Bullet Seating Depth Shortens As I Load...

Stangs55

Stangs55

Private
Supporter
Full Member
Minuteman
Supporter
Jan 26, 2010
163
126
Texas
#1
Relatively new reloader here, but I'm more than well aware of the basics and what I should/shouldn't be doing.

I'm having a problem with my Redding Competition seating die for my .223. After I set my depth and start seating bullets, the seating depth will progressively shorten as I load. For example, I reloaded 100 rounds of .223 tonight on my Big Boss 2 with a Redding shell holder. If I set my first bullet to seat at 2.260, by the 15 or 20th round, it will seat at 2.270 and so on... I'll load 2.260 +/-0.001 for a few rounds then all of a sudden it's 2.263...I can adjust the micrometer, reseat that round to 2.260 and continue on. But then it'll jump again...

I'm pretty certain it's not my technique as this is a progressive change as I load.

What am I missing here? Is there something in the die that needs to be tightened/adjusted?

I am not having these problems with my Redding competition seating die for my .308.

(for completeness' sake, I'm simply setting the die as per Redding's instructions: cam all the way up, touch the plate, then back it off until you see the numbers, then tighten the nut down)

Thanks in advance.

EDIT: And yes, this is true when measuring from the ogive
 
Last edited:
#2
Well, it seems logical to me that something isn't locked down on the die body or the stem? The micrometer readout does not change, right?

Whatever it is, it's not good, I'd stop using it until you figure it out. BB
 
#4
TeaRex said:
Is it possible that your projectiles or seating stem are dirty and grunge is slowly building up and causing the bullets to be seated deeper and deeper?


Sent from my iPhone using Tapatalk
Click to expand...

I don't think so as my COAL gets longer and not shorter...

I ended up calling Redding and they asked me to send the die back for inspection...
 
#5
Stang, it sounds like you are just getting bullets with variance, which is completely normal. The only way to ensure the same seating depth whether you measure from the ogive, or by OAL, is to seat, check, adjust and seat again, and check again. I made this video early this week covering it. FFWD to about 6:50, where I talk about the comp seating die.


<iframe width="480" height="360" src="//www.youtube.com/embed/ohbkIfvU6D4" frameborder="0" allowfullscreen></iframe>
 
Last edited:
#6
Yep, I agree with mijp5. Its variation in the bullets. Your OAL gage measures on a different location on the ogive than the seating cup in your die. Any variation in dimensions of those two locations will cause a change in seating depth or a change in measurement. What bullets are you using?
 
#8
It is not changing progressively. First off, if you leave the dial set at one setting, you are seating at different points on every bullet's ogive. Secondly, there can be quite a bit of variance in each bullet's meplat relative to one another. There is nothing wrong with your die. You have to seat each bullet to length individually.
 
#10
Yes, it is possible and very likely. Remember, that seating stem seats well above the point on the ogive of land engagement. Watch the video I posted, and skip to 6:50
 
#12
Also keep in mind that your OAL gage is very likely not measuring the at the same location as where the lands touch the ogive. So between seating cup, measuring device and the real location of land contact, any dimensional variation in the bullet can have a significant affect on those 3 locations when measured from the case head.

Try a different lot of SMK's or even another brand of bullets and see if the variation changes.

One more thing, use your OAL gage to measure your bullets from ogive to bullet base. See if there is variation there.
 
Last edited:
#13
Stangs55 said:
So I can expect the ogive measurements to vary by 0.01 ??!
Click to expand...

You are talking as if .01" is a huge measurement. Put it into perspective: take your micrometer or calipers and open it up .01". How many pieces of paper can you fit in there? 2? That is well within the expected variance of bullet dimensions. Like I said, the comp seating die is not a set and forget piece of equipment. It is a dynamic instrument, and the micrometer was meant to be turned. If you are loading for an AR15, which it sounds like you are, set the micrometer on the die and seat a bullet to 2.26". Then seat a bunch more. When you are done, measure them, and take the longer ones, reset the mic, and seat them again. No way around this.
 
#14
mijp5 said:
Yes, it is possible and very likely. Remember, that seating stem seats well above the point on the ogive of land engagement. Watch the video I posted, and skip to 6:50
Click to expand...

