Getting Consistent COAL and Seating Depth

[mbeavers1]

I have Hornady Match Grade dies and seater. The sizing die FL sizes and allows you to change the neck tension by inserting different bushings. The seating die has a micrometer. For a chosen COAL, it seems that I have to back off the micrometer a bit and "walk it in" to get the correct COAL otherwise I end up with some rounds with shorter lengths. Any idea what is causing this - bullet tolerances, maybe an issue with cases not uniformly sized, irregular neck tension?

 

[Sawfish]

I have Hornady Match Grade dies and seater. The sizing die FL sizes and allows you to change the neck tension by inserting different bushings. The seating die has a micrometer. For a chosen COAL, it seems that I have to back off the micrometer a bit and "walk it in" to get the correct COAL otherwise I end up with some rounds with shorter lengths. Any idea what is causing this - bullet tolerances, maybe an issue with cases not uniformly sized, irregular neck tension?

I suspect it is bullet tolerance. I had this problem with some Sierra Game King bullets a few years back. I noticed the different cartridge lengths so I pulled the bullets, measured them, and sent samples to Sierra. The response was that the excessive difference was due to a worn bullet forming die during production. Sierra replaced all of the bullets and threw in some swag to compensate for the inconvenience. I never noticed any difference in accuracy, and the deer certainly did not complain. IMHO, sometimes we spend too much time obsessing over minor issues when we should be hunting. No offense intended, as I am guilty of the same thing.

 

[rayporter]

how much difference do you have?.

if you are not touching the lands it probably wont be noticeable -at least for hunting. if you are paper punching with others you might get beat.

are you sure you don't have the necks too tight? too small a bushing will cause the brass to flex as you seat a bullet.

and do measure the bullets base to ogive to see how much they vary-you may need to segregate them.

sometimes if you have vld bullets and the seating stem was not ground deep enough for the nose of the bullet the nose will contact first instead of the ogive contacting the stem first. I have had wild depths from this. it was common when vld bullets first came out but not so much now.

any way I frequently do what you are doing to get them all the same depth.

 

[tdot]

I've found in similar situations that if I seat the bullet roughly 75% to 95% of the way by not pulling the handle all the way down on the press, then dropping the ram, rotating the case 90 degrees and finish the seating on a 2nd stroke of the press. The seating variation pretty well dissapeared.

I hope that made sense.

What I traced it back to was how the bullet nose was engaged by the seating stem, if it was off even the slightest bit, it would yield a different seating depth. By partially seating the bullet, they are consistently aligned and then engaged at the exact same spot on the seating stem on the 2nd stroke.

 

[mbeavers1]

I totally get you on obsessing about things that really don't matter... Unfortunately, I'm an engineer and therefore have a slight case of OCD.

 

[mbeavers1]

how much difference do you have?.

- Sometimes 0.005", but occasionally 0.010"

if you are not touching the lands it probably wont be noticeable -at least for hunting. if you are paper punching with others you might get beat.

- I stay off the lands and they are always shorter than desired COAL. If they come out longer, then I walk them in.

are you sure you don't have the necks too tight? too small a bushing will cause the brass to flex as you seat a bullet.

- I am sizing them to 0.002 smaller than the OD of the neck with a bullet

and do measure the bullets base to ogive to see how much they vary-you may need to segregate them.

sometimes if you have vld bullets and the seating stem was not ground deep enough for the nose of the bullet the nose will contact first instead of the ogive contacting the stem first. I have had wild depths from this. it was common when vld bullets first came out but not so much now.

- I am aware of this one an using a stem for VLD bullets that is already drilled deeper. I checked it on several different bullets to make sure it didnt bottom out on the tip of the bullet.

any way I frequently do what you are doing to get them all the same depth.

- Good to hear! I am still pretty new at this so its good to know that I am not the only one with this problem.

 

[tdhanses]

Don’t load to COAL, load to a consistent ogive. I had this same issue when I first started but bullet tips are not perfect and will give you a variance.

 

[bradb]

Also watch your neck tension

 

[mbeavers1]

Don’t load to COAL, load to a consistent ogive. I had this same issue when I first started but bullet tips are not perfect and will give you a variance.

Sorry, I was a bit unclear on this. I am measuring case head to ogive using a properly sized comparator. I am not simply using a micrometer to measure case head to bullet tip.

 

[mbeavers1]

Also watch your neck tension

This is one of the things that I thought could be causing it. I read lots of stuff but its hard to sort the 'wheat from the chaff' so to say. As I said, my dies allow me to adjust neck tension by changing the neck sizing bushing when FL sizing. Currently i am using 0.002" below the OD of loaded neck.

One thing that I have read is that using steel pin tumbler (and I do) cleans the ID of the neck too much and that its better to leave a little bit of carbon inside to act as a lubricant. No idea if that is true or an urban legend.

