Dummy round

[LTH]

About two weeks ago I made two dummy rounds.
The first was a seated bullet in a resized split case neck to measure lands to bolt.
The second was to seat a bullet to a tested coal of 3.320" for a nosler 165 gr. 3006 to adjust my die.

I measured them both today and both of them moved .002" longer.

Is this normal ?

 

[LiveLife]

Perhaps inconsistency in caliper usage or wear on calipers?

 

[rcmodel]

No, it is not normal, or explainable.

I'd go for an irrational error with your measuring tool also.

If still in doubt?

Run then through the seater die at the same setting and see if they are .002" shorter?

rc

 

[LTH]

Thanks , I will check it against the die and see about the calipers.

 

[fguffey]

The first was a seated bullet in a resized split case neck to measure

I am the fan of bullet hold, I want all the bullet hold I can get. Splitting the neck reduces bullet hold.

About two weeks ago I made two dummy rounds.

I make transfers, I want to transfer the dimensions of the chamber to the seating die.

F. Guffey

 

[rcmodel]

I have never loaded a dummy round in my life.

Load the starting load, seated to Max length.

And keep seating slightly deeper until it cambers in your gun.

Then go Choot'm!
And work up the powder charge.

rc

 

[BCRider]

I've made some of my own dummies to use for action cycle testing. It's a lot cheaper than buying snap caps! ! ! ! !

I drill a 3/32 hole through the case walls on two cross axes so I can tell them at a glance.

Those without cannelure grooves also get a filler of correctly sized wood dowel as a "powder charge" to support the bullet from being set back further in the case.

 

[gamestalker]

I would bet that the bullet got pulled up when you chambered it and removed it. The bullet sticks in the lands, then when you remove it it gets pulled up. I do it a bit differently now, as I've actually had the same thing happen.

It takes a bit longer, but what I do is seat the bullet deeper and deeper while test chambering it by hand, remove the bolt. When I can just barely feel it sticking in the lands when pushing on the cartridge as hard as I can, but it will fall back out by gravity alone with the barrel vertical, I consider that as .000" off the lands.

Once I have made that determination, I then get an accurate measurement of the seating die from stem to base, then I write that number down for that specific bullet / part number. So when I want to seat that particular bullet say .015" off the lands, I know my seating stem to die base will need to be .015" shorter than the .000" number recorded.

FYI, most, if not all bullets will have some variance at the olgive. With standard grade bullets, the olgive location can vary by as much as .010" or so. Match grade bullets aren't as inconsistent, but they will still have some inconsistency, usually .003" or so.

GS

 

[RetiredUSNChief]

There may also be a rather significant repeatability issue with some of the cheaper calipers.

Repeatability being the ability of the caliper in question to repeatedly obtain the same measurement on the same object over several measurements.

Make sure it's zeroed before use.

It's also a good idea to have a known standard to measure with the caliper as well. For smaller measurements, a set of feeler gauges would work just fine. But for larger objects the size of cartridges, a one or two inch setting standard would be nice. This way, if your caliper is ever in question, you can pull out a setting standard and compare the caliper measurement of it.

 

[gamestalker]

Good advice about making certain the measuring device is delivering accurate assessments. I check mine with feeler gauges.

GS

 

[Jesse Heywood]

Two things to improve your measuring.
If you don't have one, a bullet comparator lets you measure to the same place on a bullet, which is needed to check on soft point bullets.

Second is to keep your caliper faces clean.

 

[LTH]

I bought some feeler gauges and my two calipers are good.

I put my 20 off the lands round back into the die and had to take it down 2 thou.
Who knows , I might have dropped em just right.

I am using o rings with my dies and used a sharpie for a scribe.

I re- did everything again and I'll keep an eyeball on em' .

Thanks for the feeler gauge suggestion Retired USN Chief , I totally forgot about those gauges.
I only use the coin type for spark plugs these days.
I used to use the flat ones like I bought today for the points in distributors .

 

[LTH]

Thanks JH , I have the oal gauge and head space comparators.

For the NBT 165 gr. .30 cal. is 1.290 " long and so I dug through my pile till I found one .
I set my die to their tested coal and then took my ogive measurement, which actually put me 20 thou. off the lands.

I definitely do need to learn how to use calipers correctly. Tricky tricky

 

[Jesse Heywood]

With my shaky hands I try to measure with everything at rest on the bench. Set up with blocks so all is level. That way the part and caliper can be left in a stable position and the measure can be read without my hands on anything. You might try that for learning how to repeat the measure. It should help you figure things out.

 

[LTH]

I'll have to give that a try JH.