5.7x28mm Trials (pic heavy)

[Trent]

Walkalong; I had no idea either. I went to their website to see if they have any replacement parts since I only really need new lenses. On the home page under warranty they listed that info out and I'm like.. Oh REALLY?

Evidently you could hit it with a load of 00-buckshot and be OK - they do say "any condition"...

That's a really neat feature. Not sure what retail is but Midway lists them at $129 (which is a LOT less than I remember paying 8 or 12 or whatever years ago.)

 

[Mr.Revolverguy]

That was one of the factors that persuaded me to purchase this model.

Oh and let me clarify I was not saying Kudo's for shooting your Chrony, it was for all the work your doing

 

[Trent]

Revolverguy; you are welcome.

The saga will continue... I hope you find it useful by the time it's through.

I've got Longshot loads worked up with Remington 7 1/2 and CCI #41 arsenal primers waiting to test, once the Chronograph is fixed up. Both of those are "hotter" primers than the CCI #400 primers so I'm starting the load .5gr lower. I'm planning on doing 4.6 through 5.4gr Longshot powder tests with them, using the 40gr Hornaday V-Max.

I'm also going to proceed with a 5.7 and 5.8gr test load out of the PS90 using CCI#400 to see if I can nail down the "unsafe" level. Want to get velocity data off of those though, so I need to wait for the chrony to work again...

Now that I know there is a noticeable difference with Longshot ignition on "powder forward" or "powder back", I will test this each time.

BTW, a piece of trivia; with a 40gr hornaday bullet seated to match the SS197 round, my cases are "at capacity" at 5.8gr of Longshot. So powder forward or powder back should not make any difference at that point. But that's a pretty hot load out of the rifle. I lost a primer at 2339fps, which is about the mark where 5.8gr would be if the fps gain trend continues past 5.6gr.

Also, I *have* confirmed that the lost primer in the first round of testing at 5.5 grains was due to a misthrow of powder; there were not any serious pressure signs at 5.6 grains, with "powder forward" or "neutral"; however, I had flattened primers, increased recoil, and increased noise with "powder rear".

 

[Trent]

To be continued....

 

[Havok7416]

Trent, any news back from Redding on their dies?

 

[Trent]

Yes when I heard back from Redding, they said "our dies are manufactured to SAAMI specs and we do not customize them." (I'd asked them to turn it down so the shoulder would be shoved back to the correct spot.)

I tried arguing that while the die might be set up to SAAMI specs, the resized rounds definitely are NOT put back to factory spec. No avail. After convincing them it wasn't "user error", they suggested perhaps the die itself was defective and offered a replacement.

By that point I'd moved on to other projects/pursuits. Will pick the 5.7x28 reloading back up next winter. (Too damn busy in spring/summer/fall to bother with reloading; I do all my loading in the winter months)

Hoping this fall I'll have a new lathe to replace my broken one (dead motor). If so I'll turn the die down myself.

 

[barnbwt]

While you're at it, let's all see if there's a way to model the 5.7 ignition somehow. From what I understand, the process is so fast that internal-ballistics programs like Quickload are unable to accurately determine peak pressures or estimated velocities. I assume the little round is simply outside the parameters of their field of equations and non-linear effects take over. So the reloaders/wildcatters have to approach the problem like they did in the old days, and waste a bunch of ammo, time, and (possibly) firearms in the process.

I'm trying to design/build a locked-breech gas operated 5.7x28 (MP7 clone) this year, and it's gonna be real fun to have to guess at the pressure dynamics, and then a ton of time/money/effort later, hope to hell I can open the gas port up enough to get the thing reliable. I know it's possible, H&K did it with the 4.6x30 MP7, which is a fun-size G36. But lord knows how they figured out a starting point for their gas system (they probably forged the first prototypes from diamonds in a furnace powered by burning money, no doubt)

Good to know about the Redding Dies; I'll just keep saving brass, for now.

TCB