how far from the lands?

[Deadboyreloads]

I just got the Hornady lock and load overall length gauge. once i find the length to the lands for .270 win, how far should i back off the lands.

[m&p45acp10+1]

I load all of my loads to magazine length as defined by SAAMI. I tried that loading closer to the lands thing with several rifles. While it did give a wee tiny bit of extra accuracy it was such a pain in the posterior that I quit doing it. The loads I worked up in all the rifles I load for give MOA or better on a crappy day, loaded to the same length as factory ammo.

[noylj]

"Typically" many start about 0.02" of the lede. Find a good load, and then adjust the COL to fine tune accuracy.

[AllenJ]

It depends on what bullet you are using. With Berger's I try and get them as close as possible without touching. With my 243 it turned .75" groups into .33" but with a 7mm Remington Mag it did not seem to make a difference though. With Barnes I keep them off about .05" but to tell the truth I've never really experimented with different distances. I read .05" in a Barnes newsletter and the 243 shot .25" groups, so I figured I'd leave well enough alone. Keep in mind the closer you move the bullet to the lands the higher your pressure is going to be. If you are using a max load and want to move the bullet closer to the lands I would suggest reducing the powder charge and re-work up the load.

[WWWJD]

Agree with M&P. I have a Remington 700 with a lead length too long to do it at all. It's not stopped me from shooting 1/2 moa groups with certain loads at or close to the standard OAL. Even if I could, I don't much care for feeding one at a time because I'm over mag length. Just seems like a lot of inconvenience for little to no payback.

Probably not the case for some, but my seating depth tests wound up inconclusive and a waste of bullets & powder.

[Nathan]

I consider 0.030" a good starting. With a hunting load, I wouldn't go closer than 0.020" because I never want a bullet stuck in the lands. Bergers like to be near 0.

[black mamba]

Since pressure decreases as you move away from the lands, I start at .015" to work up pressure loads, then try the same charge at .030" and .045". Using the seating depth that is most accurate with the max load, I back off the charge in 1/2 grain increments until I find the best accuracy. It's usually within a grain of max, so you only give up about 40-50 fps. Accuracy trumps an inch or two of bullet drop every time, for me.

[Unclenick]

You can start with the bullet touching the lands or even 0.010" into the lands, as long as you work your load up there. This is what Berger used to recommend with their VLD designs. Then they learned it didn't work well for everyone, so they switched to the system described here.

[Scottish Highlander]

Hi all,
I've read your link Unklenick which is a good post but I was wondering if your statement
" You can start with the bullet touching the lands or even 0.010" into the lands "

is generally for the Berger bullets only or if you can look at it fully throughout the whole reloading manufacturers with there bullets. I am by no means questioning you but I've read and was led to beleave touching the lands was BAD news as that would induce pressure increase.

Thanks Jamie

[Bart B.]

Yes, loading bullets so the seat into the lands increases pressure. How much depends on a long list of things.

So does using heavier bullets. Tighter neck tension. Hotter primers.

Cut back a grain and you should be fine.

Or, work up from 8% below listed max then test for what you think's a good pressure sign.

[reynolds357]

I start load workup in the lands on all my loads where the magazine will allow it. I then find my pet powder charge. I then play with seat depth as the last variable in my load. (except WBY. chamberings)

[Scottish Highlander]

So really this is where a chronograph is a must for reloading I'd say.

Eg......If you loaded a 150 grain ballistic tip boat tail into a brass case and you had it touching the lands and started with the lowest powder weight in the book. You may find that because of that, the pressure could be up but so would the velocity. As you seated the bullet deeper in graduations of 0.002 you would see the velocity drop and also the pressure would to. This is when you would increase the powder grains by 0.2 grain to bump up the velocity again. And at some point you would find that one load some where in the middle your personal rifle would say YES this is where I want to be at with this bullet and you'd be shooting 1/2 inch @ 100 yards consistently or tighter.

