Powder charge vs seating depth

[BJung]

Is seating depth that important for handgun loads?

If I assemble a relay of testloads with varying powder charge and find accuracy load, how can changing the bullet seating depth matter when doing so increases or decreased the pressure that the accuracy charge established?

If I am correct here, would it be best to find the longest cartridge that will feed and then conduct an accuracy load test from there?

 

[tightgroup tiger]

Is seating depth that important for handgun loads?

If I understand your question:
It depends on the handgun load.
If your dealing with something like a 9mm that barely has any air space in the case, then changing seating depth changes pressure rapidly. Changing pressure changes velocity, and that changes trajectory.

If dealing with something like 38 special, changing the seating depth barely has an affect on it because of all the air space in the case. Your accuracy load doesn't change pressure near as rapidly so the accuracy node would be wider and more forgiving.

 

[Blue68f100]

Only change 1 variable at a time when testing. This way you will know the effect. Other wise you will just be guessing on which caused it.

Determine you OAL first, load dummy rounds and check feeding in your guns. Then do the ladder test with the powder.

On a 9mm if you reduce the OAL by 0.030" using a fast burn powder you can increase the pressure by over 30kpsi. The reason you determine OAL first.

 

[Charlie98]

If I am correct here, would it be best to find the longest cartridge that will feed and then conduct an accuracy load test from there?

That's what I do, but as Tiger mentions, some cartridges are more sensitive to OAL... like the 9mm.

In revolver cartridges, seating depth can have a significant effect on cartridge performance, but those variables are not there in most autoloaders; in fact, I've not found significant differences in changing seating depth for autoloading cartridges... besides the aforementioned pressure, and feeding.

 

[Walkalong]

For .32 ACP, 9MM, .40 S&W, .& 45 ACP I pick an OAL that feeds 100% and work up the load. Maybe tweaking OAL could increase accuracy if I was good enough, dunno, because most of my loads shoot better than I can hold.

The smaller the case and the higher the pressure a handgun caliber runs at the less forgiving changes in OAL are. 9MM is a good example of one.

.38 Spl was a great example on the other end, low pressure and lots of extra case space.

For revolver rounds I almost always seat to the cannelure or crimp groove and call it good for OAL, work up from there.

Either way though, I am picking an OAL up front and rarely change it during load development for pistols.

 

[Archie]

Pretty much what Walkalong said.
For autopistols, the finished round has to be short enough to fit in the magazine and long enough to cycle through to chambering. The the bullet must be short enough to not impinge on the leade.
For revolvers, the finished round has to be short enough to NOT stick out the front of the cylinder.
So I determine what the length should be, then start with a starting load and work up. I've never had a problem in that fashion.

The main auto pistol for which I load is .45 ACP. I'm done experimenting and load for a hardball duplication load.
I load for .38 Special; two loads. One is a defense load duplicating the "FBI" load (aka Chicago load, Metro Load and likely more) of a 158 grain lead SWC hollow point at about 850 to 900 fps. (Mine is a high but standard pressure load; commercially it is classed as +p.)

In any event, my experience negates the need to measure each round to the nearest thousandth.

 

[BJung]

There's a lot I can say here. First, I loaded my .45 loads with the bullet just off the lands and able to seat into the magazine and feed. I worked my load up to 5gr Bullseye and I'm satisfied. Yet, now I'm thinking that if I seat it deeper, I would change the charge of BE to find the most accurate load for that OAL. Yet, would it be the most accurate as a bullet closer to the rifling be more accurate? Then there is crimp. For my .45, I dial my crimp die just enough so the case is straight. Is this what you're doing?

As for the .38 special, I seat 148wc flush to the mouth or to the second grease groove so it's as long as a .357mag loaded with a WC to the first groove. I have a 38-150 LHP Lee bullet load as well. I'm set my crimp die so the case mouth is straight but am wondering if a crime from 1/4 turn of the die past the setting where it would reshape the case straight would be better.

Getting to the autopistols, I also wonder if a slight crimp helps or a setting where the case is straight. As for seating, do you look up what is the most common seating depth posted? My first tests with seating depth brings me back to where the accuracy load was determined with just the accuracy load.

 

[HEAVY METAL 1]

My Ruger P89 9mm can shoot tighter groups with commercial lead bullets seated longer than book length. They fit and function in the magazine just fine. None of my other handguns shows any such improvements on target with tweaks to seating length.

 

[lordpaxman]

Yet, would it be the most accurate as a bullet closer to the rifling be more accurate? Then there is crimp. For my .45, I dial my crimp die just enough so the case is straight. Is this what you're doing?

