FN 5.7x28

[White35]

New member, looking for some information on a particular question for reloading this cartridge. I've seen over on the fivesevenforum that some/many people can fire 5.7 reloads in the FiveseveN pistol without the lacquer coating on the cases, and it function. I think it seems like this is usually done with a chamber polishing also. My question for people with experience with loading this cartridge, is if I stripped the coating from the cases, and loaded 55gr projos, to fire at slower than normal speeds, say somewhere around 1,000 fps, would these function the pistol just fine, and not cause any danger pressures? I feel like this would work fine but I want to make sure. I do not have a FiveseveN currently but I am saving up for one, so I can't test this out on my own currently. Any help would be much appreciated.

 

[KansasSasquatch]

I believe that it's actually a polymer coating, not lacquer. Personally I wouldn't even try reloading them without the coating. In my experience with a 5.7 pistol, if there's even a tiny spot of the coating missing the chances of having feeding issues is pretty high. I'd also be leery of using a 55gr bullet. 45gr bullets are the heaviest that I've seen published data for. Using a 55gr bullet would eat up case capacity in a cartridge that's already extremely finicky when it comes to pressures. I know that you can find data from other reloaders that have tested their own loads, but I personally won't use that data. You CAN do so at your own risk, but I do NOT advise it.

 

[White35]

I've heard so many terms for the coating I've defaulted to calling it lacquer, seems the most prevalent. And what I've seen so far, there's a fair amount of people on the fivesevenforum that shoot 55gr as subsonics, which is basically what I want to do, just for cheap practice ammo. I joined that forum and asked this same question, no responses after about two days. All the other info is already there basically so I probably won't be active on it, trying to not use more than two forums if possible, I'm also on the 458SOCOM forum. I'll take your warnings into account, but I feel pretty confident 55gr bullets can be loaded safely because people on the fivesevenforums are doing it just fine. Not trying to answer my own question, I just would love to hear from someone that loads 5.7 about their opinions on it. And if it functioned halfway reliably that would be fine for practice, jamming every other round tho would be extremely obnoxious.

 

[KansasSasquatch]

Using 55gr bullets absolutely makes no sense to me. The original purpose of the cartridge was to have a small, fast moving projectile that would defeat light body armor. A 55gr subsonic does not accomplish that. Civilians can't buy "the good stuff" but some of the off-the-shelf offerings will still penetrate some soft armor. Even using 55gr as practice ammo seems pointless, to me, as the point of impact is very likely going to change quite a bit. 40gr Hornady V-Max are used in some of the commercial loadings and they can be had for almost the same price as 55gr FMJ if you buy them in larger quantities.

 

[GBExpat]

Here is a Thread that may be of interest to you:

http://www.thehighroad.org/showthread.php?t=739404&highlight=5.7x28

 

[jmorris]

Never loaded for one but after playing with a P90 a few weeks ago I wouldn't mind having one.

FWIW in the linked post, last photo in post #4, I don't think that kind of damage was caused by .060" setback. Does show some things that are different about the 5.7 pistol though, like the recoil spring over the barrel.

 

[Havok7416]

The exploded FiveSeveN is a fairly famous example of the tempermental nature of the cartridge. In the linked post above or a similar one, Trent mentioned testing American Eagle ammo and getting horrendous setback. His theory was that without the glue that holds in FN bullets, setback would be far more likely.

Issues with the cases, pressure, load range and powder selection have caused me to move my plans for loading 5.7x28 to the back burner.

 

[GBExpat]

After following, with great interest, Trent's Adventures in 5.7x28 Reloading I completely abandoned any thought of owning any 5.7 firearm, since I will not own a CF firearm for which I cannot reasonably reload.

Too bad, because I would really like to own a 5.7 rifle/pistol pair.

 

[Rule3]

After following, with great interest, Trent's Adventures in 5.7x28 Reloading I completely abandoned any thought of owning any 5.7 firearm, since I will not own a CF firearm for which I cannot reasonably reload.

Too bad, because I would really like to own a 5.7 rifle/pistol pair.

+1 on that.

My thoughts also!. I have had several chances to buy a 5.7 like new in box for a very good price. After researching the hassle with loading for it I decided it was not worth it, I have shot them and it is a fun great gun. Actually the factory ammo has not increased very much since it originally came out. It is still around $20 something a box of fifty. But that said, still expensive at the rate I would pull the trigger

There is more to loading the round than just the coating and just no something I would want to fuss with. Sure guys load it but not for me.

 

[Rodentman]

I reload it fine, it's just more time consuming since the cases need to be lubed and trimmed which you rarely need to do with straight walled pistol brass. I use 40g bullets only, and keep the loads reasonable. I wash the brass in soapy water and rinse it rather than tumbling it and I never had an issue with either the pistol or my PS90. And I have an AR upper for it than just hums right along.

It's not my favorite to reload due to the extra time and attention required but I have not had any problems at all.