 

[rayporter]

,004 is plus or minus .002 which is ok but more than .005 is too much

a bushing .002 under is usually light to about right.

what about brass thickness at the neck? and age of brass. I really doubt the tumbling has that effect on the brass but you could try dipping the necks in graphite as a check. or run a brush with some lube into the neck. lightly lubed. and shootem that day. the lube can deteriorate powder over enough time.

are you sure the nose of the bullet is not contacting the stem inside? that has caused me to have variations like you are getting.

just thinking out loud here- what about the shell holder contacting the die?
you did mention case lengths, so how do you size or bump? I don't think this is the problem cause the press should just seat and not care what the case length is.

and that brings us back to the bullets.

 

[mbeavers1]

,004 is plus or minus .002 which is ok but more than .005 is too much

a bushing .002 under is usually light to about right.

what about brass thickness at the neck? and age of brass. I really doubt the tumbling has that effect on the brass but you could try dipping the necks in graphite as a check. or run a brush with some lube into the neck. lightly lubed. and shootem that day. the lube can deteriorate powder over enough time.

are you sure the nose of the bullet is not contacting the stem inside? that has caused me to have variations like you are getting.

just thinking out loud here- what about the shell holder contacting the die?
you did mention case lengths, so how do you size or bump? I don't think this is the problem cause the press should just seat and not care what the case length is.

and that brings us back to the bullets.

Brass is mostly once-fired. I use the Redding Comp Shell Holders and a FL sizing die to bump the shoulder back 0.002-ish".

I have not done anything with the necks (ie. neck turning) to get a completely even thickness. This one has crossed my mind.

The seating die never contacts the shell holder, only when sizing.

 

[rayporter]

neck turning is over rated. it wont be your fix.

I do neck turn nearly all my brass but it certainly don't show up for all the work involved [except for a few paper punchers for competition.]

 

[LaHunter]

I have Hornady Match Grade dies and seater. The sizing die FL sizes and allows you to change the neck tension by inserting different bushings. The seating die has a micrometer. For a chosen COAL, it seems that I have to back off the micrometer a bit and "walk it in" to get the correct COAL otherwise I end up with some rounds with shorter lengths. Any idea what is causing this - bullet tolerances, maybe an issue with cases not uniformly sized, irregular neck tension?

I am assuming you mean CBTO (Cartridge Base To Ogive) and not COAL.
How much variation? +/- .0015" is what I typically get with 7mm 160 grain Nosler AB bullets
1) Try a Redding Competition Bullet Seating Die. These are very good seating dies.
2) Bullets of the same brand/type/wt will vary lot to lot when measuring base to ogive. Even within the same lot, there will be variation.
3) I typically set my seating die so my CBTO is long, then 'walk' it down to get my target length when I start with a new lot of bullets. It may take 3-5 cartridges to get is set exactly where it needs to be.
3) When seating the bullet, seat it, rotate the cartridge and seat it again, and repeat. I typically do this 5 times and rotate the cartridge between each time.

Edit: Also, your bullet seating die and the tool that you are using to measure CBTO do not contact the bullet in the same location. Additionally, these contact points are also different from where the rifling will contact the bullet.

Hope this makes sense and helps

 

[mbeavers1]

I am assuming you mean CBTO (Cartridge Base To Ogive) and not COAL.
How much variation? +/- .0015" is what I typically get with 7mm 160 grain Nosler AB bullets
1) Try a Redding Competition Bullet Seating Die. These are very good seating dies.
2) Bullets of the same brand/type/wt will vary lot to lot when measuring base to ogive. Even within the same lot, there will be variation.
3) I typically set my seating die so my CBTO is long, then 'walk' it down to get my target length when I start with a new lot of bullets. It may take 3-5 cartridges to get is set exactly where it needs to be.
3) When seating the bullet, seat it, rotate the cartridge and seat it again, and repeat. I typically do this 5 times and rotate the cartridge between each time.

Edit: Also, your bullet seating die and the tool that you are using to measure CBTO do not contact the bullet in the same location. Additionally, these contact points are also different from where the rifling will contact the bullet.

Hope this makes sense and helps

Yes, I mean CBTO.

The variation is significantly more than 0.0015", up to 0.005". Bullets are all from the same lot. I havent really measured the bullets themselves, but sounds like I need to. I may have to break down and go for the Redding dies, but Im surprised that the "top of the line" Hornady would be that much worse.

 

[LaHunter]

I read in one of your posts that the ram is not contacting the seating die. This could be at least part of your issue.
Also, what bullets are you using?

 

[BRTreedogs]

If your seat is pushing in the tip vs the og this could happen.
Bullet tips are inconsistent.
That's why they have a vld seating stem.

Remove the seating stem and see if the cup is deep enough to make contact with the og

 

[4ester]

I’ve seen bullets in a red (H) and black (N) boxes have that much variance in seating depth.

I’ve also found that using an expander mandrel and a little graphite inside the necks makes seating more consistent.


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[Vandy321]

Not sure if it's been mentioned or not, but a compressed load can do that as well...or so I'm told.

Not sure if it's the correct answer or not, but with a slightly compressed load, I get the same thing sometimes, even with a forster Co-Ax and redding comp micrometer die and VLD stem. I have found running it through at the same setting a 2nd time fixes it...that or back it off a few thou after each round and just take the time to get it exact.

 

[GLB]

As mentioned already get a comparator tool and measure from the ogive. you will still get some variation but it’s more accurate than measuring from the bullet tip.