Sorry, I just got around to watching the video as I usually browse the hide on my phone.

I've gotta say that that is the best video on seating depth I've watched. Very very well done. I've taught myself reloading through lots of books and even more videos...but your video explained everything in a more practical and straightforward way than anything else I've watched. As a relatively new reloader but someone who's spent a lot of time educating himself...I feel that I have a very good grasp on the basic, intermediate, and even some advanced reloading concepts. But what I lack is seeing real life examples of how these concepts and techniques play out on the bench. Your video translates this extremely well. I look forward to more!
 
#17
mijp5 said:
I did another quick video on sizing too if you want to check that out.
Click to expand...

Another awesome video. Please keep them coming!

Makes me really want to add a T7 to my bench... I'm only using a Big Boss II right now with one set of calipers...so taking my comparator on/off the calipers and swapping dies takes alot of time...
 
#18
are yall seriously gettin .01" variance off the ogives? i have the cheap lee dies for some calibers and have loaded sierra, hornady, speer, and even some 175 smk factory 2nds and never seen that much difference, and my rcbs are the same... .001" is usually the worst and most of the time its less than that...even measuring OAL from to the tip is less than .01" just about every time unless i one bullet has a messed up tip thats visibly obvious
 
#19
Stangs55 said:
Another awesome video. Please keep them coming!

Makes me really want to add a T7 to my bench... I'm only using a Big Boss II right now with one set of calipers...so taking my comparator on/off the calipers and swapping dies takes alot of time...
Click to expand...

Yes, it is tough to do these steps in a reasonable manner with a single stage press. You can definitely do it with calipers, but I was never really all that confident in using calipers. They require the measurements to be taken with the jaws in the exact same spot on the brass, in the exact same orientation. Even when I measure the distance to the lands with the sinclair tool, I get different measurements depending on how I am holding the calipers. This is why I am a big fan of the instant indicator. It is a press mounted measuring device that has no play, especially when employing a slight amount of cam over with the press.
 
#20
morganlamprecht said:
are yall seriously gettin .01" variance off the ogives? i have the cheap lee dies for some calibers and have loaded sierra, hornady, speer, and even some 175 smk factory 2nds and never seen that much difference, and my rcbs are the same... .001" is usually the worst and most of the time its less than that...even measuring OAL from to the tip is less than .01" just about every time unless i one bullet has a messed up tip thats visibly obvious
Click to expand...

If you simply set your seating die at one setting and seat a bunch of bullets, you can definitely see that variance. It depends on the bullets you are using too.
 
#21
nope...i usually grab 5-10 out of the box im going to load, set one to my intended ogive length and then seat all the rest and measure to see variance...ive used at least 4 different style bullets from sierra and hornady mostly (in .260, .308, and .223) and .001" is the worst on the ogive...never even close to .01"...in my AR for example i load my 60 gr vmaxs so the COAL is 2.255" (to the tip) and cant rememeber ever getting one shorter than 2.250 or longer than 2.260"...ive also read and talked to far more experienced loaders than myself and have always heard u set the die and leave it...dont chase overall length (to the tip) because it will vary but ogive should be very consistent (thats y its better to measure from it) changing seating depth can change neck tension...so once my die is set, it stays
 
Last edited:
#22
mijp5 said:
Yes, it is tough to do these steps in a reasonable manner with a single stage press. You can definitely do it with calipers, but I was never really all that confident in using calipers. They require the measurements to be taken with the jaws in the exact same spot on the brass, in the exact same orientation. Even when I measure the distance to the lands with the sinclair tool, I get different measurements depending on how I am holding the calipers. This is why I am a big fan of the instant indicator. It is a press mounted measuring device that has no play, especially when employing a slight amount of cam over with the press.
Click to expand...

I think I may pickup some hornady quick change bushings and an instant indicator. It won't be as fast as the T7, but should allow me to adopt a similar method. Thanks again!
 
#23
Stangs55 said:
I think I may pickup some hornady quick change bushings and an instant indicator. It won't be as fast as the T7, but should allow me to adopt a similar method. Thanks again!
Click to expand...

