COAL vs. how deep you seat the bullet

[Maximumbob54]

First off, let me say I follow the manual to the letter. I don't screw around and make guesses at loading. If the load book says it's fine, then I roll them out low and work them up to what I want within the limit. None of my loads are hot and heavy in the first place. My issue is just why the lowest common denominator type answer like a Cartridge Over All Length and not just a bullet mass in grains with amount of seating depth compared to what amount of powder gives this amount of pressure and it's all in a graph? What am I missing here?

 

[Ron H.]

Sir, a few reasons, mainly having to do with too many variables.

Bullets of a given weight in a given caliber can still have very different shapes, as well as different crimp groove locations, which affects seating depth and working case volume.

Jacketed bullets also have a higher coefficient of friction than lead, which means they're harder to push down the bore, and which raises pressures, all else being equal.

And if you're talking about loads that have to fit in a box magazine, that also affects permissible overall length.

There's just too many different variables to make a useful universal graph.

Hope this helps, and Semper Fi.

Ron H.

 

[Rule3]

Hmmmm, this sounds vaguely familiar

 

[Kinman]

I will give this reply due to the fact that I have recently dealt with the COL issue. It is my understanding that the COL's listed in reloading manuals are the "standard" or recommended length. There are other variables to be considered. I have been messing around with an old '93 model small ring mauser. When I tried reloading to the "standard" COL the groups achieved were miserable, I did a little research and found that it is necessary to extend the COL in order to reach the lands, the bullets used back in the day were longer than the standard 7 x 57 of today. One of the things that is necessary when developing a "custom" load is make sure it is only used the rifle it is developed for. I ended up reloading with a COL that was barely short of the magazine box length, that round delivered the best group. In a modern 7 x 57 chambered rifle it would probably make closing the action negligible. Not to belabour this thread but some bullet manufactures (Barnes) also recommend achieving a COL that brings the final length just short of the lands.

 

[Skip Sackett]

First off, are we just talking handgun cartridges? Because rifle reloading is a whole nutter matter.

In the case of a handgun, too long is not that big of an issue. Usually, and especially in a revolver, you aren't going to "run into something" that will cause pressures to increase. If things get that long in say, a 38spl, most likely, you are not going to get the cylinder closed. In an auto, I suppose that you can run into similar trouble BUT, again, the action shouldn't close if too far out of battery, and still, no kaboom.

The problem is in handgun cartridges where the OAL is shortened and there is more bullet in the case than the "recipe" expected. Now, if you are doing your reloading correctly, starting low and working up will save you precious body parts and maybe even a loving bystander or two. No harm, no foul. The problem comes into play when you are using a super fast handgun powder and reduce the amount of "free space" in a case with the same amount of projectile weight. Depending on the powder, you can have a real bad episode on your hands.

Case in point: 40S&W, 180gr bullet, Clays powder, bullet setback of .060" or something more with a full charge. What are you going to have when you pull that trigger? Right, you don't know and in the wrong handgun, you could have a catastrophe.

There are other factors that play a part too, bearing surface being one of them. BUT, I firmly believe, you don't have to agree with this, that seating depth is the most critical thing to causing a dangerous pressure spike that a reloader/handloader can overlook or change.

Listen, Elmer Keith's whole premise on the designs of his bullets rests on this one point: More bullet outside the case reduces pressures inside the case. Fill that extra space with powder and then the pressure can be raised to new and exciting levels! (Just an attempt at some dry humor.)

The reality is, more empty space in a straight walled pistol cartridge, same amount of powder and bullet weight will reduce the pressure in the case. Seat the bullet deeper, pressures increase.

Just my

 

[Maximumbob54]

Sir, a few reasons, mainly having to do with too many variables.

Bullets of a given weight in a given caliber can still have very different shapes, as well as different crimp groove locations, which affects seating depth and working case volume.

Jacketed bullets also have a higher coefficient of friction than lead, which means they're harder to push down the bore, and which raises pressures, all else being equal.

And if you're talking about loads that have to fit in a box magazine, that also affects permissible overall length.

There's just too many different variables to make a useful universal graph.

