It shouldn't work, but it does....

[Ian]

300 BLK, 16" AR-15, Lee 230 TL bullet with one coat of ASBB tumbled powder coat. Front band is .305x.307 on most of them, rifle's throat entrance is .310". Nose doesn't get to bore size until about 1/8" in front of the front band, even with the coating. Loaded over 10 grains of RX-7 because they were too fast with my 10.4 grain standard load with the ACE bullet uncoated and lubed with standard lube in the grooves.

25 yard target was a single hole that five bullets went through. This 50 yard target shows three sight adjustments, shot with a digital NV scope that isn't very good for daytime target work. Target was uphill significantly, some yawing is shown and some oblong holes are due to the elevation. How this undersized, out of round wonder manages to group is beyond my ability to comprehend. Some things are like falling off a log, and some things NASA can't figure out.

 

[Brad]

Looks good to me. Sometimes it doesn't matter why it works as long as it does.

And Darth Maul? Are you a Star Wars geek?

 

[Ian]

Mebbe, a little.

Hey, it's big, black, evilly ugly, and very quiet. The other one goes by Precinct 30, due to the short OAL and urban swat camo.

Just got through shaking and baking another 80 Lee bullets, have 65 or so baking right now, which is all I had left from the last casting session. Keeping up with several, hungry 300 Blackouts with a 2C mould is going to suck.

 

[Brad]

Yeah, a 2 cav isn't gonna do it long term. That is what I have for mine and it doesn't keep up without a bunch of work.

My wife is a huge Star Wars geek. We have a house full of various memorabilia. I mean full.

 

[fiver]

you umm know you can do 2 coats... just sayin.

I don't have enough imagination to name my guns.
I have 2 with names one I sorta named [my old trap gun] and one got named for me.
the xcb rifle got named Goofy by a couple of guy's at the range.

 

[Ian]

I did two coats on the first batch a couple weekends ago, but with the bullet being out of round to begin with and my coatings not being sprayed, they get pretty knobby. They did shoot, though, which encouraged me to do the single-coat tests. If it works, I'm not going to screw with it. The main reason I did this is because one of my new barrels has a TIGHT chamber, .309" throat entrance, and the ammo that works best in the others with .3095" bullets won't chamber.

 

[Todd M]

That is amazing. Goes to show every rifle/mold/load/day/guy behind the trigger is different.

 

[Ian]

Shooting .30 caliber at 1,020 fps is very forgiving of many sins. That bullet with a single coat, fired from my larger-throated 300s, can move the driving portion completely past the case mouth before any part of the bullet touches the barrel. It's like throwing a hot dog weiner down a hallway. However, it shoots pretty well, I suspect due to a combination of tight chamber neck clearance that keeps the launch reasonably straight, and the hard, slick powder coating that can help guide the bullet nose to center without getting itself damaged too badly.

 

[Todd M]

I had not thought of pc guarding against leading from a long jump from case neck to rifling but makes sense. I've used pc, before I had my Lyman 45. May have to again for undersized boolits.

 

[Ian]

Not leading so much as acting like a protective jacket (same as copper or paper) to help the nose funnel through the throat...once it travels far enough forward to touch something, that is. Bare lead doesn't do well bouncing around in a throat, it's like shooting a steel plate at an oblique angle, the bullet will tend to flatten out if it contacts one side of the throat hard during launch. I figure the PC gives a tiny bit of strength to the surface, but mainly slickness to help it glide rather than drag if it gets a crooked start. Just theorizing, FWIW. All I know is I stuff them together, make them as consistent as I can, as true as I can, and they shoot plenty well enough for me. Some systems will respond favorably or unfavorably to the slightest adjustment and are very persnickety about ammo, but the 300 Blackout with heavy bullets at subsonic velocities, has been quite agreeable in my experience, tolerating poor bullet quality, poor fit, low powder burn efficiency, and sloppy case prep with no significant complaints.

