Seating depth - does it even matter?

[Dobeman887]

I will try to be the second voice of reason. I tried chasing the lands when long range shooting was much less popular and knowledge was not as readily available. I did it for 2 barrels. It made accuracy WORSE, as the powder charge needed to be changed to bring it back.

Sometimes I throw the barrel away after the initial load stops shooting. If it is a screamer barrel, or I am being cheap, I can usually get more rounds out of it by moving the bullet out and adding powder. This is after 100s or 1000s of rounds though. Also, it is with chasing sub 1/2 moa for 10 rounds. I have never owned a hunting rifle/caliber that would consistently put nearly all 10 round groups under 1/2 moa. For very good 3/4 - 1 moa rifles it is not very easy to see. For good to average 1.25 moa to 2 moa rifles it is very difficult to see a difference. This is with 10 shot groups or more. Shooting less than 10 shots will definitely lie to you. 10 shots will occasionally, but I rarely shoot more as I feel it is "good enough."

TLDR version, only do it if you love to experiment and prove things to yourself. Chasing the lands is not beneficial to accuracy. It is detrimental.

Thanks for the input. I have only made 10 rounds so far to test, so maybe I won't take it any further than that.

 

[Dobeman887]

To update all of you on a lesson I learned from "chasing the lands", be very careful when increasing bullet seating depth. There are 13 pages of posts here, and I wish I had read them all before increasing my OAL. Bottom line, THE CLOSER THAT BULLET GETS TO THE LANDS, THE HIGHER THE PRESSURE BECOMES. I was lucky with my 270 and it simply destroyed the primer, rear of case. It could have been much worse. At this point, I will not chase the lands anymore and just stick to suggested OAL's.

 

[Fireflyfishing]

Yes, it matters.

 

[JGRaider]

To update all of you on a lesson I learned from "chasing the lands", be very careful when increasing bullet seating depth. There are 13 pages of posts here, and I wish I had read them all before increasing my OAL. Bottom line, THE CLOSER THAT BULLET GETS TO THE LANDS, THE HIGHER THE PRESSURE BECOMES. I was lucky with my 270 and it simply destroyed the primer, rear of case. It could have been much worse. At this point, I will not chase the lands anymore and just stick to suggested OAL's.

Yep, that's why you should start at max mag box length, or just off the lands, then increase charges until pressure is found. Only one way to go from there, and that's to seat deeper if need be.

 

[parshal]

If increasing COAL brings you to destroyed cases you're load is overpressure already.

 

[Harvey_NW]

Yes, it matters.

13 pages and only 1 example that falls outside the expected variability with a 17 cal that has a super short bearing surface.

If you claim that it matters, please provide proof.

 

[Fireflyfishing]

13 pages and only 1 example that falls outside the expected variability with a 17 cal that has a super short bearing surface.

If you claim that it matters, please provide proof.

Here ya go. Here’s a 15 shot group after I completed a seating depth test. This was obviously the winner. I only used 6 shots each on the 3 different seating tests I completed each load was 0.015” difference. According to the Hornady app, this is 15 shots under 1 moa.

 

[Harvey_NW]

View attachment 937461
Here ya go. Here’s a 15 shot group after I completed a seating depth test. This was obviously the winner. I only used 6 shots each on the 3 different seating tests I completed each load was 0.015” difference. According to the Hornady app, this is 15 shots under 1 moa.

Awesome, please also post the test results so we can factor in sample sizes and apply the statistical variabilities to see if your results align. Otherwise, this proves nothing besides you and your rifle shoot well.

 

[Fireflyfishing]

Awesome, please also post the test results so we can factor in sample sizes and apply the statistical variabilities to see if your results align. Otherwise, this proves nothing besides you and your rifle shoot well.

Unfortunately, I didn’t shoot photos of the test loads. What I can tell you is the other groups that didn’t make the cut were over 1 MOA with 6 shots. That led me to pick the load with the group above.

The bottom line, I’ve found it to be very beneficial after I have found a good powder and bullet combo. I go through the seating depth test process after the before mentioned combo is found. I consistently have good results in several different rifles.

As others have mentioned, sometimes it doesn’t matter. I have an AR that shoots mag length 77SMKs just over 1 MOA with a 30 round mag. I produce those loads in large quantity from my Dillon press, not individually from a single stage press.

