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Jumbopanda
07-28-2013, 01:44 AM
Today I went to the range to fire my new 300 Blackout AR for the first time. It's a 16" AAC MPW, and I had three types of handloads available:

1. Hornady 130gr SP 0.308" over 19.0gr of Lil Gun ~2150 fps
2. NOE 314129 140gr (cast with straight WW) with Hornady gas check, tumble lubed with 45/45/10, sized to 0.310", over 16.5gr of Lil Gun ~1900 fps
3. NOE 311365 200gr (cast with approximate hardball alloy) PLAIN BASE, coated with Hi-Tek, sized to 0.310", over 11.0gr to 13.5gr of Reloader 7, ~1100-1300 fps

Brass was formed from mixed .223 brass, about half of which was Lake City. Cases used with 311365 were annealed, while the rest were not (those were loaded before I decided to start annealing).

The target was placed at 50 meters.


First I shot a few rounds of the Hornady jacketed rounds to zero the gun and establish a baseline for accuracy. I was able to consistently shoot about 1.5 MOA. Pretty good.

Then I shot some of the 311365s and found that none of them would print with any sort of consistency. Some loads were crimped and some were not, but all were terrible. When I finally got a group down on paper, it was roughly 10 MOA. There was no keyholing. I fired about 200 rounds and never saw any improvement.

Then came the 314129s, which were so bad that they weren't even worth blasting. I never got a group on paper but after firing at the berm at ~120 meters, I'd estimate that they were shooting 30-40 MOA! I might as well have been shooting a smoothbore musket.


When I got home I examined the gun and cleaned it. The bore was very clean after a couple of passes with a Boresnake, so leading was not a problem. However, the muzzle brake was a different story. It was coated in a substantial amount of lead deposits. I scrubbed it with a brush and saw that a stubborn shiny layer of lead maybe 0.01" thick remained.



So...any ideas as to why my cast boolits are so terribad? :sad:

MaryB
07-28-2013, 02:11 AM
my guess is the brake is scrubbing off enough lead to ruin the bullet profile and it is no longer aerodynamic

WILCO
07-28-2013, 02:16 AM
There is a train of thought that one shouldn't mix full metal jacket and cast boolit shooting in the same session without fully scrubbing the copper from the barrel. All other variables are too many to mention without going into great detail. Suffice it to say that one's best move is to stop, regroup and focus on one type of cast boolit with liberal study and experimentation, with a myriad of components such as alloy mix, powder charges/brands, lubes, seating depths, crimping pressures and what not. In other words, accuracy is an investment in time, it's not a race. Hope this helps.

steve4102
07-28-2013, 02:20 AM
I might as well have been shooting a smoothbore musket.


When I got home I examined the gun and cleaned it. The bore was very clean after a couple of passes with a Boresnake, so leading was not a problem.

I'm new to lead so take whatever I say with a huge grain of salt.
What barrel leading I have encountered cannot be removed with a bore snake, not even a lot of passes. It takes a good solvent, a Lewis lead remover or a Chore-Boy. You may have indeed been shooting a smooth bore.

I also do not shoot lead bullets over the top of Copper jacketed bullets. I've found that any copper fouling in the bore just attracts lead and makes leading worse.

Did you go back to jacketed after you shot the lead? If so, were thay all over the place as well or were they back on target?

What kind of optic/sights are you using? Are you sure they are tight and secure?

Jumbopanda
07-28-2013, 02:45 AM
I'm new to lead so take whatever I say with a huge grain of salt.
What barrel leading I have encountered cannot be removed with a bore snake, not even a lot of passes. It takes a good solvent, a Lewis lead remover or a Chore-Boy. You may have indeed been shooting a smooth bore.

I also do not shoot lead bullets over the top of Copper jacketed bullets. I've found that any copper fouling in the bore just attracts lead and makes leading worse.

Did you go back to jacketed after you shot the lead? If so, were thay all over the place as well or were they back on target?

What kind of optic/sights are you using? Are you sure they are tight and secure?

The jacketed bullets were consistently accurate before and after using lead. I'm using a Nightforce NXS Compact 1-4x Mil-Dot reticle on a Larue mount. It's quite secure.