 

[300BLK]

If you were shooting that "less than ideal" fitting bullet from a manually operated action, I doubt you would be concerned. Seat it out to engage, maybe not even take the flare off the case mouth, and let the throat do the sizing. The gas gun adds the complication of needing the bullet to remain stationary in the case during cycling, so heavy neck tension and/or crimping is required (unless you have 100% or more load density). The polyester(?) coating is slicker than the bare bullet, so enhances velocity, but won't prevent the underlying metal from being dented. It does prevent the metal to metal (lead to steel) contact abrasion without the need of a dirt holding "lube", and may allow the "taper" to self align.

If you want to see just how tough the powder coating is, start with just slightly smaller than bore diameter bullets and coat them. I suspect that it will take several "shake and bake" coatings to build up .010", but at that point the coating is deeper than the rifling. Shoot them side by side with single coat bullets of the same final diameter over the same powder charges, and I suspect that you'll see a noticeable difference in group size.

Back to your results, yes, encouraging to say the least. The relatively low pressure and velocity are "kinder" to your less than perfectly fitting projectiles. I've been thinking of trying some 200gr over Reloader 7 to see how they perform at "just enough to cycle" with carbine length gas. They won't be subsonic, and I don't have a can to further enhance the gas, but they should be quieter than 1900fps+ at 60Kpsi.

 

[300BLK]

I loaded some of these http://noebulletmolds.com/NV/produc...cts_id=1857&osCsid=cfogna0hrfehvl02o0gpp9smv3 over 11-12.5gr Reloader 7 in Sig headstamped cases, CCI 400 primers, 2.230" OAL. My 16" barrel is 1-8" twist with carbine length gas. Sized .311", the bullets were snug in the throat with most of the leading band exposed. I expected to need more powder with the 203gr bullet, but even 11.0gr functioned properly (H2 buffer and M16 BCG). Imagine my surprise to see oval holes at 50 yards! Ian's Lee is 1.363" vs my 1.200"! 12.5gr DID produce round holes, and Reloader 7 burned pretty cleanly even at 11.5gr (when I pulled the BCG and looked through the barrel).

 

[Ian]

After I finish lunch and put a muzzle brake on my new 1:7 upper, I'm going to go solve this twist rate mystery in the BLK once and for all. I'll shoot side by side with a similar, carbine-length gas sytem, 16" barrel and see if the holes don't get more round.

 

[Ian]

Ok answered that question. I'm going to be buying more 7"-twist barrels.

 

[fiver]

chuckling over here.
might as well make them pistol length gas tubes while your at it.

 

[Ian]

Yeah, the pistol-length tubes eat everything and beg for more, the carbine tubes are finicky as heck. This 1:7 has a .106" gas port, which even with my suppressor and the hammer nose rounded doesn't fully lock back the bolt at 10.0 grains RX-7. 10.4 grains is bumping supersonic with these powdercoated Lee 230 bullets. They're slippery as a wet eel. The other 16" one, 1:8 twist, had to drill it to .120" before it would lock the bolt back reliably. I tell you, though, the difference in ejection port noise is dramatic, and I'll do what it takes to make the carbine-length systems work.

 

[fiver]

I worked a load for a buddy using 10grs of 4227 and the 208gr A-max.
his pistol length had good ejection and full lock back, I'm sure I could go lower but he was stoked about them the way they were.
the muzzle end was quiet but I'm sure there was a bit of noise from the ejection port.
I have been thinking of buying the same upper he has just to muck about with some of the same jacketed loads and see just how far down I can get things to run.

 

[Ian]

I shoot left-handed, so the ejection port noise is of particular interest to me. With a carbine system, I don't notice the noise at all. With a pistol system, it always irritates the tinnitus in my right ear and makes me think "Dang, that was just a little bit uncomfortable". So when I remember, I stick a foam plug in my right ear when shooting my pistol-length 300 BLK ARs. If I don't remember before, it doesn't take but two or three shots for me to go digging around for an earplug.

 

[300BLK]

Are you noticing ejection port noise because you're running cans, or because of the pistol length gas? I expected my 10.5" to be louder than my 16", but can't say that is the case. The 16" has an A2, and the pistol has a larger (?) flash hider.

 

[Ian]

I mean strictly suppressed. The pistol system is louder on both 10.5" barrels and on 16" compared to 16" with carbine-length gas system. I can measure it with an SPL meter at my right ear and get about 9 dB difference.