A word of caution with the 450 Bushmaster round and cast lead bullets

bpost

I purchased the 325 grain bullet mold as listed in the 50th Lyman Reloading manual.  I had a lot of 1680 that works well with the 250 Grain FTX jacketed bullets.  The load listed using 1680 for the cast bullet seemed reasonable so I tired it.  Using magnum SR primers the load was 1.5 grains below book max.

It was disappointing to say the least.  Ignition of this ball powder was spotty at best.  There was a noticeable delay in ignition with  a huge muzzle flash.  Unburned powder and smoked cases were present on every shot.

I just tried the book max load for this bullet using IMR 4227.

It is perfect, shooting very well with good case expansion sealing the gasses, accuracy is excellent at 100 yards. 

Another issue is feeding cast blunt nosed bullets in AR rifles.  These bullets refuse to chamber at all.  When trying to eject the stuck case it pulled the bullet out of the case dumping powder into the action.  A Ruger American Rifle feeds this round perfectly.  I can only assume the leade is different in the Ruger barrels compared to the AR barrels.  I have had zero issues with the AR using jacketed bullets killing deer with authority.

If you use cast bullets in the 450BM you might want to stay away from ball powders to avoid the headaches I had with them.

Grunt2

Not a good idea shooting cast bullets in any gas operated weapon...Like the AR...Doesn't take long to plug the gas tube with lead.

bpost

Grunt2 said:

Not a good idea shooting cast bullets in any gas operated weapon...Like the AR...Doesn't take long to plug the gas tube with lead.

My experience with cast loads has been quite good as long as they have a gas check and full lube grooves of Alox/Beeswax.  After 100's of rounds in the SKS there is no sign of any lead in the gas system.  There is some evidence of lube getting in the gas tube but it comes out with a quick scrub with Lacquer thinner and a gun patch.

I cast mostly straight wheel weights sometimes throwing in some Linotype for grins and giggles.  Making sure they are sized .001 over groove diameter has also proven to be helpful.  I have not shot enough cast bullets in the AR to get data either way.  If I do I will keep you posted, I have heard of gas tubes getting blocked in the past.