Ok well I'm beginning to think this reloading has wayyyyyy more involved in it than I'd first presumed. The magazine on my rifle doesn't allow me to chamber reloaded bullets over a certain length which really eliminates getting closer to the lands than I already am.....unless I just drop them in and close the bolt as a single shot.

Note to myself BUY A CHRONOGRAPH lol

Jamie

[Bart B.]

Jamie, I don't think a chronograph will help reloaders to develop a load for best accuracy. Only for the highest velocity. And seldom are both objectives met with the same recipe of components. There's too many competitive rifle shooters who win matches and set records with their handloads and do not use nor own a chronograph. And game animals will never know the difference between being smacked with a bullet arriving 50 fps faster or slower than another one.

The only folks I know of that used a chronograph for anything in developing accurate loads were the USA arsenals making .30-06 and 7.62 NATO match ammo. Velocity spreads had to be within 30 fps of the standard muzzle velocity for each. That requirement's in place because all the rifles that ammo was designed for had the same sights. With good accuracy and muzzle velocity specs met, one could use the same sight settings for all ranges and be within about 1/2 MOA of exact.

Besides, the barrel you use to develop a load for will not shoot a given recipe from loading data for a given bullet at the same velocity as the developer got. Your barrel, 99.9% of the time, will have a different cross sectional bore area that the one used to develop that data's load.

Unless one can shoot their rifle into 1/3 MOA or less at 100 yards, I don't think it's worth the expense (barrel life and components) to keep adjusting bullet seating depth in search of better accuracy. Load them to fit the magazine for general use or just short of the lands for single loading. If the bullets are reasonably straight on the case, few people will ever tell the difference in accuracy unless they shoot test groups with at least 30 rounds in each one; maybe not even then.

[Nathan]

. . . .I don't think a chronograph will help reloaders to develop a load for best accuracy. Only for the highest velocity. And seldom are both objectives met with the same recipe of components. There's too many competitive rifle shooters who win matches and set records with their handloads and do not use nor own a chronograph. And game animals will never know the difference between being smacked with a bullet arriving 50 fps faster or slower than another one.

This is an interesting point. That is why I use a chronograph. I find that the point where my standard deviation is minimized and I got best accuracy while testing is the point where I should set my load. This is because the 2 are related and I might have a small error in shooting, but the chrony usually does not make mistakes.

Using on paper results only caused me to load up 500 of a load before and wonder why it wasn't quite as accurate later on. After chrony, I don't have this issue.

So, how do you guys develop 2 variable loads. I usually pick one. Set the other variable at a best guess. Then develop the first variable. Then make a second set of loads to develop the other one. Trouble is the variables are interrelated!

[Scottish Highlander]

That's fair enough Bart B but wouldn't a chronograph give me an indication of pressures ?

I continually read on here that most pet loads aren't max powder loads.

So if I had a crono at least if I started of at a certain powder weight eg.. 40 grains. Then seat the bullets at different depths from the lands then you would get an indication from the crono what the pressure was doing. If I seated a bullet and case to a max OAL 2.80" and loaded 20 cases all at 40 grains.
First 5 cases being OAL of 2.80"
Next 5 cases at 2.82"
Next 5 cases at 2.84"
Next 5 cases at 2.86"

Fired all 20 shots on paper @ 100 yards measuring through a chronograph then surely there would be a difference in velocity because your closing the gap from Lands. If the manual stated for that particular bullet and powder was an average velocity of 2750 ft / sec and you were getting around about that but slowly creeping up and with the last 5 loaded bullets that were seated at 2.86" OAL you knew that you were landing 0.002 of the lands and the velocity spiked up to 3200 ft / sec on the first shot you fired but no pressure signs on the case then at least the crono would be giving you an indication of what was happening and that you were kissing the lands. Or wouldn't this be the case ??

