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How accurate should COL be?

 
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  #22  
Old 10-16-2011, 09:24 AM
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Re: How accurate should COL be?

siegrisj, questions;
What comparator tool are you measuring with?
What outside diameter do your sized necks measure, and then your loaded necks?
How do you set your die in the press for seating?
This might help.

As mentioned ogive radius variance leads to differing datum distances between seater plug and comparator tool. But what you measure with a comparator is closer to leade contact datum, so this is what your seating needs to be taken to. There really is no getting around this, so accurate seating is not a set-n-forget operation, even with hand dies(which eliminate press tolerances).
You might consider Hornady's 'MicroJust' accessory for your die:
Hornady Manufacturing Company :: Reloading :: Metallic Reloading :: Dies & Die Accessories :: Die Accessories :: Miscellaneous Die Accessories :: MicroJust™ Seating Stem 1 Each
It replaces the adjustment plug at the top of your die & provides micrometer adjustments to your seating. Wit this you can sneak into same seating based on your comparator measure.
Don't fret over the rubber bushing in your die as this just preloads threading to prevent relaxing of settings. It's a good thing.

I use Wilson hand dies for all seating, with micrometer adjustments on them. This is about as accurate as it gets, but I do need to check every single OgvOAL, and occassionally I need to re-seat with a tweak of the mic setting. Sometimes, hatefully, I have to hammer pull the bullet and seat another(something wrong with that one anyway).
Quality consistent bullets really pay off here. Custom benchrest bullets practically take you to set-n-forget, but check anyway.
For a comparator I use a Sinclair 'nut' and caliper. I've tried a few other types but the nut just works best for me. It's chrome plated 10thou under cal holes give me consistent readings.
I had zero luck with the Stoney Point style aluminum caliper attachments.
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  #23  
Old 10-17-2011, 03:25 PM
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Re: How accurate should COL be?

As Mikecr previously stated, seating to a consistent "ogvOAL" is not difficult with the right setup.

But, equally important is the evenness and squareness of the case head surface combined with one's measuring technique and tools.

I usually rotate the cartridge a few spins while holding slight tension on the caliper just to be sure I'm not canted or measuring a high spot.

-- richard
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  #24  
Old 10-17-2011, 03:58 PM
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Join Date: Oct 2010
Location: Southern Oregon
Posts: 28
Re: How accurate should COL be?

Quote:
Originally Posted by Ken Synder
Here is a little trick a lot of us do out of habit and forget that it is even being performed. Dont seat your bullet all in 1 stroke of the press. Seat about half way then lift the handle off the cartridge and spin it about 90 degrees then seat all the way with second stroke, doing this will yield a more uniform length and a straighter bullet.
Someone else mentioned the exact same thing on a different forum at pretty much the exact same time. I'm going to chalk that up as a clue I never knew about that technique and will definitely give it a try. What other pro tips have you forgotten about that I never knew?


Quote:
Originally Posted by Mikecr View Post
siegrisj, questions;
What comparator tool are you measuring with?
What outside diameter do your sized necks measure, and then your loaded necks?
How do you set your die in the press for seating?
This might help.

As mentioned ogive radius variance leads to differing datum distances between seater plug and comparator tool. But what you measure with a comparator is closer to leade contact datum, so this is what your seating needs to be taken to. There really is no getting around this, so accurate seating is not a set-n-forget operation, even with hand dies(which eliminate press tolerances).
You might consider Hornady's 'MicroJust' accessory for your die:
Hornady Manufacturing Company :: Reloading :: Metallic Reloading :: Dies & Die Accessories :: Die Accessories :: Miscellaneous Die Accessories :: MicroJust™ Seating Stem 1 Each
It replaces the adjustment plug at the top of your die & provides micrometer adjustments to your seating. Wit this you can sneak into same seating based on your comparator measure.
Don't fret over the rubber bushing in your die as this just preloads threading to prevent relaxing of settings. It's a good thing.

