Seating depth

[bulldog284]

Hello fellow shooters,

im have a problem getting consistent bullet seating at the same length. I’m using lapua bullets all sorted from base to ogives using forester Coax press Redding competition dies and forester dies. the lengths very from .0003 to .0004. measuring the lengths with a digital calliper and a Hornady comparator off the ogive.

what am I over lookin?

 

[PigButtons]

No offense intended but I'm not sure what you are measuring or what you see as a problem. Some more details will probably help. Even if there's 0.0003 to 0.0004 difference between all rounds, that's three to four ten thousandths on an inch. I'm not sure about all but most digital calipers have at least that big a margin of error.

 

[old codger]

You are over thinking this. Call it good and go shoot them.

 

[RegionRat]

You are basically reporting a batch range that is at the measurement uncertainty level of most of the equipment used to measure rounds, which is like saying zero variance.

Congrats.

 

[divingin]

Is your decimal place in the correct spot? I don't think you can consistently measure the difference between .0003" and .0004" with a set of calipers, and that's before you throw in the Hornady comparator.

 

[Bill Norris]

Absolutely, if you got them that close then don't sweat the small stuff.

 

[Straightshooter1]

Hello fellow shooters,

im have a problem getting consistent bullet seating at the same length. I’m using lapua bullets all sorted from base to ogives using forester Coax press Redding competition dies and forester dies. the lengths very from .0003 to .0004. measuring the lengths with a digital calliper and a Hornady comparator off the ogive.

what am I over lookin?

Variations in neck tension (often having to do with variations in neck thickness) along with how the necks are sized can result in such variations in seating depth. Sometimes when necks to too clean and results in unusual force need to seat bullets and when using a Co-Ax press, the amount of leverage it has can make it hard to discern differences in seating pressure. Lubing the necks for seating can help mitigate some of this "problem" your having.

 

[rsbhunter]

Do you anneal? Although, as others have stated, if you meant .0003 to .0004 (ten thousandth) , teach me how to get that close!!! Calipers are normally only accurate to .001. But anyway, that falls within what most shooters would be thrilled to get....I don't know that anyone would be able to shoot to a level to tell the difference... rsbhunter

 

[Dave M.]

Hello fellow shooters,

im have a problem getting consistent bullet seating at the same length. I’m using lapua bullets all sorted from base to ogives using forester Coax press Redding competition dies and forester dies. the lengths very from .0003 to .0004. measuring the lengths with a digital calliper and a Hornady comparator off the ogive.

what am I over lookin?

I’d say get a better seating die with the proper seating stem (ie Wilson micrometer seater with a VLD stem and use a good arbor press). Next, what type of calipers are you using? And there are much better comparators that are easier to get more consistent results.
Dave

 

[Nick Caprinolo]

Do you have any idea how minor .0003 is?

 

[Papa Charlie]

I don't know of any caliper that will measure into the tenths accurately. Are you sure you don't mean 0.003-0.004 as in Thousandths not Tenths?

 

[Jud96]

No digital calipers I’m aware of have a resolution finer than 0.0005 and even then they’re only guaranteed for +- .001 most of the time. Even if you could measure it, seating depths with a +- tolerance of .0004 would be great. I strive for all loaded ammo to be +-.001 but I’m not a BR shooter just a precision enthusiast. I think you meant that you’re seeing a .003-.004 variation, which is not good. I would make sure your seating stem fits your bullets well and check your calibers for accuracy. If that checks out well then you have a serious issues with neck tension or the condition of your case necks.

 

[David Christian]

Lets assume the OP had the decimal place off by a digit. Now, lets try to answer the question.

Is he measuring final loaded round distance of case base to ogive? Or, did he sort bullets base to ogive? Depending on this answer I can go in many different directions in possible remedies.

Loaded round to ogive may correlate to lots of potential issues with the seating die.

Bullet sorting measurement differences relate to a crapy lot of bullets and imo a measurement that does not matter at a grad scale.

 

[6BRA]

Bullets are different on an individual basis, from the ogive to the tip. Even from the same lot..the nose regions aren't the same. CBTO is how to seat

 

[Ned Ludd]

There are two critical contact points on a bullet that can affect generating consistent seating depth. The first is the point out toward the meplat where the seating die stem "pushes" on the bullet during the seating stroke with the press. The second is the point just above the bearing surface where the caliper inserts seats when we measure cartridge base-to-ogive length. Maintaining consistent distance between these two contact points is critical for uniform seating depth. However, both of those points lie in the nose region of the bullet, which is outside the region you used to length-sort bullets (i.e. base-to-ogive). In other words, your BTO sorting procedure is not doing much, if anything, to sort the bullets by the distance between the two critical contact points (see attached image below).

In my hands, there is much greater length variance within the nose region of bullets from a given Lot# than there is in the boattail/bearing surface. Bob Green and perhaps a few others have made bullet sorting tools that allow one to sort bullets based on the length between the two critical contact points to help improve seating depth uniformity (i.e. Bob Green Comparator). Alternatively, you might try sorting bullets by overall length instead of BTO. This is sort of a poor man's Bob Green comparator, but it can sometimes help improve seating depth uniformity because as I mentioned previously, most of the bullet length variance I have observed/measured lies in the nose region of the bullet, not the boattail/bearing surface. In other words, sorting by OAL is somewhat analogous to sorting by nose length, which is where the two critical contact points reside.

 

[bulldog284]

hello
yes I made a mistake with the decimal point it’s .003-.004 , the neck have not been turned or anhealed using lapua brass, and mitioya calipers

 

[Jud96]

What bullets? Also, check to make sure your primers aren’t sitting proud because your calipers could be registering off those and not the back of the case.

 

[big5ifty]

Is the seating die a Forster ?

 

[CharlieNC]

If you can feel seating force differences associated with different depths, it's time to start annealing.

 

[paulT]

Is the seating die a Forster ?

Forster custom honned the bullet seating stem for 20x bullets with my Forster micro seater die which yeilds lower loaded round runnout than my wilson inline seater with arbor press.