65 Receiver Set with Polymer mags from PF (HOPEFULLY)

[PrecisionFirearms]

No - It wont work so the idea is not worth pursuing.

Settled a old question decisively.

I don't think we have the power to have Magpul make a 6.5 Grendel Pmag. I will however look around at SHOT for another company that may be willing to produce a polymer mag. Not Lancer since they still have steel feed lips.

I would like to see a polymer mag that doesn't score the brass, allows drops, can be run over with a tank, get shot through, survives a sand storm, and still perform flawlessly and reload itself.

[cory]

There is no 30 round plastic or metal mag for the Grendel. If some billionaire wished to make one they could take the width of the AK mag and design it to the Grendel case taper. If a lower could be made with the new mags and match the AR platform then it would be feasible, but then it would only work with the new Grendel mags. All of my older AA magazines have functioned flawlessly in my rifles but a strong 30 round P-mag would be nice . If a dedicated 6.5 Grendel rifle were built with new mags it would be another choice for for Grendel owners to argue about pros and cons LOL.

Exactly. The curvature may not work for the Grendel, but this does give us a good idea of where to start at looking for the nominal width and the amount of material it'll take to make a polymer Grendel mag that won't swell.

Whats the outer width of the AK Pmag? Any chance it's less than the inner width of the AR15 magwell?

[cory]

I have not failed. I've just found 10,000 ways that won't work.

Thomas A. Edison

[PrecisionFirearms]

LOL Cory!

AK Pmag 1.010
AR Mag Well .920

308 AR Pmag 1.110

[Nukes]

I have not failed. I've just found 10,000 ways that won't work.

Thomas A. Edison

Nikola Tesla wasn't laughing.

[montana]

Nikola Tesla wasn't laughing.

Now that's the truth!

[LRRPF52]

Yeah, Edison definitely kept trying, but his approach was to stab in the dark with very wide parameters. Tesla knew the advanced mathematics and electron flow theory, and was always thinking about the most efficient ways to do things with minimal loss of energy.

If he were still alive, we'd have Phased Plasma Rifles in the 40 W range. If you stack a bunch of phased primary resonators from the Tesla Coil capacitor, in a handheld device, you could have something matching that description actually.

Edison is an example of what not to do. Tesla looked forward to working with him, then left his employ after accepting that Edison was clueless about the theory and science behind distribution of electricity.

The whole idea here is pushing the performance of the Grendel case with a new receiver set that can take polymer mags, but why then limit ourselves to a Grendel case if we're building a new receiver set and magazine.

One answer to that could be that the AR15 magazine size is one of the most efficient ways of carrying a lot of ammunition in a small space on the soldier's load, which is a military application only problem and solution. We then have to ask where the optimum magazine size/capacity/cartridge performance/weight data points are.

If 5.56 NATO STANAG mag size/capacity/performance/weight is considered the minimum, and 7.62 NATO SR25 is considered the maximum, where do you want to cover down?

The harder we push for performance, the closer we get to the penalties of 7.62 NATO.
The tighter we restrict to 5.56 NATO dimensions, the more the existing 6.5 Grendel advocates for itself.

If we want to push the pressures, we definitely need a whole new upper receiver, barrel extension, and barrel tenon diameter. There are a bunch of guys learning the hard way right now about this with .473" diameter head cases stuffed into the AR15, pushing the pressures from 55-60ksi with only .136" wall thickness.

[Michael]

Yeah, Edison definitely kept trying, but his approach was to stab in the dark with very wide parameters. Tesla knew the advanced mathematics and electron flow theory, and was always thinking about the most efficient ways to do things with minimal loss of energy.

If he were still alive, we'd have Phased Plasma Rifles in the 40 W range. If you stack a bunch of phased primary resonators from the Tesla Coil capacitor, in a handheld device, you could have something matching that description actually.

Edison is an example of what not to do. Tesla looked forward to working with him, then left his employ after accepting that Edison was clueless about the theory and science behind distribution of electricity.

