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OMG Seating stem accuracy difference

Subwrx300

Subwrx300

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Jan 15, 2014
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So I've wanted to test this for a while and finally got around to it. For compressed loads, the bullets can get marked/damaged pretty easily, and if seating stem doesn't fit bullet PERFECTLY, I suspected it would cause accuracy issues.

Today, I found my proof...

224 Valkyrie, Hornady 2nd fire brass, BR2 primers, 26.8gr H4350 seated to 2.302 OAL for all rounds. The only variables: two different seating stems/dies.

Die #1 Hornady Custom grade VLD seating stem (the bigger opening of the two stems provided in package). Unpolished, right out of the box.

Die #2 Redding seating stem ground by hand using bullet coated in valve grinding compound and finish lapped with #000 steelwool and JB2 borepaste. This has been my die for last several hundred rounds and it's been working well, but I just decided to buy a new set for giggles to test this.

5 rounds using Hornady stem (Red Sharpie)
5 rounds with Redding (Green Sharpie)
6 with Hornady stem but using pulled bullets (Black Sharpie, previously loaded, not fired and separated for use in a new load). All bullets marked with sharpie to ensure I could identify which shot was which on paper.

I shot the bullets randomly (loaded 6 rounds into mag in mixed sequence red, green, black.) Then the next 10 using same method (mixed order red, green, black). Fired rapidly (no more than 2-3 seconds between shots) and continuously between the two mags.

Shot at 388yds ; Target speaks for itself:

7048031


Color me stupified... I never thought I'd EVER see that kind of difference due to anular marks on the bullet from seating.

Conclusion: if you are shooting compressed loads or getting bad seating stem marks on loaded rounds, polish your stem until you get ZERO marks on bullets. Consistentcy should improve dramatically at distance.
 
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Great test idea, and top notch results. Definitely showcases a point of potential weakness in gear choices/quality. I've wondered myself, "what's going on inside that seating die?". Concentricity gauge/tool may be the only other way to tell if seated crooked. Thanks for sharing!
 
There are better ways to overcome seating issues: use a lighter case with more case volume. Use a long drop tube and trickle in slowly. Use Imperial dry lube on the inside of the necks. Then you won’t have to lap your seating stem every time you open a new lot of bullets.
 
Scopes said:
Could you post a pic of the marks the seat stem is leaving on the bullets?
Click to expand...

Unmodified Hornady Seating stem
7048778


Vs lapped Redding stem to fit 88 ELD
7048782


I've reloaded the same test (5 Redding custom lapped vs 5 Hornady unmodified) to confirm results of last test. Plus I've lapped the Hornady stem and seated bullets at various points in the polishing process to see at what point (if at all) the groups get better.

7048785


Should be able to shoot it later this week (possibly tomorrow afternoon).

If results are repeatable, would at least support the results found previously. I'm also hoping that the Hornady stem (after polishing) shows continuous improvement over the original profile.

Here's a close up of some of the intermediate stages:
7048788

7048789
 
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good info

ive got a long throated 223 ive been playing with them in and have been plagued with random/wild fliers

i noticed the small marks from the redding stem (factory, no polish) but shot them anyways...1 out of every 3-5 rounds seemed to throw one bullet out regardless of charge weight/jump

havent had any issues getting the berger 80 vld's to shoot well, but they dont deform from the seating stem either
 
morganlamprecht said:
good info...im guessing these are 88 eld's?

ive got a long throated 223 ive been playing with them in and have been plagued with random/wild fliers

i noticed the small marks from the redding stem (factory, no polish) but shot them anyways...1 out of every 3-5 rounds seemed to throw one bullet out regardless of charge weight/jump

havent had any issues getting the berger 80 vld's to shoot well, but they dont deform from the seating stem either
Click to expand...
Spot on: 88 ELDs. I think we have the same seating stem. Here's a photo of mine after polished/lapped to fit the 88s. Plus a few photos of the stem.

I drilled it deeper to ensure no contact with tip of bullet (about 1/4" deeper with maybe a 1/16" drill bit) and then ground/lapped the crap out of it to ensure uniform contact over greater surface area.

