Bullet seating depth vs. pressure vs. powder charge

[webby4x4]

I was in the shop reloading yesterday and I started to wonder... could you effectively load a smaller powder charge and simply seat the bullet a few hundred thousands of an inch deeper?

I obviously didn't do this, because, well... I'm new, and I don't want to do anything stupid. But, if I'm loading my .45 ACP and charge with 3.5 grains of Bullseye w/ a 200 grn SWC cast boolit, could I effectively load, say, 3.3 grains and seat the boolit .002" deeper?

I'm not really interested in doing this as I don't believe this will equate to much of a savings (and I kind of like all 10 fingers ), so this question is really just to satisfy my curiosity about seating depth, pressure and powder charge.

Rick

[rn22723]

Do not interpolate anything! Stick to standard data! BAD IDEA! VERY BAD!

[webby4x4]

I hestitated to even post this thread, because I figured someone wouldn't read the whole thing and would assume that this is something I planned on doing - it's NOT something I plan on doing, I'm wondering about the pressure effects is all.

I'm not really interested in doing this as I don't believe this will equate to much of a savings (and I kind of like all 10 fingers ), so this question is really just to satisfy my curiosity about seating depth, pressure and powder charge.

Again - I don't plan on doing this, but I couldn't find any data in any of my books about seating depth, except for the general warnings.

FWIW - I have books that show varying OAL for the rounds that I load (e.g. 9 mm, .45 ACP, etc.), so I typically go with the longer OAL to reduce pressure.

RW

[rn22723]

You do what you want, but unless you work in a ballistics lab you have no real way to measure pressure....and it is not a linear progression more like an exponential progression. Are you willing to deviate from standard data?

[Slamfire]

Gun Digest, maybe an 80's issue, had a technical article measuring pressures in a revolver. One of the reloading companies had created a special pressure testing revolver.

The data on pressure, powder charges, and variations in seating depth were surprising as all get out. I can recall a little depth change taking a 38 Spl target load into the +P region.

Phillip Sharpe, in his reloading handbook, his reloading data was not OAL, but was documented in terms of seating depth. So while the 80's data was news to me, Mr. Sharpe knew about it prior to WWII.

But, if I'm loading my .45 ACP and charge with 3.5 grains of Bullseye w/ a 200 grn SWC cast boolit, could I effectively load, say, 3.3 grains and seat the boolit .002" deeper

That is a light target load. I doubt .002" is going to show much of anything, especially as my 45 ACP GI bullets seating depth vary much more because their ogive varys so much.

However, if you increase seating depth by 0.2" of an inch, something is going to happen.

The basic problem for all of us is that without measuring equipment, you don't know what is going on. Not till you have gone way over the line.

Short of running for the hills and living in a cave, just be careful. Watch for signs of gross pressure, sticking cases, leaking primers or blown primers. Shune maximum loads. If your maximum load is working well, be aware that any change, of case, primer, bullet, etc, can cause problems.

[webby4x4]

and it is not a linear progression more like an exponential progression

RN - This is what I was looking for. Once again, I was NOT trying to do this nor did I want to... I was trying to understand the variances here.

Slamfire - thanks, this was really helpful! That is exactly what I was trying to understand here.

Overall, I'm a VERY conservative (and safe) reloader not only because I'm new at this (and am learning volumes each day), but mostly because I'm relaoding for the following reasons:
1) It's a great outlet and a very relaxing hobby for me
2) I'm only interested in tight grouping - I could care less about pushing the limits of anything (I tend to stick to the lower end of all loads (e.g. my books state that .45 ACP recommended load is 3.5 grns of Bullseye with a max load of 4.8 grns - I've loaded 7 different powder charges and have maxed out at 4.3 grns of bullseye powder)
3) I'm intrested in saving money.

Thanks again,
Rick

[Sevens]

There's a couple ways to save a teeny bit of money that would go further than shaving two tenths of a grain on powder per round.

First would be to pick a different powder. Compare the charges of Unique with AA#2 or 231 or Bullseye or Power Pistol across the same caliber and you can see quickly is many calibers how some powders simply use a smaller charge weight... lower charge weight obviously means more loaded rounds per pound.

If you buy your powder in a 4 or 8 pound can, you'll save more money than shaving 0.2 grains from a single loaded round. If you buy your powder from someone who sells powder MUCH cheaper than your local shop, you can also save a heap, much more than 0.2 grain per round.

If you use a lighter bullet (and it's still acceptable for the task), you'll need a bit more powder to send it to the target, but you can typically save a good bit on your bullet costs. In .45, compare 500 rounds of 185 gr with 500 rounds of 230 grain.

If you ever get in to bullet casting, you can save more money than getting your powder for free! Casting is not for everyone, though.

