SEATING DEPTH MAX INTO LANDS

[SST2500]

I’ve been doing some seating depth ladders on the new Hornady 6mm 110gr. A-tip bullets. Started at 0.010 into the lands and then did a ladder test backing out to 0.020, 0.040 and 0.060 from the lands. The best load was 0.010 into the lands shooting a 0.360” group. I shot this same load today in fairly windy (15mph at 1 to 2 O’clock) with 0.015 into the lands. Best group (last one) was absolutely one hole for 4 rounds. Fifth round dropped out but was still touching. Haven’t measured the group yet but suspect its in the 3’s again. (Probably my shooting). The question is just how far can I go into the lands without getting some major pressure issues. The 0.015 into the lands rounds are causing some stiff bolt closing so I’m worried about going deeper but the groups are shrinking. Any suggestions from the benchrest crowd?????

 

[NorCalMikie]

Build your loads with the bullets seated into the lands and adjust from there.

I have found that a given load with the bullet jammed .010 into the lands won't show pressure compared to a jump to the lands. The jumped load will show pressure but that same load "jammed" won't.
And you can go even higher before you start seeing pressure signs. Me? I pick/back down to a lower node so I'am not beating up my brass.

 

[Pres100]

At some point , if you are getting stiff bolt closing from only bullet contact, would you not run the risk of pushing the bullet into the case instead of further into the lands?
I guess that would also depend on what kind of neck tension you were running.

 

[JEFFPPC]

I am confused by the numbers your giving. Do you mean your starting .100 in? If so I have never started more than .050 in. Give us the numbers again. If you start at .010 you can not back out and have great numbers. I would start .020 in and back up .003 at a time to I find a sweet spot then revisit powder a tenth or .2 each way and then recheck seating depth .02 each way. An important issue with this long bullet will be your throat. If it's too short and a lot of bullet is intruding down into your case you will be building pressure. I like the bullet pressure ring to be about half way down the neck to start then I am never below the neck shoulder junction with the pressure ring.

 

[338 dude]

I’ve been doing some seating depth ladders on the new Hornady 6mm 110gr. A-tip bullets. Started at 0.010 into the lands and then did a ladder test backing out to 0.020, 0.040 and 0.060 from the lands. The best load was 0.010 into the lands shooting a 0.360” group. I shot this same load today in fairly windy (15mph at 1 to 2 O’clock) with 0.015 into the lands. Best group (last one) was absolutely one hole for 4 rounds. Fifth round dropped out but was still touching. Haven’t measured the group yet but suspect its in the 3’s again. (Probably my shooting). The question is just how far can I go into the lands without getting some major pressure issues. The 0.015 into the lands rounds are causing some stiff bolt closing so I’m worried about going deeper but the groups are shrinking. Any suggestions from the benchrest crowd?????

The farthest that I have ran into the lands is .020 with that being said work it just like you would a ladder for your powder proceed slowly .002 to .003 at a time and watch for pressure signs every rifle is different

 

[Falfan2017]

More than .010-.015 and you can feel it in bolt close and May be seating your bullet deeper depending on neck tension. That may not be a problem though. There’s even people who leave their ammo out very long without much neck tension and let the chamber finish seating the bullet. I imagine that load is jammed way more than .015.

 

[SST2500]

To answer JEFFPPC. No I started the original load at 0.010" INTO the lands. The ladder test after that was run ALL out of the lands by the amount noted. I have run some ladder test with the 6.5 Creedmoor all the way out to .100 OFF the lands and found some very very accurate nodes at .050 to .060" off the lands. This rifle just seems to shoot best with the bullet Jammed at 0.015" into the lands.
I'm only running 0.002 of neck tension so it is quite likely that with the stiff bolt closing at 0.015 into the lands, I am pushing the bullet back into the case. I guess I need to chamber some of those rounds and then check base to ogive length to see if they are getting compressed into the case. Obviously, there is a point of no return where the bullet will definitely be forced into the case by the rifling. Thanks for the info. I'll run a ladder test (once I reach the point of no return) backing off by 0.002 or 0.003 each time to narrow down the best depth. Thanks again for all the suggestions.

 

[Texas10]

I think you've already hit the sweet spot with the seating depth. As far as pressure goes, you won't increase pressure by going further into the lands, so feel free to move it in or out a few thou to see if any improvement is available. If you're experiencing stiff bolt close, you're probably at hard jam where neck tension may come more into play than where your seating die places the bullet.

If you're using a bushing die, you might try changing bushings to a lighter neck tension. Just beware that if you should need to eject a live round, you may end up leaving the bullet in the barrel and dumping the charge in the action. If you're shooting in competition, this will likely kill your chances of completing the match.