Jumbopanda
07-28-2013, 02:58 AM
There is a train of thought that one shouldn't mix full metal jacket and cast boolit shooting in the same session without fully scrubbing the copper from the barrel. All other variables are too many to mention without going into great detail. Suffice it to say that one's best move is to stop, regroup and focus on one type of cast boolit with liberal study and experimentation, with a myriad of components such as alloy mix, powder charges/brands, lubes, seating depths, crimping pressures and what not. In other words, accuracy is an investment in time, it's not a race. Hope this helps.

I see what you are saying, but I really don't know what to do right now. The cast boolits I tried were not just moderately inaccurate and in need some some slight refinement. They are so awful that I really can't think of any explanation, and wouldn't know what to change. All of the loads I had were consistently terrible.

303Guy
07-28-2013, 03:02 AM
I have had minute of berm with some paper patched boolits. Thing is, the boolit holes were nice and round, indicating no boolit yaw. I suspect the problem was base edge feathering/base damage from too high a pressure for the alloy. A round impact hole indicates the boolit is spinning properly. If the bore looks clean then maybe it is. Do you have any idea of the pressure of those load? 19.5 grs of Lil'Gun under a 130gr bullet in a 300 AAC Blackout is a 42,000 CUP load. Yours could be up around 40,000 CUP.

WILCO
07-28-2013, 03:39 AM
They are so awful that I really can't think of any explanation, and wouldn't know what to change. All of the loads I had were consistently terrible.

That's where taking a break comes into play. Then go back to square one with research. Understanding that lead boolits behave differently is key. You're situation could be anything. Twist rate? Alloy too hard? Lube all wrong for stated velocities? Powder wrong type for cast boolit activities? Have a shot of whiskey and do some research. You're not reinventing the wheel. It'll be okay.

WILCO
07-28-2013, 03:45 AM
Here's some links: http://castboolits.gunloads.com/showthread.php?195381-300-blackout-cast-bullet-loads-for-ar-15

http://castboolits.gunloads.com/showthread.php?171710-300-Blackout-cast-load-data

http://castboolits.gunloads.com/showthread.php?148150-300-blackout-cast-bullet-accuracy

http://castboolits.gunloads.com/showthread.php?197602-load-data-for-155gr-cast-in-300-aac-blackout

http://www.handloadersbench.com/forum91/24128.html

http://www.ar15.com/forums/t_3_121/560557_Cast_bullets_in_a__300_BLK_AR_15_.html

http://www.midwayusa.com/product/938614/lee-2-cavity-bullet-mold-tl309-230-5r-30-caliber-309-diameter-230-grain-300-aac-blackout-tumble-lube-5-ogive-radius

http://www.ar15.com/archive/topic.html?b=3&f=121&t=567950

Jumbopanda
07-28-2013, 05:36 AM
I have had minute of berm with some paper patched boolits. Thing is, the boolit holes were nice and round, indicating no boolit yaw. I suspect the problem was base edge feathering/base damage from too high a pressure for the alloy. A round impact hole indicates the boolit is spinning properly. If the bore looks clean then maybe it is. Do you have any idea of the pressure of those load? 19.5 grs of Lil'Gun under a 130gr bullet in a 300 AAC Blackout is a 42,000 CUP load. Yours could be up around 40,000 CUP.

I'm not really worried about the 140gr GC loads at the moment. I'd rather focus more on the 200gr plain base, because I intended for that to be my primary plinking bullet due to the low cost. I wanted to load them at subsonic velocities, but found out that they won't reliably cycle the action and lock the bolt back unless they're going around 1200fps, which is fine because I don't own a suppressor anyways. As long as they are reliable and reasonably accurate, they will serve my purposes just fine. I honestly don't have any idea what kind of pressure is behind those loads, but I'd be surprised if it was much more than 30k. They've got to be much lower pressure than your normal supersonic loadings, but a bit higher than normal subsonic loads.

I'm using an approximate hardball alloy that I made from wheel weights and foundry type. I estimate it at around 2.75% tin and 5.5% antimony. Hardness should be very close to real hardball. I suppose I could use something even harder...but I'd be surprised if this alloy was too soft for this application. I won't rule it out though.

runfiverun
07-28-2013, 09:32 AM
since you didn't do the basics of measuring and fitting.
you'll have to fall back on just slowing things down.
take your 200 gr boolit and slow it down to the 8-900 fps area and start over.

longbow
07-28-2013, 10:31 AM
Can't help with 300 Blackout but may be able to offer some suggestions on the cast boolits.