The whole idea here is pushing the performance of the Grendel case with a new receiver set that can take polymer mags, but why then limit ourselves to a Grendel case if we're building a new receiver set and magazine.

One answer to that could be that the AR15 magazine size is one of the most efficient ways of carrying a lot of ammunition in a small space on the soldier's load, which is a military application only problem and solution. We then have to ask where the optimum magazine size/capacity/cartridge performance/weight data points are.

If 5.56 NATO STANAG mag size/capacity/performance/weight is considered the minimum, and 7.62 NATO SR25 is considered the maximum, where do you want to cover down?

The harder we push for performance, the closer we get to the penalties of 7.62 NATO.
The tighter we restrict to 5.56 NATO dimensions, the more the existing 6.5 Grendel advocates for itself.

If we want to push the pressures, we definitely need a whole new upper receiver, barrel extension, and barrel tenon diameter. There are a bunch of guys learning the hard way right now about this with .473" diameter head cases stuffed into the AR15, pushing the pressures from 55-60ksi with only .136" wall thickness.

As ussual, well stated.

Super Moderator...snicker...Sorry...puts me in a mind of Wile E. Coyote...Super Genius.

Sorry, been off the net a while.

[NugginFutz]

If we want to push the pressures, we definitely need a whole new upper receiver, barrel extension, and barrel tenon diameter. There are a bunch of guys learning the hard way right now about this with .473" diameter head cases stuffed into the AR15, pushing the pressures from 55-60ksi with only .136" wall thickness.

Which group of entrepreneurs is working through this? Have they experienced any KB's or bolt / extension failures? I'm aware of some new wildcatting going on, with some very aggressive expectations. I've not heard of any setbacks, though.

[PrecisionFirearms]

LRRPF52

We will do some talking over dinner at SHOT!

Mark Hostetter

[cory]

....
The whole idea here is pushing the performance of the Grendel case with a new receiver set that can take polymer mags, but why then limit ourselves to a Grendel case if we're building a new receiver set and magazine.

One answer to that could be that the AR15 magazine size is one of the most efficient ways of carrying a lot of ammunition in a small space on the soldier's load, which is a military application only problem and solution. We then have to ask where the optimum magazine size/capacity/cartridge performance/weight data points are.

If 5.56 NATO STANAG mag size/capacity/performance/weight is considered the minimum, and 7.62 NATO SR25 is considered the maximum, where do you want to cover down?

The harder we push for performance, the closer we get to the penalties of 7.62 NATO.
The tighter we restrict to 5.56 NATO dimensions, the more the existing 6.5 Grendel advocates for itself.

If we want to push the pressures, we definitely need a whole new upper receiver, barrel extension, and barrel tenon diameter. There are a bunch of guys learning the hard way right now about this with .473" diameter head cases stuffed into the AR15, pushing the pressures from 55-60ksi with only .136" wall thickness.

Are you not the one who advocates for the Grendel to be used as a LMG and DMR/Light Sniper Rifle? The latter would never happen with the current magazine options. And no reliability is not the problem. It's that annoying rattle when you load the magazines near max. It's rather hard to conceal your position when every time you move, it sounds like a monkey playing in the junkyard.

The fact is the Grendel in the AR15 does leave performance on the table, even if we want to keep the 55ksi max. This is especially true with solids. It would be nice if we could make use of the Barnes 127gr LRX. To bad we don't have a magazine that would allow us to load it long enough to get useable velocity.

You may think that the performance increase is negligible and I do tend to side with you. However, the market has shown that it'll pay premiums for marginal improvements (weight reduction, .....). The 6.8 has taken a huge share of the marketplace because of nothing other than dedicated marketing. We need to do something to take back that market share. Only then will we get more Grendel dedicated products brought to the market. I want more affordable bullet options! haha

Nobody, who has ever did a magazine change under pressure, will tell you that .308 mags are the answer (except some NFL lineman). Forget about magazine retention. They're just to big.

