Determining the starting charge for a semi-auto?

[.308 Norma]

I'm happier if I leave the chronograph in the garage until I have found the load I like.

Ha! Ha! Ha! Ha! Be happy you're not like me - I once worked up a load an accurate load for my wife's 7mm-08 that killed mule deer as effectively as any round I've ever seen. And going by what it said in the Hornady manual, I figured it was kicking 139gr. bullets out at a little over 2800fps. Then my wife gave me a chronograph for Christmas. I found out my magic 7mm-08 "Deer Slayer" round is only kicking bullets out at around 2600fps!
I didn't change it - I'm not that obsessed with velocity. I haven't told my wife her 7mm-08 isn't as fast as I told her it is though.

 

[mdi]

Whole lotta opinions, but I have been reloading 30 years and have, 99% of the time started with the "starting loads" as listed in my manuals. What's the down side? Oh No! More reloading? . When working up a load for new gun I'll get some cheap factory ammo and take that to the range along with my reloads (I only buy factory ammo when I get a new gun, one box). I load up 2 magazines or cylinders full with each load, and will have fodder for after I finish firing the reloads. If a reload won't cycle the action, I can take the 14-20 rounds home and still have something to shoot. But I rarely take one gun to the range...

 

[Walkalong]

Luckily, our shooting "range" is a county gravel pit a couple of miles south of the house. The only problem we have with shooting there is that we usually come home with a bag of trash.

Agh, the good ole days when I could drive to the edge of town and shoot in a gravel pit or where someone had simply dug out some dirt. No one cared or were worried about law suits.

 

[bullseye308]

This is how I do mine. I load 30 of each and lately I have been taking 3-5 9mm's to test loads in. I usually run 5 through each gun, take notes as I go, and whatever looks promising gets to eat the leftovers before going home. Just to make sure, you know.

 

[RecoilRob]

Momentum is what creates the operating force in most auto-pistols and the heavy bullet generates more at milder charge weights. Consider the 147 @ 950. 147x950=139650 139650 divided by 115=1214 which would be the velocity equal to the momentum. That's a pretty snorty load where the 950 heavy bullet is very mild so I try to take this into account when choosing where to start. And as said some guns need more 'oomph' to run, and this tends to be more apparent IMHO with the little guns with minimal slide mass that need their springs to do more of the work holding the slide closed.
The Keltec carry guns come to mind here. They try to use springs as light as they can to allow the guns to run with light bullets...but heavy enough to prevent the guns getting battered to death by heavy bullets. Asking a light-weight gun to run anything you stuff in it is asking too much for me so I run heavy springs and bullets which run fine and the guns are happy....just don't try to run light bullets or they'll choke every time.

 

[.308 Norma]

Momentum is what creates the operating force in most auto-pistols and the heavy bullet generates more at milder charge weights. Consider the 147 @ 950. 147x950=139650 139650 divided by 115=1214 which would be the velocity equal to the momentum.

Okay, now you've got me curious. I was following you until you divided 139650 by 115. Where did the 115 come from?
I'm a bit of a math buff, and you got me to wondering if once I find a load using 124gr bullets that generates enough momentum to make my new 9mm work, I could calculate that momentum and use that figure to approximate a starting load for a different bullet weight in the same gun.
My new 9mm Smith is sprung "heavier" than my wife's 9mm Sig, and probably the 9mm Glock I had too. So I know whatever momentum figure I come up with only applies to that gun.
Thanks. And thanks for peaking my interest.

 

[WessonOil]

As a rule, if these are standard target loads that I'm not competing with, I tend to go towards the middle.
Since I use a Lee press with pre-measured disks, I go for the one that's closest.
If they're for competition, I load at least 50 up at lowest charge, and 50 up at the next to lowest, then test them for function.

The way I shoot my semi-autos, needing a maximum load is not anything I'm concerned about.
However, with my revolvers which I will shoot 100 yards on out, I approach maximum published loads.

 

[Robert101]

I've always found the starting loads to cycle my semi-automatics. This applies to my Glocks, Dan Wesson, Springfield Armory, Browning, Bersa, and more. This is also applying to all of my calibers as well (10MM, 45 Automatic, 380, and 9MM) I guess I've been lucky according to some posts here. I usually try and find the bottom of the cycle load and then increase about a grain for reliability - that is in my target loads.

