seating depth question

[holdover]

I had reloaded some rounds a few months back , had them boxed up, nose down , not loose. When I checked the OAL , a lot of them were longer than I seated them .

I was wondering if my neck tension may have been to loose and slowly pushed out. I was using a a size 44 bushing for 223 rounds. Should I drop it to 43 bushing? Is this something that happens overtime? will dropping the bushing down and increasing the tension affect my accuracy?

 

[Carlos Hathcock]

Not sure if these are pistol or rifle ammo but there should be plenty enough neck tension to prevent movement. Not sure how they could possibly be "longer". Perhaps inital recording or measuring error?

 

[diggs223]

Compressed load ?

 

[Tisto]

Sometimes a compressed powder charge can push the seated bullet out a little. It's not all that uncommon. Was this load a compressed charge ? Are you certain the charge weight is correct ? Did they all grow to the same length ? (If they did, I sespect they were all seated to the wrong length.) Have you double checked your caliper ? Lots of places to look for errors.

 

[Mosinitis]

Hollow point bullets (if that's what you loaded) have ragged tips. Base to tip OAL will vary from round to round, can be upto ten thousandths difference. Base to ogive measurement is still consistent.

 

[holdover]

All helpfull things to look at , These were some of my first loads, I dont think they were compressed but they may have been . I may have made some mistakes , but not really sure how. Now I have to go back and check them all , Not sure if I should pull the bullets or just try reseating them . I did have some issues with my seating die recently and sent it back to Redding to take a look at It should be another week or two before I get it back

 

[holdover]

Its an AR rifle, So I wasnt loading to my JAM point and subtracting, I just loaded them up beneath MAG length , 2.258 and was going to work down from there. But when I checked them they were above the 2.260 Max , some as high as 2.265 ,

I dont think they were compressed , But maybe it happened.

Some of my loads are

77 gr, smk N135 powder, 19-22.5 gr. OAL 2.258

77 gr, smk CFE powder, 22-24 gr. OAL 2.258

55 gr, Hornady Benchmark powder, 20-22.2 gr. OAL 2.258


77 gr, smk N135 powder, 19-22.5 gr. OAL 2.258


77 gr, Lapua CFE, 22-24 gr. OAL 2.258

77 gr, smk Varget powder, 23.5 gr. OAL 2.258


??????????

 

[Mosinitis]

SMK's are hollow points, rugged tips. The differences you are seeing are normal. 2.265" is the maximum limit I use for magazine feeding. That's with aluminum GI mags. Plastic mags have less clearance.
All of these rounds can be shot through GI mags.
Also you can shoot longer ones single loaded, just in case.
No need to disassemble anything. You can run them through seating die again to push them in a few thousands more.

It's really only a matter of fitting them in the magazine. No safety or accuracy issues are at stake.

 

[holdover]

Now that you brought it up, I thought that seating , is one of more important parts to accurizing your loads.

The idea of shot to shot consistency, One shot being as close to identical as the last and that seating depth plays a part in that , along with everything else to some extent .

I was watching Eric Cortinas you tube channel , and he described finding the right seating depth or "Node" by working away from the max by 2k each time. each style or type of bullet is going to shoot different and you test them by adjusting the depth .

David Tubbs said that ""A vertical string of shots is due to powder issues while a horizonal string is due to seating depth""

I had no idea when I got involved in reloading that it could be so meticulous.But I know one thing about shooting is that you must reduce all the variables as possible in order to identify what is happening on the target. the whole chain of events must be under control from your ammo to scope mounts, scope, shooting position , trigger pull , breathing , ect.