Sizing to 0.310" maybe a bit small. Have you slugged bore and throat?

I ran into accuracy issues with my NOE 0.314" x 129 gr. in my .303. In my case. I need 0.315" boolit so lapped out the mould to 0.316" then size back. My RCBS dies were sizing necks to "standard" .303 which is for 0.311"/0.312" boolits so TIGHT for 0.315" boolits. The brass was sizing the narrow driving bands down quite a bit. Annealing helped but getting a Lee Collet die and sizing to give about 0.002" neck tension really helped.

You shouldn't be seeing that much of a difference but did you check the inside neck dimension? It is possible that you are sizing/deforming the boolits when seated if necks are tight. So check inside neck diameter and if tight size less or ream to suit boolits.

What is your rifling twist? I found that my .303's with 1:10" twist were hard on ACWW if I pushed velocity. Oven heat treating helped there. You might try water dropping or oven heat treating to get BHN up for the ACWW boolits.

Try R5R's suggestion of dropping velocity then work it up until accuracy drops off then try harder boolits to see if it helps.

My suggestions are to check basic sizes and make sure boolits fit throat, brass fits boolits (not too much neck tension) and BHN suits velocity/rifling twist.

Longbow

Pilgrim
07-28-2013, 10:44 AM
Lead loading up in the muzzle brake is a serious clue!! The very fact that lead is in the muzzle brake means its very likely that the boolits are being damaged in the bore. Shooting jacketed BEFORE lead is a receipe for trouble. Copper residue more often than not strips lead off of the lead boolits, and accuracy will be non-existent since the boolits are then being damaged in the bore. Shooting jacketed AFTER lead removes all of the lead residue so you have absolutely no clue what is happening in the bore with the lead! No offense, but you need to do a bit of reading before your next attempts with lead. Your alloy is probably OK. But your boolits need to be nearly perfect, if not perfect. Make sure you aren't damaging your boolits while seating them (Adequate flare? Undersize necks? Seated straight?, etc). Take the muzzle brake off before shooting lead next time to be sure the brake isn't causing your problem. Make sure your bore is free of copper fouling and expect to have to fire anywhere from one or two to eight or ten rounds to season the barrel with lead before shooting for group. If your boolits are not starting to group while seasoning the barrel, they aren't gonna group well later. Is the crown of your barrel damaged? I could go on but won't...read a bit from the stickies and start over. If your barrel is reasonably smooth, lead accuracy isn't all that tough to accomplish IF you follow a few simple steps/rules. FWIW Pilgrim

Jumbopanda
07-28-2013, 05:47 PM
Can't help with 300 Blackout but may be able to offer some suggestions on the cast boolits.

Sizing to 0.310" maybe a bit small. Have you slugged bore and throat?

I ran into accuracy issues with my NOE 0.314" x 129 gr. in my .303. In my case. I need 0.315" boolit so lapped out the mould to 0.316" then size back. My RCBS dies were sizing necks to "standard" .303 which is for 0.311"/0.312" boolits so TIGHT for 0.315" boolits. The brass was sizing the narrow driving bands down quite a bit. Annealing helped but getting a Lee Collet die and sizing to give about 0.002" neck tension really helped.

You shouldn't be seeing that much of a difference but did you check the inside neck dimension? It is possible that you are sizing/deforming the boolits when seated if necks are tight. So check inside neck diameter and if tight size less or ream to suit boolits.

What is your rifling twist? I found that my .303's with 1:10" twist were hard on ACWW if I pushed velocity. Oven heat treating helped there. You might try water dropping or oven heat treating to get BHN up for the ACWW boolits.

Try R5R's suggestion of dropping velocity then work it up until accuracy drops off then try harder boolits to see if it helps.

My suggestions are to check basic sizes and make sure boolits fit throat, brass fits boolits (not too much neck tension) and BHN suits velocity/rifling twist.

Longbow

I don't think the size should be a problem; 300 Blackout has a nominal bore diameter of 0.308", and since this is a new production gun I can't see it being off by much. Commercial cast bullet companies that produce bullets for 300 Blackout usually size to 0.309". I suppose I could slug the bore...but is that a common practice for brand new guns? I always thought it was more of an issue with milsurps.

