could you have a steel case like the FN, but with a SIG style steel base, to allow high pressures too?  or combine the steel base with a polymer case

The True Velocity polymer case already has a steel base.  It would be possible to make a two-part steel case, but that would likely add cost.  It would probably make more sense to just design a one-piece steel case that could handle higher pressures.   

At this point in time, it is unclear whether raising max chamber pressure is the best option.  There are advantages, for example, more work can be done in a shorter distance, meaning shorter barrels for the same velocity, but there is not yet a lot of experience to know the tradeoffs.  Some potential downsides are: more expensive materials, reduced service life of components,  significant weight increase and sensitivity to dirt, sand, snow, etc.

YouTube

Does The US Military's New Combat Rifle Kinda Suck?

Today we take a look at the military's new combat rifle, the XM7.Be sure to save 25% at Sylvan Arms with code "Brandon"Thanks to SDI! Again, it's SDI.edu for...

He mentions several issues with his 13" 7.62x51 version.

-HEAVY. Whereas the NGSW was quoted at 8.38lbs, he says his 7.62 13" clocks in at a whopping 8.9lbs. SIG themselves list the 13" 7.62 at 8.6lbs. Whether this means the NGSW will also be heavier is unknown, but SIG's past issues with the MCX 5.56 platform has been one of ever increasing weight. 

-Charging handle is very stiff. The Spear uses a unusual, very long and skinny recoil spring. He describes the T-handle as borderline unusable, while the side charging handle is very stiff. Much stiffer than the 7.62 SCAR 17.

-Magazine over-insertion. This one is surprising - a too firm insertion of the magazine will cause it to over insert and jam the weapon, preventing the bolt from being able to close / chamber a new round. From the video this happens with not all that much force either; well below the level of force one would expect an adrenalized soldier to use in a firefight. This is probably easy to solve, but until it's solved its a potentially lethal flaw. 

Recent twitter post from PEO Soldier

https://twitter.com/PEOSoldier/status/1661454518435848193

PdM Next Gen Squad Weapons recently took delivery of #XM7 Rifles and #XM250 Automatic Rifles for Production Quality Testing. Testing has begun and will finish in August. Be sure to check back for updates as we progress through PQT. This summer is really heating up!”

Potential design flaw for NGSW XM7?

Recently its been discovered that the SPEAR-LT (5.56 civilian/leo version of 6.8 SPEAR XM7) has issues with barrel shifting upon load / impact.

Basically if lateral pressure is applied to the barrel it will lose zero - and stay off target even once the pressure is no longer applied. Ie you whack the barrel going in a door, the barrel can get canted to the left and stay a bit canted.

Why is unknown yet, but most likely culprit is some flaw in the barrel to receiver interface.

YouTube

SIG Sauer Firearms MCX Spear LT Barrel Deflection PART THREE

This is the 3rd and FINAL installment of the MCX Spear LT and the barrel issues that we saw. In this video, we explore MCX barrel deviation and provide valu...

2nd source:

https://www.instagram.com/reel/CsmmB6-tnFa/

Claim that this is a 7.62/6.8 SPEAR with same issue (but little further context given)

https://www.instagram.com/reel/CsrOkiwoKup/

Google drive detailed Analysis (excellent)

https://drive.google.com/file/d/17d-jDJePHyNIDEIONoofD7VI7Ys8qJfk/view

Excerpt; problem seems more acute with left pressure vs right

And another test with near identical results

AS I understand it the barrel doesn't shift, the handguard does and it only effects POI IF using sights mounted to the handguard.

Harrison Beene (harrisonbeen) said:

AS I understand it the barrel doesn't shift, the handguard does and it only effects POI IF using sights mounted to the handguard

From the video test, it seems the barrel is indeed shifting.

He has the green laser mounted to the receiver (not the rail) and then has a laser boresight in the weapons chamber, showing where the barrel is oriented. At the start of the test both lasers are zero'd dead true one on top of the other. Then by moving the barrel the red boresighted laser shifts permanently/semi permanently to one side or the other, while the green laser mounted to the receiver stays in its initial centered zero. 

It is unknown to what extent this issue exists ie just some guns, just the 5.56 guns, or the entire 5.56-7.62-6.8 SPEAR family. 

I'll update with any more info I can find.

*edit* a new video shows the barrel is very easy to move.

YouTube

Sig Spear Wobbly Barrel #sigsauer

I can't tell from that if the barrel is moving in the receiver or if the handrail is moving in relation to the barrel.

I can make my rifle do that if I loosen all the screws.

I get it, there are 10s of thousands of people that hate the SIG deal, the caliber choice, the ideas etc.

In 2007 I spent about $40,000 trying to show the military that if the 6.8SPC barrels were made to the correct specs(different from what the mainstream is still producing) they could propel 110gr bullets to 2800fps out of a 16" barrel just like Holland, Murray and Lawton said it could. Sure I proved it, did it matter, no it didn't because Mattis couldn't get approval from congress even though he thought the 6.8 would be a great improvement.  Now I don't waste time thinking about what the military should do, I just make whatever wildcat I think would work best for me and shoot it.

Everyone thought the SCAR was the best thing since sliced bread, same with the 416, didn't last long did it?  All the guys that think we need something besides a 5.56 in a DI M4 are still shooting a 5.56 in a M4. The questions I have now is, just because the military awards contracts does it really mean the military will finally change or are they just testing something else for a few years and wasting a lot of tax money.  2-How long does some other caliber/rifle need to be fielded for it to be considered a change?

Sig Sauer USA  aka ''designed on computer tested on the customer'' so what is new, the product they launch is typically trash for the first 2+ years before they come up with an improved version.

Mr. T (MrT4) said:

the product they launch is typically trash for the first 2+ years before they come up with an improved version

Well whats odd here is this is the 3rd iteration of the MCX, which has been on the market since ~2015. And the SPEAR is based on work done for the NGSW, which we know has been getting tested for a few years now. 

...

It's funny you mention 'designed on the computer.' 

The Air Force was recently saying much the same - that computer simulation is not an adequate replacement for real world testing.

https://www.thedrive.com/the-war-zone/air-force-boss-gives-reality-check-on-over-hyped-digital-engineering-revolution