Seating stem runs down about .378" onto bullet when seating.
7050454
7050455
7050456
 
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im gunna knock mine out tonight and see what it does

i used to only shoot 80 vld's in my 223 and never had this issue even with slightly compressed loads, but ive noticed the hornady's seem much softer and some of them even deform with just the neck tension from new out of the bag lake city brass
 
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I'll throw my two cents in here.. I inherited a reloading kit that had all Hornady custom match grade dies. Ive been reloading for two years now..been impressed with my groups so far. But recently I got a magentospeed and made myself a concentricity guage. Lets just say my eyes have been opened. I am not as good a reloader as ive been telling myself.) Runout on ogive of 105g bthp in .243 was an average of .008. About the same with 6.5 CM. I immediately ordered a forster bench rest seating die. But now while im waiting for it..on backorder. I tried every little trick I could find on youtube and on forums to reduce runout. Nothing helped. So just for the heck of it I polished the seating stem for the 243 die. I used 1500g sandpaper rolled up while stem was spinning in drill. Then I used polishing compound(blue bar from chrome polishing kits) on q-tips to get the inside of the stem a mirror polish that left zero ring on ogive when spinning it in the stem. Before it had been so rough it cut a groove into the projectile. Well it reduced my average runout to about .0025. Very happy with it now. I tried the same with Both the 6.5 CM stems that come with the die set but I made no difference. One seats with .002 runout..the next three will be .008.
 
morganlamprecht said:
im gunna knock mine out tonight and see what it does

i used to only shoot 80 vld's in my 223 and never had this issue even with slightly compressed loads, but ive noticed the hornady's seem much softer and some of them even deform with just the neck tension from new out of the bag lake city brass
Click to expand...
100% matches my experience also. The jacket between the plastic tip and lower down the ogive is super thin on the 88s.
 
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Subwrx300 said:
100% matches my experience also. The jacket between the plastic tip and lower down the ogive is super thin on the 88s.
Click to expand...
This seems to match my experience as well using a Forster Benchrest die. However I’m using the 75 ELD. I suspect those are similar construction. This may explain my random fliers and why I get a phenomenal group one time and a wide group the next.
I’ll polish the seater next time I load these up!
 
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Farmerdanss said:
I'll throw my two cents in here.. I inherited a reloading kit that had all Hornady custom match grade dies. Ive been reloading for two years now..been impressed with my groups so far. But recently I got a magentospeed and made myself a concentricity guage. Lets just say my eyes have been opened. I am not as good a reloader as ive been telling myself.) Runout on ogive of 105g bthp in .243 was an average of .008. About the same with 6.5 CM. I immediately ordered a forster bench rest seating die. But now while im waiting for it..on backorder. I tried every little trick I could find on youtube and on forums to reduce runout. Nothing helped. So just for the heck of it I polished the seating stem for the 243 die. I used 1500g sandpaper rolled up while stem was spinning in drill. Then I used polishing compound(blue bar from chrome polishing kits) on q-tips to get the inside of the stem a mirror polish that left zero ring on ogive when spinning it in the stem. Before it had been so rough it cut a groove into the projectile. Well it reduced my average runout to about .0025. Very happy with it now. I tried the same with Both the 6.5 CM stems that come with the die set but I made no difference. One seats with .002 runout..the next three will be .008.
Click to expand...
I think the polished stem should help bullet align itself a bit better while seating but, to be clear this test wasn't about runout. The bullet TIR on all cartridges measured between .000 to .004" regardless of which stem or how much it was polished.

It was specifically to test effect of seating stem rings.

Runout can definitely be important but I found it can be deceptive to measure at times. For instance, I just measured a series 10 cases from the new test (not yet fired) and the neck runout on loaded cartridge was .000-.002. The Ogive runout was different and varied from .000-.004. That means that the TIR was partially due to brass/neck and partly due to bullet alignment.

I'm running a Forster Coax which may be part of the issue. Not sure I like the way the floating she'll holder/die works on this press with certain cartridges. But that's a different topic altogether...
 
