Got a ?

[Axis II]

So I found a sweet spot of both speed and accuracy with 50-55gr v max in 223rem and asked a buddy awhile ago if he would take it to his 400yard range and see how it shoots from 100-400yards and record how much drop for me and also see if the vortex bdc retical can be used for 300-400yards and it dawned on me, I wanted to adjust my seating depth as I'm about 20k off the lands and see if I can shrink the groups anymore.

Now say he shoots the rifle tomorrow at 300yards and it's 5" low with a 100yards zero would just moving closer to the lands mess with the drop? I'm worried he checks it at 400yards and tells me that it's this number on my turrets and I go changing seat depths or even charge a little bit and he just wasted time and ammo.

 

[witchhunter]

It could make a difference depending on how much you change the seating depth. Finish you load workup, then measure your drops. Load workups takes a lot of time to finally get it to 100 percent. It only takes an afternoon to confirm drops.

 

[Legionnaire]

I'm no expert in precision hand loading. How much difference might changing the seating depth have on drop? Can't be much, can it?

 

[Demi-human]

I would tend to think that the drop would only be affected if the velocity has changed. If one is chasing the lands it is to keep the bullet more in line with the center axis of the barrel. Closer to the lands will equal a higher pressure, which can be thwarted with a reduction in charge weight. Greater axial precision in bullet alignment will be less dynamic than keeping within the velocity range of the accuracy node.
That is, until one starts measuring their groups in tenths.

That's how I come to see it anyways.

 

[Axis II]

when i was coloring the bullet to check for the lands i was about 5-10k off it and on a good day i could send 5 shots in 1/4 MOA @100yards sometimes i wasn't sure i hit it 5 times the group was so tight. i since started using a hornady oal tool and moved back to 20k off the lands for safety reasons and groups aren't the best 1/2-1 inch 5 shot groups. I have a good charge out of all the testing and he can only shoot Wednesday as this is on his hunting farm and time is limited and seasons close so don't want to wait too long. Im just trying to find what turret numbers i need to be for that load but in a week or so wanted to seat closer to the lands for more accuracy.

 

[Demi-human]

There are many reasons not to do it the way I have. (Oh boy, that is an understatement!) But here it goes anyway.
When I start working a load, I place and measure the bullet to be at the land's plus five thousandths. Them I work up to the maximum pressure my primers look comfortable with. My firing pin hole is slightly chamfered so this is my limit regardless of book charges. Having the bullets seated this way first gives me the highest pressure in the beginning. All things considered. Being close or into the lands is not necessarily dangerous, if one knows what (and why) one is doing. I wouldn't take a higher end load and just jam the lands for more accuracy. That may just blow up in one's face, literally.

So if it shot well at ten thousandths and no other adjustments were made besides the deeper seating, you may need to increase the charge. Moving away from the lands, even ten thousanths, will lower pressure and could move the velocity out of the accuracy node.
Conversely, I have read that some bullets prefer a jump, up to eighty hundredths some more. I forget which, seems they were for hunting.

The only way to know is to test. Which takes time, that you don't have.

I wish I could be more helpful.

 

[Bartojc]

I think the correct answer is changing seating depth could change POI. Personally I have never seen it change enough to matter. You need to know though that my groups do not measure .25" so I may not notice. I also do not chase the lands with any loads either. I'm typically .020 - .030 off.

-Jeff

 

[Blue68f100]

Changing the OAL is tuning process we use to get the most accuracy out of our loads. In doing so you will change the POI some, for better or worst that is the big question. These minor tweaks as small as they are change the pressure in the cartridge. Normally we only change 0.005" at a time, some less depending on how close you are to the lands. Most modern guns that are not built for BE competition have long leads (free bore) so reaching some may be a challenge.

I would recommend in not changing your OAL till you can actually test and see the results. A little can goes a log way.

 

[LoonWulf]

I agree with the other guys. Finalize your coal, and any other changes you want to make with your loads, THEN drop chart them.
More accurate groups will likely give you more realistic drop numbers as well, as there is less "averaging" that needs to be done.

To answer your question, drop with the same bullet is a function of VELOCITY. If you change your coal enough to affect your velocity than yes youll change your drops.
I would guess that out to 400yds, your coal changes will not affect your velocity enough to change your drops.