Thread: what causes differences in OAL with a comparator ?

Greetings,
I have noted some distinct changes in the ogive position and shape, enough to be detected by eye. Additionally the projectiles in a box are not all made in the same die so they will vary in shape slightly. I just start with 1mm jump where I can which works for me.
GPM.

So that is 0.08mm over target and 0.04mm under target

or to translate into imperial... 0.003" under and 0.0015" over

My sense of proportion has to ask what is the problem?

Originally Posted by LBD

So that is 0.08mm over target and 0.04mm under target

or to translate into imperial... 0.003" under and 0.0015" over

My sense of proportion has to ask what is the problem?

no problem, just asking what the cauyse can be, aswell as what should be considered too high and too low from the target

Originally Posted by dannyb

Where could one obtain said Sinclair ogive inserts ? sorry can't google from work

https://www.brtshooterssupply.com.au.../sinclair-int/

Haven't bought anything from Sinclairs/Brownells for yonks.

Haven't checked stock levels though.

Originally Posted by Larskramer

no problem, just asking what the cauyse can be, aswell as what should be considered too high and too low from the target

It might be interesting to now look at the bullet OAL and compare with the comparator OAL... if there is no common theme then you have a pretty good indication that the projectile shapes vary (ie ogive to tip) even if the weights are exactly the same.

Another thing to have a look at , would be to measure the projectile length with the comparator and see how they vary.

No one has mentioned pressure, and consistency of caliper use.
We all tink we can repeatably apply the same force and therefore get the same measurement on the same object. Try it with your eyes closed or the caliper held so you can watch the dial. Measure the same thing 5 times and see if you stay within .001 " because that is the +/- measurement
that is giving the issue. ( +/- 1 gives a range of 3)

Use a wibbly wobbly bullet not a flat piece of steel.

I am surprised that none of the reloading companies have come up with a hydraulic device to take the human error out and give consistent pressure...... maybe if they did we wouldnt need to measure anymore.
I think also you need to take out your seating stem and check it fits your orgive and isn't bottoming out on the tip of the projectile.

Yeah definitely can manipulate the calipers a little to give you that range. It is the same when seating the bullet to make sure the ram pressure is consistent. AMP guys came up with an electric bullet seater and lots of interesting guff on seating pressure. Not cheap though.

I’ve found variable neck tension causes “spring back” when loading. I had this real bad in the last batch of 7mm rem mag I loaded. I could feel it in the press when projectiles were harder or softer to seat then the “normal”. The observation always aligned with my measurements immediately afterwards. Soft to seat were seated further in the case (a real prick when it goes beyond what you want) and hard to seat were seated too long and need an adjustment and pushed further.