COAL Precision Question

[Squaregrouper]

I'm pretty sure I'm fine, but wanted to ask before I actually shoot...
I loaded some reasonably mild plinking loads for .300 Blackout, but can't get my OAL length <.003 consistent. My target OAL is 2.145" and measurements are between 2.142" and 2.148". If I'm well within SAAMI specs for the combo of: bullet, powder and OAL do I need to be concerned with the OAL tolerances if cheap plinking is my only goal? I'm happy with 1 minute of paper @ 100yds.
The load is as follows:
147gr M80 pull downs
Working up 15.5gr, 15.8gr and 16gr of H110 (within .1gr tolerance)
CCI 400 primers
2.145" OAL (+/-.003")

This is a common combo with 16.5gr of H110, so I don't think the OAL tolerances will matter much, aside from a slight accuracy fluctuation. However, remember I'm using pulled M80 projectiles out of an 8.5" PSA barrel.

 

[stu929]

With pull down and lead tip bullets you can get a lot of bad reading from minor dmg to the tip.

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[stu929]

Oh and ive never heard of great accuracy from gi pulldown bullets. That may be a lofty goal of 1 MOA. Good luck.

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[Squaregrouper]

Oh and ive never heard of great accuracy from gi pulldown bullets. That may be a lofty goal of 1 MOA. Good luck.

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Your first reply makes a lot of sense- thanks for pointing that out. I have previously been loading .30-40 Krag and .303 Savage and have been within .001" OAL.
1 MOP (minute of paper) is my goal, not 1 MOA. Sometimes it is referred to as "Minute of bad guy" or "minute of center mass".

 

[stu929]

Your first reply makes a lot of sense- thanks for pointing that out. I have previously been loading .30-40 Krag and .303 Savage and have been within .001" OAL.
1 MOP (minute of paper) is my goal, not 1 MOA. Sometimes it is referred to as "Minute of bad guy" or "minute of center mass".

Rgr... misread!

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[Squaregrouper]

I have been stumped because even if my converted 5.56 brass wasn't precise OAL, it would have affected seating depth, not OAL, correct?

 

[ap1]

Case length should not affect overall length because the seating die does not use the case as
the guide for length, it used the shell holder or presses throw as a stop point
You never said what kind of press or dies you are using. If you are using a Progressive press and
the shell plate is loose that can affect your COAL. If the bullets were damaged when they were
pulled they won't rest in the seating cup consistently. Don't kid yourself, you want accuracy and
you don't want this to happen when you are using good components. Work the problem out now.

 

[StickShaker]

Most seating dies don't push on the tip of the bullet so it's normal to see fluctuations on less than premium bullets. If you want a more precise measurement, Hornady and a few others sell an adapter that attaches to your calipers that measures from the bullet ogive, the same place or close to where the seater is pushing on the bullet. It's normally not necessary unless you are going for high precision shooting.

 

[Squaregrouper]

Thanks for the responses and putting my mind at ease.
I am using a Lee single stage press and Lee dies. Although "Minute Of Paper" was an exaggeration, I was trying to clarify that I'm using surplus, pulled bullets and shooting them out of a 8.5" barrel. A charge fluctuation of .1gr or OAL tolerance of .003" won't help with accuracy, but look at what I'm starting with. I have no delusions of creating match grade .300AAC with my components.

I have been loading small quantity, oddball cartridges for several years. The .300AAC is the my first hand load for the sole purpose of saving money.

 

[Klunatic]

A better measurement is to get a bullet comparator and measure to the Ogive. Almost all bullets will vary in OAL even jacketed bullets. The ogive is pretty consistent on bullets and really is the more important measurement when it comes to bullet accuracy. As this is were the bullet first contacts the lands of the barrel.

 

[StickShaker]

Thanks for the responses and putting my mind at ease.
I am using a Lee single stage press and Lee dies. Although "Minute Of Paper" was an exaggeration, I was trying to clarify that I'm using surplus, pulled bullets and shooting them out of a 8.5" barrel. A charge fluctuation of .1gr or OAL tolerance of .003" won't help with accuracy, but look at what I'm starting with. I have no delusions of creating match grade .300AAC with my components.

I have been loading small quantity, oddball cartridges for several years. The .300AAC is the my first hand load for the sole purpose of saving money.

Your seating depth consistency is most likely spot on but you can't confirm that unless you measure from the ogive like I mentioned in my previous post. Not a necessary step IMO.

 

[Major03]

Given your goal, I wouldn't worry about it.

 

[DarrellA]

Agree on getting a bullet comparator.

I measure CBTO for overall length computations. Much more likely to get consistent results.