Hope this helps, and Semper Fi.

Ron H.

Different shapes is all about the top half of the bullet with a few minor exeptions like HBWC's. The bottom half of the bullet should be fairly uniform in handgun and with rifle you will get a minor difference in flat base vs. boat tail profile.

We already have lead vs. jacketed load data so I don't see how this would be much different.

If a load doesn't fit your cylinder or magazine, then it just wasn't made to fit that gun. So yes, COAL can prevent you from fitting a cartridge, but that's true of current loads with certain bullets already. Go 77 grains or larger and you have a tough time fitting in most AR's. That doesn't mean you just stick with the same COAL and seat them deeper...

Hmmmm, this sounds vaguely familiar

I know, I'm still stuck in the mud on this issue. I keep feeling like I'm right at the edge of understanding it and then I fell on my face. I'm hoping that if I keep bringing it up then either I will peice something together or someone will have a burst of brilliance.

I will give this reply due to the fact that I have recently dealt with the COL issue. It is my understanding that the COL's listed in reloading manuals are the "standard" or recommended length. There are other variables to be considered. I have been messing around with an old '93 model small ring mauser. When I tried reloading to the "standard" COL the groups achieved were miserable, I did a little research and found that it is necessary to extend the COL in order to reach the lands, the bullets used back in the day were longer than the standard 7 x 57 of today. One of the things that is necessary when developing a "custom" load is make sure it is only used the rifle it is developed for. I ended up reloading with a COL that was barely short of the magazine box length, that round delivered the best group. In a modern 7 x 57 chambered rifle it would probably make closing the action negligible. Not to belabour this thread but some bullet manufactures (Barnes) also recommend achieving a COL that brings the final length just short of the lands.

I think there will always be room for making a call on your load for it being gun specific. I already make a couple of loads for a certain gun that favors them. My issue is the current standard guidelines leave a LOT of gray area when you are loading. Most, not all, but most cases have a fairly uniform volume. I'm not including milsurp cases since they were made load specific to the weapon in the first place. The more of that volume you use, the less volume remains for the gas to expand in and thus more pressure with the same amount of powder. Seating depth would still leave some variables in the shady area, but it still seems like it would be better than just seat them all to this over all length...

First off, are we just talking handgun cartridges? Because rifle reloading is a whole nutter matter.

In the case of a handgun, too long is not that big of an issue. Usually, and especially in a revolver, you aren't going to "run into something" that will cause pressures to increase. If things get that long in say, a 38spl, most likely, you are not going to get the cylinder closed. In an auto, I suppose that you can run into similar trouble BUT, again, the action shouldn't close if too far out of battery, and still, no kaboom.

The problem is in handgun cartridges where the OAL is shortened and there is more bullet in the case than the "recipe" expected. Now, if you are doing your reloading correctly, starting low and working up will save you precious body parts and maybe even a loving bystander or two. No harm, no foul. The problem comes into play when you are using a super fast handgun powder and reduce the amount of "free space" in a case with the same amount of projectile weight. Depending on the powder, you can have a real bad episode on your hands.

Case in point: 40S&W, 180gr bullet, Clays powder, bullet setback of .060" or something more with a full charge. What are you going to have when you pull that trigger? Right, you don't know and in the wrong handgun, you could have a catastrophe.

There are other factors that play a part too, bearing surface being one of them. BUT, I firmly believe, you don't have to agree with this, that seating depth is the most critical thing to causing a dangerous pressure spike that a reloader/handloader can overlook or change.

Listen, Elmer Keith's whole premise on the designs of his bullets rests on this one point: More bullet outside the case reduces pressures inside the case. Fill that extra space with powder and then the pressure can be raised to new and exciting levels! (Just an attempt at some dry humor.)

The reality is, more empty space in a straight walled pistol cartridge, same amount of powder and bullet weight will reduce the pressure in the case. Seat the bullet deeper, pressures increase.

Just my

I'm only talking same same for both handgun and rifle in that the same volume + the same powder + a decrease/increase in case volume from bullet seating depth = a increase/decrease in pressure generated by powder during ignition. I highlight in bold what you said since I feel like I'm saying the same thing. And yes, more bullet outside the case means more volume inside the case and thus less pressure made by the same amount of powder. So once again... Seating depth would seem to be a better way of looking at this issue than COAL...