 

[dbduff]

I think you've already hit the sweet spot with the seating depth. As far as pressure goes, you won't increase pressure by going further into the lands, so feel free to move it in or out a few thou to see if any improvement is available. If you're experiencing stiff bolt close, you're probably at hard jam where neck tension may come more into play than where your seating die places the bullet.

If you're using a bushing die, you might try changing bushings to a lighter neck tension. Just beware that if you should need to eject a live round, you may end up leaving the bullet in the barrel and dumping the charge in the action. If you're shooting in competition, this will likely kill your chances of completing the match.

Oh, yeah. That’s a show stopper!

 

[Rat Rifle]

The difference between “touch” and “hard jam” is the maximum we can play “into the lands”. True or False?

Forcing the case beyond “hard jam” is pushing the bullet farther down the case neck. True or False?

Thanks

 

[JFrank]

Maybe

 

[jackson1]

Got believe at some point your chamber and bolt function as a seating die. Must be great for inducing lug wear. Just my $0.02.

 

[Texas10]

The difference between “touch” and “hard jam” is the maximum we can play “into the lands”. True or False?

Forcing the case beyond “hard jam” is pushing the bullet farther down the case neck. True or False?

Thanks

Correct on both counts. At some point the bullet cannot be reliably forced further into the lands by neck tension alone, so the bullet will slide back into the case as the bolt is forced closed. I don't shoot cast lead bullets so this method may or may not apply to that type of loading.

Beware that if taking these measurements with a new, never shot barrel, there will be remarkable changes in the dimensions as the lands in the leade get knocked down with wear. This is when the hard jam method of measurement becomes more reliable.

If your interested in measuring "touch", I came up with a clever way to measure "touch" in a new barrel, just as a starting point prior to doing any handloading for that barrel. I made use of the natural ability of the cartridge fit to the chamber to displace air inside the barrel.

I layed the barrel (by itself, not installed on an action) on the workbench. Loaded a dummy cartridge with the desired bullet and inserted it only part way into the chamber.

I then plugged the muzzle end with my thumb and popped the cartridge home in the chamber using my index finger. It stuck, of course, so I pulled it out and seated it a bit deeper.

I kept repeating this while seating deeper until the cartridge would start to spring back from the compressed air in the barrel. That was my touch dimension, and it was an amazingly reliable method.

 

[Alex Wheeler]

The difference between “touch” and “hard jam” is the maximum we can play “into the lands”. True or False?

Forcing the case beyond “hard jam” is pushing the bullet farther down the case neck. True or False?

Thanks

True. Hard jam is not a place I like to be. It will vary due to neck tension and neck friction. The point you can chamber one without it moving is my max.

 

[JEFFPPC]

I understand touch, I can see it. I can detetmine with touch as a baseline how far in or out the lands I am. I never liked the term jamb, seems like people have different definitions for it and different ways to achieve it, whatever it is. But as a more direct answer to the OP I have shot as much as .040 to .050 and achieved excellent accuracy with the smaller 6 cases. I seldom jump. Today found a happy seating depth with 110 SMK at .002 and .004 in the lands. 4 back to back 2 shot groups hole in hole. It shows promise.

 

[Firearmsunlimited]

+.005 may prove to be your golden standard. Start getting into the lands beyond =.010 and if you have to unload your rifle without discharging it you may end up with a stuck bullet and powder all over. Powder in a trigger group isn't a fun situation.

 

[JFrank]

I’ve been doing some seating depth ladders on the new Hornady 6mm 110gr. A-tip bullets. Started at 0.010 into the lands and then did a ladder test backing out to 0.020, 0.040 and 0.060 from the lands. The best load was 0.010 into the lands shooting a 0.360” group. I shot this same load today in fairly windy (15mph at 1 to 2 O’clock) with 0.015 into the lands. Best group (last one) was absolutely one hole for 4 rounds. Fifth round dropped out but was still touching. Haven’t measured the group yet but suspect its in the 3’s again. (Probably my shooting). The question is just how far can I go into the lands without getting some major pressure issues. The 0.015 into the lands rounds are causing some stiff bolt closing so I’m worried about going deeper but the groups are shrinking. Any suggestions from the benchrest crowd?????

These 500y samples are +.025 with about .0025 NT ( enough to hold a dummy round inserted and ejected without loss of BTO length.) So it can be done

 

[Alex Wheeler]

If your confident in that powder charge, you need to load 3 each of +.025 .023 .021 .018 and 3 each of +.010 .008 .006 .004. Seat the rest at +.025 and bring your seating die. Shoot those 2 group sets at Deep Creek Friday night. Then final seat your ammo based on what you see.

 

[JFrank]

Alex, can someone be in the pits on friday's during sight in ?

 

[Alex Wheeler]

Yes, but you can color your bullets and no one will need to be