Awesome pictures, Trent. Since you seem to be the go-to guy of anything PS90, I have a question for you. Have you handled/fired a P90 or a PS90 that's been converted to a SBR with 10.4" barrel?
I am bent on the P90 or facsimile (a converted PS90 in my case) and wonder what differences in accuracy a loss of 5" gets you.
We got SBR rights recently in IL for C&R holders, but last I checked, the ATF was still denying applications saying "legislative intent wasn't for..." (can't remember the rest.
So the two representatives which wrote / sponsored the bill in each house wrote the ATF letters of clarification specifying legislative intent. I was going to give it some time before I send in my app.
I have one PS90 rifle I will get converted to an SBR next year - and also have an accuracy benchmark well established. So I'll know if it loses anything.
I'm also always googling American Eagle FMJ (or AE5728A) vs ballistic gel with no luck. I'd like to see the results and suspect it might be a bit more impressive than the energies my suggest. I'm curious at what point that stubby 40gr FMJ tumbles. I'm aware it's a round intended for plinking, but I like the idea of something that provides a bit more penetration than explosive expansion.
American Eagle FMJ was a very accurate load but I had feed problems with the batch of ammo I had. Next year I'll try it again with a different lot; if it doesn't get better, I'll disavow the ammo entirely.
When I roll my own ammo this winter, things will get more interesting. It will be tough to beat the accuracy of the Hornaday 40 gr round, but I'll try.
What am I talking about?! It's not like I'd ever plan on using it for defense or anything....
Again, 50 rounds affords one a lot of follow up shots.
I actually have both AE5728A and SS195SR on hand and I don't even have the PS90 yet. I find if I at least have the ammo for a firearm I want, I end up with it... though I've had this ammo for a while now.
I have only shot the SS195LF. Not familiar with "SR". I have a few boxes of SS195LF left, I use it in my pistol when I'm wanting more accuracy; for some reason it shoots a LOT better in the pistol. The downside is it isn't shelf-stable, the primers they use purportedly have a shelf life of 7-10 years. I'm keeping the last few boxes as a reference point so I have a comparator when I make my own ammo this winter.
You have probably researched this, but just in case, if you decide to reload for the 5.7X28, it has its own little idiosyncrasies, mostly concerning the shoulder. The 5.7 has a ton of good info about it. I even have a couple of old threads there from when I tried it out in an AR 57. The PS90 is a better platform for the 5.7 IMHO.
Yes, the case dimensions are critical. The earliest dies produced by Lee were straight walled and caused all sorts of problems, leading many to think the round wasn't reloadable at all, since it'd jam in the magazine. Newer dies are dimensionally accurate. 5.7x28 has a very slight taper to the case, and the LENGTH of the case from base to shoulder has to be *precise*.
When it's fired, the case expands and grabs the chamber - as the pressure drops, the dry film lube coating allows the cartridge to begin sliding rearward. There is no "locking lugs" on the PS90, as there is with conventional rifles, it's straight blowback operation.
This means that the case WILL stretch significantly.
Now, that tapered case, and the shoulder at the end of it, are critical to headspacing (there are no locking lugs). Fortunately the PS90 was gifted with a "safety sear" (serving the same function as an auto-sear in machineguns), not allowing the rifle to fire if the bolt isn't fully forward. Lack of a forward assist means you can't get that round in battery if it is dimensionally incorrect; so it's pretty safe.
However! Due to the relative ease of converting a firearm with a "safety sear" to full automatic operation, some newer models LACK the safety sear entirely.
This is a BIG problem for reloading as you can actually chamber and fire out of battery rounds which are not dimensionally correct. The result of firing an unsupported 5.7x28mm round in a rifle is catastrophic.
Before shooting reloads, make sure your rifle DOES have the safety sear in the trigger pack. You'll see a little piece in the forward section of the trigger pack, which has a curved knob that sticks up. This rides the bolt, and when it's depressed, releases the hammer to the second stage - where it is held back by the main sear.
(Also, if you own an older PS90 gun, take care not to try to mess with the trigger pack, it's not user servicable, there are blind-pins that you can't remove to take parts out of it.)
Anyway enough of that side-track.
The casing itself has that dry film lubricant on it. Many people have tried (and failed) to find another substance that functions the same as it. IF YOU TUMBLE YOUR BRASS YOU WILL STRIP THIS DRY FILM LUBE. You'll know it too, visual inspection will make it look like it's peeling blisters from a sunburn. That case is now junk.
The only way to safely clean the brass is in an ultrasonic cleaner using chemicals which will not strip that dry film lubricant.
Simple Green is one such solvent which is not only non-toxic, but won't strip the dry film lube off of it. It's also readily available (and an
awesome general purpose firearms cleaner...)
Once the casings are clean you have to *carefully* set the sizing dies up so they resize to the precise dimensions (length) of the original cartridge!
After that, it's pretty much just like any other cartridge. Primer, powder, seat a bullet, and done.
(That's the extent of my research so far, from memory, if anyone has stuff to add by all means... add!)