MiHec 311410 Cramer

[Captain_Howdy]

I need to look this Eric guy up...I have seen his other work but I have the gas checked version and I would have thought it would be difficult to remove the front groove. My 300 BLK has a 1 in 8 twist which may be too fast for this design or maybe my alloy...that is why I thought it may shoot better without the forward groove as that would give it more bearing surface... who knows.

[cbrick]

My 300 BLK has a 1 in 8 twist which may be too fast for this design or maybe my alloy...that is why I thought it may shoot better without the forward groove as that would give it more bearing surface... who knows.

1 in 8" . . . How fast are you driving this boolit? The twist could well be a major part of the problem/grouping.

Erik probably can remove the crimp groove and give it a larger front band for more bearing surface but nobody will be more surprised than me if that turns out to be the problem. I've never done this and I have been surprised a time or two before.

Post #140 has the link to Erik, it would be interesting to see what he has to say. He is a very honest up front kind of guy, he won't tell you something he doesn't believe.

Rick

[longbow]

At 1:8" twist maybe that is the problem (or part of it anyway) if you are pushing them fairly fast or using a fast powder giving fast acceleration.

Oven heat treating is easy enough to try to see if harder boolits help. I run the oven to about 450 F for about 1/2 hour then cold water quench the boolits. I don't have a hardness testers (should get one) but the OHT boolits are noticeably harder than air cooled.

Like I said, I was having problems with 200 gr. boolits skidding in my .303's but oven heat treating fixed that. 130 gr. is pretty light but 1:8" twist is pretty fast if they are being pushed hard.

Just a thought.

Oh, and another thought, one of the reasons I wanted to add a groove diameter "band" in front of the crimp groove was to fill the throat of my .303 chamber because this short boolit has a ways to jump to meet rifling in my guns. I have been seating to just behind the crimp groove (not crimping) to allow some of the full body diameter into the throat. So far accuracy is more than acceptable fort me and I have not done any fine tuning at all. You might try seating out further or at least play with seating depth a bit to see if that changes anything.

Longbow

[longbow]

Another thought just occurred to me too.

I was having problems with the neck tension swaging boolits down a couple thou in my .303 brass. The cause there was that my RCBS dies size brass to SAAMI specs for 0.311" bullet. I am using 0.315" cast for my 0.315"+ throat and 0.314" groove diameters so opening that brass back up using a cast boolit. This was swaging the relatively narrow driving bands down on my NOE 0.314" x 129 gr. These also had gas checks on them but driving bands still swaged.

Annealing the brass helped some and making a larger expander button for 0.313" inside neck diameter about solved it and gave good accuracy. Now I am using a Lee collet die with a 0.313" mandrel in it.

I don't know much about 300 BLK except that it is made from .223 brass and has thicker neck than 300 Whisper. Could it be possible that your brass is sizing down boolits when seating? Pulling a boolit should tell you. If so try annealing if you haven't already or try expanding the neck for less neck tension.

Longbow

[Captain_Howdy]

a 1-8 twist is pretty standard for a 300 BLK. I am attempting to run these in the 1800-2000 fps range. But I kinda knew I might have issues with it at these speeds. I backed off the pressure and did hit a sweet spot...or a better spot. After slowing them down even more they did open back up. I may try water dropping them. That might help. My barrel is a match chamber so its tight and I really don't want to have to hassle with pulling a jammed round so I sized mine to 309 which chamber fine. I do NOT crimp these. I have seated these at various depths...I haven't noticed a large difference but these are short and like longer seating for my gun. I have seen people have really good results with cast running at subs with other bullets...I think its just maybe a speed versus bearing surface thing...but I will try doing some hard cast who knows it may make a difference.

[longbow]

What powder are you using? Just wondering if fast, then maybe a slower powder for gentler acceleration.

I would try water dropping or oven heat treating. If you have some already cast just take a few and try oven heat treating to see if harder helps. They may be skidding as they enter the rifling if too soft. Something to try anyway and easy to do.

Have you tried the solids or just HP's? So far all I have shot are the deep HP's but do have some of the others cast.

I will have to shoot over the chronograph to see what velocities I am getting.

Longbow

[Captain_Howdy]

so far I am shooting solids...I have only tried 2 powders so far H110 and Lil Gun which are the most common high velocity powders for the 300 BLK. My own experiments have shown h110 to be more accurate which would almost seem to be opposite of what I would have expected really. Actually I have some that I can throw in the oven and harden...I had almost forgotten about them...but probably 20 or 30 that I didn't lube properly and set aside...I can treat them then lube again.