If you are gonna be removing the instant indicator, you are gonna have to do it with the dial attached. It will be tricky, because you don't want to budge it and throw off the zero.
 
#24
I'm not that concerned about an exact distance as far as a jump to the lands. Some feel it is essential but I figure the difference in ogive on a bullet is one thing I can live with.

But, what I found misleading is this:

I reloaded 100 rounds of .223 tonight on my Big Boss 2 with a Redding shell holder. If I set my first bullet to seat at 2.260, by the 15 or 20th round, it will seat at 2.270 and so on...
Click to expand...

In other words, it's not random, his measurements are always longer OAL the more he continues to seat his bullets. Maybe that isn't what he meant, but I did not read that his measurements were all different, longer and shorter.

I think mijp5 has as good a solution as possible to account for the slight manufacturing differences in bullets. However, if your accuracy depends on "that precision" for seating depth, and you see it on paper; I'm a little skeptical. BB
 
#25
Good video. Wish I would have went with a T7 press...

I get the same issue on .233 69/77 SMK's, trying to load to a COAL they are all over the place. I think its the variation between ogive to meplat. Strangely enough on 7mm 175/180 SMK's (loading to X distance off the lands) they are all within .0005 to .001" of each other in measuring cartridge base to ogive. (using redding comp dies in both cases)

You just have to adjust the seating die so that all of them are 2.260" or less.
 
#26
What type of calipers are you using to measure the rounds?

In the past I have seen some of the digital ones drift as they sat for a few minutes.

Also depending on your thumb that can skew the results as well. I personally have problems with getting the same force each and every time.

So much so I've been thinking about making a spring loaded thumb rest for my caliper.
 
#27
I would like to make something clear. I don't subscribe to the notion that ammo must be loaded to the thousandth of an inch in order to shoot well. I started loading on a 550 with plenty of play, and just went to town without checking every single round. All that ammo shot well. The reason why I load to the nearest thousandth is because I can. I enjoy reloading very much. When I sit down and I am not under the gun to bang out 200 rounds for shooting the next morning, I take my time. Kind of like art. I am almost certain that I can shoot ammo loaded in my 550 just about as well as that loaded in my T7. But like I said, I am doing it for the enjoyment and satisfaction that I created something extraordinarily precise.
 
#29
Stangs55 said:
SMK bullets mostly.

I get a bit of variance...but off by 0.01 is too much! And why does it progressively change?
Click to expand...

I recently bought 1500 175 gr Sierra SMK's. Three boxes of 500 and three different bullet lengths, both base to ogive and OAL bullet length. What pissed me off was that the three different lengths were mixed in the three boxes, not one bullet length in one, another in the next, etc. Apparently there are some worn dies being mixed with new dies on the production line.

I also find it useful to use a "Dead Length Seater Die". Lee makes one that is merely a seating die with the crimp ring left out. You first run the die body down firm against the shell holder then adjust the seating length with the screw. Don't care for the overall quality of Lee dies for precision so I use a quick "tool" to make my other seating dies "Dead Length Dies". Just take a cut washer that has an ID that will just slip over the case and sit on the shell holder. Insert the case, drop the washer over it, adjust the die down till it's tight against the washer (can even "cam over" if you want) then adjust the seating plug for desired seating depth. When I use this method, every finished cartridge reads the same when measured from case head to ogive. This is all the rifle "see's" so that's all I worry about. The washer takes out of play any crimping and the die is loaded against the shell holder. This eliminates any effect "play" in the press linkage may have on the finished cartridge. The distance from the bottom of the shell holder and the seating plug "ring" is always the same.
 
You must log in or register to reply here.

Similar threads

U
Different neck tension and seating depth from round to round
Replies
18
Views
560
ma smith
ma smith
N
Seating depth, what’s acceptable variation?
Replies
33
Views
907
CK1.0
CK1.0
J
seating depth test 8208xbr/77gr smk
Replies
23
Views
981
FredHammer
FredHammer
T
Seating Depth / Lands Measurement Way Off?
Replies
9
Views
202
_Thor_
T
Thumper580
Poor precision with competition seating dies.
Replies
20
Views
611
ShootnFool8
ShootnFool8
Top Bottom
Back
Home
Forums
Merch
Alerts