Bullet Seating Troubles with Microjust

[SkunkedAgain]

Howdy folks!

After years of reloading 300 WM without focusing on load development I decided to do a full progression. The issues I'm having is my bullet seating seams to vary by +/- 0.005. I'm using Hornady Custom Dies with a Microjust bullet seating stem. I bought everything used a number of years ago and have always had issues with the bullet seating depth.

I used to think it was from using factory second bullets, but I no longer think that's the case. These bullets are Speed Grand Slams and Barnes LRXs.

I verify bullet seating depth by measuring CBTO.

Any thoughts on the Microjust? Anyone seen something like this?

 

[YZ-80]

I've had .002-.003 variation even using Redding micrometer seating dies. This will happen a few times per batch. I typically load about 24 rounds at a time. I don't sweat it most of the time but usually correct it if it exceeds .005 or so. I chalk it up to the variance that one might expect. I use CBTO as my reference as well. When you compare that to the variance you might see with COL with inconsistent meplats or even ballistic tips, I don't think it's a big deal. I'm sure it may keep some folks up a night. That's what bourbon is for (when you're done reloading).

 

[cajun]

What you are probably seeing is bto difference in the bullets themselves. Speers and barnes are not exactly precision bullets. That's not saying they wont shoot fine at normal ranges.

 

[Mikecr]

What you are probably seeing is bto difference in the bullets themselves.

I don't see how BTO in itself is meaningful for this.
This, because BTO includes base and bearing lengths, neither affecting CBTO.
It also include ogive radius, which does contribute, but this would have to be compared alone among the bullet lot to eliminate.

Usually this problem (as big as it is here) occurs from High & high variance of seating forces, and/or a sloppy press.

 

[cajun]

I don't see how BTO in itself is meaningful for this.
This, because BTO includes base and bearing lengths, neither affecting CBTO.
It also include ogive radius, which does contribute, but this would have to be compared alone among the bullet lot to eliminate.

Usually this problem (as big as it is here) occurs from High & high variance of seating forces, and/or a sloppy press.

If your measuring base to ogive and the bullets have a difference in ogive length it's the same as trying to measure coal and the bullets themselves have different lengths.

 

[biednick]

Pull out the seating stem and grab a bullet and a sharpie. Color the bullet with the sharpie. Put the bullet in the seating stem as if it were being seated and spin it. That should create a ring in the sharpie on the bullet near the ogive. If it doesn't the tip is contacting the seating stem first, which will cause inconsistencies in bullet OAL to become inconsistencies in CBTO. You can drill the hole in the seating stem a little deeper to correct it. I had to drill out my Microjust stems.

 

[jensenj71]

I have the most trouble when the contact area between the bullet and the seating stem is small or sharp. There is some deformation in the contact area with seating pressure that seems to produce a variation in bullet seating depth. I have placed a bullet in a drill and used seating compound to increase the contact area. I still back the seater off 0.003 or 0.004, seat the bullet, measure and adjust seater accordingly to hit my target for each loaded round. Seems like the deformation occurs during the first seating op and I can dial in the adjustment.

 

[cajun]

For reference I just measured some speer btsp's I have on hand. The bto measurement of the bullets varied about .008. Most were with in .003-.005 but the es was .008. So wether you are measuring off the tip or the ogive if the bullets themselves have a difference in length then your measured cbto or coal with have this same variance. This is why some target guys sort bullets by bto length.

 

[Phil Rizzo]

I won't mention names but I loaded some TGK bullets that had up to .010" variation from bullet base to ogive. Thought it was my seating setup until I reached in that green box and checked several.
They still shot tiny groups at 100, handed the gun to a guy that won't shoot past 200 and I'll never hear a peep! It was his preference to use them.

 

[Phil Rizzo]

Howdy folks!

After years of reloading 300 WM without focusing on load development I decided to do a full progression. The issues I'm having is my bullet seating seams to vary by +/- 0.005. I'm using Hornady Custom Dies with a Microjust bullet seating stem. I bought everything used a number of years ago and have always had issues with the bullet seating depth.

I used to think it was from using factory second bullets, but I no longer think that's the case. These bullets are Speed Grand Slams and Barnes LRXs.

I verify bullet seating depth by measuring CBTO.

Any thoughts on the Microjust? Anyone seen something like this?

I liked my Microjust equipment so much it converted me to LE Wilson seating blank dies and an arbor press. With that unit 1 thou means 1 thou, and runout doesn't exist.
And I tried multiple seating stems before changing.

 

[SkunkedAgain]

Thanks guys, y'all gave me a lot to chew on! I took the whole seating die apart and cleaned it pretty good. Didn't find any problems with the Microjust. I'll be working on my seating stems, I'll make sure the tips aren't hitting and if that isn't it I'll bust out the valve lapping compound and finesse the seating stem.

 

[L.Sherm]

I'm sorry but in my opinion BTO means nothing either in sorting bullets but exactly were your stem contacts the bullet. Some BR guys will just measure OAL some will measure the bearing surface some will measure couple different things. Were the stem contacts the bullet consistently is the key and it isn't on the Ogive.

 

[Mikecr]

wether you are measuring off the tip or the ogive if the bullets themselves have a difference in length then your measured cbto or coal with have this same variance. This is why some target guys sort bullets by bto length.

That's dead wrong. The seating stem and your CBTO measuring tool contact at completely different datums.
You and your target friends need to think this through, from what BTO actually is, to what seating is actually doing.

I'll make sure the tips aren't hitting and if that isn't it I'll bust out the valve lapping compound and finesse the seating stem.

Making sure the tips are not bottoming out is correct, but don't open your stem mouth to cause higher contact on the ogives.
Doing that will amplify stem wedging with seating force, making the problem worse.

 

[chav0_12]

I see a few thousands in CBTO differences when loading Bergers and Hornadys. It's variances in the bullets not my seating die. I seat about 10 thousandths long then measure then adjust the die to get the CBTO measurement right where I want it, run it back into the seating die and done. The Hornady dies are good enough dies to do this with too.