newb: almost ready to reload...

[burningsquirrels]

just some newb questions.

1. in reloading data i see where people put 'chamber pressures'. how do they measure this? i was just wondering because after a search i found this reference that there is no reliable warning sign that you're getting too high in chamber pressures whilst another reloader offers this method for estimating. i assume 33,000 psi is pretty darn high with the 135gn tcj bullets, ain't it?

2. the reason i ask is that i'm about to start reloading 40 S&W... while my first rounds will be rounds that "just work", i know i'll quickly need to ensure they meet USPSA major power factor requirements and i'm reading all these warnings on the web (like this PDF) and by word of mouth when i shoot with other reloaders.

the gun is a 4.4" barreled CZ-40b. right now on my bench that is halfway built, i have a lee load-master that i'm starting to set up with help from the web, and a box of both 135grn and 180grn flat point bullets. i picked up a pound of bullseye powder, but people seem to point me to both titegroup and longshot. seems like longshot, by factory reload data, produces less chamber pressure than titegroup, but titegroup is what more people are steering me towards. also got a couple trays of CCI 550 magnum small pistol primers.

some of the data i'll be using also comes from here (but loaded down considerably), hogdon, alliant, maash's ipsc list, and my lee modern reloading book.

am i on the right track or on the fast road to losing my hands and eyesight? lol.

my original thread was here:

http://thehighroad.org/showthread.php?t=371691

 

[mkl]

Accurate measures of chamber pressure are possible only with fairly sohphisticated instrumentation. The loading books measure it in their labs with such equipment.

Pressure "signs" are about all the average reloader has to go on, and as you have found there are many opinions on how good the "signs" are. As you get more experience, you will find that you will use some of the signs when you are expermenting with loads for which there is little or no published data.

For the beginner, you should start with the load books, and only the load books. Start at the minimum. Check the suggested load in Book "A" against the same load in Book "B."

The best device available to the handloader to measure the relative intensity of the load is a chronograph. I beleive that "power factor" is a function of velocity and bullet weight, so you will need a chronograph to know if your loads are making USAPA major.

Good starting chronographs are available for under $100.00.

Load up a cartridge using loading book data for the "start" end of the suggested range. Chronograph the load. If it is close to the velocity given in your book, your pressure is okay.

As you work up from the bottom end loads, keep a close eye on the velocity. If you attain a top load velocity with less powder then stop. You are very close to the pressure of the top load in your book. There is no hard and fast rule as to how much to step up powder charges as you work your way up from the minimum, but no more than 5% per step is probably okay until you get close to the top. I personally approach the top 15% of the range at 3% increase at a time steps (e.g. five test loads of three to five shots each).

Smokeless powder pressure/burn rate is not linear. As the pressure gets higher, the powder burns faster. I'm not sure this is a logarithmic rate or not, but I think of it that way.

Your idea of starting off very low just to get experience as to how to make you gun go "bang" with your loads is a good one. It will build confidence and let you work out any sizing or length (feeding) issues at very safe pressures.

Hope this helps.

 

[Texastbird]

With Bullseye powder, Alliant lists the maximum load that produces 33,600 pressure. If you read the main page, it recommends that you reduce the load by ten percent for a starting point. You always need to work up toward maximum pressure in your gun, and check for pressure signs before you go any hotter(more powder). I don't know about what it takes to make major, but you usually wouldn't want to go any hotter than that for target shooting. Also their load lists a standard primer, not a magnum primer. That might make a difference in the chamber pressure.

 

[burningsquirrels]

thanks for the info guys... just about all my shooting is uspsa (1-2x a week, 300 rounds), save the weekly thursday night plinking (100 rounds). i might as well load both plink and action pistol ammo the same so i am used to the major power factor.

what are the common pressure signs? so far i've read about the case expanding at the base, and primers being pushed backwards out of the case.

 

[mkl]

what are the common pressure signs?

I can't resist this comment: "When your pistol starts coming apart." Extractor separates from slide, magazine blows out the bottom, case left in chamber after extractor pulls off rim, bolt/slide stop beat all to heck, etc.

Some may disagree with me, but the fundamental problem is that some brass really will not show significant pressure signs until you are in the 55,000+ psi range. I'm not familiar with the 40 S&W, but I know that in my 357 mags, I don't get any head expansion, web expansion, or primer protrusion at the top end loads, and SAAMI lists those at 48,000 psi. Someone familiar with the 40 S&W will have to comment on the strenght of that case.

The chronograph method as I described in my first post is the only really safe way to be sure you are not exceeding the chamber pressure for which your gun is designed.

 

[burningsquirrels]

how's that $70 F1 chrony lookin'? seems basic and all i really need is for it to say the velocity. seems like the reviews at midway and on here indicate it's a simple and straightfoward unit. only problem is that the only time i'd be able to use it is at an indoor rage. perhaps i can bring an incandescent lamp with me.

 

[mkl]

The Chrony would probably be fine.

Ask some users, there may be enough light at an indoor range to use it as is.

I use an $89.00 Pact I that I bought years ago, and I have used it in my garage with only the overhead garage light and it worked fine. Just for the record, I was measuring my pellet gun velocities, not my 45-70!

 

[mkl]

Check out this thread: http://www.thehighroad.org/showthread.php?t=355457&highlight=led

Post #6 sounds just right for an indoor range if you have a lighting problem.

Never thought about it until after I posted the above, but fluorescent lights do turn off and on 60 times a second. Perhaps this is the problem at an indoor range that would screw up a chronograph.

 

[jfh]

mki offered exceedingly good observations and advice.

1. AFAICT, there are NO reliable pressure signs at safe pressures.

2. What there are available are entirely specific--e.g., how that particular firearm "reacts" to a particular case, particular bullet, primer, powder, etc., etc.

For further reading about this, go to this post, and see this picture. That's the initial take--explanations are found in this post, and the link to the whole thread is http://www.thehighroad.org/showthread.php?t=289578

FYI--a moderator at another forum worked up that mischarged load, and his calculations show about 55K to 72K pressure for those five rounds. Note that there is little cratering, and no piercing or leakage.

Get the chrono; using that and a good recipe book (Lyman Pistol and Revolver, Speer 14, and many others) will teach you a lot about how to load safely.

Jim H.

 

[burningsquirrels]

thanks guys. i'll pick up a chrono. until it comes, i think i'll just start 15% low tomorrow just to see what it's like. the load data i'm going to use is from hogdon. i need 1250 fps with the 135 grn bullet to meet major power factor.

case hornady
barrel 4" 1:16" twist
case length .845"
primer: winchester SP

135 grn bullet
COL 1.125"

start load
10.5 grn longshot powder
vel 1367
28,100 psi

max load
12.0 grn longshot powder
vel 1480
32,400 psi

i figure i could start at 9.5 and leave it there until i get a chrono... i'll trade in that bullseye powder and the cci magnum 550 for the longshot powder and wsp... thinking about ordering that basic F1 chrony timer for $70... what do you guys think?