a matter of enough support getting behind it.

[stanc]

There has been a lot of industry resistance to supporting the Grendel, since so many companies knee-jerked onto the 6.8 SPC bandwagon. There has been a not so subtle effort to attack the Grendel, cut out products from manufacturers who were offering both 5/8x24 and 9/16x24 thread patterns in favor of the 5/8x24...

I always thought that 9/16x24 threads were illogical. Being unique to 6.5 Grendel, it eliminated the option of using 6.8 and 7.62 muzzle devices. Not one of Bill's smartest moves, IMO.

The width of the magazine doesn't need to be the same over the entire height...hint hint.

No, it doesn't. A polymer mag could be made with thick walls for that portion which extends below the mag well, and thin walls for the upper part that's contained by the well. The mag well would reinforce the top part of the magazine, preventing the mag from bulging after it's inserted.

However, isn't it likely the top part of a loaded mag would bulge enough to hinder (if not prevent) insertion into the mag well, in addition to keeping a full or partially full mag from dropping free?

We will have a polymer mag for the Grendel within the near future. It's just a matter of enough support getting behind it.

Well...maybe. I keep coming back to the inescapable fact that nobody has yet made a polymer mag for 6.8 SPC, despite the considerable industry support for that cartridge.

[LRRPF52]

I used to think the 9/16 thread was crazy too, but now I know why Bill chose it. At the time, there weren't a lot of alternate calibers for the AR, as most of the AR10's were target barrels. Armalite decided to be different, and went with a 5/8x24 thread pattern so nobody could use any other muzzle devices other than from them on their carbines and 20" guns with threads. The 9/16 actually pre-dates them since it was used on the British L1A1, since you couldn't go larger than 9/16" on those barrel profiles.

As the popularity of AR10's surged, and everybody started making them, they went with a 5/8x24" pattern to ride in on the Armalite coat tails. Suppressor-makers followed suit, and 5/8x24 became more and more popular, to the point that everyone associates it with the standard for .308 pipes. Kinda funny history behind it all...

[pinzgauer]

However, isn't it likely the top part of a loaded mag would bulge enough to hinder (if not prevent) insertion into the mag well, in addition to keeping a full or partially full mag from dropping free?

'Zackly right, Stan. All the folks speculating need to spend $14.50, get a pmag, and load it with Grendel. And watch it flex & bulge. :-) Stick int the mag well. Periodically spew cartridges & create jams. Then drop it and watch what happens. (speed ejection of the cartridges)

Now much of that is due to the narrow stack due to the thicker walls creating side pressure on the mag walls. But those walls are thick in poly mags for a reason! Without that you lose significant rigidity and strength.

I'm not saying it won't work for lower capacities, heck, they work as is in my rifles when loaded to 10 or less. But not something I'd trust, much less consider superior.

My gut sense is that there is some answer waiting out there with metal inserts possibly. But what is the advantage of that over just a basic, functional metal mag?

[stanc]

'Zackly right, Stan. All the folks speculating need to spend $14.50, get a pmag, and load it with Grendel. And watch it flex & bulge. :-) Stick int the mag well. Periodically spew cartridges & create jams. Then drop it and watch what happens. (speed ejection of the cartridges)

Now much of that is due to the narrow stack due to the thicker walls creating side pressure on the mag walls. But those walls are thick in poly mags for a reason! Without that you lose significant rigidity and strength.

If what LRRP has in mind by his "hint hint" is what I described -- a polymer mag with thick walls for that portion which extends below the mag well, and thin walls for the upper part that's contained by the well -- it seems to me that idea could be tested via the method used by sneaky one:

Get one of the straight-body, 20-rd P-Mags, file the interior of the side walls to the needed thickness, and reinforce the exterior of the side walls below the mag well line.

For $14, plus a couple sheets of plastic or aluminum, a bit of glue or duct tape, and some time using a couple of files, one could determine if that concept would actually work.

[Bill Alexander]

For $14 some aluminum or plastic, a bit of glue and duct tape and the expense of a lot of time, one could prove almost without doubt that this is not the way to construct a magazine with even a remote chance of working!

Magazines require a stable design with correctly manufactured parts and mostly expensive tooling (to maintain repeatable stability)

If one stops to think, the route to a polymer magazine is through a hybrid design as demonstrated in this thread, hell the base design lies within these pages. The trick is to stop rushing and think about what you want to actually achieve. Take the materials you are considering and examine carefully how they respond to the loadings you are imposing. Look at the manufacturing routes and the most effective way to combine the materials to get to where you want. Look at your design envelope. Start by listing the properties you need within the sections of the magazine and then select materials based upon this. The figure how they must interact to get the best contribution from each. No! I am not going to teach everyone and the world composite engineering.

The magazine design exists in concept and we are slowly progressing towards a possible solution. Tooling cost is the biggest impediment as there is a co-molding component which hugely increases costs. In the meantime we have a solid supply from ASC and D&H are moving happily forward.

[LRRPF52]

Roger that. Injection molding plates are $10k+ per, and that's if you have them made in the People's Republic of Communist China.

I think there's enough strength in the front of the mag and the rear of the mag, but I have no real issues with my CProducts mags anyway...so far, other than the sharp edges on the floor plate and bottom of the mag body. I'll probably get Ranger plates to mitigate the snag hazard for my skin and clothing...

[BjornF16]

I'll probably get Ranger plates to mitigate the snag hazard for my skin and clothing...

Will those fit the 4/10 round magazines?

[LRRPF52]

Not sure...I've always seen them on 30rd mags.