All measurements are for example only

Jamie

[reynolds357]

S.H. I have two chronographs and rarely drag either one of them out of the closet for load development. I have found that accuracy and velocity rarely have any coorelation to each other. You can use the chronograph to identify velocity consistency, but you can also use the vertical string, or lack thereof to do the same thing. Pressure signs can be pretty accurately read from the cases. I usually develop an accurate load and then find out how fast it is. When I load develop with a chronograph, I have habit of developing loads for velocity and not accuracy.

[Bart B.]

Best accuracy often happens with loads whose velocity and peak pressure numbers' standard deviation is not the lowest.

Yes, more velocity with a given load caused by more powder in the case means more pressure. How much more's only a guess without proper measuring systems.

And a listed load claimed most accurate in the rifle it was developed with may well have a different peak pressure than your barrel does with the same load. Not to mention the fact that your barrel may well shoot with less accuracy than the listed load does if you can get it to shoot bullets out at the same speed.

Fact; there is no correllation between consistant velocity and pressure numbers versus best accuracy. Best examples are when a very good lot of ammo's issued to several dozen folks shooting 600 through 1000 yard matches and it shoots at the same great accuracy level (1/2 to 3/4 MOA) across all sorts of chamber, bore and groove dimensions with different amounts of bullet jump to the rifling. Both muzzle velocity and peak pressure are not the same across all barrels; just the accuracy.

Best accuracy typically happens when the pressure curve's very repeatable and pushes bullets out with reasonable velocity standard deviation. And the bullets exit the barrel on the muzzle's up swing just before it reaches the top and starts back down. This makes bullets leaving slower depart at a slightly higher angle to compensate for their greater drop down range. The opposite's the situation with faster bullets. You start messing with powder charges and get that bullet exit point in the wrong place in the muzzle axis' whip arc and accuracy gets worse. The Brits proved this over a century ago. with their .303 cartridges.

[Unclenick]

Jaimie,

The biggest pressure change with bullet contact that I've seen measured is this one from RSI (copied here with permission from Jim Ristow):

Originally Posted by RSI

Here's a classic good load for 6PPC. The only difference between all these traces is the first 3 were seated right on the lands. The last 4 were 30 thousands of an inch off the lands. Note the substantially reduced pressure and overall reduction in energy.

That's about 20% change. It will correspond to about 7% to 10% difference in powder charge depending on the load and rifle. I like to use the tried and true 10% reduction normally associated with load workups when starting with a bullet in the lands. Still another option is soft-seating. Mid Tompkins told a class I took that he relies on this method. The neck is sized so that it holds the bullet, but you can still move it with your fingers. It is seated out long, then loaded singly and closing the bold then finishes seating the bullets. The only drawback to this loading method occurs if you have to eject an unfired round for any reason. Often the bullet sticks in the throat and is pulled out as you extract the case, so you have to be careful to be muzzle-up and to capture the case to avoid spilling powder all throughout your action and not forget to use a cleaning rod to knock the bullet out before your try to chamber another. Obviously that knocks this method out at ranges that don't allow muzzles to point into the air for reasons of fall-zone hazard.

The Berger recommendation is for their secant ogive bullets. Tangent ogive bullets are more forgiving of seating depth variation. This is the reason for the newer Berger Hybrid design, which has a tangent ogive where the ogive meets the bullet bearing surface, that switches over to secant profile as the ogive starts to narrow.

Whether or not bullet tilt will matter to your gun much is yet another variable. Some guns, especially those with tight match chambers, do not seem to be as adversely impacted by bullet tilt or exact jump to the lands as looser commercial and military chambers are. Tight bores can straighten them further. I put up a diagram of measured results of bullet tilt in another thread for a tight benchrest chamber verses a military '03 NM chamber. It represents tilted bullets with the high sides indexed at 90° intervals around the chamber. I'll put it below as an FYI. Note that if you measure your high sides and orient them all to the same direction in the chamber, you cut the total error in half.



If you are interested in the effect of bullet tilt on your gun, I would copy Harold Vaughn's method and intentionally bend about 0.004" of runout into some loaded rounds by using a neck-size hole in your bench or other convenient place. Abbatiello found that with the .30-06 NM loads, that was about as much tilt as made any difference. Greater tilt than 0.0040"-0.0045" had no additional effect on group size. The bore seemed to straighten any additional tilt out, so it didn't stay with the bullet through the bore.