 

[Acer-m14]

last i knew .. just seat the bullet in the case all the way .. so just the tip shows .. lol

had to .. lmao

 

[gun_slinger_boy]

.002-.007 is negligible. That being said, did you check to make sure every single round was at 2.258 before you boxed them up? If not then they may not have been uniform in the first place. Also, did you use the same exact components? Same bullets, primers, cases? Did you measure each and every bullet and casing to make sure they were all the same exact length? You can also look at the seating depth of the primers. Especially if priming on a progressive press. There could be some primers that are seated slightly more proud/deeper due to different seating pressure. Giving them a tiny squeeze on a hand primer can correct the variation. But again .002-.007 is inconsequential. Open (try to open) your calipers up to .002 and see just how little that really is.

 

[holdover]

A lot of nopes.

 

[Mosinitis]

They should be consistent where it counts, where they are going to engage the bore. The tip doesn't touch anything in the bore, so it doesn't matter. If you want to verify consistency of the seating depth, you need to measure OAL of a loaded round from BASE TO OGIVE. To do that you need to use bullet comparator.

 

[Mosinitis]

You are overthinking it, because you encountered nuances you didn't expect. Once you put them behind you, it gets much simpler. Your seating depth is probably consistent for bullets of the same type if you measure it with bullet comparator.

 

[gun_slinger_boy]

Just to be clear I'm not into ultra precision reloading/shooting. I know what it takes though (did it a few times for "fun") to clone ammunition and it can be mind numbing. IMO. You can get super anal down to measuring and weighing each and every component. Uniforming pockets and flash holes etc etc. Have you ever weighed your brass? The average shooter (me) won't benefit from that level of precision.

 

[holdover]

No have'nt gone that far, just trying to find a good accurate load for my rifle, and make sure Im doing it right. I may separate them by head stamp, but thats about it ,Like you said, its not going to make a huge difference unless your shooting past 5-600 yards.

 

[ManualF150]

This is the whole fun of reloading.

You can control the tolerances a lot more to suite your needs.

 

[holdover]

They should be consistent where it counts, where they are going to engage the bore. The tip doesn't touch anything in the bore, so it doesn't matter. If you want to verify consistency of the seating depth, you need to measure OAL of a loaded round from BASE TO OGIVE. To do that you need to use bullet comparator.

I picked up a comparator the other day . I already had the OAL gauge. Now I measured the JAM with the OAL gauge in 6.5 Creedmoore.

Lapua 123 gr bullet.
Jam point 2.865 base to tip
-15 = 2.850

This should be my starting point working backwards away from the lands firing a group every 3k until I get consecutive good groups.

Ok , after zeroing out the comparator, I get a reading of 2.319 to the Ogive. How do I set up my die to give me that ? I have to read from the overall length No? Not excatly sure what to do with the ogive number. Its probably so simple I overlooked it. I saw Eric Cortina measure from the bottom of the die to the bottom of the lockring as a start point but that was for a full length sizing die , I dint know if it would work on the seating die. Newbie . what can I say?

 

[Acer-m14]

don't know if will help any .,. took me a bit to find this video again ..

 

[Mosinitis]

What kind of OAL gage you are using and what does "JAM" stands for?
What are trying to accomplish?

 

[holdover]

Hornady OAL gauge , Hornady bullet comparator.

Eric Cortina:

Useing a case that is prepped exactly like the one your going to fire

Jump, bullet does not touch the lands,
In the lands, Bullet just barely touches the lands,
Jam, bullet is jammed into the lands until its stuck.

Bullet cannot be loaded to JAM point because it can be dangerous, so its necessary to subtract 15-20K from the jam for your starting point.

Jam - 15k is starting point, working down away from jam point every 3K until you have 2 good consecutive groupings. Once you have your 2 groups, say 2.824,and 2.828. you begin to fine tune your shots , say 2.825, 2.826, 2.827.

Lapua 123 gr bullet.

Jam - 2.865
-15K
starting point 2.850
2.847
2.844
2.841
2.828
2.824

working your way down the seating ladder until you find 2 consecutive groups that shoot well.

Each style type or weight of bullet is going to be different and must be done separately and written down . Not every single loaded round, but every type. Once you have your numbers for that round, record it , and go from there.