[xacex]

So far I am seeing best accuracy with the 300BO with H110/W296 over Lil gun as well. It is odd because the heavier weight lee 155 shoots best with lil gun, but not this lighter weight boolit. I am seeing better accuracy with the short pin, followed by the long pins, then the solid. I was hoping to get the solid working good for deer, but may settle with the short pin. I am still getting full penetration of up to 4 gallons of water after fragmentation at 100 yards, so it should give full pass through the vitals in deer size game. The affect of expansion is devastating to say the least. I am still trying to get my groups below 2 inches, but with P/C it has not happened yet consistently. Each piece of brass is sorted by year,trimmed the same with the shoulder out as far as I can and close to fired case length, trimmed max length, and powder charge hand weighed to the 1/10th grain. Boolits are also weighed to 1/10th grain. Playing with annealing the necks, and I am using a heavy crimp. Boolits are P/C,SOWW with copper added, and heat treated.BHN 16-18.
Other things I have done is trigger work to drop the pull to 3 pounds which has helped, and I may take the barrel off and true up the upper receiver. I have the barrel pretty tight to get the gas tube port lined up. I have never shot MOA with the gun, and jacketed boolits have actually given worse accuracy so time will tell. It is still good for hunting, and fun to shoot when milk jugs are easy game at 100 yards.

[cbrick]

I went back in this thread to Captain Howdy's September fifth post and I haven't seen where anyone mentioned leading, just accuracy problems. Things I did notice is the H-110, 1 in 8 twist and light boolits. H-110 is a powder that doesn't give good accuracy until it's loaded up near a book max charge. Until it builds the pressure it needs to burn well accuracy suffers, typical of ball powder & especially H-110. I've tried downloading H-110 in revolvers with dismal results. One way to help it burn is heavy for caliber boolits, it burns better before the boolit gets going. That won't help much trying to use this boolit. Increasing the charge of H-110 would/could be a solution except then your up against the 1 in 8 twist and driving them fast.

Oven heat treating could help. I would also try using the slowest stick powder that will get the velocity up to a reasonable point though I'm not sure about the 1800-2000 fps mentioned by Captain with the twist your working with. To be honest I've never heard of anyone successfully driving cast that fast with that twist rate, could have been done but I haven't heard of it.

I can't offer load advice because I don't load for that cartridge but it will be interesting to see what you come up with. I suspect it will be a BHN of around 18, a stick powder and settling for a bit more sedate velocity. All because of the twist rate, tough nut to crack but please keep us informed.

Rick

[HARRYMPOPE]

"Until it builds the pressure it needs to burn well accuracy suffers, typical of ball powder & especially H-110. I've tried downloading H-110 in revolvers with dismal results."

18-20g H110 or 296 in a 308 Win with no filler is a top load.It defies logic but it has won many matches. The RCBS Cast manual gives loads for it.Downloaded in a 44 mag is was ok for me down to 19g with the HG #503 in linotype.any lower it was all over the place.

[Old School Big Bore]

You guys are making me jealous. I'd sure like to find one of these molds available, as all my rifles that aren't .44s are .30s. I've been thinking about getting a Blackout upper but if I did I'd look for a 10" twist after reading the posts here. I recently bought four of MP's 4-cav brass HBWC molds; one is in .310 for my Blackhawk, and it'll be loaded at poofy .32 S&W levels, but I also want to reverse a few as cup points for low velocity SPLAT loads in .30 Carbine, .30-30, .303 Brit, .308, .30-06 and .300 WinMag. cbrick, how are you getting the .32-20 brass to work in your Blackhawk? Did you flycut reliefs for the rims? I tried running .32-20 brass into a .30 Carbine sizer but the mouths are so thin that, so sized, I couldn't get any retention on a .312 bullet even without running them over any expander button at all, and the rims interfered with the cases entering the chambers (My Blackhawk is an older 3-screw with the full-length cylinder / enclosed heads). I was thinking of trying a short .30 neck sizer or trying to figure out what diameter Lee push-through to get the necks tight enough, and using a hand-turned reamer to countersink the chambers enough for the rims (the amount of sink would not go beyond the depth that the extractor cut on .30 Carb comes to). Ed <><

[cbrick]

The cylinder on my New Model Blackhawk isn't recessed, the rims sit flat on the cylinder and no cutting needed. It sounds like your saying you have an Old Model BH, I wasn't aware they were chambered in 30 Carbine but I guess they were if that's what you have.

The 32-20 brass is thinner than 30 Carbine brass and has to be sized with the 32-20 die, the 30 Carbine sizing die won't work on 32-20 brass. Re-sizing after firing brings the case back to the 32-20 bottle neck/hour glass shape and holds the boolit perfectly. The 32-20 brass being thinner has 5% more volume in water weight than the 30 Carbine brass.

Rick

[xacex]

Might as well post this here too.