We need 25-30 magazines that work reliably and don't rattle. Narrowing the ID of the magazine maybe a solution for getting a polymer magazine that doesn't rattle. However, I suspect that this magazine in a 25-30 variant would be so long that firing from the prone would not be feasible.

Of course the smallest package that meets requirements is always the best answer on the battlefield. The 5.56 does a great job with this. However, that package seems it's just to small to meet requirements. We may need to look at going the width of the AR10 magwell, with the length + 0.100" of the AR15 magwell. We can still keep weight and size down by keeping AR15 BCG and extension.

[LRRPF52]

Which group of entrepreneurs is working through this? Have they experienced any KB's or bolt / extension failures? I'm aware of some new wildcatting going on, with some very aggressive expectations. I've not heard of any setbacks, though.

Word I'm getting through back channels right now is unusual brass diameter stretching just above the web, which is exactly what you would expect. Chambers are egging out, as guys have been encouraged to throttle them to 60ksi no problem. It will all be buried, but I don't expect Kabooms, just case head separations when midway through the chamber, the diameter increases, and the extraction cycle does what it does under pressure. I doubt the extensions or bolts will fail. Chamber walls...that's the weakness. Run the hoop stress on a .136" chamber wall in the AR15 diameter tenon even at 55ksi and see what happens.

http://lassengunsmithing.com/html/CylinderStress.htm

Use the thick wall cylinder function on the right.
Inside diameter = inside of the chamber. Check the diagram for the chamber prints and enter that data.
Wall thickness = minimum od of the thread relief - ID /2
Chamber pressure = the working pressure you are using
Then hit calculate.
There's a reason the .458 SOCOM and .50 Beowulf have operating pressures in the mid-30ksi range, and it isn't because of the bolt.

[LRRPF52]

Are you not the one who advocates for the Grendel to be used as a LMG and DMR/Light Sniper Rifle? The latter would never happen with the current magazine options. And no reliability is not the problem. It's that annoying rattle when you load the magazines near max. It's rather hard to conceal your position when every time you move, it sounds like a monkey playing in the junkyard.

The fact is the Grendel in the AR15 does leave performance on the table, even if we want to keep the 55ksi max. This is especially true with solids. It would be nice if we could make use of the Barnes 127gr LRX. To bad we don't have a magazine that would allow us to load it long enough to get useable velocity.

You may think that the performance increase is negligible and I do tend to side with you. However, the market has shown that it'll pay premiums for marginal improvements (weight reduction, .....). The 6.8 has taken a huge share of the marketplace because of nothing other than dedicated marketing. We need to do something to take back that market share. Only then will we get more Grendel dedicated products brought to the market. I want more affordable bullet options! haha

Nobody, who has ever did a magazine change under pressure, will tell you that .308 mags are the answer (except some NFL lineman). Forget about magazine retention. They're just to big.

We need 25-30 magazines that work reliably and don't rattle. Narrowing the ID of the magazine maybe a solution for getting a polymer magazine that doesn't rattle. However, I suspect that this magazine in a 25-30 variant would be so long that firing from the prone would not be feasible.

Of course the smallest package that meets requirements is always the best answer on the battlefield. The 5.56 does a great job with this. However, that package seems it's just to small to meet requirements. We may need to look at going the width of the AR10 magwell, with the length + 0.100" of the AR15 magwell. We can still keep weight and size down by keeping AR15 BCG and extension.

An LMG will be built around the cartridge, once the cartridge performance requirements are established.

For a DM/SASS carbine, I agree that a rifle needs to built around the cartridge. There is a lot of competition right now for such a system, so any discussions about it are best kept offline.

[jurassic]

Have you done anything to the PRI mags to make them work?

[PrecisionFirearms]

Nope, Load 'em and use 'em

[jurassic]

Nope, Load 'em and use 'em

Thanks.