Cortina states that its not necessary to find the lands because due to throat erosion after a few hundred rounds it changes and groups will begin to open up again . thats when you have to redo your measurements once again .

This cant be done on an AR because magazine length is to short , (unless you want to load one at a time) so starting point is mag length max of 2.260 and work down from there.


Going back to my orginal question , Im not sure how or what to do with the Ogive measurement. How would I set up my die to go off that measurement?


I have a Redding competion seating die, but my depths, or OAL seems to vary a bit. I sent it back to Redding to have them take a look and I dont have one at the moment.

 

[holdover]

I watched Cortina do his sizing bump of 2K , but Im not sure what the purpose of it is. He does it on a full length sizing die and bumps his shoulder back 2k , but never says why he does it.

 

[Mosinitis]

The actual number base to ogive is not important. You should be looking at a difference between base to ogive of a loaded round and that of measuring dummy round where bullet is pushed into the lands and using the same bullet comparator. Just subtract and the result will be your jump.

For magazine use rounds, this doesn't matter. Ammo has to fit into magazine, so that will be a limiting factor.

For single loading, I do chase the throat as it erodes over the life of a barrel. My desired jump is 0.030" (thirty thousandth) give or take 0.005". I don't think it makes a lot of difference, I just do it.

Dummy measuring round consists of the bullet I am measuring for, specially modified case and Hornady OAL gage that jams it into lands. You need a special modified case for this.

Just to make sure we are talking about the same Hornady OAL gage, it's one of these, straight or angled.

 

[holdover]

I have the same Hornady straight one with 223,6.5 modified case. ( the ones you buy not order)

 

[holdover]

The actual number base to ogive is not important. You should be looking at a difference between base to ogive of a loaded round and that of measuring dummy round where bullet is pushed into the lands and using the same bullet comparator. Just subtract and the result will be your jump.

For magazine use rounds, this doesn't matter. Ammo has to fit into magazine, so that will be a limiting factor.

For single loading, I do chase the throat as it erodes over the life of a barrel. My desired jump is 0.030" (thirty thousandth) give or take 0.005". I don't think it makes a lot of difference, I just do it.

Dummy measuring round consists of the bullet I am measuring for, specially modified case and Hornady OAL gage that jams it into lands. You need a special modified case for this.

Just to make sure we are talking about the same Hornady OAL gage, it's one of these, straight or angled.

View attachment 153132

Ahhhhhhhhhh, Ok. I missed the subtraction part.

 

[holdover]

For single loading, I do chase the throat as it erodes over the life of a barrel. My desired jump is 0.030" (thirty thousandth) give or take 0.005". I don't think it makes a lot of difference, I just do it.

I would imagine it might make a little difference if your loading different bullets , because the jump isnt going to be the same if they are different sized bullets ,If your shooting a 77 gr VLD bullet, the jump will be different than a 77 gr spitzer. I would think. But then again hes shooting a 5K bench rest rifle. At 1 or 2 hundred yards it may not be noticeable.


Check this out 4 out 5 into .30 group at 1k yards!!

 

[Mosinitis]

I watched only the beginning of chasing the lands first video. He is right, exact jump is not important. It just have to be big enough so all of the rounds stay off the lands due to various possible errors. My choice of 0.030" assures that. I measure and adjust seating depth every 500 rounds. This is how I do it, nothing scientific about it.
My best groups were shot with that jump, so did few of my colleagues. It's a good enough number.

That said there are bullets that shoot better when jammed into the lands, but that's another rabbit hole you don't need to get into.

 

[Mosinitis]

I would imagine it might make a little difference if your loading different bullets , because the jump isnt going to be the same if they are different sized bullets ,If your shooting a 77 gr VLD bullet, the jump will be different than a 77 gr spitzer. I would think. But then again hes shooting a 5K bench rest rifle. At 1 or 2 hundred yards it may not be noticeable.