1. 20 shots fired over the chronograph to establish a baseline. Immediately started to fire some groups while still warm.
2. These were coated with ebay blue PC, ASBBTC, and baked at 400F for 20 minutes
3. Bullet was a Mihec 311410 H/P with medium pin weighing 130 grains. Culled to the nearest grain. 50/50Pb,ww, sized .310.
4. 17.7 grains H110 velocity average was 2161.5FPS, spread 73. First 10 over the chronograph were still single digit SD then jumped into the 20’s.Min 2119FPS, max 2192FPS, shots a second .20.
5. This was a new 300 blackout AR15 build with a pistol gas carbine barrel from CMMG. Less than 200 rounds through it so far. 1/7 twist!
6. I have not compared traditionally lubed bullets or jacketed with this one yet. Still fresh, and needs to be broken in.
7. GC were annealed aluminum that I made with a FreechexIII.
8. I will show the first group and the last, first was 5 shots, and last group was 11 shots.
9. It took about 5 groups plus the warm up shots over the chronograph before it really started to deteriorate. The first 3 or four groups were all about 2 inches total. After 20 shots I should have cleaned it, but I was just having too much fun with my son by my side with 2 blackouts going at the same time. By 60 rounds the groups were consistently 4 inches. All groups were shot at 100 yards. Almost there but we are over 2000FPS! It should not be hard to keep it under 2 inches at 2200FPS from this point. BTW, this is jacketed velocity territory for the 300 blackout.

I am just starting to work up a load for this boolit, and this is a starting point for me. I did a ladder to see how hard I could push it and got up to 19 grains before I decided that was enough. No cratoring in the primers, but the ejector started to mark the brass. I have not tested down to the 10th of a grain on charge, case weight, or boolit weight so there is some hope to make an improvement there as well. These were loaded on a progressive press.

[longbow]

Can't comment on loads or accuracy for 300 Blackout but I love mine in my .303 Lee Enfields. I am running somewhat lower velocity than you based on load data (have not chronographed it yet) but accuracy is running around 1 1/2" at 50 yards from my Lee Enfields and terminal performance with the deep HP is impressive! Milk jugs beware!

I have to do more load development yet but I am very happy with my mould.

I am shooting plain base over COW + graphite filler.

I have to ask... why a gas check with powder coated boolits? I thought one of the benefits of powder coating was no GC required. Just curious.

Longbow

[xacex]

I have to ask... why a gas check with powder coated boolits? I thought one of the benefits of powder coating was no GC required. Just curious.

Longbow

I tried molds with a plain base, but did not get the accuracy of the gas checked boolit even with P/C. Powder coat is not a cure all, and the gas gun seems to like it better that way. With subsonic boolits I do not use a gas check, but did test between G/C and not with the lee 309-230, and even with subsonic the results were more accurate with a check. The pressure in these little cases gets up there with the pistol powder so it may be deforming the bases unless hard alloy is used, or gas check is used. The powder coating process seems to anneal the lead unless water dropped after P/C as well.

So far sub 2" at 100 yards is not bad, and larger groups as the barrel heats up and fouls with powder residue, but not any larger than 4" at 100. For pushing these over 2000fps with powder coat thats not bad. Could it be better? Oh yes! I am working on it, but my limitations are time, and good magnification to get a better group along with load development, and alloy composition.

[yondering]

Xacex - looking at your accuracy testing and details above - try the same loads, with copper checks instead of aluminum. I've found some interesting accuracy differences with aluminum checks in an AR action, at least with the 300 Blk and pistol gas. I was getting gas cutting in one spot on the aluminum checks when they pass the gas port when using Lil'Gun powder. Haven't recovered any with H110 to see if it's the same issue, but the accuracy still isn't as good as with copper checks.

BTW if anyone wants to sell one of these molds, I'd sure like one.

[milsurpcollector1970]

Hes still got some I just bought one

Xacex - looking at your accuracy testing and details above - try the same loads, with copper checks instead of aluminum. I've found some interesting accuracy differences with aluminum checks in an AR action, at least with the 300 Blk and pistol gas. I was getting gas cutting in one spot on the aluminum checks when they pass the gas port when using Lil'Gun powder. Haven't recovered any with H110 to see if it's the same issue, but the accuracy still isn't as good as with copper checks.

BTW if anyone wants to sell one of these molds, I'd sure like one.

[xacex]

Xacex - looking at your accuracy testing and details above - try the same loads, with copper checks instead of aluminum. I've found some interesting accuracy differences with aluminum checks in an AR action, at least with the 300 Blk and pistol gas. I was getting gas cutting in one spot on the aluminum checks when they pass the gas port when using Lil'Gun powder. Haven't recovered any with H110 to see if it's the same issue, but the accuracy still isn't as good as with copper checks.

BTW if anyone wants to sell one of these molds, I'd sure like one.

I will have to try out some copper checks. Dont have any here since I started making my own aluminum ones. I will have to look around and see if I can find some copper sheet to see if I can make good copper ones as well with the freechexIII.