I haven’t seen any appreciable change in groups sizes varying COL for short range pistol loads. If you’re worried about velocity I’d suggest a chrono, that way you can vary COL all day and still hit the same V. I’m more concerned with PF so I need to definitely know V.
Regarding crimp, for taper I remove the bell, for roll its a slight roll for light calibers, and heavy for heavy calibers. I started using case gauges to determine if the crimp was sufficient. Good luck.

 

[243winxb]

45acp- https://www.thehighroad.org/index.php?threads/seating-depth-and-accuracy.829902/

In Chart- The roll crimp is for revolvers. Taper for auto. Seat & taper crimp in seperate operations.

 

[Rocambole]

Arent't there several factors to take into consideration? In Scandinavia, 38 Sp is used for target shooting and field competitions and so all the talk of stopping power is irrelevant. For these purposes, charges can be quite mild, with 105 gr SWC bullets flying at 6-700 fps, e.g. I know a guy who uses Vihtavuori N320 with a reduced load, seating the bullet on the powder without compressing it. This gives him an extreme consistency of bullet speed, as the powder is always distributed in the same manner in the cartridge. And it is not dangerous in any way if you reduce the load appropriately. The slower powder is also more forgiving than, say N310.

I have used Vihtavuori's faster N310 for both 148 gr DBWC and 105 gr SWC, but have had issues with lead build-up on the outside of the cylinder from the lead gas. So I have decided to save N310 for 32 S&W Long and use N320 for 38 instead. As for crimping, I never crimp more than to a straight wall. It's not necessary with these loads, and the cases last much longer as you reduce fatigue in the brass.

 

[CQB45ACP]

For .32 ACP, 9MM, .40 S&W, .& 45 ACP I pick an OAL that feeds 100% and work up the load. Maybe tweaking OAL could increase accuracy if I was good enough, dunno, because most of my loads shoot better than I can hold.

The smaller the case and the higher the pressure a handgun caliber runs at the less forgiving changes in OAL are. 9MM is a good example of one.

.38 Spl was a great example on the other end, low pressure and lots of extra case space.

For revolver rounds I almost always seat to the cannelure or crimp groove and call it good for OAL, work up from there.

Either way though, I am picking an OAL up front and rarely change it during load development for pistols.

That’s what I do too, now.

For 45ACP for example, I only shoot government model 1911s and I own four, each a different brand. They all like 1.250”.

So, after a couple years of monkeying around by a fraction of this or that, I haven’t adjusted my seating die in at least a year. Regardless of powder—Bullseye, BE-86, Sport Pistol, W-231, AA 2, 5, or 7–or bullet.

Load work up is a thing of the past at this point anyway.

(Good money for a Redding micrometer adjustable Competition seating die that’s just pretty to look at.)

Edit: but it is really pretty to look at

 

[ImjinScout85]

Another thing to keep in mind is the actual bullet that you are loading. Different bullets can have a different OAL depending on the style you are using. This is where case volume comes into play with different bullet designs and can effect the powder charge even though you are seating to the same OAL. One example is a a Hornady 9mm XTP bullet vs a Berrys 9mm bullet, both 9mm but the bullet length is different,

 

[tightgroup tiger]

I have several 9mm pistols so I have my shortest barrel lead and load for that, the other 9mms will just have to like it. My ammo has to fit all my 9mms, I don't have the time to deal with each and everyone of them. I will say that it's very rare that I think one pistol likes a particular load better than another, I do think that the quality of the gun has more bearing on a good group than the seating depth of the bullet.

 

[GeoDudeFlorida]

The smaller the case and the higher the pressure a handgun caliber runs at the less forgiving changes in OAL are. 9MM is a good example of one.

.38 Spl was a great example on the other end, low pressure and lots of extra case space.

This exactly but you have to know your guns and what they like, too.

For example, I use the same 148gr. HBWC made by Speer (swaged soft lead coated with a clear wax lube) for .38Spl, .357Mag (both nominal .358" groove) and .38S&W (nominal .361" groove) but with different seating depths and different charges to accommodate MY guns. I seat the .357 farther out - which is counter-intuitive but with the slightly larger case and slightly heavier charge it makes for a very consistent load. It sort of helps to avoid a big jump to the throat which "seems" to help prevent leading-up the throats. Seating to the last lube groove adds a lot of air-space to an already overlarge case so I've got lots of room gas expansion with a fast powder like Red Dot or Bullseye. Maybe it helps or maybe it's just my perception but, either way, it works for me. The .38S&W case is a lot shorter so I seat them a lot farther out to avoid over-pressure and damaging the skirt and to make it easier to load. Small case + fat fingers = dropped cartridges.


