Thanks for coaching me to success with seating depth for accuracy

[PigButtons]

A couple of weeks ago there was a thread on how important seating depth is to accuracy. I had never given it much thought because I had always found that loading to SAMMI spec and adjusting powder charges could get me to 1/4 to 1/2 MOA even if it took a couple of powder or bullet changes to get there. Then I bought a used MGM Encore rifle barrel in 308 and went to work trying to get at least a 1/2 MOA load worked up, but after four powders and three bullet selections 1.5 MOA was the best I could come up with. I have 500 Core-Lok 150 gr pull downs that I really wanted to use so I picked the best load I had found and decided to just test the theory of seating depth as an accuracy parameter. Using FC brass, CCI 200 primers, the Core-Lok bullets, and 3031 I set to work.

Since I didn't have any extra case neck to go longer I decided to go shorter and searched the site for advise. It seemed that .005 to .008 per step was the consensus, I decided to go big and seated the bullets .008 deeper. The 1.5 MOA load was now shooting just under MOA so a confirming group was shot and sure enough It held up. I tried another .008 shorter and now I was at 1/4 MOA. I NEVER expected to get such dramatic results from making that kind of adjustment and it is all because I have the good fortune of having all of you as my mentors and coaches.

Thanks to all of you that are willing to share your knowledge so freely.

 

[PigButtons]

Oh man! It just occurred to me that now I going to have to revisit all of those 1/2 MOA loads for my other rifles and do seating depth testing all over again. The joy and the pain of chasing perfection.

 

[RegionRat]

Another convert...

Glad that worked out. Sounds like a decent rig to use for testing.
You owe it to yourself to try into the lands at some point, just to see what how that looks even if you can't use it.

The more load development you can work at the range, the better you will get.

 

[PigButtons]

Another convert...

Glad that worked out. Sounds like a decent rig to use for testing.
You owe it to yourself to try into the lands at some point, just to see what how that looks even if you can't use it.

The more load development you can work at the range, the better you will get.

Thanks for the tip. I'm blessed to have a range at my house so that really helps. I'll have to go with a heavier bullet to chase the lands. This barrel has a lot of freebore.

 

[Link]

Some guys say don't chase the lands, find a big jump that your rifle likes ;]

 

[TheCZKid]

Since I didn't have any extra case neck to go longer I decided to go shorter and searched the site for advise. It seemed that .005 to .008 per step was the consensus, I decided to go big and seated the bullets .008 deeper. The 1.5 MOA load was now shooting just under MOA so a confirming group was shot and sure enough It held up. I tried another .008 shorter and now I was at 1/4 MOA. I NEVER expected to get such dramatic results from making that kind of adjustment and it is all because I have the good fortune of having all of you as my mentors and coaches.

I've watched an Erik Cortina video, he's talking to a benchrest shooter, and they say the nodes for seating depth happen in about .006 increments... so they said don't do .010 or .005 increment tests, as you might miss the node all together. Dang!! I figure a bigger cartridge might have different increments than a tiny cartridge. And freebore also would be a huge factor... I'm still trying to figure it out. I also appreciate the site and the information I get here!

This year is I really started trying to increase the accuracy of my loading, with my new 17 Hornet rifle. Shooting sage rats at 250 yards isn't easy, unless the load is really accurate. I did a seating depth ladder test with 12 loads of 3 rounds each, in .005 increments. It seemed super excessive, especially with being so hard to get primers. With my 17 Hornet I found it either liked a lot of jump, like with factory loads, or about as far out as I could seat it, and still fit in the magazine. I found the last 3 jumps of .005 were all close in group size. When I get into a "node" with seating depth, then I now go in .002 increments for final tweak.

So yeah, it makes a difference. And now, I think, I've got to go back over my loads from the past that just never were as good as I hoped, and I do lots more work to tweak!

 

[seymour fish]

Jack Neary. Lou Murdica. Tops for Cortina interviews. Look at “Winning in the Wind”, Keith Glasscocks YouTube channel, as it is Excellent.

 

[Dave M.]

Thanks for the tip. I'm blessed to have a range at my house so that really helps. I'll have to go with a heavier bullet to chase the lands. This barrel has a lot of freebore.

