We just got done with the FEA on a new bolt iteration (newer than the last one) which should bring the MAP up to 80,000 PSI, which is right about the limit for composite cases anyway. Performance up from 2,770 ft/s to 2,830 ft/s. We're still using Carpenter 158 lol.

autogun said:

PS how close can you get to that BC with an EPR-construction bullet?

Depending on design, identical. I have some schemes for that.

Farmplinker said:

Have you tried a 120-grain bullet yet? Seems like that might be wanted for a long-range loading. But like autogun says, it looks promising. Good luck with the system!

The 100gr bullet already has BC comparable to a 130 grain VLD. Going heavier sucks up a lot of volume in the case; I have heavier projectiles but they're not a good fit for the Grendel.

I chose the Grendel primarily for its problems with bolt web thickness and strength. Solve those (and it's looking like I have) and you can put about anything that fits in the AR-15's chute down the spout.

For reference, it's already producing over 500 J at 1,000 m.

Yeah, after I posted I realized a heavier bullet would probably take up too much powder space. Of course, when you present your system, you'll get, "We're leaning towards 6mm now".

I'm too salty for that. The system is designed to be flexible (6mm ARC, .224 Valkyrie, etc), and I have many others. Also, and this is critical, I don't expect anything of mine to go anywhere.

By the way , what are the current projectile manufacturing options being utilized other than lathe-turned as demand for lead-free ammo increases? 

I seem to remember that even in the past  prior to jacketed lead bullets, bullets like Balle D were pressure cast with high enough precision that they were still competitively used , pulled and reloaded 50+ years later 

The details of balle D manufacture are shown in detail in the 1916 book Cartridge Manufacture by Douglas Hamiltion. Scans can be found on the Internet. 

Mr. T (MrT4) said:

By the way , what are the current projectile manufacturing options being utilized other than lathe-turned as demand for lead-free ammo increases? 

There are a variety of machines for making bolts and screws that could be adapted to the role. They aren't particularly fast but they are simple so a lot of them is practical. Investment casting, swaging and rolling are all options for finalising billets.

I downloaded the Hamiltons book and indeed process seems similar to that used to make certain types of bolts and screws. I was surprised when R.G.C. told me that they used to pull these bullets for long range high power comps, i never taught the bullet quality was even remotely high enough for match work.

My current project of subsonic .30 cal AP for .300BLK , that is complementary to the rifle i am making ,will initially be made with a lathe-turned bullets, will see if we can progress from there i am not to keen to go into ammo manufacturing i rather stick to guns.

Mr. T (MrT4) said...

By the way , what are the current projectile manufacturing options being utilized other than lathe-turned as demand for lead-free ammo increases? 

 

It is possible that they could be pressure formed to final shape. I don't know if the tolerances would be good enough.   Those machines are relatively big and expensive, but they tend to have massive output, sometimes several parts per second. 

Screw-making machines would work too.  Twenty years ago I worked in a factory that made pneumatic tire valves (schrader valves and others).  The brass bodies of those valves are shaped, through-drilled and threaded internally and externally.  Each of our linear machining stations could produce one of those bodies in under five seconds.  At that time, the most popular machine in the world for doing that was made by Rudi Hutt.  The front page of his website shows some of the things that his machining stations machine and assemble.  https://www.rudi-hutt.de/overview/?lang=en