What is your initial COL for your initial ladder test?

My thoughts on seating depth’s effect on accuracy has evolved. I’m starting to think that it’s more about the bullet’s position in the case neck than its relationship to the lands.

I’ll stop there as I don’t want to hijack the OPs thread.

Find your lands and start 0.020” off. It’s as good a place as any

For rifle I normally use what the mfg suggest for a starting point. For handgun, what I determine that will work in my gun(s).

Through experimenting and testing over the last few years, this what I’ve found to be relevant, or at least it appears to be. Lol
where you start isn’t near as important as where you end up.
Seating changes won’t make huge differences in point of impact but definitely impact shape and tendencies.
Seating changes do effect case pressure but I haven’t been able to document exactly how much using a chronograph only on paper as posted below a 300 yard example.

I normally start a load work-up/test with the bullet manufacturer's book OAL. Chasing the lands is the last step for me to find "The Load"..

BJung said:

A fellow shooter years ago use to load his 7rm beyond max until his primers were flat, the primer pockets gave out, or his bolt was sticking. Then, he'd back out his load. I think his COL was .0015" of the lands.

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I would ask this guy to let me know before he pulls the trigger, so I can stand in the parking lot. lol
1) Find the lands 2) Back off .03 or so and load in incremental distances of .005 or of your choice.3) Start with a 10% reduction off of powder max and work your load up to your liking and watch for differences in bullet groups.
This is Hornady's method. Now the problem is a lot of people start with the powder first until they think they have found a good load and then start play with bullet seating towards the lands. Problem #1 is they can waste a lot of powder and may find "their great load" isn't all that great when the bullet nears the lands. Problem #2 is some people believe they have to achieved maximum load to achieve maximum accuracy, which is quite a false myth. Fit the load to what you are going to use it for. Ya don't need powder to kill an elephant to shoot a deer, or miss a deer because of excessive recoil. Problem #3 Bullet to lands is always going to be more important than the load. Some guns like some powders better; yes. Your gun will have several "sweet spots" for seating bullets. You choose the one you want. I'm in about the middle. That prevents me from jamming the gun while hunting with a bullet that deforms a tip because it's too far forward in the magazine, for example. "Aim small, miss small." movie quote from "Last of the Mohicans". The actor was taught how to correctly shoot a rifle by an expert and ad-libbed his instructions in the movie.

BJung said:

What is your initial COL when you begin testing to find the best powder charge for your load combination? I have tended to start just off the lands. After I find the powder charge that fit the nodes, I'd make a second set of tests by seating depth.

A well known youtube contributor begins his loads just off Jam. He forces his bullet into the lands where the bolt can close, then he backs off the bullet from there. I'm afraid of excess pressure but that's what he claims is the best.

A fellow shooter years ago use to load his 7rm beyond max until his primers were flat, the primer pockets gave out, or his bolt was sticking. Then, he'd back out his load. I think his COL was .0015" of the lands.

What do you do?

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Does the published COL fit in all of my magazines? Yes----->it's good to go.-----> No? That's never happened to me before.

I’m presuming you mean rifle. Pistol is a whole different animal.
I try use Berger’s suggestion, after establishing a node:
https://bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/
Good luck.

I'll either start with the oal out of the manual or .020 off. Either is just a starting place.

I'm probably the odd man out. Wouldn't be the first time. My effort is to load hunting ammo for factory sporter rifles........so my goal is to duplicate factory ammo velocity, with accuracy to 1 MOA or better. One of the rifles I'm loading for is new enough it came with an 1 MOA guarantee, which was based on use of factory match ammo. Some of upper end custom gun outfits lower that to as low as 3/8" MOA.....again, based on factory match ammo. None of that is loaded to the lands of any gun, and certainly not to these guns. So with that, I realized it is possible to load ammo to SAMMI specs and have some chance of getting to my 1 MOA or better. Have already done that consistently with one gun. Working on the others as time permits.

Loading to suggested OAL, with a crimp......will also assure this will function as hunting ammo, with no feeding problems, and if for some reason something I load for one caliber ends up in another gun of same caliber, it will probably go bang and have no issue.

I have also seen enough evidence to convince me that one can then fine tune a load by changing seating depth. So I'm loading about 0.020 longer than load data OAL, with plan to find an accuracy node with powder, then fine tune it with a set of loads seated an incremental 0.003 per step to find additional accuracy nodes. Find a good, safe, accurate load and lock it down.

Update: Shot this test load from rifle mentioned above. 308 loaded to SAMMI spec of 2.810. 46.5 gr Varget under 150 Hornady flat base Interlock. So not loaded to lands or recommended OAL of 2.735. Load was slightly compressed and chrony had loads cooking along at 2,925 fps ave.