[Rust]

I use the ranger plates on my c-products 10 round mags. They work quite well on them. The angle of the floor plate is a little different than a 223/556 mag but they lock up solidly. The one thing I have had to do with them was to trim the spring stack down on the 5 round mags so they would fit all 5 rounds.

[ofreen]

For what it is worth, I received 3 of the AR Stoner marked 10 round mags from Midway last week and took them out a couple of days ago. They all worked correctly. The only issue with one of them is getting the 10th round in is a little stiff.

[Rambozo]

No, it doesn't. A polymer mag could be made with thick walls for that portion which extends below the mag well, and thin walls for the upper part that's contained by the well. The mag well would reinforce the top part of the magazine, preventing the mag from bulging after it's inserted.

However, isn't it likely the top part of a loaded mag would bulge enough to hinder (if not prevent) insertion into the mag well, in addition to keeping a full or partially full mag from dropping free?

Why is wall thickness even an issue? Couldn't you just keep the thickness the same and adjust the stack width by increasing magazine length? It just be a longer magazine with a narrower stack. Why wouldn't that work?

[stanc]

Why is wall thickness even an issue? Couldn't you just keep the thickness the same and adjust the stack width by increasing magazine length? It just be a longer magazine with a narrower stack. Why wouldn't that work?

I think a "proper" double stack is necessary for two reasons:

(1) to keep magazine length to a minimum; and (2) to correctly align the top rounds with the barrel feed ramps.

What you propose would result in a significantly longer and heavier magazine, and because of the reduced stack width, it might not permit reliable chambering.

[pinzgauer]

You guys need to go back and look at the photo's I posted. The narrower stack creates spreading forces from the springs which cause the mag to bulge badly, much worse than it does with a proper stack. IE: The springs creates sideways (spreading) force rather than just vertical. In a proper stack each cartridge is in contact with the ones directly above and below in addition to the opposite column. Narrow stack only contacts at angles, creating the spreading force.

Regarding thinner walls, there is a reason the magpuls are so thick... it's about the only way without steel reinforcement to keep the walls from flexing and allowing the feed lips to spread. This is the problem with many past plastic mags, and even some current ones. drop or even jar the mag while not in the gun, it flexes, and rounds come spewing out. (Ram-line mini-14/AR mags were notorious about this, as are some others).

There is a reason even magpul provides a cover.... it takes the spring pressure off the lips and eliminates any chance of flex out of the gun. For the most part you can rap a 5.56 magpul and it won't spew cartridges though, but it's right at the ragged edge.

[stanc]

You guys need to go back and look at the photo's I posted. The narrower stack creates spreading forces from the springs which cause the mag to bulge badly, much worse than it does with a proper stack. IE: The springs creates sideways (spreading) force rather than just vertical. In a proper stack each cartridge is in contact with the ones directly above and below in addition to the opposite column. Narrow stack only contacts at angles, creating the spreading force.

Waddaya mean, "You guys"? :p

I understand the issues, but I do think it'd be possible to build a magazine like Rambozo proposes. Make the walls thick enough and they won't flex even with the narrower cartridge stack. The trouble is, such a magazine almost certainly wouldn't be viable for use in existing rifles.

[pinzgauer]

Waddaya mean, "You guys"? :p

Sorry, did not mean that the way it sounded. How bout: "there is a visual depiction of the issues caused by the narrow stack in an earlier post which may prove informative".

I understand the issues, but I do think it'd be possible to build a magazine like Rambozo proposes. Make the walls thick enough and they won't flex even with the narrower cartridge stack. The trouble is, such a magazine almost certainly wouldn't be viable for use in existing rifles.

Sure, you could make a Grendel / 6.8 pmag if it did not have to fit in standard mag wells. I'm sure there would be a huge market for that! From memory I think there is at least one plastic AR-10 mag. (Magpul 20 rd??)

wait, I see a market for filler blocks to allow AR-10 mags to be used in grendel barrelled AR-10's.

[stanc]

Sorry, did not mean that the way it sounded. How bout: "there is a visual depiction of the issues caused by the narrow stack in an earlier post which may prove informative".

Nope. That's saying the same thing, just in different words.

As I said, I understand the issues, so I won't learn anything I didn't already know by going back and rereading your earlier post.

Sure, you could make a Grendel / 6.8 pmag if it did not have to fit in standard mag wells. I'm sure there would be a huge market for that! From memory I think there is at least one plastic AR-10 mag. (Magpul 20 rd??)

wait, I see a market for filler blocks to allow AR-10 mags to be used in grendel barrelled AR-10's.

Ah, sarcasm. Ain't it fun to indulge in?

But, I think such an extra-thick walled magazine would fit in standard mag wells. The reason I doubt it'd be viable is because the closer spacing of the cartridges might not align properly with the feed ramps, and also because most shooters wouldn't like the extra-long mag.

[Rambozo]

I think a "proper" double stack is necessary for two reasons:

(1) to keep magazine length to a minimum; and (2) to correctly align the top rounds with the barrel feed ramps.

What you propose would result in a significantly longer and heavier magazine, and because of the reduced stack width, it might not permit reliable chambering.

I doubt that it would require a significant shift in the stack. Still, it isn't as if feed lip, follower, or mag geometry can't be also tailored to fit the different stack width.

[pinzgauer]

But, I think such an extra-thick walled magazine would fit in standard mag wells. The reason I doubt it'd be viable is because the closer spacing of the cartridges might not align properly with the feed ramps, and also because most shooters wouldn't like the extra-long mag.

OK, gotcha. Make the mag walls thicker to handle the side pressure due to the narrow stack.

You'd probably be down to a 15-20 round mag to keep the same form factor as a 5.56 30 round. You'd have to really want a plastic mag badly to accept that compromise, especially when 25 round metal mags work fine.