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+--- Thread: Max Chamber Pressure (/showthread.php?tid=901)
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RE: Max Chamber Pressure - English Rifleman - 04-26-2023
(04-25-2023, 06:48 PM)grayfox Wrote: Can you get hodgdon's leverevolution over there? or perhaps CFE223? These 2 powders have the longest "legs" for 6Arc heavier bullets.Leverevolution i have not seen (Not looked really Hard)
Also according to several users (I myself use the GRT tool, which is free), QL is difficult to set up for accurate modeling of these shorter, fatter cartridges, like Grendel and 6 Arc.
I find I have to first calibrate the model by trying to duplicate mfr load data, then re-calibrate again when I get some chrono data on my own barrel.
If you do not have a chrony, I would heartily recommend to get one. Personally I like the magnetospeed the best as it is easy to set up and portable, and doesn't require a cold firing line so you can do setup 15-20 ft downrange. Cheaper than the lab-radar outfits. But any chrony you can get will be a help.
Just ordered some CFE223 to try.
My Quickload data keeps comming back with both of those powders, But highly recomends Reloader Swiss Blends of powder.
However Currently there is unlikly to be a delivery of Any RS powders in 2023.
Which has put a strain on the already suffering powders supply in the UK.
Currently in the stores there is Zero Powder & Zero Primers & Very Very low stocks of bullets.
So out of the top 5 Powders Quickload recomends CFE223 is the only one currently in stock.
( which afger tonight, the very low stock of CFE will Zero too
)I do own a Magneto speed V3, Very nice bit of kit.
And for the first time i am going to try Mr Newberrys OCW loading, Always used ladder before and managed to find good loads, but where allways very fussy and had to be dead on CBTO lenght to shoot nice.
RE: Max Chamber Pressure - grayfox - 04-26-2023
Not knocking the OCW method by any means, but the best results I have been getting is with the optimal barrel timing method, via Chris Long.
In many respects I think the ocw works best when the cartridge has room for several nodes and loads... whereas the 6.5 grendel and 6Arc have much less powder space, so the workup range is more limited.
With CFE and bullet weight down to as low as 80 grs, there's room to do workups. I load a sinlge load-ladder of 0.3 grs delta over the range I can do for thepowder/bullet (hornady data), then plot on a graph, to examine where to concentrate. For 24" barrrel I can suggest MV's to concentrate your look-around, so build some 4-round loads at those charges, I don't worry about actual zero yet, until after I have found the powder wt and do perhaps seating-depth range of ~0.010 per step. Best grouping depth of the best-MV/SD combo gets the vote.
About the plot, in a mechanical system I expect the powder/MV graph to be close to linear, a well-behaved system ought to increase MV as powder charge increases. Once you have a node it will self-perform fairly tolerant of any powder changes, mine go no more than 0.1 or maybe 0.2.
Example, my 22" unitah (bolt action), shoots the 103 eldx at 2733, sd around 6. Not the highest node but a consistent one.
I adapted my approach from Chris Long's work (on the web) on OBT, and acoustic wave theory.
RE: Max Chamber Pressure - grayfox - 04-26-2023
I shoot a 107 smk in my 22" uintah with Lever, the MV is <52ksi for my node at 2718. 2700-ish is a fairly wide node btw.
In Hornady's 108-110 data (your 107 might go 10-20 fps faster than the 108), max CFE is listed (gas gun) at 29.1, 2575, so <52 ksi.
Their table below this data extrapolates the 18" barrel in the data to 22", and 2695.
So 2 possible nodes for you in CFE, ~2625 MV and 2700 MV. Factory 108's in my 22" shoot 2650-2660, sd I forget but usually <1.0"/100 yds.
You could work up from, say, 27.5 grs to the 29.1 and see what kind of MV's and SD you get.
RE: Max Chamber Pressure - CZ527 Guy - 04-27-2023
alwie
Hornady did finaly reply.
And as Grayfox suggested this is what they said.
""Are you referring to the 2750 on the box? if so we are capable of achieving that without pressure issues because we have access to powders and blends that reloaders do not so we can get more speed with less pressure
Hornady/SnapSafe Tech team""
"Why cant we have the super secret powder??"
Similar reason to why Kernel Sanders & Coke a Cola do not share their Recipe!
RE: Max Chamber Pressure - English Rifleman - 04-27-2023
Thanks Grayfox
Great info.
i will look up Chris Long method and see how it works.
Also thanks for the 107 108 Loads.
Many thanks
RE: Max Chamber Pressure - trianglevelvet - 04-30-2023
To answer OP's question -
The case can handle 62kpsi.
But the AR-15 style bolt can occasionally shear off a lug if the bolt is weak or if the upper isn't squared perfectly.
So both grendel and ARC are set at 52kpsi to keep bolt thrust down.
That being said, some people with well crafted AR's and very high quality bolts have run bolt gun pressures without failure. There are some extra beefed up bolts out there that exist.
The words AT OWN RISK apply.