So I'm still stuck in the mud. Bullet profile with COAL still seems like it have a vast amount more variable to it than bullet seating depth ever would.

 

[Titegroups]

Thats the trouble with using COAL, is doesn't take into account bullet shapes but is a compromise.

 

[s&wchad]

I’ll address rifle cartridge OAL. If you’re only reading the recipes in the manuals, you’re missing “the rest of the story”. If you have a Nosler reloading manual, go to the front of the book and look for the section titled “Proper bullet seating” (it’s on page 42 of their 5th edition). The instruction paper included with my RCBS dies covers the same material. Basically, what they say is to measure the distance from the ogive to the start of the rifling and seat your bullets .015” to .030” off the rifling for best accuracy. Companies like Sinclair Int. sell specialized tools to measure the distance, but the method outlined by Nosler and RCBS is much less expensive and it works too. They tell you to slightly deform a non-resized case mouth to form a “D”, partially insert you bullet of choice and paint the sides of the bullet with a permanent marker or Sharpie. When you close the action, the rifling seats the bullet and the deformed case mouth scrapes the ink off and shows you where it stops. Because different bullets have different shape ogives and different rifles have varying amounts of free-bore, the sweet spot varies. As mentioned in previous posts, the SAAMI OAL is designed to insure that factory produced rifles and factory produced ammunition are compatible, they’re not designed to yield maximum accuracy.

Altering the OAL is an advanced reloading technique that can provide amazing results. A friend of mine worked up some loads for his .300 Win Mag before a recent elk hunt. His rifle, a Remington 700BDL, was only grouping about 2” at 100 yards with his best load (IMR7828, 180gr Nosler Partition). We measured the distance to the rifling and found that the bullet had to jump over .125” before it reached the rifling. I suggested he load a few batches of cartridges, seating the bullets .015”, .020”, .025” and .030” off the rifling. I went back to the range with him after he worked up the loads and .025” was the sweet spot; groups were right around 1”. All of the longer loads shot substantially better than SAMMI COAL, but the .025” load was noticeably better and he ended up taking the heart out of an elk at just over 300yds. The load fit in his magazine with room to spare and there were no signs of excess pressure. My 700 in .22-250 is similar and I load 50gr Nosler BT’s almost .125” over SAMMI; it cuts my groups in half. On another rifle of mine (a custom Remington 40X chambered in 6mm PPC-USA with a .262” neck), I actually seat Rubright 65gr bullets into the rifling. This is definitely NOT recommended on anything but a benchrest gun. The gun shoots about .2” on a calm day, but once a cartridge is chambered it has to be shot. If you try to open the action on a loaded cartridge, the rifling pulls the bullet, it dumps powder into the lug cuts and the gun’s out of commission until it’s cleaned. With a 2oz Timney trigger and no safety, it's a very specialized too!

 

[Maximumbob54]

S&Wchad -

I feel bad for the gnat's wings when you clip them.

I am right there with you on optimizing the bullet in a rifle load, but I'm only talking basics. Since there is so much room for change in many rifle loads, maybe this applies more to pistol loads. But the heart of what I'm trying to say should still hold true.

And if that was my rifle, I would call her "Plum Crazy"...

The Mopar generation may have been before my time, but I'm still in awe of what kind of cars we used to make.

 

[Rule3]

The only example I can give you is the use of a 115 or 124 gr LRN in either a CZ or Browning HP.

Both of these guns have funky barrels or "leades", chambers, whatever. There is no way to use the printed load data of OAL to seat the bullets to fit these guns (using MBC bullets) the bullet is so rounded it jams in the barrel using the "preferred" OAL.

I need to seat them much deeper in order for them to chamber. Doing so I need to reduce or at least use the min powder charge.

If I use a FMJ bullet with more of a pointed profile, all is well.

So to me, it all depends on the guns particular barrel.

OAL does not work well with bullets that have a cannelure as you normally would seat to the goove but most manuals have a "trim to length" which is a fraction shorter and most handgun brass is not trimmed to that length.