The neck dimension is something that I put A LOT of thought into. I made a number of expander plugs before I settled on one that I felt was just right. Currently I'm expanding with a 0.309" plug with a step (like the Lyman M die) to help guide the bullet in straight. The seating plug that I'm using is shaped specifically for this boolit. My brass is also annealed. I've pulled loaded bullets to check for any reduction in size and found that the bottom driving band can get squeezed down by a mere 0.0005", while the middle and top driving bands remain at 0.310".

Most 300 Blackout barrels come in 1:8 or 1:7 twist these days, as they are designed to stabilize 200-240gr bullets at subsonic velocities. Mine is 1:7. How fast did you push your boolits? I didn't think 1200 fps was very fast, and the gun won't cycle with the bullets going slower than that, at least not with this powder. I'll definitely try lower velocities though, just to be sure. I can't heat treat the boolits because I'm using Hi-Tek coating, which requires heat to cure. I've found that that heat will anneal heat treated bullets.

detox
07-28-2013, 05:47 PM
What is the twist rate of your barrel? Most Blackout barrels have a fast twist rate 1/7 which is too fast for your soft alloy. Try water quenching your alloy or use hard linotype alloy. I bet your barrel still has lead inside. Shoot a couple of jacket boolits to maybe clear barrel of lead then try shooting HARDER cast again. Try to keep velocity under 1600fps. Size boolits .309"-.310"

detox
07-28-2013, 05:55 PM
Throw away the High Tech coating. You need a harder alloy with good lube...alox should work. Lube before and after sizing

High Tech should work better in slower twist of 1/12

Jumbopanda
07-28-2013, 05:55 PM
What is the twist rate of your barrel? Most Blackout barrels have a fast twist rate 1/7 which is too fast for your soft alloy. Try water quenching your alloy or use hard linotype alloy. I bet your barrel still has lead inside. Shoot a couple of jacket boolits to maybe clear barrel of lead then try shooting HARDER cast again. Try to keep velocity under 1600fps. Size boolits .309"-.310"

What are the guidelines for twist rate vs. boolit hardness vs. velocity?



I'll heat treat some boolits today and then tumble lube them with 45/45/10.

detox
07-28-2013, 06:02 PM
Linotype will cast larger boolits and fill mould better than the hardball alloy.

detox
07-28-2013, 06:09 PM
What are the guidelines for twist rate vs. boolit hardness vs. velocity?


A muzzle brake that is free from lead.

longbow
07-28-2013, 06:49 PM
1:7"! Yikes! That's fast. My Lee Enfields are 1:10" and recovered NOE 316299's and boolits from home made moulds showed some swaging of rifling to result in wider grooves than lands in the boolits (Rifling in the barrel has equal width lands and grooves). My boolits didn't skip the rifling but the lands did swage wider grooves in the boolits and gas cutting followed. I did not see any significant leading but accuracy was poor.

Lighter boolits did not seem to suffer but the 200 gr. did so I have to guess the rotational inertia is the culprit ~ they just weren't hard enough to take the fast twist. That would also depend on powder burn rate and acceleration too. Slow powders may not be a problem due to slower acceleration.

After oven heat treating accuracy improved considerably and recovered boolits did not show any signs of skidding/swaging by lands.

I do not recall specifics of the load but would guess velocity at around 1800 FPS so not real fast. For the most part I load IMR4227 at 18 to 22 grs. under cast boolits in the Enfields.

You are shooting the 311365 at fairly low velocity but in a very fast twist. I would try oven heat treating some boolits and give it another go.

Alternately take some of the same load and shoot into something you can recover boolits from then take a look at the rifling and check for gas cutting. If there is no swaging and no gas cutting then that shouldn't be part of your problem. If there is then you will have to deal with it by adjusting boolit fit and hardness.

Sounds like your necks are not doing any significant resizing though the driving bands on the NOE 0.314" x 129 gr. are narrow and "fragile" so may see a bit more sizing at seating than heavier drive bands. The 311365 should be okay though from what you are saying.

Again, no experience with 300 Blackout but I would slug the throat and size boolits to just fit the throat. They may be fine now but it wouldn't hurt to check.

My thoughts anyway.

I am sure you will get other advice too. Keep working at it, you'll get 'er beat in the end.