 

[LiveLife]

I've always found the starting loads to cycle my semi-automatics. This applies to my Glocks, Dan Wesson, Springfield Armory, Browning, Bersa, and more.

Perhaps your recoil springs are well worn? I consider recoil spring a consumable item that gets replaced when worn. A light load that will reliably cycle the slide on a pistol with worn recoil spring may not reliably cycle the slide on a pistol with new/newer recoil spring.

Hodgdon load data currently lists Start/Max charges of 4.3 - 4.8 gr of W231/HP-38 for 115 gr Lead RN and 1999 Winchester load data lists 4.4 - 4.9 gr of W231 for 115 gr FMJ.

4.3 - 4.4 gr with 115 gr FMJ/plated RN loaded to 1.130" will not reliably cycle the slide of my Glocks, especially with new recoil spring assembly. 4.5-4.6 gr will start to reliably cycle the slide with 4.7-4.8 gr producing greater accuracy.

But now I have a different 9mm semi-auto (Smith Shield 9mm), which seem to be sprung pretty "hard" compared to some of the other 9's I've had. ... I’d like ... a load that will cycle the action without beating up the gun ... 124gr Hornady HP-XTPs and Power Pistol

If you want to determine a load that will reliably cycle the slide and extract/eject spent cases, you may still need to conduct powder work up from start charge as barrels are different with varying groove diameter and leade length, different recoil spring rate etc. and may reliably cycle the slide at different powder charge than your old pistol.

You can work up from start charge until you reach a charge that will reliably cycle the slide and go up in .1 gr increment until you have acceptable level of accuracy. A charge load that will barely cycle the slide may not produce good accuracy.

As others posted, chances are you may not get reliable slide cycling until mid range load of Power Pistol. I will be using BE-86 for my Shield 9mm with 124 gr FMJ/JHP bullets.

 

[RecoilRob]

Okay, now you've got me curious. I was following you until you divided 139650 by 115. Where did the 115 come from?
I'm a bit of a math buff, and you got me to wondering if once I find a load using 124gr bullets that generates enough momentum to make my new 9mm work, I could calculate that momentum and use that figure to approximate a starting load for a different bullet weight in the same gun.
My new 9mm Smith is sprung "heavier" than my wife's 9mm Sig, and probably the 9mm Glock I had too. So I know whatever momentum figure I come up with only applies to that gun.
Thanks. And thanks for peaking my interest.

My pleasure! I was comparing 147 to 115 grain projectiles. Projo weight x velocity = momentum Momentum divided by projo weight = velocity So a mild (standard pressure) 147 generates momentum = to a maximum (or over max...depending on powder and where you get your data) 115 load. And...I do think that the heavier bullet 'works' on the action a bit longer so even though the lighter bullet can generate the same momentum, the fact that it happens more quickly tends to make it less effective at pushing the action into motion.
Brings up the old 'heavy bullet vs light bullet' argument. One fellow used to equate this to trying to close a heavy safe door either by punching it (light bullet) or pushing it (heavy bullet). Might not be true...but isn't that part of the allure of firearms as we try to figure out what is what?

 

[.308 Norma]

My pleasure! I was comparing 147 to 115 grain projectiles. Projo weight x velocity = momentum Momentum divided by projo weight = velocity So a mild (standard pressure) 147 generates momentum = to a maximum (or over max...depending on powder and where you get your data) 115 load. And...I do think that the heavier bullet 'works' on the action a bit longer so even though the lighter bullet can generate the same momentum, the fact that it happens more quickly tends to make it less effective at pushing the action into motion.
Brings up the old 'heavy bullet vs light bullet' argument. One fellow used to equate this to trying to close a heavy safe door either by punching it (light bullet) or pushing it (heavy bullet). Might not be true...but isn't that part of the allure of firearms as we try to figure out what is what?

Oh, okay. Got it. Thanks!
Yes, that does make sense to me also that a heavier bullet would work the action longer than a lighter bullet even though they generate the same momentum. And yes, part of the allure of firearms, and for me, handloading is trying to figure out what's what. Working up different loads for my new 9mm with the use of a calculator is going to be fun!