30 HRT

[rsilvers]

FYI. this is what a 70,000psi proof load looks like after being fired in a AR.

300 BLK and 223 proof loads are 72,000 psi. The fact that you have one with a blown primer just means that it was shot in a rifle that failed the proof test due to a tight chamber, bore, or short headspace.

[rsilvers]

The 30 HRT uses 6.8 mags not "special" mags.

6.8 mags are special.

[rsilvers]

How do you guess it's 65,000PSI?

Because you are obviously quoting loads that are over pressure, yet at the same time - shootable, so they are likely between 58,000 psi and proof-round pressure (proof rounds are shootable) of about 72,000 psi. I split the difference.

[constructor]

300 BLK and 223 proof loads are 72,000 psi. The fact that you have one with a blown primer just means that it was shot in a rifle that failed the proof test due to a tight chamber, bore, or short headspace.

You do know proof loads are made to test the strength of the bolt and barrel don't you??

[constructor]

Because you are obviously quoting loads that are over pressure, yet at the same time - shootable, so they are likely between 58,000 psi and proof-round pressure (proof rounds are shootable) of about 72,000 psi. I split the difference.

Prove to me the loads I use in a 30HRT are over pressure.

[constructor]

The fact that you have one with a blown primer just means that it was shot in a rifle that failed the proof test due to short headspace.

Did you really just post that?
That is a Hornady proof load used to make sure the barrel and bolt will withstand a 70,000 psi charge so it doesn't break if it gets an over charged load. Any higher pressure will rupture the case as you can see the case is already bulging above the groove. If the case ruptures all of the pressure will be released into the carrier and mag well and destroy the rifle whether the bolt or barrel fail or not. If anyone was to size the case so there was NO play between the back of the case and the face of the bolt it would make no difference at all. The spec that says the ammo should be sized from .000-.008 below the go gauge is to make sure there is enough room for the bolt to lock in.
The go gauge fits the no go does not. The chamber was obviously large enough for the cartridge to go in and the bolt to lock behind it.
I can assure you the barrel bore area is larger than the SAAMI spec for a 6.8 much larger than the 10 twist barrels that are on the market.

ETA-
"The standard proof test consist of firing two overloaded cartridges that produce 25% more chamber pressure then the C.I.P. specified maximum pressure limit for the same cartridge in its commercial version. The standard proof of pistol, revolver and rimfire cartridges is performed with overloaded cartridges that produce 30% more chamber pressure than the C.I.P maximum pressure limit for the same cartridge in its commercial version. There are only two overloaded firings to avoid excessive stress to the arm, especially the barrel which is the main part suffering this overload beside the chamber (when not part of the barrel) and the locking mechanism. After the test, the arm is disassembled by the proof house technicians for nondestructive testing looking for Magnetic flux leakage through fluoroscopic lamp in a dark room. Many manufacturers, including Glock Ges.m.b.H., package the casings from a firearm's proof ammunition in a sealed envelope accompanying the firearm so that authorities in C.I.P.-signatory states and civilian purchasers in other countries can conduct an independent examination if they desire.

Before the year 2006 the standard test consisted of firing two overloaded cartridges producing 30% more chamber pressure then the C.I.P. specified maximum chamber gas pressure limit for the same cartridge in its commercial version.

Voluntarily testing beyond the current legally required standard test benchmark is often also possible for consumers who intend the use their firearms under extreme conditions (hot climates, long strings of shots, etc.). In case a firearm passes such a proof-test a pass mark termed superior proof mark is stamped in every successfully tested firearm."

[AR15barrels]

It's funny to me that it took the standardization of the whisper as the blackout to finally give us a good supply of factory produced barrels that we can rechamber into HRT's as the very reason the HRT exists is to solve the subsonic lack-of-gas problem that subsonic loaded carbine gassed whisper barrels have.

I had the first two sets of headspace gauges ground for it, one set for Marty and one set for me...

[rsilvers]

the very reason the HRT exists is to solve the subsonic lack-of-gas problem that subsonic loaded carbine gassed whisper barrels have.

The solution to that problem - and I agree it was a problem historically - was to use powder that is more compatible with ARs. A1680, RE-7, and H4198 are some examples.

[constructor]

It's funny to me that it took the standardization of the whisper as the blackout to finally give us a good supply of factory produced barrels that we can rechamber into HRT's as the very reason the HRT exists is to solve the subsonic lack-of-gas problem that subsonic loaded carbine gassed whisper barrels have.

I had the first two sets of headspace gauges ground for it, one set for Marty and one set for me...

Agree..if you are looking for a 8 or 7 twist barrel. If I start building 30 Herretts they will be for hunting, 11 twist and 5R, 16" mid gas.

[320pf]

The solution to that problem - and I agree it was a problem historically - was to use powder that is more compatible with ARs. A1680, RE-7, and H4198 are some examples.

It's funny to me that it took the standardization of the whisper as the blackout to finally give us a good supply of factory produced barrels that we can rechamber into HRT's as the very reason the HRT exists is to solve the subsonic lack-of-gas problem that subsonic loaded carbine gassed whisper barrels have.

I had the first two sets of headspace gauges ground for it, one set for Marty and one set for me...

A carbon length gas system on a 16-inch the 300 BLK/Whisper is only useful for guns that are set up to shoot primarily supersonic loads. A properly set up 16 inch barrel with a pistol length gas system will shoot subsonic loads with bullets weighing 150 to 240 gn. It will also shoot super sonic loads and only give up about 25-50 fps to the carbine length gas system. Moreover, a correctly designed gas system will not need an adjustable gas block either, and will work with powders like 2400, W296, H110, A#9, Lil'Gun, 4227, A1680, and 4198. Did I leave one out?