exceeding published maximum loads (6.8 SPC)

[rkh]

THR:

Hear me out. I know the first rule of reloading is never to exceed published maximums, but relatively recent developments with the 6.8 SPC suggest to me that it's now possible to push the cartridge to new levels of performance.

For those of you that aren't familiar with the chambering's history, Remington screwed up when it submitted the SAAMI spec by getting the chamber dimensions wrong. As a result, the expected performance couldn't be achieved without serious overpressure issues, and manufacturers immediately downloaded their 6.8 offerings.

Nowadays, finely tuned 6.8 barrels are available with more generous chamber dimensions, slower rifling twist rates, and fewer and shallower lands/grooves. Although it's possible to safely fire old "hot" 6.8 factory rounds in the new barrels, no powder manufacturer that I'm aware of has released updated loading data.

I'd like to push the envelope on this cartridge, and start working up to some of the unofficial loads that are floating around on AR15.com, but I've never previously had to be concerned about pressure issues, and really don't know what to look for.

I know that bulged brass and blown primers are a bad sign, but would one slowly working up to a "Kaboom!" level load always see obvious signs well before reaching dangerous pressure levels?

I think the 6.8 has a lot to offer, and it makes me sad that Remington screwed it up. I'd be thrilled if I could make my rifle safely perform as it was originally intended to, and would really appreciate any input anyone here could offer.

thanks
rkh

 

[R.W.Dale]

but would one slowly working up to a "Kaboom!" level load always see obvious signs well before reaching dangerous pressure levels?

NO

Typically by the time you see ANY sort of high pressure indications (if you see any) your pressures are already sky high.

 

[Stinger]

Typically by the time you see ANY sort of high pressure indications (if you see any) your pressures are already sky high.

Amen.

If you don't have pressure testing equipment then you should't exceed published loads. I know some do, many have forever, but it is just bad practice. If you can't reach the velocity you want, change powders, or heck, change calibers. Don't gamble with your life.

 

[Zak Smith]

Strongly recommend against until you know exactly what you are doing. There has definitely been ammo that would blow primers in most commercial uppers, but would run fine in the original uppers (Barrett, PRI).

 

[rkh]

Where would you suggest I go to read up on pressure testing equipment?

thanks

 

[GunTech]

Depends on if you are shooting 6.8 in an AR, or a bolt action. The upper limit on the AR is lower than most people realize. In my 6.8 CZ-527, I could go much higher without any issues, but my preference is to always stay under recommended max pressure. You really don't gain much in performance as pressure increases past a certain point.

 

[jeepmor]

Once you find an accurate load, which is typically below max recommended loading anyhow, what's the point.

Not worth the risk to me. I have other hobbies that I push the envelope on, not this one. This hobby is about accuracy, precision, and cost savings, not how I can turn my firearm into a bomb.

However, the THR member Clark has a lot of data in regards to hot loadings, you should discuss this matter with him, I would.

 

[jrumsey]

Rkh :
I bought into the 6.8 SPC early on before there was any published data. when I started to work up loads that others were using pressure signs started to show long before reaching their max charge weight for the load. At this point I used a lower charge from working up where there were no pressure signs.

People used to get mad when I would post that in my experience their loads were to hot, and I can understand this to a point. With not being able to reach the promised land for the data from Remington, many tried to find a way to reach it anyway. All this while ignoring standard loading practices, not good in my book.

The 6.8 Spc as chambered in the AR15 in itself has limits, bolt thrust, and pressure are the biggest issues. Look at the case and it's water capacity compared to other cartridges in roughly the same class and what powders and charge weights they use, this should give some idea as to what to expect from cartridges like the 6.8.

Yes it it is to bad that the 6.8 did not live up to its original specifications, but when you look at what it is instead of what it should have been it really isn't to bad either. Just remember that sometimes more is not better.

Joe

 

[R.W.Dale]

Where would you suggest I go to read up on pressure testing equipment?

thanks

If you want a 6.8 then buy a 6.8, If you want 270win performance from a 6.8 then buy the .270. But don't try to turn the 6.8 into sumpin it's not, after all how much difference do you think 200 fps will really make. NONE NADA ZIP ZILCH

 

[carnaby]

The Accu-Trigger, Savage Arms way of saying that they don't trust you not to shoot yourself if they gave you a good trigger.

krochus, I think that oughta read "The Accu-Trigger, Savage Arms Lawyers way of saying that they don't trust you not to sue Savage Arms if you shoot yourself with a good trigger.