Longbow

Jumbopanda
07-28-2013, 07:31 PM
I just came across another clue. Originally I mentioned that there was no leading in the barrel, but it turns out I was incorrect. I examined the barrel from the chamber end and saw a clean bore, but today I examined it from the muzzle and did see a fair amount of leading. The problem is, I am not sure how much of a role the 200gr load played in this compared to the 140gr supersonics. I'm sure the supersonics were the main culprit, since they were driven much faster, at much higher pressures, made of a softer alloy, and much less accurate. I think this probably supports the theory that these boolits aren't hard enough for the barrel's twist rate.

mpmarty
07-28-2013, 07:48 PM
velocity of a load has zero to do with cycling the action. Use a slower powder and reduce the speed.

Jumbopanda
07-28-2013, 07:50 PM
velocity of a load has zero to do with cycling the action. Use a slower powder and reduce the speed.

As far as I know, Reloader 7 is by far the slowest powder for which any load data exists for 300 Blackout.

john hayslip
07-28-2013, 08:04 PM
I skipped a bunch of responses so someone else may have suggested it but I'd take off the brake and shoot a few. It may be that the bullets (lead ones) are expanding on exiting - particularly if you have lead uniformly distributed all the way round. Take off the brake and try a few and see what happens. If the alloy is soft the force of the powder can expand them as they leave the barrel. I've seen some pictures where revolvers were shot w/o the barrel and they expanded to big size. The brake is only a few thousandths larger in diameter than the bore.

longbow
07-28-2013, 08:18 PM
John brings up another good point. It is possible that the PB 311365 is seeing base edge erosion as it passes through the muzzle brake if clearance is close enough for gas to scoot between the boolit and "bore" but still relatively tight.

No muzzle brake experience here either and I assumed the brake opened into a larger chamber then tight again at the boolit exit but if it actually creates an undersize boolit situation due to close clearance then gas erosion is a possibility. But then here I am speculating and I am sure there are others who have muzzle brakes and shoot cast boolits who can give you the straight goods from hands on experience.

I am sure you will find a cause and solution and I will be interested to find out just what it is.

Longbow

leeggen
07-28-2013, 09:38 PM
Jumbopanda
As you read and learn from the books and forum you will find out that as you work "A" load for your ar you really need to stay with only changing ONE thing at a time. You shot jacketed and several cast before checking your rifle. Only do one thing at a time and you can see things change much easier. You are definantly excited about your round and should be, but reloading is only part of the equation. Sending those rounds down range is another part of its own. So clean all lead and copper out then shoot just your lead rounds and change only one thing at a time until you are happy with evrything. I beleive it is a myth as to jacketted cleaning lead from a barrel, Just think about that real long and hard and read several of the threads on here about it and make your own conclusions.
oh and if you will search here a little there is a Google search just for csatboolits that one of our members setup for us to search things easier than the one at the top of the page.
CD

Jim..47
07-28-2013, 10:55 PM
Jumbopanda
I beleive it is a myth as to jacketted cleaning lead from a barrel, Just think about that real long and hard and read several of the threads on here about it and make your own conclusions.

CD


That is also what I've read. The copper jackets simply polish the lead and make it shinier (shinny'er). Good luck. I'm following your thread because I also have some remo0te interest in 300 blackout.

canyon-ghost
07-28-2013, 11:01 PM
There is a train of thought that one shouldn't mix full metal jacket and cast boolit shooting in the same session without fully scrubbing the copper from the barrel

That holds true. Some guns tolerate both, others just smear the lead all over copper fouling. I'm not an advocate of the ladder approach. I believe a person should adjust powder charges painstakingly at .1 grain intervals and test them all! There is one particular powder charge that will be superbly more accurate than the rest.

Good Luck,
Ron

Jumbopanda
07-28-2013, 11:25 PM
Jumbopanda
As you read and learn from the books and forum you will find out that as you work "A" load for your ar you really need to stay with only changing ONE thing at a time. You shot jacketed and several cast before checking your rifle. Only do one thing at a time and you can see things change much easier. You are definantly excited about your round and should be, but reloading is only part of the equation. Sending those rounds down range is another part of its own. So clean all lead and copper out then shoot just your lead rounds and change only one thing at a time until you are happy with evrything. I beleive it is a myth as to jacketted cleaning lead from a barrel, Just think about that real long and hard and read several of the threads on here about it and make your own conclusions.
oh and if you will search here a little there is a Google search just for csatboolits that one of our members setup for us to search things easier than the one at the top of the page.
CD

True, I don't head to the range often enough so when I do go, I get overly excited and try to do too many things at once. Some were saying that I shouldn't have shot jacketed bullets, but since this was my first time firing this rifle, those jacketed bullets did help me eliminate all doubt about the rifle's inherent accuracy, as well as my shooting ability.