Theoretically, you could increase pressure by seating deeper, but as it was said, it's not a linear thing. And you need to make sure you ammo feeds and you case mouth tension is up to the task.

[webby4x4]

Great info, Sevens - thank you.

I do indeed cast my own bullets (I've cast about 3,000 so far, but have only reloaded about 500 to date).

I've started with Bullseye simply because it can be used in all of my handgun loads. Ironically, in almost every load, it requires the least amount of powder (as compared to Unique or 231 at least), but I don't have any data in my books on AA#2 or Power Pistol - I'll have to do some research on that!

I haven't sucked it up yet and bought an 8# keg yet, as I still have a few other things to buy (a tumbler/vibrator to start). Thank God my father gave me 40 years of reloading equipment, that saved me $1,000+ in doing this!

Thanks again for the info.

Rick

[Shane Tuttle]

Originally Posted by rn22723

Do not interpolate anything! Stick to standard data! BAD IDEA! VERY BAD!

Originally Posted by rn22723

You do what you want, but unless you work in a ballistics lab you have no real way to measure pressure....and it is not a linear progression more like an exponential progression. Are you willing to deviate from standard data?

What kind of "standard data" are you using? Have you ever looked at a typical load for even a common cartridge? Hornady, Speer, Lyman, Barnes, etc. can't even agree on a set load.

Webby, there's almost ALWAYS differences in data. Generally speaking, read up on more than 2 sources for a specific load. If each of the max charges are very close using the same COAL, knock it down by 10% while using that OAL.

Observe the characteristics in your gun:
Items such as cycling. Is your gun not cycling well? Are the spent cases ejecting erraticly?
As Slamfire stated, check for sticking cases, etc. Look for case head separation, higher than stated velocities, bullet tumbling on target.

Another big one is watching for malfunctions due to the chosen length. If you have COAL that's too long you can have failure to feed issues. Also, if the bullet isn't seated enough, it could be pushed into the case by the rifling when chambered. This isn't good. Too short OAL will raise pressures exponentially. Yet moderate incrimental changes when experimenting carefully is normal in the art of reloading.

Bottom line is don't make drastic changes when experimenting with loads for your gun. If you choose to shorten OAL, keep the powder charge on the low end of suggested load data. And ask questions...

[webby4x4]

Thanks Tuttle - great reply, chock full of good information.

I started digging through more of my manuals on this and found an interesting excerpt from the Lyman 44th edition (I know it's old, but it's one of 25 manuals my father gave me) and I just ordered the latest Lyman reloading manual. Here's essentially what it said...(see linked picture)

"PRESSURE SECTION: Deep Seating Bullets - Oddly enough, our testing indicates that considerable variations in the seating depth of jacketed bullets does not appreciably increase or decrease pressure. Lead bullets will, however, up pressures when they are seated too deeply. The base of a lead allow bullet has a tendency to expand when it is seated below the shoulder".
Very interesting indeed...

Nonetheless, I'll stick with the suggested OAL of my loads and split the difference between the manuals.

On a more odd note, here is what I've found as it relates to my 9mm...

Lyman 42nd Edition - 1.165" OAL
Lyman 43rd Edition - 1.169" OAL
Lyman 44th Edition - 1.169" OAL

Rounds that I've purchased:
Blazer Brass 115gn FMJ - 1.148" OAL
Remington UMC 115gn FMJ - 1.101" OAL
Winchester 115 gn FMJ - 1.163" OAL



ASSUMPTION 1:
Use the reloading and casting manuals that I have to get to average OAL for my 9mm load. Unfortunately, I couldn't find any information on Lee's website about loads... thus, I tried to find a similar shape, size and weight cast bullet in my manuals, and get to the average OAL. Is this a correct assumption?

ASSUMPTION 2:
The ogive varies from manufacturer to manufacturer, but the seated depth is likely the same between them (give or take). This should explain the BIG differences between the factory load FMJ's, right?



Thanks,
Rick

[steve4102]

Do not interpolate anything! Stick to standard data! BAD IDEA! VERY BAD!

Not sure what you mean by "Standard Data". Which one of these would you call standard?
45ACP, 185gr Hornady HP-XTP

Lyman 48, COL 1.175.-------------Hornady #7 COL 1.230
Clays 4.6gr max.------------------Clays 4.9gr Max
Bullseye 6.0.----------------------Bullseye 7.0gr
231 6.1.--------------------------231 7.2gr
AA#5 9.2.------------------------AA#5 10.4gr
WSF 8.0gr.-----------------------WSF 8.2gr





45ACP, 200gr Speer GD-HP
Lyman 48 COL 1.178.---------------Speer #13 COL 1.200
Unique 6.5gr max.------------------Unique 7.3gr
HS-6 9.0gr.------------------------HS-6 9.5gr
Power Pistol 7.4gr.-----------------Power Pistol 8.3gr
Bullseye 5.7gr.---------------------Bullseye 5.8gr
WSF 7.3gr.------------------------WSF 7.2gr
AA#5 8.5gr.-----------------------AA#5 9.0gr
231 6.2gr.-------------------------231 6.3gr

Note the difference in seating depth and how it relates to max powder charge. Pretty much all over the place.

