Mini .30 cal: 300BO vs 7.62x39 vs 300HAM’R

[dellet]

I may be weird but I look at the difficulty of making loadable cases and actual loading. 7.62-39 boxer primed brass is hard to find around here, never seen it for sale locally. Making 300blk cases is a long slow process, that may have been necessary for subsonic very heavy bullets but does nothing for the hunting bullets we are discussing here. The Hamr is one pass through a sizing die and ready to load. Comparisons of factory loaded ammo seem to be valid with a semi auto due to pressure but not a bolt action.

Just a minor correction on 300BO vs 300HAM’R case conversion. Both of these cartridges can be formed from .223/5.56 cases. To form / convert cases for either of these cartridges it is basically same steps and amount of work by either:
1) Trim excess material off .223 donor case and then run it through FL Sizing Die to form the new neck and shoulders; or
2) Run the .223 donor case through the FL Sizing Die and then trim off excess material

- For 300BO the .223 donor case is cut at the case body / shoulder junction. The new neck is formed from the case body material from donor case.

- For 300HAM’R the .223 donor case is cut at the junction of case neck and top of the shoulder. The new neck is formed out of shoulder material from donor case. This results in 300HAM’R case being approx. 1/4” longer than 300BO.

and there is no difference in brass for subs/supers.

Converting brass only makes Cents, if you can’t buy any. The time involved doesn’t even return $10 per hour, when you consider new, once fired or already converted brass is available for $35 per hundred or less. Thats hoping you can spend less than 2 min per case, including the time spent collecting it.

The only savings is that the time you spend processing, you can’t spend on the range shooting up consumables like powder primers and bullets.

If you enjoy doing it, then cost isn’t a factor.

Starline brass for both cartridges is $35 per 100 and is probably better quality and more consistent than most people produce converting.

 

[ebb]

Thats not what I meant. The 300BLK is shorter and gets a whole new neck from the parent 223 case. I assume it is made that way so there is room in the magazine for a sub sonic load where a very long 220 SMK is going to be used. But the discussion here has been mostly about lighter 125 -130 weight bullets. JD Jones had more in mind than the perfect deer/hog cartridge, and his design took that into consideration. I was not aware that Starline brass could be had so cheap.

 

[Oso]

Yes, 300BO case is made from shortening a .223/5.56 case and then forming a new neck. It’s shorter case length is needed in order to fit the long heavy bullets (190gr-240gr) and still fit within 2.26” AR15 mag length limit.

The 300HAM’R case is also made from shortening a .223/5.56 case and then forming a new neck. The 300HAM’R case is designed specifically for only supersonic bullets (shorter 90gr-150gr), which are shorter then heavy subsonic projectiles. As result the 300HAM’R is shorter case length than 223 case, but not as short as 300BO case.

Although the brass case length is different for the .223 (5.56x45mm), 300 HAM’R (7.62x41mm), 300BO (7.62x35mm), all three of these cases have the same maximum cartridge overall length of 2.26” when loaded into an AR15. Keep in mind that due to its size and shape, each specific projectile may have a recommended COAL that is shorter than the max coal.

 

[ebb]

I did not know that the 223 needed to be cut of to be formed into a HamR. I read somewhere, maybe on the Texas hunter form that it was one trip through the HamR dies and it was good. Like this??? https://loaddata.com/Cartridge/30-223-30-Apache/6663

 

[dellet]

If you really want to split rabbits(hares), the parent case for both 300 whisper and 300 Blackout is not the 223. It is the 221 Fireball. Basically 1.400” long

The Model 7 Remington marketed by AAC, actually has a 221 Fireball bolt, not a 223 bolt. Yes, they are different. The extractor and ejector are clocked different on the bolt face.

The 700 sold by Remington used a 223 bolt.

There have been probably a dozen 30 caliber 223 wildcats over the years. The 30 Apache/30-223 was a straight neck up and shoot it mostly for single shots.

 

[Dufas]

I had trouble expanding the neck for x40 or x41, too many splits. BO just sizes DOWN for the neck. Annealing didn't help much.

 

[dellet]

I had trouble expanding the neck for x40 or x41, too many splits. BO just sizes DOWN for the neck. Annealing didn't help much.

Either using the wrong tool completely, or trying to expand more than one caliber at a time.

Or if you chopped the neck first, it can leave a ragged edge. If you don’t clean that up, it acts like a pre installed split. Expanding it just makes it bigger.

 

[rockhound78]

I go from 223 to 30 apache in one swipe thru a Lee 30-30 size die with a tapered expander. Works well. do split a few but not many. Can't do that with my 30/221 dies

 

[Oso]

Sorry I have been tied up. I meant to post a couple of pictures comparing the case forming for the two cartridges.
Case #1 is Factory 300HAM'R.