Agreed … in my particular case, the TIR seems to be always less than .002, usually less than .001. Not a runout problem. But I was getting faint rings from the seating stem. Gonna see if this will help.
 
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I measured some jacket thickness on 88ELDs near the tip to ogive transition (where seating stem contacts) and the 88 ELDs measured .012-.013 vs a 77gr SMK which measured .015-.016. might seam like much but that's about 25%-30% more material which could be the difference between a failure and holding together.

A few bullets below for reference (not super scientific measurements and there could be better way to separate jacket to get precise measurements). Measured with tip of caliper:

90SMK - .014-.15
88ELDM - .012-.013
80VLD Berger .022-.023
75ELDM - .015-.016
77 SMK - .015-.016

Interestingly, the 80 BergerVLD was TOUGH to separate from core. Might be part of reason for the improved consistentcy.

I'm going to look for a better way of separating and measuring jackets. Might be cool experiment.
 
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Well the stem wasn’t the issue for me...the 88s just suck outta this barrel, even with the stem polished up

I tried 8208, varget, and 2000mr...all had bad random fliers...couldn’t really get anything usable outta charge tests

Switched to 80.5 full bore and 77 otm Berger’s and it hammers with pretty much any charge with 8208 and 2000mr

Even the 53/60 grain vmax’s shot better than the 88s in this 6.5 twist
 
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On my 80ELD’s running compressed Varget, I get horrible seating stem deformations on the copper jackets. The loads shoot good, .8-.85” at 200y out of a RPR. I’m using a rcbs micro seater, and have often wondered if I need to do something to address this. Now that I’ve seen your idea, I know what to do.
Just use a bullet with some lapping compound to hone the stem to fit the round? Then give it a final polish to smooth out any imperfections?

Is that the general idea?
 
I might have missed it but did you measure concentricity of the loaded cartridges?
Just curious.
 
M_16_4_REAL said:
On my 80ELD’s running compressed Varget, I get horrible seating stem deformations on the copper jackets. The loads shoot good, .8-.85” at 200y out of a RPR. I’m using a rcbs micro seater, and have often wondered if I need to do something to address this. Now that I’ve seen your idea, I know what to do.
Just use a bullet with some lapping compound to hone the stem to fit the round? Then give it a final polish to smooth out any imperfections?

Is that the general idea?
Click to expand...
Exactly. There are a couple of good videos on YouTube and Sierra wrote an article a how-to article a while back when the TMKs launched.

Bullet Seating Advice — How to Avoid Ring Marks on Your Bullets « Daily Bulletin

Here's a helpful hint for hand-loaders from Sierra Bullets. While this article focuses on Sierra's new Tipped Match-King bullets, the recommended solutions apply to other bullet types as well.
bulletin.accurateshooter.com bulletin.accurateshooter.com

You have the right idea. To do it well, you will sacrifice about 5-15+ bullets depending on how different the stem is from bullet shape, but in general, it takes me about 30min and 10 bullets to get a solid fit/polish.
 
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Juggerxxx said:
I might have missed it but did you measure concentricity of the loaded cartridges?
Just curious.
Click to expand...
Yes. They all (every type regardless of seating stem or condition) had TIR of .000-.003, which is plenty concentric for 1/2 MOA precision if load allows. My bolt guns practice brass/ ammo is usually around .001-.005 with old mixed lot Hornady brass and it shoots around half minute. I usually toss brass that around .007+ or more runout. Either necks are worn or case is changing shape/thickness and sizing unevenly.
 
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Just about to shut it down for the night, but of course it’s hard to turn off the tinkering mind. Just had a thought, lmk what you think.

I wonder it instead of honing you could use a small amount of jb weld in the stem with a bullet as a template to get a perfect match on the dimensions?
Fill the stem up with compound, insert a loaded round with wax or brass lube on the bullet, and let it sit overnight. That way the jb would make perfect contact with the round across the entire diameter.
 
Yeah, that'll work too. Cast bullet shooters have been using acraglas gel and/or jbweld to match seaters to bullets for awhile now.
 
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