I think it’s worth mentioning several of the bullet manufactures have a published method they recommend for a seat depth test. Berger being one of them. That’s the test I used. Erik Cortina has a vid with his version of a seating depth test.

 

[Harvey_NW]

I think it’s worth mentioning several of the bullet manufactures have a published method they recommend for a seat depth test. Berger being one of them. That’s the test I used. Erik Cortina has a vid with his version of a seating depth test.

I think it's also worth mentioning that every time ballisticians try to prove their testing methods with statistically valid samples, there is no fundamental difference in the cones of fire within the variability parameters.

Cortina is funny, he's the epitome of "it works, but I won't prove it to you", just like his tuners. If they really did, he would have no problem burning a free barrel down shooting valid sample sizes to prove it. And if he was really the best and had it figured out, he would win every single match. But instead he still gets beat by other shooters with top tier equipment and experience.

So, I guess I'll continue to wait and see proof that it matters *sigh*.

 

[khuber84]

I think it's also worth mentioning that every time ballisticians try to prove their testing methods with statistically valid samples, there is no fundamental difference in the cones of fire within the variability parameters.

Cortina is funny, he's the epitome of "it works, but I won't prove it to you", just like his tuners. If they really did, he would have no problem burning a free barrel down shooting valid sample sizes to prove it. And if he was really the best and had it figured out, he would win every single match. But instead he still gets beat by other shooters with top tier equipment and experience.

So, I guess I'll continue to wait and see proof that it matters *sigh*.

The Rokslide standard 1 moa 10 shot group doesn't require much tuning. The competitive benchrest fClass standards of half minute at 1k yards, require a lil more work on the reloading bench obviously.

 

[JGRaider]

I think it's also worth mentioning that every time ballisticians try to prove their testing methods with statistically valid samples, there is no fundamental difference in the cones of fire within the variability parameters.

Cortina is funny, he's the epitome of "it works, but I won't prove it to you", just like his tuners. If they really did, he would have no problem burning a free barrel down shooting valid sample sizes to prove it. And if he was really the best and had it figured out, he would win every single match. But instead he still gets beat by other shooters with top tier equipment and experience.

So, I guess I'll continue to wait and see proof that it matters *sigh*.

Guys like Cortina are worth listening to IMO. They've earned more trophies/award/accolades than 99% of any one else out there.

 

[Harvey_NW]

The Rokslide standard 1 moa 10 shot group doesn't require much tuning. The competitive benchrest fClass standards of half minute at 1k yards, require a lil more work on the reloading bench obviously.

I guess that's part of my question, is it work on the bench, or equipment? Do regular rifles just not respond to the changes in the same way?

For example - I have a 9.5lb factory Tikka T3X 6.5 PRC that's been touched up with an AW2 reamer, and throated for 143's to be about .050" off lands with boat tail edge seated to neck/shoulder. Throwing charges with a chargemaster, quick double check on a beam, seating with Hornady die on a Rock Chucker, did zero "load work" besides working up to pressure, and it repeatedly shoots 10 shot groups into .6-.7" and holds impressive vertical out to 1k, I need more wind practice.

Is it possible that someone like Cortina with custom dies, highest quality press, V4 auto trickler & FX-120i, top of the line barrels, perfectly chambered with True Bore Alignment System technology (I think that's what it's called, been a minute since I've listened to him), blueprinted, trued, timed, bushed firing pin Borden action, glued into a chassis, finished at 20lbs, is just always more likely to get better precision?

Even when coach Kieth from Winning In The Wind did his own test, the groups started to stabilize with larger samples.

Sorry to beat it to death, but I started this thread as an opportunity for someone to post their proof, since Hornady hasn't tested every single combo. Appreciate the input.

Guys like Cortina are worth listening to IMO. They've earned more trophies/award/accolades than 99% of any one else out there.

I listened to every single Cortina youtube video (+ many Winning In The Wind, F-Class John, Ultimate Reloader, Panhandle Precision, etc.) up to maybe a year ago. There is some great knowledge there, but also a lot of claims that I can't get to repeat in my hunting rifles. See my comment above, and that just may be what it is, 2 completely different systems and levels of shooters.

 

[JGRaider]

I guess that's part of my question, is it work on the bench, or equipment? Do regular rifles just not respond to the changes in the same way?