Case #2 is .223 donor case having been run through 300HAM'R FL Sizing Die.
> New shoulder formed from donor case body.
> New case neck formed from donor case shoulder. Excess length needs to be trimmed.

Case #3 is .223 (donor case).

Case #4 is .223 donor case having been run through 300BO FL Sizing Die.
> New shoulder formed from donor case body.
> New case neck formed from donor case body. Excess length needs to be trimmed.

Case #5 is Factory 300BO.

 

[Oso]

I had trouble expanding the neck for x40 or x41, too many splits. BO just sizes DOWN for the neck. Annealing didn't help much.

Converting .223/5.56 into 300HAM'R has some additional challenges than 300BO. It is common to get splits or voids when forming the 300HAM'R, especially if using range brass. The location of material on donor case (case shoulder) that is converted into new neck on 300HAM'R takes a lot of abuse from feed ramp and lugs during chambering and extraction. Tiny dents and superficial knicks and gouges found on .223/5.56 donor brass (fired/range brass) become critical during 300HAM’R case conversion as neck and shoulder area are expanded outward to fit .30 cal projectile.

Annealing the donor cases beforehand makes a big difference. Doing some QC work at beginning to sort out cases with any damage along shoulder area makes a big difference. Gradually expanding the case neck in a couple of steps decreases the stress on case leading to fewer splits.

As Dellet pointed out forming/converting cases may not make sense with the wide availability of factory cases.

 

[std7mag]

Kids!!
Get off my lawn!!

30 M1 Carbine Paratrooper with a 1911.

Both are good for what ails ya.
Or tries to assail ya.

 

[Oso]

*** News from Shot Show 2026 ***
> new 30cal intermediate cartridges the “30 Epic” by Olympus Arms

Appears to be same concept as 300HAM’R. The 30 Epic focuses on supersonic lightweight .30 cal. bullets for use in AR15 platform. The 300HAM’R is based on .223 Rem case, whereas the 30 Epic is based on 6.8 SPC case.
30 Epic cartridge

 

[ebb]

Dellet you are right I had the discussion with JD himself and he was quick to point out 221 brass. back then before I knew what little I do now I thought 30 carbine would have been the easy button. But I don't think I understood pressure back then. DUHHH

 

[dellet]

*** News from Shot Show 2026 ***
> new 30cal intermediate cartridges the “30 Epic” by Olympus Arms

Appears to be same concept as 300HAM’R. The 30 Epic focuses on supersonic lightweight .30 cal. bullets for use in AR15 platform. The 300HAM’R is based on .223 Rem case, whereas the 30 Epic is based on 6.8 SPC case.
30 Epic cartridge

Well that just about makes the circle of stupid complete. The 6.8 SPC was based on the 30 Remington. The 30 Remington was developed as a rimless 30-30 to work in Remingtons new auto loader in 1906. A mostly forgotten artifact becomes the new hot case design by shortening it and necking it down 100 years later to fit another auto loader. Then 10 years later it gets necked back up to 30 caliber again to basically make a rimless 30 Herrett.



Any body want to see a rimmed blackout or 300 Hamr from about 150 years ago?

 

[426nut]

I've always wanted a .270 REN.
I just realized that would make it a rimmed 6.8/.277 "light" based off of the 1930's hornet case.

 

[dellet]

I've always wanted a .270 REN.
I just realized that would make it a rimmed 6.8/.277 "light" based off of the 1930's hornet case.

You’ll have to Rename it something like 270 Recon Engagement Ninja. Won’t be able to keep it on the shelves.

 

[Oso]

Agree that we are now recreating the wheel. As soon as I saw the YouTube video featuring the 30 Epic it immediately made me think of the 30 HRT (Herrett Rimless Tactical). Tomato - Tomato

Edit - contemplations while having morning coffee.
The 6.8 SPC shares similar performance with 6.5 Grendel. Ultimately, the 6.5 Grendel became clear winner based on popularity of the cartridge and the continuing focus on the parent case (6ARC, 22ARC, 338ARC). Except for desire for a proprietary cartridge, it’s hard to imagine how picking to use the SPC case would make it more marketable. A .30 Grendel would be easier plug & play.

 

[ebb]

What would the additional case capacity of the Grendel bring to the table? I thought that Remington's 30AR would be the best, but many were saying the .473 base is too big for an AR15 bolt to live very long.

 

[Oso]

The powder capacity of SPC case and Grendel case are very close and both require special bolt face. Early on in Grendel’s development (Type 1 bolt) there was a higher failure rate with the reduction of metal to fit the larger bolt face. A little bit of engineering (better metal and hardening resolved this potential failure (Type II bolt). No more problems.

My speculation without knowing more about 30 Epic case dimensions…. The advantage of Grendel case is ability to load longer projectiles while fitting in 2.26” mag length. Similar to 300HAM’R, the longer case length of SPC will limit the type/length of bullets that might fit within the mag restriction.