A Noob, 300Blkout and subsonic cast accuracy

[dave5701]

Im a little different in that I dont have an AR. 18" Old style Contender. 1:8 twist and I dont know my exact bore diameter but supposedly just the standard .308 bore. I started with 220gr gas checked (size = .309) and ran through 700x, Unique, Blue Dot, H110 and ended up with the best accuracy with H335 at about 1050fps. Group size is about 4" at 100yd. Using 150gr Hornady jacketed, group is 1" at 100yd. I would think by this, the barrel is ok. I made more brass and weighed them and used old 296 powder to measure how much each case will hold to get a consistent a case as I know how. I seat bullets right at .01 off lands. Still with these measured cases, accuracy is still the same. I dug around and found some .310, 165 grain flat points I bought for my 30-30 and tried them. I only tried Unique and Blue Dot just to see if things might be different. Nope, about 2" at 50 yards. One thing I noticed with the 165s was a slight keyholing. The black ring around the hole in the paper was slightly thicker on one side than the other, the 220's did not do that. I keep all my groups, cut themout, past in a 3 ring notebook with all the load details. I am using standard CCI small rifle. So - I know I can try other powders, bullet seating, maybe primer hole opening. What is the best thing I can try first? I dont cast, buy from someone who makes them.

[NSP64]

Buy bigger
.310 long pointy

[LongGun1]

Or .311

[dave5701]

Or .311
I found some 245gr but .309. Know where I can find a .310 or .311 already made? Montana bullet works might do this, but he is out of commission right now.

[Jupiter7]

I run 170's flat point gas checked in 10" 1/8 twist barrel but in an AR pistol, sized at .309 and tumble lubed. It is my most accurate load. Cloverleaf at 50yds freehand...with a scope. I also only run them at supersonic velocity. No chrono but from the data I'm using, I'd gander they are running around 1550-1650fps.

I'd re-evaluate a few things before I made any final decisions. First, powder choice, h335 is pretty slow burning. That old 296 sounds like just ticket for running supers. Also seating those short 165's out of the case neck far enough to almost touch the lands is a recipe for an uneven burn. I seat em short, mine are about 1.90-1.91". Of course slugging your bore will give way more insight as what to do. And assuming you cast or are thinking about, a proper mold and proper alloy along with sizing to fit will fix lots of problems. I'd buy a mold before I bought any of those 245's from mcb, 1k cast bullets will pay for the mold at those prices. I run my subs out of soft alloy, same as I run my pistol boolits, hard undersized bullets will not get you the groups you want.

[LongGun1]

I found some 245gr but .309. Know where I can find a .310 or .311 already made? Montana bullet works might do this, but he is out of commission right now.

I recently got an Accurate 311235B (5 cavity, .311, 235 gr, gas check).
http://www.accuratemolds.com/bullet_detail.php?bullet=31-235B-D.png

http://img.tapatalk.com/d/13/05/14/umamydah.jpg

I believe they have similar molds in 240 & 245 gr.

But just the boolits. ...unsure.

[Liberty'sSon]

Many people like Lil' Gun powder in 300BLK.

[runfiverun]

or just switch to a pistol primer

[dave5701]

You know I have been wondering about primers. So educate me on something. Kinda-Generally, the 300 blkout case is similar in volume to a 38 special. Again, generally, I would think since the case is small, your best bet on powders for subsonic would be pistol type powders. Now, whats up with the primer issue. DOes a pistol primer provide a hotter flash than a rifle? I would think the other way around, generally, rifle cases would be larger than pistol and require a hotter flash.

On seating a little shorter, generally with cast, does that make for better load in terms of accuracy?

[felix]

Primers produce heat AND a supersonic wave (force). The ratio of which is defined by the primer number/type. Another characteristic is the ability of the gun to fire the primer. A primer number/type has either a tough or whimpy skin/container, based upon its application intended. ... felix

[runfiverun]

i'll let you think through on what felix said.

a softer cup and flame can be very beneficial to accuracy.
no a pistol primer does not have either a hotter nor a longer duration of flame than a rifle primer.
you might be able to do a little research on the Remington bench rest primer.
why it was invented, and maybe see why it isn't a good primer in some situations.
that would really help you understand a primers role in accuracy.

[cheetah]

I'd stay with rifle primers in the Contender. Soft seating works - leave half to one rim thickness exposed in an unmounted barrel. Bullets from Hunters Supply work well for me in a 10"twist 30-30, 23" and 16" long. His 165gr is a flat plain base at .311. The 193gr is checkable ( haven't needed to ) as is the 220 gr which is also a .300 bore rider nose and both have a .311 base.
With no special attention I can bunch any of then under 2moa and the guy simply sends the bullets - no BS. We part ways on powder though - I have some good pistol powder loads but Trail Boss suits my laziness and does well enough to stay on the menu.

[cheetah]

Forgot one more idea. Given the relatively large diameter boolit and the loooong drag of the 30-30 neck, I use the .31 Lyman expander to ease some of the tension - largely so I don't engrave a boolit so deeply that I can't remove the round if I need to. The combination could lead to a tight neck fit.