Measuring to the ogive and getting large variance

[mrgreentie]

So...I'm using a Redding Competition seating die to seat .308 SMK bullets and I am getting up to .010 difference in seating depths on each round I load? I'm measuring to the ogive and wondering why the heck I would have this much variance on what should be one of the best seating dies available?

Thoughts???

 

[InTheWeeds]

Re: Measuring to the ogive and getting large variance

What are you using to measure your ogive OAL?

 

[mdmp5]

Re: Measuring to the ogive and getting large variance

The die isn't at fault. The reason you are seeing this variance inseating depth is indeed bc of ogive variance, but there is also another thing to note. The sleeve of the seater does not index off the ogive, so you are seating off one area and measuring from another. This may be frustrating, but it is expected with the variance in today's bullets. If you want every load to be exactly the same depth, you have to seat each bullet a little long, then incrementally seat a tiny bit deeper after measuring until you reach the desired depth. Tedious, but if you have a turret press and a redding instant indicator, it is manageable.

 

[krw]

Re: Measuring to the ogive and getting large variance

What does the Redding Comp Seater die index off of? I load lots of 175 SMK's for my 308, I load my length with a Sinclair Comparator, then measure length with a set of calipers. The comparator measures off the ogive, what does the die measure off of? Thanks

 

[dmgreene]

Re: Measuring to the ogive and getting large variance

Use your comparator and sort your bullets first. The last lot of 6mm 95 SMK's had variances of .010". After sorting them I found that they fell into 3 different groups. I have been told that the bullets were coming off of three different lines going into a common lot and that is the reason for difference.

 

[mrgreentie]

Re: Measuring to the ogive and getting large variance



<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dmg264</div><div class="ubbcode-body">Use your comparator and sort your bullets first. The last lot of 6mm 95 SMK's had variances of .010". After sorting them I found that they fell into 3 different groups. I have been told that the bullets were coming off of three different lines going into a common lot and that is the reason for difference.</div></div>

Genius! I didn't even think of doing that.

 

[mdmp5]

Re: Measuring to the ogive and getting large variance

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: krw</div><div class="ubbcode-body">What does the Redding Comp Seater die index off of? I load lots of 175 SMK's for my 308, I load my length with a Sinclair Comparator, then measure length with a set of calipers. The comparator measures off the ogive, what does the die measure off of? Thanks</div></div>

The die does not have a bushing in it, contrary to what I once thought. It is a sleeve with a taper down to a diameter that indexes on an area above the ogive. Here are some pics of my 300WM seater disassembled:

 

[mrgreentie]

Re: Measuring to the ogive and getting large variance

So.... As suggested, I measured my 175 gr SMK bullets and WHOA, there is a lot of variance in the lengths. They vary up to .010 and more in some instances. I separated them into lots of equal lengths, then loaded each lot, adjusting the die with each change in lot and my loads are now coming out PERFECT. I can't wait to hit the range with these precision crafted rounds of awesomeness!!!

Thanks for all your feedback!


~Mac

 

[Jumper]

Re: Measuring to the ogive and getting large variance

I used to sweat the last thousandth out of the OAL but I don't any more. I accept it as just manufacturing tolerance as it will either affect the jump to the lands or the case volume displaced by the bullet. If you strive to get all your OAL's exactly the same then your .010" variation in bullet length will be inside the case. If you dont worry about the OAL and just seat every bullet the same, then your internal case volume should be constant but your jump to the lands will vary. It comes down to which variable are you willing to live with.

 

[mdmp5]

Re: Measuring to the ogive and getting large variance

If the ogive of 1 bullet is higher than that of another, it will be pushed down a bit further, so case volume will decrease. But I wouldn't get all flustered with a bit of variance unless you are shooting benchrest.

 

[marduk185]

Re: Measuring to the ogive and getting large variance

seems to me...been checking out this stuff myself lately...that if one sorts by base to ogive lengths and then sorts those by overall length then weighs them...and load these sorted batches the variations in case volume and oal/lands jump will be miniscule. course this may be a bit obsessive compulsive.

 

[jr81452]

Re: Measuring to the ogive and getting large variance

Or you could just use an A-max next time. I've never seen more than a +/-.002 base to ogive variance out of one lot. Lot to lot uniformity has been up to a .025" ES in base to ogive, but never from the same lot. Maybe I've just been lucky; maybe seirra isn't the product it used to be. You decide.