 

[White35]

Yea I'm about to pick up a 1,000 42gr frangibles for $68 from Rocky Mountain Reloading. I'll stick them back for 5.7 later on, or .223 if nothing else.

 

[KansasSasquatch]

Yea I'm about to pick up a 1,000 42gr frangibles for $68 from Rocky Mountain Reloading. I'll stick them back for 5.7 later on, or .223 if nothing else.

Keep in mind that frangible bullets tend to be longer than lead core bullets of the same weight. This will decrease case capacity and the bullets will have more bearing surface. Both of those will increase pressures (probably dramatically in 5.7x28), so you will probably need to use data for lead core bullets weighing 45gr or 50gr to keep the pressure low enough. OR even better, try to find data for 42gr frangibles, but that probably won't be found in a reloading manual and is still pretty risky.

 

[White35]

Yes I know this, and these are about the same length as 55gr projos.

 

[Trent]

I believe that it's actually a polymer coating, not lacquer.

I've actually drawn my own conclusion that it's nothing more than teflon. No scientific backing to that claim, though. We need someone with one of those fancy apparatus to give us the chemical composition of some scrapings, someday.

To the OP:

My question for people with experience with loading this cartridge, is if I stripped the coating from the cases, and loaded 55gr projos, to fire at slower than normal speeds, say somewhere around 1,000 fps, would these function the pistol just fine, and not cause any danger pressures?

You are courting disaster with this.

It's not about "loading at slower than normal speeds" so much as it is getting that heavy projectile launched with the given combustion space.

The 5.7 pistol is already notoriously tricky to load for and get decent performance because you're dealing with a bottlenecked cartridge with a tiny chamber, and a short barrel. You have to use a powder hot enough to get the bullet moving quickly as it travels those wee few inches, but NOT hot enough to exceed chamber pressure, rupture the (very thin) casing, and cause a catastrophic failure of the (relatively flimsy) frame.

When you strip the "lacquer" you are defeating one of the design elements that *helps* make the round safe. 5.7 works a little different than other firearms in that the chamber is tapered and the casing is DESIGNED to slip and move rearward while it's still under very high pressure; the PS90 and 5.7 are straight blowback. If you defeat this coating the ass end of the cartridge moves but the middle and front of the casing is still seized tightly against the chamber. The casing rips in two and you blow up a gun, and get a trip to the ER to learn what "debraiding a wound" means, and discover how atrociously painful that procedure is. If you are especially unlucky, your wife gets to open the pickle jars for you the rest of your life.

Now, that above scenario is assuming you are using a normal 40 grain bullet. When you use a 55 grain bullet you REALLY up the chances of a case rupturing and ruining your day. When you go from 40 to 55 grain you are now working at a mass 137.5% of the original design.

Remember that old "equal and opposite reaction" fact?

The pressure to get the bullet moving is pushing forwards AND backwards. It now takes FAR more energy - to propel a mass 137% of the original you have to have expend FAR more than 137% energy. the reaction curve of the smokeless powder ignition is rapidly accelerated, as the bullet is getting started slower and the bulk of the powder ignites while the bullet is in the first few mm of travel - smokeless burns faster when it is contained, remember - and the forces involved spike well above what the design was planned for.

The "option" is to use a slower burning powder to offset this ramp up in forces, but there simply isn't enough barrel length to take advantage of it.

Bottom line; do not go through with your idea. It is unsafe.

You may read about people saying "oh it's fine, blahblahblah" - but seriously, the physics behind what is happening is not copacetic. They want to risk their hands and expensive gun, fine. Their hands and gun to risk.

But no way in hell would I ever advise someone that this is a good idea and I'm not going to do that today!

The only stupid question is one that is never asked. Thank you for taking the time to post and learn - I hope what I've written helps you on your decision.

Go buy some 40 gr V-max, use an ultrasonic cleaner with simple green diluted 10:1 for 10 minutes (no more!) to clean your cases, and call it a day man. They'll shoot just fine as long as you stick to published data.

 

[KansasSasquatch]

I've actually drawn my own conclusion that it's nothing more than teflon. No scientific backing to that claim, though. We need someone with one of those fancy apparatus to give us the chemical composition of some scrapings, someday.

Teflon is a polymer. Using teflon would certainly make sense. It's low coefficient of friction, hydrophobic properties, low chemical reactivity, and thermoplasticity would most likely make it a good candidate for a coating on 5.7x28 casings. If it is teflon, heating the brass before sizing could potentially increase the life of the coating. Upon firing the teflon should soften from heat. When it cools it hardens. So resizing could potentially crack the coating. The problem is that the temperature needed to soften teflon is so close to the temperature needed to anneal brass. I guess it doesn't matter. The brass is normally done for before the coating is.

To the OP:

You are courting disaster with this.

I agree. I'm not sure exactly how accurate all of your info is but you've certainly presented it in a logical manner. It would be hard to argue against what you've presented.