Newbie question on conundrum

[tubesthatglow]

I clearly see the need to cast for throat and chamber size assessment for best accuracy. I used melted sulfur for chamber/throat/bore measurement.
However, when I cast a bullet to throat/chamber then the cast bullet is hard to fit in case opening even after belled.
I do also use Lee factory crimp dies.
I load and cast for 38 S&W, 357 mag and 38 special, 44 mag, 45 acp , 45 colt , 300 Savage(not casting) and starting 300 Blackout.
I have been reloading form 2 years and casting for 9 months.

[Wayne Smith]

I have no idea how stable the sulfer is over time for precise measurements. Someone will be along soon who does, though. We also need to know if you use a micrometer to make your measurements.
You are risking overpressure if there is not room in the chamber for the brass to expand and release the boolit. My guess is that 1) your measurements may not be sufficiently accurate, and 2) you did not figure room for expansion and release of the boolit when you decided how to size your boolits.

[Paul D. Heppner]

What diameters are your sizing dies? Are you getting spring back with your alloy after sizing. What alloy are you using? Have you had your micrometer or calipers checked against a standard. We need more info.

[MostlyLeverGuns]

What are you using to expand case necks before seating your cast bullets? A neck expanding die like a Lyman 'M' die or Lee neck expanding die, maybe with an NOE bullet expander plug is needed. The size of the neck expander plug is determined by the size of the bullet you are trying to seat. The neck expander plug has a step a couple thousandths larger than your bullet and the rest .001" to .003" smaller, depending on what works for you. Most handgun dies have a bell step to open case so lead bullets aren't damaged. Just bell enough to let bullet start.

[blackthorn]

Sulfur neither expands nor contracts. Sulfur is often used to anchor machine mounting bolts in concrete. Sulfur, along with 10% or so graphite makes an excellent chamber cast.

[mdi]

How hard is it to seat the bullets in a sized/flared case? Neck tension is what holds a bullet in place so the neck ID needs to be .002"-.003" smaller than the bullet OD. Seat a bullet, then pull it with an impact puller and measure with micrometers. Is the case swaging the bullet? If not, it's OK, if the bullet is swaged more than .001", then look at case preparation for possible problems...

[GWM]

I do also use Lee factory crimp dies.

Well if you use the Lee Factory Crimp Die then it will swage down your boolit and mess up everything since it incorporates a sizing ring. Pull a boolit from the finished round after using that die and measure it. And then you should probably stop using it ;)

[gwpercle]

The best advice I can share with you is...Don't over think all of this.
I started with a Lyman cast Bullet Handbook and sized the boolit to whatever diameter was shown in the manual. First, size them to fit the barrel. If problems show up , then start looking at throats/chambers. Second, you have to be able to load and unload a round, start making the boolit too large and you might have problems here.
My advice is to size them to book reccomendations, shoot and see how they work.
It's impossible to size boolits to three different dimensions, so go with barrel bore dimension first.
At least that is how I've done it for the last 50+ years, and sized to bore will usually do the trick .
Gary

[blikseme300]

Which FCD's are being used? Lee, in their infinite wisdom, uses the same name for two different kinds of crimp dies. The collet type works well and won't size down the CB but the "squeeze the whole cartridge" type typically causes under-sized CB's. The former is typically what is available for rifle and the latter for pistol but there are some collet types available for some pistol cartridges.

Lee does have or have custom made collet FCD's for 44Mag, 45Colt and 300BLK.

To add to the mix often sizing dies are too aggressive with sizing down and this causes trouble when needing to size up to be able to seat the proper size of CB. This is often seen when pistol reloads have a distinct Coke bottle appearance. Custom or modified sizing dies prevent this overworking of the brass.

[whisler]

As Wayne Smith intimated, did you allow for brass thickness when you figured size of the boolit from your chamber cast?