I'm not a competitive shooter and really could care less how the crowd at USPCA or IPSC or whatever the big boys with the pricey toys call themselves - that's their thing and it's fine but its not for me - I just care about keeping my skills at their current meager level for as long as possible and that means trigger time.

 

[CQB45ACP]

This exactly but you have to know your guns and what they like, too.

For example, I use the same 148gr. HBWC made by Speer (swaged soft lead coated with a clear wax lube) for .38Spl, .357Mag (both nominal .358" groove) and .38S&W (nominal .361" groove) but with different seating depths and different charges to accommodate MY guns. I seat the .357 farther out - which is counter-intuitive but with the slightly larger case and slightly heavier charge it makes for a very consistent load. It sort of helps to avoid a big jump to the throat which "seems" to help prevent leading-up the throats. Seating to the last lube groove adds a lot of air-space to an already overlarge case so I've got lots of room gas expansion with a fast powder like Red Dot or Bullseye. Maybe it helps or maybe it's just my perception but, either way, it works for me. The .38S&W case is a lot shorter so I seat them a lot farther out to avoid over-pressure and damaging the skirt and to make it easier to load. Small case + fat fingers = dropped cartridges.
View attachment 1088634

I'm not a competitive shooter and really could care less how the crowd at USPCA or IPSC or whatever the big boys with the pricey toys call themselves - that's their thing and it's fine but its not for me - I just care about keeping my skills at their current meager level for as long as possible and that means trigger time.

Yep trigger time…that really is the key.

When I was young and first worked at the FBI, a couple of us would get to the range in the DOJ building before the public tours started. We’d shoot and shoot and shoot on the taxpayers dime (but only government owned 38spl in those days—good old model 10).

I can’t describe how completely comfortable I was with a revolver in either hand (not to be confused with skill however). Mostly we’d shoot factory Winchester ammo but someone also rolled their own and we’d shoot it too. I could pick up on the very slightest difference in loads or thought I could anyway. OAL did make a difference to me in those days with a revolver.

There was an old gunsmith who’d clean our firearms for us. “Don’t want you to mess up your pretty clothes” he’d say.

Pre-pandemic I’d occasionally go to one range at 830am when it opened, shoot a couple hundred rounds of my own 45ACP, then run some errands and let my old hands rest up, and on the way home stop at a different range for a couple hundred of my 9mm. Briefly, I was nearly as comfortable as when I was young.

Now, just a couple years later, I haven’t been to the ophthalmologist for years so my shooting glasses are hopelessly dated and it takes my hands a full day to recover from just a hundred or so rounds, and OAL only matters to the pistol.

 

[GeoDudeFlorida]

Yep trigger time…that really is the key.

When I was young and first worked at the FBI, a couple of us would get to the range in the DOJ building before the public tours started. We’d shoot and shoot and shoot on the taxpayers dime (but only government owned 38spl in those days—good old model 10).

I can’t describe how completely comfortable I was with a revolver in either hand (not to be confused with skill however). Mostly we’d shoot factory Winchester ammo but someone also rolled their own and we’d shoot it too. I could pick up on the very slightest difference in loads or thought I could anyway. OAL did make a difference to me in those days with a revolver.

There was an old gunsmith who’d clean our firearms for us. “Don’t want you to mess up your pretty clothes” he’d say.

Pre-pandemic I’d occasionally go to one range at 830am when it opened, shoot a couple hundred rounds of my own 45ACP, then run some errands and let my old hands rest up, and on the way home stop at a different range for a couple hundred of my 9mm. Briefly, I was nearly as comfortable as when I was young.

Now, just a couple years later, I haven’t been to the ophthalmologist for years so my shooting glasses are hopelessly dated and it takes my hands a full day to recover from just a hundred or so rounds, and OAL only matters to the pistol.

I got a hard lesson in cartridge length a few years back when I tried loading Hornady 180gr. SSP for the .35Rem in .357Max cases for my newly improved HandiRifle. I ran them through a .357" sizing die to bring them down from .358" and seated to the cannelure with a light roll crimp. They plunked fine and seemed to be an ideal combo - especially since I got them at clearance pricing! . I ran 10 up a short ladder using W296 looking for 2000-2100fps and the first one read a little under (don't recall how much) but wouldn't extract. I opened and closed the action a few times but it didn't budge. Took a knife tip to get it out and the neck was broken when I got it out. There were small chunks missing and it looked like some hungry critter had gnawed on it. WT...huh???? I shot another, same velocity - no target because I was just checking speed not accuracy with this ladder - but I did see a puff of dirt next to the previous puff of dirt so I know the bullet was flying fairly straight and level. same problem: wouldn't' extract. It took a while but I finally figured out with the bullet seated to the cannelure FOR A .35REM! in the .357Max case, I was running the ogive into the lead and creating too much pressure, especially for a hot burn powder like W296, and the necks were being brazed onto the chamber mouth. Primers looked fine, though. I trimmed the cases a little short for book (Hornady bullets - figured I'd have to trim the cases short! ) and switched to some "cooler" powders - IMR 4227 and 2400 - and it was all good. Great bullet for a quartering shot to the base of the rib cage. It goes though the deep tissue like a buzz saw - gets the job done but it's messy to clean out the carcass.

