getting different OAL's each round?

[bassin93]

I have found that it is the meplat that is usually the culprit. If you look closely you will see how the point of the meplat is not flat. Using the meplat trimmer you will find that your oal will improve significantly.

 

[Kevin Thomas]

I have found that it is the meplat that is usually the culprit. If you look closely you will see how the point of the meplat is not flat. Using the meplat trimmer you will find that your oal will improve significantly.

That's really not the reason to be trimming/uniforming meplats.

 

[bassin93]

Kevin, I know that is not the reason for trimming the meplat but if you look at the meplat on berger or the smk you will notice it is not uniform and may have a poiint on one side making it slightly longer where the next one will be more uniform thus giving you a longer ogive to tip length

When you trim them in a meplat trimmer, the bullet shoulders on the ogive and will give you a consistent ogive to meplat length. Usually a seating die also supports the bullet on the ogive when seating and therefore you get a consistent OAL with each cartridge loaded.

Sure, a meplat trimmer is designed to give you a more consistent B.C., but it will also give you a consistent OAL.

 

[Mikecr]

bassin93, you should go back to BOSS & Kevins earlier posts, and read them carefully.

bigsal5353, no you should not allow rounds to be off a few thousandths as measured at the ogives. You really need to determine the problem. This is because most barrels are accuracy sensitive to distance from ogive to lands. It's fairly critical..

It is either your:
measurement
press
seater plug to bullet
neck tension
brass fit to die

You might try Sinclair's 'NUT' type comparator. I found it more consistent than caliper attachments.
hand check to make sure the bullet tips are not bottoming out in the seater plug.
If your seating pressure is too high, your neck sizing too much.
Makes sure the case will insert fully by hand, without interference.

 

[bassin93]

Boss Hoss is perfectly correct here, the bullets themselves vary a bit in length. This is a natural result of the forming operation and has virtually no effect on how well the bullets shoot. When you're seating a bullet, it's being done (the actual seating) by the forward portion of the ogive, not the tip. The relationship of ogive to leade, or rifling, is what's critical to accuracy. The slight variation in length, which you'll see as variations in OAL from round to round does not play into this relationship.

Mike, this is what I am referring to, by using a meplat trimmer, you make the measurement from the ogive to the meplat the same on all the bullets and since your seater plug shoulders on the ogive of the bullet and is seated to the same depth, the OAL should be the same.

I am not sure what else I am missing here.

 

[Mikecr]

Alright bassin, I think I'm following you, and trimming WOULD work to normalize OAL.
But as Kevin mentioned, this is not what meplat trimming is for.
And within context of earlier post:

just seat them normally, check the loaded rounds for ogive positioning via a comparator, and forget about the OAL.

 

[bassin93]

Mike, I know the trimmer is for making the B.C. consistent. I just knew that by trimming them also made the ogive to point consistent also and might take care of his problem. Sometimes I just don't explain things clearly enough

 

[Mikecr]

It will not take care of his 'problem':

MY question is: do I let my rounds be off a few thousandths from 3.871 (which is the length I want measuring from the ogive) in either direction

bigsal is not measuring OAL to the tips, so this isn't the variance he's talking about.
His concern is more valid..
****, I'm stubborn!

 

[bigsal5353]

mikecr: you are correct.. I'm probably using the wrong words... but when I say my "OAL" i'm using a comparator for that mesurement, so thats from the base of the case to the ogive... I have cleaned my seater die, and next im gonna concentrate on keepin consistent pressure on the ram when Im seating my bulelts

 

[gcamp54]

Bigsal,
Love reading this thread. Learning lots from the experts as usual. I have the same problem. I use the Redding Comp seater. Loading 190 Berger VLDs into my 300wm. I checked my seating stem and it rides on the ogive only. The tip isn't close to bottoming out on the stem. I try and use the same pressure when seating. But I still get from .000-.002 difference. At this point I'm backing off the seater .002 every time and advance it if needed. That way I get it right on. I use a Sinclair comparator and don't think my measurements are off. I also make sure my primers are seated well and don't think that's causing problems with my measurements. I wish I could solve this problem too. I'll keep reading to see if I get anymore ideas. Let us know how yours turns out.


Gordon

 

[Mikecr]

I'd make sure the competition die body kisses the shellholder on camover.
You must also do all you can to reduce seating force variance. Lower tension/annealing/proper inside chamfering..

If you still measure variance, there may be ogive radius variance present with your bullets.
This leads to changes between your seater stem datums, and your comparator datums.
The only actions here are to keep bullets in same lot, and/or to cull them by ogive radius with a comparator offered by Bob Green.
This can be a pain(and expensive), but if your system is sensitive to seating depth as mine seem to be, it's worth it to get them all right(Exactly right).

 

[bassin93]

Mike, I'm guilty. I did what I have seen too many do when they read a post then ask dumb questions like "how much do you want for it" when the price is listed in the original post.
I skimmed through it too fast and did not read exactly what he had written. Sorry for the misunderstanding. Yes I am WRONG. Sorry. Jeff

 

[gcamp54]

I'd make sure the competition die body kisses the shellholder on camover.

That's one thing I haven't been doing. The reason is the instructions say "it's very important to allow a slight clearance between the shellholder (in it's uppermost position" and the threaded die body."

You must also do all you can to reduce seating force variance. Lower tension/annealing/proper inside chamfering..

I'm getting better at this. I haven't done any annealing yet.

If you still measure variance, there may be ogive radius variance present with your bullets.
This leads to changes between your seater stem datums, and your comparator datums.
The only actions here are to keep bullets in same lot, and/or to cull them by ogive radius with a comparator offered by Bob Green.
This can be a pain(and expensive), but if your system is sensitive to seating depth as mine seem to be, it's worth it to get them all right(Exactly right).

I did some reading on Bob Green's tool and it is impressive. Your right though. It is expensive. I would be cool to have a .0001 indicator though. This may be the next step for me when I can afford it. Thanks.

Gordon