.30 cal. Smokeless

[MrTobes]

I am working on a .30 cal smokeless build. Using a Hankins original and my own chamber design. I haven’t found any info on .30 cal. Smokeless and would like input from others who have had experience with .30 cal. Builds

 

[ElDiablo]

You and @Mnt monkey need to talk.

 

[gle3105]

Have considered doing something like this myself MrTobes.
I currently have a 375 built SML.
Been thinking about pulling the barrel & breech plug and use cartridge reamer of size TBD. Stopping short of cutting the full length of the cartridge reamer for the lightest volume load.
Reason being on a lighter load the bullet would still be in the rifling and or bit of the throat. Don’t want to push the bullet into the chamber.
If more powder needed no big deal being in barrel.

I recall Tom Post of Swinglock experimented with this. He built some great SML’s. And a .284 cal IIRC.

 

[abaleena94]

I heard Tom Post put a positive stop before the powder chamber in his small cal builds. His powder chamber in those small cal builds was necked down like a brass case would be on a center fire cartridge. Im not sure what the purpose for necking down the powder chamber was, but im sure he had a reason. One reason for the stop in the barrel was that it stopped the bullet from going past the shoulder at the end of the barrel and into the powder chamber. If the bullet could go past that shoulder, it would get hung up and cause a catastrophic event. The other purpose for the stop I heard was to allow for some airspace in the powder charge. Im not sure what the purpose of the airspace was, but im sure tom post had a reason. Unfortunately I heard Tom post doesn't build muzzleloaders anymore and only builds sizing dies now.
I heard someone else mention that they have a 30 cal smokeless build with a large powder chamber. They said they were using H4350. They were told by their builder that they were NOT TO GO BELOW 55gr. of powder. Im not sure why they had a minimum powder charge but I certainly believe what the builder said. Their load was 62 gr. of powder with either Hornaday or Berger 150 gr flat base target bullets. They said with a 100 yard zero, it would cover 500 yards with 7.25 moa at 3250 fps. The bullets were full formed to the barrel. Ive heard with calibers below .40 , obtration into the rifling becomes a major problem. So full forming bullets in a sizing die becomes a necessity.

 

[anonymouscowherd]

I heard Tom Post put a positive stop before the powder chamber in his small cal builds. His powder chamber in those small cal builds was necked down like a brass case would be on a center fire cartridge. Im not sure what the purpose for necking down the powder chamber was, but im sure he had a reason. One reason for the stop in the barrel was that it stopped the bullet from going past the shoulder at the end of the barrel and into the powder chamber. If the bullet could go past that shoulder, it would get hung up and cause a catastrophic event. The other purpose for the stop I heard was to allow for some airspace in the powder charge. Im not sure what the purpose of the airspace was, but im sure tom post had a reason. Unfortunately I heard Tom post doesn't build muzzleloaders anymore and only builds sizing dies now.
I heard someone else mention that they have a 30 cal smokeless build with a large powder chamber. They said they were using H4350. They were told by their builder that they were NOT TO GO BELOW 55gr. of powder. Im not sure why they had a minimum powder charge but I certainly believe what the builder said. Their load was 62 gr. of powder with either Hornaday or Berger 150 gr flat base target bullets. They said with a 100 yard zero, it would cover 500 yards with 7.25 moa at 3250 fps. The bullets were full formed to the barrel. Ive heard with calibers below .40 , obtration into the rifling becomes a major problem. So full forming bullets in a sizing die becomes a necessity.

Designing a powder chamber around the dimensions of an existing case would let you have a good reference for load data and pressures generated by simply following load data for that round. Personally if I were gonna do that I'd get a custom reamer made and go just a hair undersize at the neck, and then run it in short so that a bullet shoved all the way down to the stop point would be as if it were seated to the proper depth in a brass case.

When reloading metallic ammo, you'll quickly discover that MOST loads have some to a lot of air space in them. On the other hand, compressed loads are common with some powders in some calibers.... Reducing or eliminating air space will drastically change pressure levels and the pressure curve.

And while we all 'know' you can blow a gun up by over charging (double charge etc)... some powders are known for causing kabooms when there isn't enough case fill. It doesn't always happen, and the exact cause isn't known but there are plenty of information on 44 mag revolvers and similar that blew up wtih a below published starting charge of Win231 or IMR4227 because the shooter wanted some "lighter loads". Other powders like Tite Group are seemingly immune to this (4.0gr or 0.34cc of volume in a 762x39 case...)

Some very interesting reading can be done on a good reloading data site, comparing two cartridges that have same/similar bullet weights and bore diameters but different case capacities. Good example is 762x39 and 300 blackout