Check this out 4 out 5 into .30 group at 1k yards!!



QUOTE]

Yes the measurement will hold only for the same type of bullet. You have to measure for each type.

[/

Yes the measurement will hold only for the same type of bullet. You have to measure for each type.

The target in that video is electronic target, actual holes can differ. Also you don't know how many times he tried this before getting them on top of each other.

In my shooting career there were a number of hard to believe results. Things like this happen, but they are not what you can expect or produce on demand. The later is what counts.

 

[Xae289]

Hornady OAL gauge , Hornady bullet comparator.

Eric Cortina:

Useing a case that is prepped exactly like the one your going to fire

Jump, bullet does not touch the lands,
In the lands, Bullet just barely touches the lands,
Jam, bullet is jammed into the lands until its stuck.

Bullet cannot be loaded to JAM point because it can be dangerous, so its necessary to subtract 15-20K from the jam for your starting point.

Jam - 15k is starting point, working down away from jam point every 3K until you have 2 good consecutive groupings. Once you have your 2 groups, say 2.824,and 2.828. you begin to fine tune your shots , say 2.825, 2.826, 2.827.

Lapua 123 gr bullet.

Jam - 2.865
-15K
starting point 2.850
2.847
2.844
2.841
2.828
2.824

working your way down the seating ladder until you find 2 consecutive groups that shoot well.

Each style type or weight of bullet is going to be different and must be done separately and written down . Not every single loaded round, but every type. Once you have your numbers for that round, record it , and go from there.

Cortina states that its not necessary to find the lands because due to throat erosion after a few hundred rounds it changes and groups will begin to open up again . thats when you have to redo your measurements once again .

This cant be done on an AR because magazine length is to short , (unless you want to load one at a time) so starting point is mag length max of 2.260 and work down from there.


Going back to my orginal question , Im not sure how or what to do with the Ogive measurement. How would I set up my die to go off that measurement?


I have a Redding competion seating die, but my depths, or OAL seems to vary a bit. I sent it back to Redding to have them take a look and I dont have one at the moment.

You're not setting your dies up to use that ogive measurement. So ogive measurement is just a way to get a more consistent seating depth measurement than measuring rim to tip. You're using it to compare the length from rim to a point on the ogive of a given diameter. Your seating dies aren't pushing down on the tip of the bullet to press it into the case, they have rings pushing on a band of the ogive.

To use them to find seating depth: Find your jam or max length allowed by your mag and measure that with the ogive comparator. Now, as you adjust your dies to seat deeper use the ogive comparator to get the seating depth relative to the jam-length round.

For example using totally made up numbers: Using an OAL measuring tool, you have a round that measures 2.505" rim to tip but that same round measures 2.262" with the ogive comparator. Forget the OAL. Set your die to seat, say 0.010" deeper. Using the ogive comparator, your next reading should be about 2.252" +/- 0.001".

 

[omfgrub]

You're not setting your dies up to use that ogive measurement. So ogive measurement is just a way to get a more consistent seating depth measurement than measuring rim to tip. You're using it to compare the length from rim to a point on the ogive of a given diameter. Your seating dies aren't pushing down on the tip of the bullet to press it into the case, they have rings pushing on a band of the ogive.

To use them to find seating depth: Find your jam or max length allowed by your mag and measure that with the ogive comparator. Now, as you adjust your dies to seat deeper use the ogive comparator to get the seating depth relative to the jam-length round.

For example using totally made up numbers: Using an OAL measuring tool, you have a round that measures 2.505" rim to tip but that same round measures 2.262" with the ogive comparator. Forget the OAL. Set your die to seat, say 0.010" deeper. Using the ogive comparator, your next reading should be about 2.252" +/- 0.001".

To oversimplify ALL of this and other posts: the only numbers that matter between the comparator and the seating dies is the delta (change in) measurement (bullet type specific).