As you've observed, many long-seated rounds are strictly for single-loading an not for magazine feeding.

As to chronographs an pressure, there are indirect ways to estimate pressure from a chronograph reading, but nothing other than direct measurement will give you a certain peak value. The average pressure behind the bullet during its time in the barrel is directly proportional to the kinetic energy of the bullet at the muzzle, which is proportional to the square of the bullet velocity. However, average pressure is determined by a combination of peak pressure and the much lower muzzle pressure. Where muzzle pressure tends to vary close to directly with powder charge, peak pressure varies exponentially with powder charge, so it is not only higher by what is typically around a factor of five or six, but any change in velocity will reflect a greater change in peak pressure than in muzzle pressure. How much greater depends on where you are in the exponential curve.

I can give you formulas for working that out from your velocity plus input from published measured pressure and velocity data for the same powder, but it's a bit of a trial. I have an incomplete Excel file for doing this. Remind me by PM in a couple of weeks and I'll try to finish it.

Meanwhile, the main value of the chronograph to the average shooter, as already mentioned, are proving the velocity consistency of your load for longer ranges. You can also use it to make charge adjustments needed to return to your original development load velocity when you get a different powder lot, change cases or primers, or get a different make of bullets that are the same weight. You can also check the effects of changing temperature conditions, barrel warming, etcetera.

[jmr40]

I don't think a chronograph will help reloaders to develop a load for best accuracy. Only for the highest velocity. And seldom are both objectives met with the same recipe of components.

I sorta agree, especially from a target shooters perspective, but as a hunter my chronograph is invaluable for developing a balance between acceptable accuracy, and bullet speed. I load primarily for 308 and 30-06. By careful powder selection I'm able to best factoy loads by around 50 fps in the 308, closer to 150 fps in the 30-06. And do it with loads 1-2 gr below max listed loads. Accuracy is between 1/2-3/4". I suppose I could be a bit more picky about accuracy, but that meets my requirements. Especially from hunting rifles.

I use my chrono just like the speedometer in my truck. To keep me out of trouble. I have no desire to load anything over what is listed in a reputable loading manual. But I don't want to buy a 30-06 and shoot it at 300 Savage speeds either. Most traditional pressure signs don't show up until you're already well above safe levels. My chronograph lets me know how fast I'm going at load levels that are still safe. Loading without a chronogaph is like driving without a speedometer, only a warning light that comes on at 90 mph.

And you don't have to be hot rodding a load to get into trouble. I've seen different guns shoot ammo from the same box more than 100 fps different with a load 2 gr below max. It would be perfectly safe in one rifle, but not the other. I've seen loads that were 3 gr below max exceed the velocity suggested for a max load. It would be very easy for someone without a chronograph to think they had a mid level, perfectly safe load when it is in fact a borderline hot load, at least in some rifles.

I don't think it's worth the expense (barrel life and components) to keep adjusting bullet seating depth in search of better accuracy. Load them to fit the magazine for general use

This is exactly what I do. I load my bullets to fit the magazine with enough room to make sure nothing will hang up even if the cartridge is at a bit of an angle in the magazine. If the bullet bumps the rifling when chambered, I seat it a little deeper until it doesn't. I quit worrying about exact seating depth a long time ago. My accuracy is good enough.

[Bart B.]

Unclenick, in those picutes of groups, what's the "inch/Degree actual/theoretical" numbers for?

Indexing rounds in SAAMI/MIL-SPEC chambers does improve accuracy with .308 Win. ammo. Especially with those with more than .003" bullet runout. Runout less than that in such chambers shows little, if any, improvement when indexed compared to rounds perfectly straight. At least in my experience with M118 and M852 7.62 NATO match ammo.