I use Wilson hand dies for all seating, with micrometer adjustments on them. This is about as accurate as it gets, but I do need to check every single OgvOAL, and occassionally I need to re-seat with a tweak of the mic setting. Sometimes, hatefully, I have to hammer pull the bullet and seat another(something wrong with that one anyway).
Quality consistent bullets really pay off here. Custom benchrest bullets practically take you to set-n-forget, but check anyway.
For a comparator I use a Sinclair 'nut' and caliper. I've tried a few other types but the nut just works best for me. It's chrome plated 10thou under cal holes give me consistent readings.
I had zero luck with the Stoney Point style aluminum caliper attachments.
Mikecr - Here's what I've grokked from reading your posts (multiple times). Lets see if I'm tracking.

Comparators have no standard size as to where they will measure on the tip of the bullet.

Ogive isn't a standardized measurement either as to where exactly the "Ogive" should be located relative to any other fixed point on the bullet. Two different comparators could measure two different "ogives" on the same bullet, and like wise, two different bullets from the same lot could measure two different ogive lengths with the same comparator.

That being said, expect some variance.

How am I doing so far?

I've thought about getting one of the micrometer adjusters to see if it would help with this issue. Do they work pretty well? I was skeptical since the dies I had didn't seem to be consistent and was starting to think the microadjust might just be a gimmick.

To answer your most recent questions:

What comparator tool are you measuring with? Hornady / stoney point. Why do you say you've had bad luck with these?

What outside diameter do your sized necks measure, and then your loaded necks? No idea, never measured it. Is this question relating to the potential deformed nose due to seating pressure that you mentioned earlier?

How do you set your die in the press for seating? Put a loaded round in the press and raise it all the way, then slowly screw down the die until it makes contact with the tip of the bullet. Lower the ram and then lock the die in place. Back out the fine adjusters a turn or so and proceed to seat a new bullet, and fine adjust it until I get the desired length.
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  #25  
Old 10-17-2011, 04:39 PM
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Re: How accurate should COL be?

Something to consider that I didn't notice in previous posts:

OAL's can vary due to variable neck tensions.

When using reloadable brass it should be sorted by brand and number of times fired to segregate cases with (potentially) various neck tensions. Brass elasticity varies by brand, thickness, work hardening, fouling build up, etc

Interior neck cleanliness is important for consistent neck tension.

Compressed loads often result in OAL's that vary, at least in my experience.

Lastly - if primers are not fully and properly seated you can get incorrect OAL measurements because the caliper blade may be resting on the primer rather than on the case head. Thus, indicating an OAL that is false. You need to look very closely across the case head while the calipers are in place to see this. Use a good backlight.

Last edited by Varmint Hunter; 10-17-2011 at 04:43 PM.
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  #26  
Old 10-17-2011, 04:43 PM
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Location: Allen, TX
Posts: 2,608
Re: How accurate should COL be?

Quote:
Originally Posted by siegrisj View Post
[...]
Comparators have no standard size as to where they will measure on the tip of the bullet.
[...]
Not only that, but the ID of the lands and the throat/lead in the chamber varies. So, it could never be better than a relative measurement anyways.

-- richard
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  #27  
Old 10-17-2011, 07:43 PM
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Join Date: Aug 2009
Location: Carlisle, PA
Posts: 478
Re: How accurate should COL be?

Quote:
Originally Posted by feelinducky View Post
I get the same problem with Barnes and it absolutly drives me nuts. I figured it was a bullet issue. It did make me more consistant with pressure through the stroke of the press and at the end of the stroke.
I have a problem with Barnes TTSX in my 7mmMAG that came up in another thread. I got some input from that thread which helped.

First, my seating die wasn't set up properly. The shell holder needs to bottom firmly on the die so that the seating stem controls the bullet depth rather than the linkage.

The other thing I just did was to measure the base to ogive contact on the 14 bullets I had left in the box. It averaged .795" with an extreme spread of 0.006". Loaded ammo exhibits a similar variation when I measure from the base of the loaded cartridge to ogive contact.

Fitch
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  #28  
Old 10-18-2011, 11:18 AM
JDS JDS is offline
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Re: How accurate should COL be?

I use a Wilson in-line seater with a micromitor top and get very consistant OAL readings. At least as consistant as the bullet lenghth out of the box.
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