 

[CQB45ACP]

I got a hard lesson in cartridge length a few years back when I tried loading Hornady 180gr. SSP for the .35Rem in .357Max cases for my newly improved HandiRifle. I ran them through a .357" sizing die to bring them down from .358" and seated to the cannelure with a light roll crimp. They plunked fine and seemed to be an ideal combo - especially since I got them at clearance pricing! . I ran 10 up a short ladder using W296 looking for 2000-2100fps and the first one read a little under (don't recall how much) but wouldn't extract. I opened and closed the action a few times but it didn't budge. Took a knife tip to get it out and the neck was broken when I got it out. There were small chunks missing and it looked like some hungry critter had gnawed on it. WT...huh???? I shot another, same velocity - no target because I was just checking speed not accuracy with this ladder - but I did see a puff of dirt next to the previous puff of dirt so I know the bullet was flying fairly straight and level. same problem: wouldn't' extract. It took a while but I finally figured out with the bullet seated to the cannelure FOR A .35REM! in the .357Max case, I was running the ogive into the lead and creating too much pressure, especially for a hot burn powder like W296, and the necks were being brazed onto the chamber mouth. Primers looked fine, though. I trimmed the cases a little short for book (Hornady bullets - figured I'd have to trim the cases short! ) and switched to some "cooler" powders - IMR 4227 and 2400 - and it was all good. Great bullet for a quartering shot to the base of the rib cage. It goes though the deep tissue like a buzz saw - gets the job done but it's messy to clean out the carcass.

Dang! Too technical for me. Actually, too frightening.
What do you hunt with it? Hogs?

 

[GeoDudeFlorida]

Dang! Too technical for me. Actually, too frightening.
What do you hunt with it? Hogs?

Whitetail. Deer. For hogs a handgun or levergun will do. They're not really impressed with us humans too much and tend not to be fearful of us as long as we don't stink like a predator.

A few of the local farms that specialize in melons and vine fruits open up their late harvest to the public for U-Pick berries and such. The place on our road stopped doing it when a guy sued them for damages to his car from the rough road. He lost in court but the lawyer and court fees plus time and travel was enough to do real damage financially to these folks. It's kinda funny - strange not ha-ha - to see the tourists and city folk who come out to pick berries on the local farms and try calling over wild pigs or deer when they wander up around dusk. The deer almost always just run off but I guess a few times one or two got ornery and scared some folks enough that they put signs up now, "DO NOT attempt to pet or feed wild animals!". Still I guess some idiots don't know a wild pig running in a pack considers them a potential meal.

Deer aren't as smart as pigs analytically in my estimation but they're about 100x more cautious which makes them about twice as people smart, I guess.

 

[CQB45ACP]

Whitetail. Deer. For hogs a handgun or levergun will do. They're not really impressed with us humans too much and tend not to be fearful of us as long as we don't stink like a predator.

A few of the local farms that specialize in melons and vine fruits open up their late harvest to the public for U-Pick berries and such. The place on our road stopped doing it when a guy sued them for damages to his car from the rough road. He lost in court but the lawyer and court fees plus time and travel was enough to do real damage financially to these folks. It's kinda funny - strange not ha-ha - to see the tourists and city folk who come out to pick berries on the local farms and try calling over wild pigs or deer when they wander up around dusk. The deer almost always just run off but I guess a few times one or two got ornery and scared some folks enough that they put signs up now, "DO NOT attempt to pet or feed wild animals!". Still I guess some idiots don't know a wild pig running in a pack considers them a potential meal.

Deer aren't as smart as pigs analytically in my estimation but they're about 100x more cautious which makes them about twice as people smart, I guess.

I thought hogs were tougher than that. We have a severe over population of deer right here at the beltway no hogs yet unless you count the idiots at il mee Korean bbq buffet.

Saw some hogs in Florida several years ago trash a Honda Accord on the turnpike somewhere. A trooper or animal warden was helping the octogenarians to his SUV for safety.

 

[Catpop]

N
Gleaned from internet years ago

 

[BJung]

Something can said about my last two tests. See here, the groups are about the same size.