Soft seating bullets is a boon to accuracy with handloads, as you mention. "Firm" seating is what I've used which is enough to hold bullets good enough for normal handling yet still seat them back a bit when chambered. These don't stay in the leade as the firm grip by the case neck pulls 'em out when unloaded rather nicely. I did this after my second need to push a bullet out with a cleaning rod down the upright barrel. But putting both back in tbvojhe case and shooting them resulted in their going to call on target.

The two .270 Win. rifles I've owned both had loaded round's head-to-shoulder length shortened a couple thousandths inch by firing pin impact. And verified by firing primed empty cases in them and measuring that distance. So, whatever bullet jump to rifling distance was set up by the bullet seater, it gets shortened a couple thousandths when fired.

Note the bullet's jump to rifling distance is best referenced to the case shoulder as it's hard against the chamber shoulder when fired. The case head is not touching the bolt face. There's a few thousandths inch spread across a bunch of cases' head to shoulder dimension. So, the "head clearance" dimension from bolt fact to case head when the round's fired will cause a small spread in the bullet's jump to the rifling even with the case head to bullet ogive reference diameter's length has zero spread.

All of which boils down to a couple of things that'll cause variables in the bullet's jump to the rifling; case headspace and shoulder setback spreads. It can easily be .005".

[Unclenick]

Originally Posted by Bart B

. . . what's the "inch/Degree actual/theoretical" numbers for?

Bart, that's the number of inches added to group diameter at 100 yards by each degree of bullet tilt. Vaughn's bullet was tilting 0.22 degrees when it was tipped 0.0035" off-axis (0.007" total indicated runout). The M72 was tilting 0.175° tipped 0.004" (0.008" TIR) off axis. It seems like right around 0.2 degrees is about as much tilt as matters. Beyond that, the bore seems to straighten any additional tilt out.

I should probably have translated the inches to moa, but just was running by the available data, which was in inches from Vaughn. It's in moa from Abbatiello, but I converted it for consistency. (At least, I think I did. I should reread and check that).

The theoretical number is what Vaughn's calculations showed you would get if the gun didn't straighten the bullet any in the bore, IIRC.

No question about the shoulder determinant. IRRC, Hatcher actually measured up to -0.006" shoulder setback from rapid chambering of the .30-06. Of course, the heavier the finished cartridge, the more momentum it has.

I use a device I made to measure from the shoulder to the bullet ogive of a cartridge. It gives the best consistency. I understand the Redding Instant Indicator will do this, too, as well as make several measurements mine won't. On the other hand, mine is caliber convertible. Just change the knurled shoulder profile nut on the bottom and the ogive riding plunger above it. Both those parts I use my actual chamber reamer to make. I can also use it to make the measurement on the Stoney Point (LNL) Overall length comparator, set the zero there, then read the number of thousandths off the lands directly on the dial. But if they are chambering hard enough to set shoulders back, the only thing I can think to do is chamber a bunch and extract them unfired for measuring until you learn how much average allowance to make for them with your components in your gun.

[Clark]

In bottle necked rifle cartridges, I seem to get the best groups jammed into the lands.

In straight wall rifle cartridges, I seem to get the best groups off the lands and roll crimped into the cannelure.

[hooligan1]

I usually start all my test loads at .010 off lands, and after I find OCW, I start tweaking in and out until I have passed through accuracy node. Its easier for me, Always done it that way, and Bambi don't seem to notice.

[603Country]

I normally start with what the Lyman 49th suggests for bullet length (unless it's a huge distance to the lands with that loading) and work up powder charges. Then I'll tinker with length.

Today I ran low on ammo for my 223, so I set up to load. Checked my data book to confirm the OALon what I had been shooting, which was 2.215. I rechecked the distance to the lands and I could load out as far as 2.28 in this rifle. I had time, powder, and bullets, so I loaded some at the 2.215 and shot a while. Good accuracy, so I'll seat em out a bit further. The closer I got to the lands, the worse the rifle shot. That confirmed the data I had from the last load session.

[noylj]

What, pray tell, is OCW?