Not counting the flyer, other 4 of those measure about 0.6 MOA. Will be curious if better accuracy nodes can be found by process outlined above, but if not, for my purposes, I can live with it right here.

Edited to include......Also used Lee Factory Crimp.

Looks good, will it repeat ?

Don't know......that was my first try with that load....but won't be my last. Also first loads ever with Varget. Reputation is well deserved.

My COL totally depends on the bullet and the gun. Some magazine rifles don't allow you to get near the lands at magazine length. With other rifle/bullet combinations, you might be able to get to the lands, but maybe not have enough bullet in the neck. I personally like to have at least a full caliber's worth of seating depth. If I do have enough bullet in the case, and am not constrained by a magazine, I like to start .010" off the lands.

Blue68f100 said:

For rifle I normally use what the mfg suggest for a starting point. For handgun, what I determine that will work in my gun(s).

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That works alright until you get a short -throated rifle like my buddy's 270 Savage 110. You always need to check that the overall length is compatible with your own gun.

Captcurt said:

That works alright until you get a short -throated rifle like my buddy's 270 Savage 110. You always need to check that the overall length is compatible with your own gun.

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I have several short throated barrels the reason i said "Normally". If I'm using Serria bullets and there data in most cases it will work, not all cases though. I have 1 gun that I have to load 0.030" shorter just to get 0.005" jump.

Howa 9700 said:

308 loaded to SAMMI spec of 2.810. 46.5 gr Varget under 150 Hornady flat base Interlock.
... Lee Factory Crimp

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Interlocks are not always the most consistent target fodder -- if anything the collet crimp may be helping here. Unless you called it, the flier is likely just bullet run out. I strongly suspect seating depth won't result in truly measurable changes beyond other environment factors. Fire a few 10-shot groups will better show your true bullet dispersion.

Howa 9700 said:

Update: Shot this test load from rifle mentioned above. 308 loaded to SAMMI spec of 2.810. 46.5 gr Varget under 150 Hornady flat base Interlock. So not loaded to lands or recommended OAL of 2.735. Load was slightly compressed and chrony had loads cooking along at 2,925 fps ave.

Not counting the flyer, other 4 of those measure about 0.6 MOA. Will be curious if better accuracy nodes can be found by process outlined above, but if not, for my purposes, I can live with it right here.

Edited to include......Also used Lee Factory Crimp.

View attachment 1051770

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Did you have a slight breeze from 2 :00 ?

Been a while since I ran a new test. I usually start .020-.030 off and go from there. I load for hunting accuracy out to 200 yards, and never find myself chasing the lands. Once I find what I think is a decent load I'll move the col +/- .005 at a time either way to see if it changes.

-Jeff

BJung said:

I try to get as much accuracy out of my factory and militaria rifles as I can by using benchrest case prep techniques. I have one Swedish M96 Target rifle that is very accurate but I'm not shooting that now.

As for the factory rifle, I plan to shoot hunting bullets. 1/2 MOA or better is my goal

I've been testing my T99 a lot recently. I found a good load with 7.7-174 Hornady FMJBT bullets with a OAL = the magazine well. The bullet never could touch the lands. At first, the best I could do was hit 8" left and down at 300 yards. I tried the load again a half year later but ran out of time plus my chronograph malfunctioned. I shot two similar loads and the impact was about the same. Shooting at an 8" red paper plate didn't help. So, I'll return this coming summer to do a better test. But, I happened to shoot two additional rounds. I neck sized and neck expanded two cases with a RCBS plug so my bullet tension would be more consistent. The seating depth was at what Ken Waters recommended and deeper. Two additional holes were printed unlike the previous test and they were both at a 1 O'clock position and about 1-1/2" apart. I don't use a spotting scope. So, if these holes are from the same bullet, I'm thinking that the closer a bullet is to the lands doesn't matter. As far away as that ogive is from the lands, there is a node with a bullet seated much farther back from the lands. Is there something valid with my hypothesis?

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For military surplus rifles. I use a different approach than factory or custom.
I have found that good neck tension and fast for cartridge powders give better accuracy.
Something between benchmark or 3031 and imr4064 or Varget and a flat baed bullet will work if anything will.

BJung said:

Maybe true. Use Reloader 19 for my 150gr bullets and Reloader 15 for my 174/180gr bullets and accuracy seems to be good. I can't explain why.

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R15 is inside that burn rate and 19 is on the edge. There isn't a definite line on burn rate.
I generally start with a slow burn rate keep moving to a faster one until it gives acceptable accuracy.
If your t99 has iron sights. You may be at your limit accuracy wise.

South Prairie Jim said:

Did you have a slight breeze from 2 :00 ?

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More like 5 to 10 from 3:00 to 4:00. But certainly a cross wind from right to left. Wind was moving my data book pages around and had the target flipping up.

If that is noticeable in a target, you guys are good.