Cartridge pressure?

[jerffey]

Good afternoon,
Just got home from day 2 of 44 special load development for my model 69 2.75 inch. Going to use this as my woods/hiking gun in NH.
Using hs-6 powder I loaded 10 rounds each of 8,9,9.5, and 10 grains under Missouri bullets rnfp 240 grain cast with a bhn of 12. Starline 44 special brass, cci 350 primers, firm crimp in the crimp groove. Oal=1.43 +/-.
So, jumping to the 10 grain charge, average velocity for 10 shots was 980 fps. This got me wondering what kind of pressures I was creating in the chambers. I'm assuming the revolver can handle it for I'm pretty sure even a relatively warm 44 special load is still lighter than a "standard" 44 magnum load.
But then I got to thinking (never a good sign) might the pressure I'm creating actually be on the higher side of what I want to feed the 69 a steady diet of? Wouldn't the shorter case, magnum primer and overbook charge bump the pressures up significantly?
I've searched the interwebs but couldn't really find a definitive way to calculate potential chamber pressures. Too many variables.
Anywho.... I figured I'd ask the fine folks here and hopefully I can be steered in the right direction.
Thanks

 

[jerffey]

Good afternoon,
Just got home from day 2 of 44 special load development for my model 69 2.75 inch. Going to use this as my woods/hiking gun in NH.
Using hs-6 powder I loaded 10 rounds each of 8,9,9.5, and 10 grains under Missouri bullets rnfp 240 grain cast with a bhn of 12. Starline 44 special brass, cci 350 primers, firm crimp in the crimp groove. Oal=1.43 +/-.
So, jumping to the 10 grain charge, average velocity for 10 shots was 980 fps. This got me wondering what kind of pressures I was creating in the chambers. I'm assuming the revolver can handle it for I'm pretty sure even a relatively warm 44 special load is still lighter than a "standard" 44 magnum load.
But then I got to thinking (never a good sign) might the pressure I'm creating actually be on the higher side of what I want to feed the 69 a steady diet of? Wouldn't the shorter case, magnum primer and overbook charge bump the pressures up significantly?
I've searched the interwebs but couldn't really find a definitive way to calculate potential chamber pressures. Too many variables.
Anywho.... I figured I'd ask the fine folks here and hopefully I can be steered in the right direction.
Thanks

I should have added.... I realize the OAL is on the shorter side but that's where the crimp groove left me, and might that add to the potential pressure also?
No overpressure signs on the fired brass

 

[Jim Watson]

That is way over Hodgdon .44 Special maximum but below .44 Magnum "start". Unfortunately Lyman does not show HS6 in either.
There is a computer program that will give you a pressure number:

start [Gordons Reloading Tool Community]

grtools.de

You could just use Magnum brass in your Magnum gun and have no doubts.

 

[stansdds]

I agree with Jim Watson, the Model 69 is chambered in 44 Magnum, so just use 44 Magnum brass. This also avoids the potential for overly hot loaded 44 Specials to find their way into a weaker revolver chambered in 44 Special.

 

[jerffey]

Yup, I completely agree with both of you. Way over Hodgdon 44 special max, but quite a few people on the forum here have used that same load to great effect. And, I was considering just light loading magnum brass, however, even a starting load of 12 grains hs-6 might be more oomph than I'm willing to contend with in an L-frame snubbie. Trying to keep the gun as controllable and light as possible. Did I mention hs-6? Lol, would really like to stick with the powder.
Question still remains: is there a cartridge pressure calculator of some sort?

And thanks for the replies folks, I should probably just get a 4" 629 to lug around with me up north.

 

[Riposte1]

I really like the .44 Spl and have several revolvers in just that caliber, so, while I don't disagree with the folks above, I am interested in .44.

HS-6 is a fine powder but I have loaded it much in .44 spl - right now I'm fiddling with 10B101 a "surplus" (not a pull-down) powder I bought off the guy who runs G.I. Brass in Owensboro Ky. - it is claimed to be like Herco - which I figure is roughly close to HS6 (not in weight but similar pressure compared to the vel) but I find it is closer still to BlueDot (I imagine it varies with air space in the case?).

I know this - it is very accurate! I am pusing 240s (honest 240s not mislabled 230-235) at 925 out of a 3" - loads seem mild but no doubt are over the normal .44 Spl pressure.

Just Ramblin'

Riposte

 

[Forrest r]

You're in the +/- 21,000psi range with that 10.0gr load of hs-6 and that 240gr swc in the 44spl brass.

Brian Pearce did an article for handloader magazine back in aug/sept 2005 (#246). In it he listed the cast rcbs 255gr leadhead keith swc and 10.0gr of hs-6 for his 22,000psi or less loads.

That 255gr swc with 10.0gr of hs-6 did 998fps in a 4 1/2" bbl'd freedom arms revolver.

 

[Chubbs103]

I was going to post a reference to the same Handloader article.

My favorite, if you are looking for this velocity, is 8grs of Power Pistol. Somehow, it is supposed to be under 15,500psi and I get an honest 970fps out of my 4 5/8 Blackhawk w/ a homecast 429421 that weights about 256gr.

 

[jerffey]

Thank you all for your input. Think I might give downloading 44 mag brass a try. But that brings up another pressure question. Would the air space between the base of bullet/top of charge in a magnum case cause some type of pressure spike? Assuming I used the same 10 grains of hs-6? Or would that gap possibly reduce the pressure? I know I am way way way overthinking this, and may seem like I'm obsessed with cartridge pressure but I kind of (weirdly) enjoy brain teaser stuff like this.