[SL1]

Webby4x4,

What you originally wrote about decreasing charge when seating bullets deeper is correct in a general sense. The only issue is trying to figure out how much powder reduction is needed to keep the same pressure as the original data when going to a deeper seating depth.

I am assuming that you are loading the .45 ACP ammo for an auto-loader. It is common for people to slightly adjust seating depth (in and out) to make individual auto-loaders feed properly. That is typically done without worrying about pressure changes in target ammo. It is probably done with full-power ammo as well, but that is a little more questionable.

Some of what was written above by others seems unnecessarily scary for the amount of seating depth change you mentioned. The differences in guns virtually assures that the pressure in yours is different from the pressure in the test gun that was used to develop your loading data. A 0.002" change in seating depth will not make a greater difference than what you are already dealing with. Also, pressures don't jump around for no reason. So long as you are in the range of loads listed in the manuals, you can expect the powders to behave reasonably predictably with changes in seating depth, charge weights, etc. The equations used to make the predictions are not "linear", but there is enough data (beyond what is in the loading manuals) to make reasonable quantitative predictions. There is even a computer program, QuickLOAD, that is pretty good for doing that. But, to be reasonably accurate with it, it takes some tuning to data from your particular rounds and gun.

So, in summary, changes on the order of 0.002" in seating depth should not make enough diifference for you to worry about in a target load for the .45 ACP that is a grain below maximum. And, reducing the powder charge by 0.2 grains to "compensate" is probably more than necessary. For an auto-loader, you should really be adjusting your cartridge length to feed realiably and then adjusting your powder charge to give you the best accuracy in your gun. The pressure will be whatever it will be, and won't be a problem so long as you stay below maximum charge weight and don't make the seating depth many thousandths more than specified with the load data you are using.

SL1

[webby4x4]

Excellent - thanks SL1.

I haven't even come close to max pressure, and to be honest, don't really care to. The gun (a 1911 Colt Gov't with some small mods to is) and all of the reloading equipment were given to me by my father. He gave me 3 accounting boxes worth of manuals, books and his "secret recipe" books too, which show that this gun shot the tighest groups with 4.0 gns of powder, using the same molds that he gave me, and the same powder (Bullseye).

I probably asked the question incorrectly to get to the answer I was looking for. I know that everyone here is very safety concious (the biggest reason why I went to these forums and not some of the other ones, because I'm the same way).

Either way, this is all GREAT information. I was starting to get a bit nervous about seating some of my bullets and boolits a smidgeon deeper to help the gun feed better.

Thanks again,
Rick

[fjlee]

Webby4x4.……
Your interest and curiosity about “deep-seating” bullets is interesting. I’ve tried to chat about this subject a couple of times on various Forums……and experienced the same thing that you are hearing. The “doomsday” folks don’t even want you to WHISPER about deep-seating. The implication seems to be that even TALKING about it will surely cause your firearm to spontaneously explode.

SL1 had a refreshing & meaningful response to your post.

If you’d like to chat with me about “deep-seating“ of bullets , I’d be eager to do that. PM or email me, and we’ll do it in private. No sense in cluttering up an excellent Forum with a p***ing contest.

In the meantime, here are some “deep-seating” info sources I’ve acquired over the years. McPherson’s stuff in particular is fascinating. This is the same McPherson that was heavily involved in writing the Users Manual for the QUICKLOAD program. I have QUICKLOAD, ((thanks to Sandy Claws)) and it’s one of the good tools to use when one wants to speculate/chat about deep-seating.

Here are info sources:

Handloaders Digest 17th Edition…….article by M. L. McPherson
“Deep-seat Revolver Bullets to Improve Accuracy and Consistency”

Here is my favorite “deep-seating” article by McPherson:
http://www.levergun.com/articles/thoughts.htm

I think the following link will have a bit of “deep seating” chat:
http://www.thehighroad.org/archive/i...p/t-62176.html

Paco Kelly over at “sixguns.com” talks once in a while about deep seating.

I think the following Ed Harris article also has some deep-seating stuff:
“Silence is Golden” Part II……..GOOGLE it.

Deep-seating of bullets is an interesting topic, with some interesting things possible. It’s hard to have a good discussion, however, when 95% of the participants are foaming at the mouth, yelling and waving their arms.

If you want, contact me and we’ll talk.

FjLee Denver CO