How far off the lands for these bullets ?

B

boatbum101

Inactive
Am starting to do load development for a new 6.5X55 rifle . I've got the following on hand & was wondering if you guys might have used them & determined what " jump " they shot best .
120gr Speer Sptz , Sierra Sptz, Nosler BT
129 Horn SP & SST
125 Nos Part
140 Speer Sptz , Sierra GK , Horn SP & SST , Nos Part
155 Lapua Mega
156 Norma Vulkan , Oryx , Alaska
160 Sierra SMP , Horn 160 RN
Like the Barnes bullets work best about .030 off , I'm wondering about the above .
 
Totally dependent on your rifle. What works in one person's rifle, even of the same make and model, probably won't be the best for yours. You're going to have to start with SAAMI and go from there.
 
To really find your sweet spot, you are going to need to load iteratively.

I would load 2 iterations of powder weights with my oal at lands -0.030". Then load iteratively varying oal. Based of bergers examples, I think my first iteration would be 0.010", 0.040", 0.070", 0.100", and 0.130".

Berger method

Their method is different than mine. I shoot 5 simultaneous round robin groups of 5.
 
I am the fan of the running start, I want my bullets to have 'that jump'; I am also the fan of knowing where the lands are located. 95% + of my rifles do not need to be checked because I have to go way out of my way to get a bullet close to the lands.

And then I have my own methods and techniques for determining the distance from the lands back to the bolt face; for me it is easier to transfer the dimensions from the chamber to the seating die.

F. Guffey
 
If it is a Swede Mauser you may find the lands beyond reach. My Swedes have freebore so long the magazine limits the length of the round way before the bullet would have any chance of hitting the lands.
 
Is it a Savage/Remington etc or a Military Sweede rifle?

Generally its worth starting out at .020.

For a K-31, I found a lot further out than that. I have to look but the report was the lead into the rifling is not tapered, square. Something about a longer run shot better.

I went from wild 4 inch erratic 5 shot groups to consistent 1 MOA groups by moving it way back.

As noted, most of the time I find the tru lands and start out at .020.

I have a press I take to the range with me and if I am doing ok, but not spot on, then I can work with seating deeper.

First loads are .020, then the rest are longer than needed and I adjust back.
 
boatbum101 asked:
...what " jump " they shot best
Click to expand...

Start with the OAL for each bullet in the published manual you are getting your load data from. From there you can move the bullet in or out incrementally until you find your sweet spot. It often varies with the gun.
 
With the following bullets COAL "jammed" with a Sinclair tool :
Horn 129 SP #2620 = 3.062"
Horn 140 SST # 26302 = 3.156"
Horn 140 SP # 2630 = 3.115"
Horn 160 RN # 2640 = 3.1475"
Sierra 160 SMP # 1750 = 3.091"
Lapua 155 Mega # E471 = 3.032"
Norma 156 Oryx = 3.055"
Norma 156 Alaska RN = 3.145"
Norma 156 Vulcan = 3.034"
Rifle is a Tikka T3 Hunter pillar & Devcon bedded w/ a steel recoil lug ( bedding came out really nice ) floated 570mm barrel . No long throat like Swede Mauser . Even at .030 off I'm still going to exceed loading data Oal's from bullet mfgers / reloading manuals & still have enough bullet shank in the case neck for sufficent bullet pull . Brass will be either Lapua ( new or FL resized from prior use in CG 69 ) or new Norma . I was actually surprised @ how short the load manual & bullet mfgers had their OAL for their load data . I remember with the Swede Mauser & CG target rifles max Oal 3.150" was no problem with 95% of the bullets I used , but I only punched paper with them . This is my first hunting rifle in this caliber . Do you guys jam with start load to fire form cases ? As far as developement I planned to start 2grs below max published data & go up in .5gr increments to find POI sweet spot . For powders I selected 4 producing top velocity & load density for each bullet .
 
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Forget the off-the-lands stuff until you have worked up the load. It's just a load tweaking technique that really doesn't matter. However, it has nothing whatever to do with the bullet weight. It's about the chamber dimension that's different for every rifle. There ain't no 'iteratively' involved. Just use the SAAAMI Max OAL given in your manual and you'll be fine.
"...MOST guns like a bullet seated close to the lands...." Nonsense. Some of 'em can prefer as much as 20 thou or more off-the-lands. There is no set distance and no formula to figure it out. It's a 100% trial and error thing that rarely makes the slightest difference.
 
In my Sako A7 308 Win using the Hornady/Stoney Point gauge I have determined that my favored 165g bullets rest on the lands with a COAL of 3.00"

That is pretty long for a 308 WIN. The magazine in my rifle will hold a COAL of 2.90" with a little room to spare so that is where I load my 308's for that rifle.

Take note that is .100" off the lands for that particular bullet in my rifle.

In another 308, a Rem 700, those rounds won't chamber.

That is why no one can give you "proven" numbers that work. You have to sort it out for YOUR rifle. I think a lot more is made of the jump than is necessary. Stick to the COAL indicated in your load data and get a good load, then fiddle with OAL if you desire. But, like F.Guffey pointed out, it's good to know WHERE the lands are even if you will still use a standard OAL.
 
In the 1995 Precision Shooting Reloading Guide, the late Dan Hackett described a 40X in 220 Swift that averaged 5-shot groups of about 0.5" with some as much as 0.7" and some as small as a little under 0.4", but no better. He was loading it with bullets 0.020" off the lands because it was general knowledge that was "best". Then one day when he switch from loading one bullet to a Nosler bullet that was 0.15" longer, he accidentally turned his micrometer the wrong way, running it in 0.15" instead. Between the 0.015" length difference and the extra 0.015" seating depth, he wound up 0.050" off the lands.

Hackett didn't notice the error until he'd got 20 rounds loaded. At that point he decided it was too much bother to pull them down and reseat them, so he would just fire these 0.050" bullets for trigger practice. To his amazement they gave him two groups 0.25" and two true bugholes in the 1's (between 0.100" and 0.199").

This Berger Tech Talk article documents that some rifles want their bullets as much as 0.130" off the lands. Heresy to some, but it works.

Item #3 in this old page is another example. An old 8 mm Mauser with shot-out throat became the most accurate hunting rifle Somchem ever tested after backing the bullets way up from the throat.

My conclusion is that most folks experimenting with bullet jump never test a wide enough range of jumps and that those limiting themselves to fussing with tiny differences often are fooling themselves with groups that are actually just randomly smaller than others. It's easy to do.
 
The most accurate hunting rifle that I have shoots 10 shots into 3/8" @ 100 yds with the bullet ogive seated 0.204" off the lands.
 
I have heard that most Weatherby Rifles have a big jump too, though I have no first hand experience with that. Whether or no a Weatherby is considered an accurate rifle is another discussion...
 
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