 

[Maximumbob54]

The only lead my BHP has seen is the truncated cone tumble lube bullets from my Lee mold. They worked fine, but they aren't round nose. Sounds like what Skip was saying about more of the bullet being outside the case. Which brings me back to my point... I hope my TC's aren't seated too far...

 

[Skip Sackett]

The only lead my BHP has seen is the truncated cone tumble lube bullets from my Lee mold. They worked fine, but they aren't round nose. Sounds like what Skip was saying about more of the bullet being outside the case. Which brings me back to my point... I hope my TC's aren't seated too far...

Measure the bullets in question, measure the bullets in the data, compare SEATING depth at OAL listed. If SEATING depth is deeper, as Rule has so wonderfully explained, reduce or use minimum loads.

It really is pretty simple to get a grasp on. I think you have it, it is just ODD to our "feed me the info and I will perform" mentality of today. When men used to do math in their heads and thought a calculator was silly. Back when folks that loaded understood what was more important, OAL or seating depth. Folks like Keith and Sharpe and ................ now, hopefully you and I.

 

[Rule3]

The only lead my BHP has seen is the truncated cone tumble lube bullets from my Lee mold. They worked fine, but they aren't round nose. Sounds like what Skip was saying about more of the bullet being outside the case. Which brings me back to my point... I hope my TC's aren't seated too far...

That's why you use the "plunk and drop test" with the barrel out of the gun. Seat them long and keep testing untill in drops in and out (with a crimp) and go with the "magic" length that works and adjust your powder if needed.

 

[Maximumbob54]

Measure the bullets in question, measure the bullets in the data, compare SEATING depth at OAL listed. If SEATING depth is deeper, as Rule has so wonderfully explained, reduce or use minimum loads.

It really is pretty simple to get a grasp on. I think you have it, it is just ODD to our "feed me the info and I will perform" mentality of today. When men used to do math in their heads and thought a calculator was silly. Back when folks that loaded understood what was more important, OAL or seating depth. Folks like Keith and Sharpe and ................ now, hopefully you and I.

I think I can at least see the light at the end of the tunnel.

That's why you use the "plunk and drop test" with the barrel out of the gun. Seat them long and keep testing untill in drops in and out (with a crimp) and go with the "magic" length that works and adjust your powder if needed.

If I load for an auto, I pull the barrel and make sure it drops in flush with the barrel hood. I find that so far all my seating depth use has worked so far. But I didn't think about how much bullet is going into the case on those TC bullets. I loaded those a while back before I got all concerned about this issue. They worked fine, but it does make me think that I didn't have to work them up at all for function. I started low and they just worked...

 

[Jamie]

That's why you use the "plunk and drop test" with the barrel out of the gun. Seat them long and keep testing untill in drops in and out (with a crimp) and go with the "magic" length that works and adjust your powder if needed.

NOW even I understand. Just got reloading equipment for Christmas, trying to pay attention to what I need to do first. First, don't blow nuthin' up! When I finally get the last bits and pieces together, (including the actual powder, bullets, primers, etc), hopefully all this will REALLY make sense.

 

[jkc]

... (Just an attempt at some dry humor.)

I was led to believe that dry humor was not appreciated in this forum.

 

[Skip Sackett]

No, humor that is labeled as humor, some forums want you to put it in purple so everyone knows you are kidding, is always appreciated.

When you get around a bunch of gun nuts, paranoid already because we have a democrat in office, threaten legal action as has taken place on other forums, (at least rumored to have taken place), people tend to react accordingly.

You will be laughed with or at, as the case may dictate, when you label your humor as such.................... (Case in point!)

I hate that we are taking time away from the OP's question, but, I usually don't let things slide too well!

 

[Maximumbob54]

I think you are getting a little deep in the cartridge on this one...

(insert knee slapping smiley here)

 

[Skip Sackett]

 

[Rule3]

I was led to believe that dry humor was not appreciated in this forum.

No, you just need to fully explain it for those who can not grasp it. (and use a lot of these things)

Just imagine if Sipowicz reloaded???