https://www.gunsandammo.com/editorial/true-velocitys-new-polymer-cased-ammuni...




Now what is radical to us reloaders is that the extended steel primer portion of the combined metal/polymer case (protruding on down into the chamber and acting much like the pressure holding brass head portion on a shotgun case) means the polymer case is able to handle much higher pressures than a brass case before the head/primer area deforms.

Those that are old enough and can remember the old Steelhead cases on 270 rifles understand this point -- while Steelheads were VERY expensive these commercial available polymer cases are actually quite a bit cheaper than normal brass cases.

The US military is using these cases to save weight and transport costs -- they are 40% lighter which cuts out ~ 40% ~ of the fuel cost to airfreight them all over the world.

They run fine in STANDARD GUNS and MACHINE GUNS perform just dandy and the new ammo is more accurate than brass cased ammo.

Up at the top of all my posts is the reference link for the source article.

The yellow orange device is called a Zero Spindle, we used them to check chuck and spindle run outs at B&D back in the day.



In that article at the top of my original post they spend a half a page addressing your exact question.  

It is well worth reading the whole article IMHO if you are a reloader or shooter.



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https://www.thefirearmblog.com/blog/2019/04/04/usmc-to-by-2-4-million-rounds-...

USMC to Buy 2.4 Million Rounds of Polymer-Cased .50 Calibre Ammunition

This stuff is headed to the war zones in a 2.4 million round live fire test.

In black powder circles, they are making pellets that you drop in the bore.
I wonder if the make a igniter to replace the cap.  

I suspect that resizing them with your existing brass cartridge dies might wind up a little bit off spec on neck and other shoulder type dimensions -- but in theory the plastic cases should be good for at least one other use before they neck split (or separate at the shoulder or do whatever else it is that they are gonna do).

Since the cases are fairly flexible, for reuse in bolt guns you may just put powder in them after decapping and new primer seating and shove a sealant coated slug back down the neck to the correct distance.   Bolt closure force will make the case shoulder length follow your chamber pretty much exactly, which will make the rounds "more accurate" compared to resized brass cases.

Since I see a red sealant on all the bullets shown so far you may have to do that each time as well.

Lee collet action neck sizer dies with one very minor mod to make room for the installed bullet (dirt easy to do this hole drilling once and then it ignores all installed bullet lengths and allows a loaded case to be "collet adjusted" for neck diameter and shoulder length by whatever amount is needed).   No more chasing reforming donuts on necks or wrong shoulder lengths or side bulged bases ...... well worth the $24 to buy that particular die per caliber that you have those kind of issues to deal with.    My guess is that they would work to adjust plastic rounds as well.

My hope is that the forceful action of bolt action rifles will have more than enough force to MAKE the plastic case fit and conform to the shoulder length and chamber of your gun, especially if it were fired there previously.

https://www.range365.com/end-brass-cartridge-cases



A company called Shell Shock Technologies (SST) has a new two-piece, nickel-aluminum-stainless steel 9mm NAS3 case that has a list of advantages, according to the, namely that it’s stronger, cheaper, and half the weight of brass. That’s big for the military, law enforcement, and anyone else who carries a number of spare magazines on the regular.

It has better corrosion resistance than brass and it’s magnetic, so spent cases at the range can be picked up easily.

These points should raise the eyebrows of anyone who reloads: the NAS3 cases have more internal volume, provide more consistent ignition, develop +P velocities without +P pressures, and—ready?—the cases won’t stretch, meaning there is no trimming required when reloading, and they can withstand 40 or more reloads.


Oh well, brass as a material is simply too weak to do the job that is needed with new high pressure guns and the proposed high pressure rounds .......    it weighs way too much for air shipping    .......   and it costs too much as a material for something that always fails at high pressure.

This stainless steel cup bottomed shell and the crimped on color anodized T-6 aluminum alloy head has a whole lot going for it, too, as it avoids all the weaknesses of plastic over-molded parts.  

If the goal is pressures north of 80,000 psi I'd put my money on this pony .......            


BTW, we need a better grade of primer material too.   Soft stainless steel primer cups ????

Coming up from the age of black powder, brass was a common material and was OK for black powder pressures.

In the nitro smokeless age, I have had it leak pressure a dozen times in very minor fashions around primers that were seated in burred holes (mostly my fault).

I have had it flow like water twice (both 7mm Remington Magnum rounds that I was really really pushing it --- strictly my fault again).  



Going for this new super fast stuff, brass ain't nearly good enough as a case material .......    

My vote is for stainless steel and heat treated & plated (or anodized) T-6 aluminum (cheaper, stronger and a whole lot better).