 

[jerffey]

Or I might just drop back to 9 grains in special cases. That load had, by far, the lowest ES of any group I tried. 24 fps through all 10.

 

[STORMINORMAN]

Yep! 44 Magnum revolvers should be able to handle up to a 36,000 psi load regardless of the length of the brass in which it is loaded...

Cheers!

P.S. You could always load 4 of your 9.0gr 44 Specials (behind an empty chamber?) & then a 44 Magnum Buffalo Bore Model 4E Lower Recoil 255gr Keith G.C... Just in case?

 

[jerffey]

Storminorman!
Very good idea. I've been thinking of purchasing a box of Underwoods' similar offering and doing just that. I'd probably go the opposite route though and load 1 of my own first then 4 of theirs. Save the expensive rounds for just in case...lol. Not overly concerned with the occasional meandering black bear or moose. At least not this time of year.

 

[halfmoonclip]

I'm headed down a similar road right now, and will likely use the 7.5 grs Unique,as I still have some. Figured the 0.10" shorter case reduces the case volume, so it's worth going with the .44 Spl brass for some sub-1k loads. I have some 1200' loads that are just tiresome in the Mountain Gun.
Moon

 

[jerffey]

Moon,
I agree completely. Have my 629-1 classic hunter for bigger boomers. Is your mountain gun one of the newer models or one of the originals? How do you like it?

 

[jerffey]

You know, seems like I'm hijacking my own thread. I still haven't found a comprehensive answer to my "is there a chamber pressure equation somewhere out there?" Jim Watson in post #3 here shows an interesting site but seems a little to high-techie for me personally.

 

[Jim Watson]

There is a quickie cheapie rule of thumb in the Lee manual but I don't know how well it would work to extrapolate a 25% overload.
But if you don't want to tackle GRT, just take Brian Pearce's word for it.

 

[STORMINORMAN]

1. NEVER trust a moose. They can hurt you bad, or WORSE...!
2. No, there is no easy "magic formula" to accurately determine pressure: way, way too many variables.

Well, except perhaps... MORE POWDER or DEEPER SEATING or HEAVIER BULLET = MORE PRESSURE

Cheers!

 

[Top O' Texas]

supposedly the magnum primer use over standard types should create more pressure with same amount of powder? some state back off 1/2 gr when using magnums. using a 629 over 2 decades of a 44mag @ max loads the n frame should be gtg. i've shot probably 10k that way. not sure about the l frames in 44mag?

 

[BC38]

Good afternoon,
Just got home from day 2 of 44 special load development for my model 69 2.75 inch. Going to use this as my woods/hiking gun in NH.
Using hs-6 powder I loaded 10 rounds each of 8,9,9.5, and 10 grains under Missouri bullets rnfp 240 grain cast with a bhn of 12. Starline 44 special brass, cci 350 primers, firm crimp in the crimp groove. Oal=1.43 +/-.
So, jumping to the 10 grain charge, average velocity for 10 shots was 980 fps. This got me wondering what kind of pressures I was creating in the chambers. I'm assuming the revolver can handle it for I'm pretty sure even a relatively warm 44 special load is still lighter than a "standard" 44 magnum load.
But then I got to thinking (never a good sign) might the pressure I'm creating actually be on the higher side of what I want to feed the 69 a steady diet of? Wouldn't the shorter case, magnum primer and overbook charge bump the pressures up significantly?
I've searched the interwebs but couldn't really find a definitive way to calculate potential chamber pressures. Too many variables.
Anywho.... I figured I'd ask the fine folks here and hopefully I can be steered in the right direction.
Thanks

Seems to me that your concerns about 10gr HS-6 in a 44spl case may be well-founded.
The only load data I have for 44 MAGNUM using HS-6 (other than the Hodgdon online data) shows a maximum charge of 9.5gr (starting charge of 8.5gr), using a 240gr LSWC bullet and the longer 44 Magnum brass. It shows a velocity of 947fps
Using 1/2gr more powder in a case that is 1/10" shorter seems likely to produce an over-pressure round, as also evidenced by your measured velocity of 980fps.
If it were me, I'd dial it back a bit. If you want to keep using the shorter 44spl brass, I'd reduce the charge to around 8.5gr, and see what kind of velocities you get.
Pressure doesn't always directly correlate with velocity, but higher than expected velocities are usually one indicator of higher pressures,
JMO, and YMMV....

 

[Forrest r]

Seems to me that your concerns about 10gr HS-6 in a 44spl case may be well-founded.
The only load data I have for 44 MAGNUM using HS-6 (other than the Hodgdon online data) shows a maximum charge of 9.5gr (starting charge of 8.5gr), using a 240gr LSWC bullet and the longer 44 Magnum brass. It shows a velocity of 947fps
Using 1/2gr more powder in a case that is 1/10" shorter seems likely to produce an over-pressure round, as also evidenced by your measured velocity of 980fps.
If it were me, I'd dial it back a bit. If you want to keep using the shorter 44spl brass, I'd reduce the charge to around 8.5gr, and see what kind of velocities you get.
Pressure doesn't always directly correlate with velocity, but higher than expected velocities are usually one indicator of higher pressures,
JMO, and YMMV....

Odd, I couldn't find anything like that on the Hodgdon website???
Found Hodgdon'd starting loads for 220gr/240gr bullets in the +/- 20,000cup range.