If it is a factory barrel you may never get anywhere near the lands. Make sure the twist rate of your barrel is acceptable for whatever bullet weight you are considering. Also, no need to chase the lands either. Better to select a wider load window for seating depth that is off the lands around .020-.050” (plenty of great Bullets that shoot great by jumping up to .080”….try the Berger Hybrids or their VLDs)
Dave

 

[ckaberna]

Oh man! It just occurred to me that now I going to have to revisit all of those 1/2 MOA loads for my other rifles and do seating depth testing all over again. The joy and the pain of chasing perfection.

Remember, at some point you have to be satisfied. If you continue to test ever possible variable it will be time for a new barrel about the time you get “the best”. Then start all over.

 

[Link]

Some guys say don't chase the lands, find a big jump that your rifle likes ;]

STOP CHASING THE LANDS

 

[D-4297]

Having shot roughly 5,000 Berger 185gr and 200gr Hybrids over the past three , three and a half years in F-class competition , I found they have two favorite seating depths . Either .005 off touch , or .020 off touch . Much like the Sierra Tipped Match Kings , they like being close to the Leade for better accuracy . This was consistent in two different rifles , and three different barrels for me . Rifle is a Kelby .308 Panda , with a 30" Krieger 5r , and Bartlein 30" 5r , chambered with 2013 FTR reamer . But whatever bullet you do use , finding the right seating depth is crucial to achieving the best , and most consistent accuracy .

Distance ? I do my initial load work-ups at 100 yards to get a very tight , hopefully round-ish group ,. Proof it a second time at 100 , on a different day , and then take it to 600 yards . As long as I'm holding a X-ring water-line , meaning Maximum vertical no higher than X-ring , I may play with seating depth a small amount to see if it will improve the group .

 

[Ned Ludd]

In terms of precision, seating depth is a big deal...huge, in fact, as you have discovered. Congrats on your success at using it to noticeably tighten up your groups. Sometimes, things as simple as how to use seating depth can be an epiphany, and it's usually very satisfying when that happens.

FWIW - I view .005" seating depth increments as very coarse, as I'm sure many here do also. I typically use increments of .003". If you use seating depth increments as large as .005" or .008", it is possible to completely miss a seating depth optimum, if it happens to be a bit narrow, which is not at all uncommon. Not every setup/load will have optimal seating depth windows that are .005" to .008" (or more) wide. If you choose to cover a wider seating depth range initially by using a more coarse increment, it's not a bad idea to go back and repeat the seating depth test to fully cover what you believe to be the optimal window using a finer increment. That way, you can better define both edges/margins of the window and make a more informed decision as to where within it you want to seat your bullets. Some prefer to seat to the middle of the window, I generally try to seat closer toward the leading edge (i.e. slightly longer CBTO), although still solidly within the optimal window. The idea of doing that is so that you have a bit more headroom with respect to land erosion before seating depth testing needs to be revisited.

 

[Orr89rocz]

In terms of precision, seating depth is a big deal...huge, in fact, as you have discovered. Congrats on your success at using it to noticeably tighten up your groups. Sometimes, things as simple as how to use seating depth can be an epiphany, and it's usually very satisfying when that happens.

FWIW - I view .005" seating depth increments as very coarse, as I'm sure many here do also. I typically use increments of .003". If you use seating depth increments as large as .005" or .008", it is possible to completely miss a seating depth optimum, if it happens to be a bit narrow, which is not at all uncommon. Not every setup/load will have optimal seating depth windows that are .005" to .008" (or more) wide. If you choose to cover a wider seating depth range initially by using a more coarse increment, it's not a bad idea to go back and repeat the seating depth test to fully cover what you believe to be the optimal window using a finer increment. That way, you can better define both edges/margins of the window and make a more informed decision as to where within it you want to seat your bullets. Some prefer to seat to the middle of the window, I generally try to seat closer toward the leading edge (i.e. slightly longer CBTO), although still solidly within the optimal window. The idea of doing that is so that you have a bit more headroom with respect to land erosion before seating depth testing needs to be revisited.

With components and supplies so hard to get I been tryin to do coarse adjustments, almost like the berger test method of .010-.015 jumps over a long span like .015, .030, .045, .060. Etc
Usually something stands out then i test somewhere closer, say .030 and .045 looked best, i’ll try .035 and .040. Then if any of those worked i’ll try say .033 or .042. Further splitting the differences. Then reverify another day to be sure.