Shotgun pattern out of an AR15?

[deerstalkerks]

I just recieved my Noe .278 103 grain flat base powder coat mold. And casted up some beautiful 104 to 105 grain bullets. Loaded up some with different powders and I'm lucky to be able to hit a 2' by 3' piece of paper at 50 yds. Started at the bottom of the load chart and work up no change! they all measure right at .278 and get resized after powder coating. Any ideas what went wrong? Barrel is a 1-11" twist in a 6.8 spc ar15..

[BK7saum]

Just because you are at the starting load doesnt mean you aren't exceeding pressure for the alloy. What is your alloy and BHN.

I just saw the flat base part. You are definitely over pressure for what the bullet can take.

You need a gas check mold if you want to wrinf out the 6.8 amd approach jacketed bullet velocities.

[JohnH]

In my 300 BO, I found I had to water drop after powder coating to get any accuracy. I also gun a gas check even though I don't run any kind of lube. PC, water drop, add gas when sizing. Size as soon as possible after water dropping, the added hardness will make sizing harder than it needs to be.

[BK7saum]

What are your velocities? or book velocities for the charge. i would stay below 1400fps or at least 1600 fps if i was shooting flat base bullets.

A moderately hard alloy with gas check would probably run well at the start loads.

[upnorthwis]

My experience was that without gas check I couldn't hold minute of berm. With gas check was holding 2-1/2" at 100 yds.

[Larry Gibson]

Lack of a GC, as mentioned is probably the main problem. The invention and use of GCs is for a reason......you have re-discovered that reason.......

[Tom_in_AZ]

Gas check them!


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[deerstalkerks]

thanks guys, It seems like i'm trying to push to fast. the bullet mold is design to have No gas check. Just powder coat. I might try some Redot powder and slow it down. going back out Monday to try it again. Thanks..

[Larry Gibson]

PC is not a substitute for a GC in many applications such as in the AR15 If you want the action to function. What cartridge?

[Old Caster]

Make sure you are not swaging down the size of your bullet when they are shoved into the neck. You may have to use a tool that expands the neck a few thousandths of an inch. Try pulling one out with an inertia puller and measure them before and after. If you don't want to expand your brass, you will need to go to a harder bullet so they won't be swaged. A GC will keep this from happening too.

[Winger Ed.]

From what I've heard, the AR platform is problematic at best with cast.
Without gas checks, you're already starting on the wrong side of the curve.