Reloading for PS90

Reloading info for the 5.7x28mm

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JPiet
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Reloading for PS90

Post by JPiet » 02 Jan 2020, 10:04

Hi guys, I'm new here, so greetings from frosty Finland...

I rescued a PS90 from stupid legislation-thing recently (they passed new firearms act here that bans SBR's for good...). I run a gunsmith's shop so no problems with licenses.

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However, factory ammo seems not to be available in any form in Europe, only way to run this thing is reloading. Got a Hornady die set from Brownells and very limited supply of brass... Couple of things concern me a little though...

1. I'm a bit scared to go for shotgun powders, but it seems rifle powders have their own issues. Vihtavuori is my first choice, so I'm starting with N110 and 36 grain varmint grenades. YouTube has told me about pressure not making any actual marks before catastrophe and the lacquer thing.
2. Started with guesstimate 7 grain load. This is slower powder than most of you guys use, but I'm guessing that those loads are designed for pistol barrel, so my 260 mm barrel should help with that, right?
3. No time yet to hit the range with proper ladder-test, but fired two rounds in my basement. The shoulder travels! Please see pic. Normal or down with the load? From top, 7 grs fired brass, 7,5 grains and formatted.

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Any advice on the load? Hoping to find the time to get to the range during weekend.

Cheers,
Janne Pietiläinen

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panzermk2
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Re: Reloading for PS90

Post by panzermk2 » 03 Jan 2020, 12:54

Welcome to the forum.

You need to spend some time in our reloading section. It has detailed reloading data including powder selections, charges and projectiles. The loads list have bee vetted by our group including the moderator of that section.
Jay Wolf
Pr. Elite Ammunition

"Engineers, the oompa-loompas of science!"

Be'ein Tachbulot Yipol Am Veteshua Berov Yoetz
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FNFbobcat
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Re: Reloading for PS90

Post by FNFbobcat » 22 Nov 2020, 18:34

Thanks for posting the pictures.

This confirms my suspicion about the cause of case stretching.

When FNH designed this cartridge, reliability was obviously a primary concern. I feel confident that brass preservation for reloading was not. In fact. I suspect FN's lawyers would be happy if it were not possible to reload the 5.7x28.
I have purchased once fired brass without knowledge of which type of firearm it was shot from. About half is unusable because it shows the telltale ring just below the shoulder that indicates excessive shoulder movement and incipient case failure.

Brass integrity in this cartridge is dependent upon the bullet exiting the muzzle and allowing pressure to drop before the barrel and bolt face disengage. This is only possible with light bullets, fast powders and short barrels. I suspect that stretched brass is a result of absence of one or more of these three conditions. The problem is exacerbated in the 90 by the straight blow-back action.

Has anyone here been able to fire brass from their P90/PS90 without experiencing significant shoulder movement? Without further evidence, I would consider brass fired from a P/PS 90 to be un-reloadable without the expectation of subsequent shoulder separation.

Thanks for feedback.

Buffman
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Re: Reloading for PS90

Post by Buffman » 27 Nov 2020, 20:31

The DBX is the only 5.7 gun so far that has literally no shoulder movement.

Skywriter25
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Re: Reloading for PS90

Post by Skywriter25 » 09 Jan 2021, 17:53

FNFbobcat wrote:
22 Nov 2020, 18:34
...
Has anyone here been able to fire brass from their P90/PS90 without experiencing significant shoulder movement? Without further evidence, I would consider brass fired from a P/PS 90 to be un-reloadable without the expectation of subsequent shoulder separation.
...
Hello FNFbobcat,

In answer to your question to shoulder movement on the PS90...

I have a PS90 and am just getting into reloading the 5.7x28 for it. I have around 150 cases fired from that gun. The once-fired cases (some FN and Federal) all seem fine on shoulder movement - my understanding is that FN makes all the brass anyway. My "project" is to determine if, and how many times, I can safely reload the 5.7x28 before the case is unsafe.

Here is what I have done so far (using an unloaded, never-fired factory case for control):

I hand cleaned 10 cases and resized them with REDDING dies. The polymer coating looks brand new and the case dimensions were good. I reloaded the 10 cases using 40 gr Hornady V-MAX bullets, 4.4 gr of Hodgdon universal powder and TulAmmo KVB-223 small rifle primers. All 10 fired and cycled perfectly. The grouping was close to the 10 factory loaded rounds I used as control so the reloads seem to have equivalent accuracy. The recoil seemed slightly less with the reloads (not that the PS90 has a lot of recoil, anyway). I didn't have a chronograph so I couldn't compare velocity but I have one on order to use in my next round of tests.

After that second firing, the 10 cases still looked fine and the shoulders were good. I cleaned, resized and inspected them. Case dimensions were good, but case length was up to around 29.25 mm. When I get the correct length pilot I ordered, I will trim the twice-fired cases and cycle them again.

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panzermk2
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Re: Reloading for PS90

Post by panzermk2 » 11 Jan 2021, 10:57

More shoulder movement on the PS90 over the pistol is normal.

Do you have pictures of your brass so we can see the amount of movement ?
Jay Wolf
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"Engineers, the oompa-loompas of science!"

Be'ein Tachbulot Yipol Am Veteshua Berov Yoetz
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