For example - I have a 9.5lb factory Tikka T3X 6.5 PRC that's been touched up with an AW2 reamer, and throated for 143's to be about .050" off lands with boat tail edge seated to neck/shoulder. Throwing charges with a chargemaster, quick double check on a beam, seating with Hornady die on a Rock Chucker, did zero "load work" besides working up to pressure, and it repeatedly shoots 10 shot groups into .6-.7" and holds impressive vertical out to 1k, I need more wind practice.

Is it possible that someone like Cortina with custom dies, highest quality press, V4 auto trickler & FX-120i, top of the line barrels, perfectly chambered with True Bore Alignment System technology (I think that's what it's called, been a minute since I've listened to him), blueprinted, trued, timed, bushed firing pin Borden action, glued into a chassis, finished at 20lbs, is just always more likely to get better precision?

Even when coach Kieth from Winning In The Wind did his own test, the groups started to stabilize with larger samples.

Sorry to beat it to death, but I started this thread as an opportunity for someone to post their proof, since Hornady hasn't tested every single combo. Appreciate the input.


I listened to every single Cortina youtube video (+ many Winning In The Wind, F-Class John, Ultimate Reloader, Panhandle Precision, etc.) up to maybe a year ago. There is some great knowledge there, but also a lot of claims that I can't get to repeat in my hunting rifles. See my comment above, and that just may be what it is, 2 completely different systems and levels of shooters.

Quite possibly he is a much better marksman than you are, or, once again, 99% of everyone out there. Lot's of people have great equipment and precision reloads, but lack the skill to do what the great ones do......aka there's only one David Tubb. Those guys can beat you with your own equipment.

 

[khuber84]

The big league shooters that have had success doing it a certain way, feel thats the only way. They turn necks, use mandrel, weight sort cases and bullets, sort bullets by oal and base to ogive. All this is done in the name of consistency to eliminate any erroneous deviation, dispersion or. "flyers" if you would.

Guys that compete in 600 and 1k comps, tune their rifles at that distance. I have shot quite a few 10 shot groups in the 2s and 3s with 6br variants. I've shot 20 shot groups that are half moa at 100y from 6gt and 65cm. I still don't think any of those rifles would be highly competitive at 1k yards even with the most talented of shooters. I cannot expect a rifle to perform at top level at a distance it wasn't validated at with load development. Half moa 10 shot groups at 100y don't equal half moa 10 shot groups at 1k yards. My opinion and observations have led me to believe this.

 

[Dan Carey]

For example - I have a 9.5lb factory Tikka T3X 6.5 PRC that's been touched up with an AW2 reamer, and throated for 143's to be about .050" off lands with boat tail edge seated to neck/shoulder.

I would like to know this works? Specifically, what the reamer does to the Tikka factory chamber? Not the throater, I know about that.

 

[khuber84]

I would like to know this works? Specifically, what the reamer does to the Tikka factory chamber? Not the throater, I know about that.

Opens base of chamber from saami 533, to 535 at 0.200 line. Give brass more room to expand and contract upon ignition. Allows for longer brass life before clickers occur. Good tight die is still desirable.

Can be done with proper tools without taking off the barrel, but it's easier with barrel removed from action.

 

[Packmansion]

Seating depth is not a critical variable. Load development that requires more than 30 rounds is a waste of time. 10 max for work up, 20 at max for collecting sd, average and getting a group size. Knowing your sd and average are cirtical for your accuracy, far more critical than your group size at 100 yards. These are my very strong opinions based on my experience and my engineering background. Seating depth tests are a waste of time and you're better off improving your skills and spending the money on practice than turning everything into a half assed grade school science experiment.

 

[huntnful]

Remind me after hunting season to shoot groups with my current seating depths, and then with the bullets .250 deeper. It’d be a good test. If something simply just doesn’t matter, test it at the extremes to find out.

 

[Packmansion]

My point is for someone to collect data on each powder charge and depth that is statically significant you have to load 20 rounds for each charge and depth. This would require at minimum 100 rounds and if we did the whole rain dance ceremony that a lot of folks do during load development would be in at min 280 rounds. If you are not willing to collect good data your are wasting your time waiting for a convenient lie to present itself. "My gun opens up on the 4 shot due to heat". "That was a flier". "That was a cold bore". Your are waiting for the noise to present data you like. When your group size opens up you are starting to see reality a reality you might be refusing to accept.