Now I just need to figure out how to clean all this lead out of my muzzle brake. I've already done many passes through the barrel with a chore boy, and I think I got 95% of the lead out (there's still a tiny hint of it remaining that doesn't want to budge). The brake on the other hand, is absolutely filthy and caked with thick lead deposits.I scraped the areas that I could reach with a bronze tool, but I cannot reach the area just in front of the muzzle.

303Guy
07-29-2013, 04:57 AM
1:7"! Yikes! That's fast.
Yup. The Blackout is designed for 230gr subsonic bullets, never mind boolits. Target velocity is 1050 fps or so.

Lil'Gun seems to produce the lowest pressure for velocity but a curious thing is 9gr Lil'Gun under a 220gr bullet produces a higher pressure than 8.7gr under a 230gr but produces the same velocity.

243winxb
07-29-2013, 05:22 PM
Brass was formed from mixed .223 brass, Check the loaded rounds neck diameter. It should not be larger than .334" If larger, brass needs to be neck reamed

Jumbopanda
07-29-2013, 05:48 PM
Check the loaded rounds neck diameter. It should not be larger than .334" If larger, brass needs to be neck reamed

None of the brass that I loaded was that thick. The only brand of .223 brass that I had issues with was S&B, which was immediately discarded upon discovery because they were SO thick that they wouldn't even form properly.

canyon-ghost
07-29-2013, 07:41 PM
(there's still a tiny hint of it remaining that doesn't want to budge).

Believe it or not, that's probably the part clinging to copper fouling. I've had it stuck down so hard that I had to clean 4 times in a row. Lucky for me, it was in a revolver. I used Hoppes #9 and it came out better but, I did clean with mineral spirits and a bronze brush a lot (a whole lot). Glad to see you enjoying the rifle. If you get past the difference in velocity with cast bullets, they can be a lot of fun. Usually, they shoot a lot slower. I've had 5 tenths grain of powder difference between jacketed reloads and lead in a 22 hornet. Most lead shoots slower and pushes back instead of having muzzle climb.

Good Luck,
Ron

C.F.Plinker
07-29-2013, 07:59 PM
Can you soak the brake in a solution of equal parts hydrogen peroxide and vinegar? I had completely leaded up the brake on a S&W model 41 and repeated soakings (until the bubbles stop) greatly speeded up the process of removing the lead.

Jumbopanda
07-29-2013, 08:17 PM
Can you soak the brake in a solution of equal parts hydrogen peroxide and vinegar? I had completely leaded up the brake on a S&W model 41 and repeated soakings (until the bubbles stop) greatly speeded up the process of removing the lead.

I considered it, but apparently the chemical reaction produces lead acetate, which is pretty toxic and can be absorbed through skin. And it can't just be poured down the drain, at least not legally.

I'll probably just take the brake off and give it a good scrubbing at some point. I'd have to reapply the Rocksett, but oh well.

popper
07-30-2013, 10:04 AM
Slower powder (335, 4895), drop the H-T for now, PC will work. Add some Cu to the melt & dump the tin, heat treat. The 1:7 twist is tough on CBs. My AR10 (1:10)uses 165 gr, good stiff load of the above powder, PC & GC - no leading 1 1/2" groups. You may want to open the gas port & get an adjustable gas block to allow action to cycle.

C.F.Plinker
07-30-2013, 01:47 PM
I considered it, but apparently the chemical reaction produces lead acetate, which is pretty toxic and can be absorbed through skin. And it can't just be poured down the drain, at least not legally.

I'll probably just take the brake off and give it a good scrubbing at some point. I'd have to reapply the Rocksett, but oh well.

The Outer's Foul-Out could also be used to clean your muzzle brake. Do their cleaning solution contain lead acetate or create it during the cleaning process?

Jumbopanda
07-30-2013, 06:57 PM
The Outer's Foul-Out could also be used to clean your muzzle brake. Do their cleaning solution contain lead acetate or create it during the cleaning process?

50/50 hydrogen peroxide and vinegar reacts with lead to form lead acetate.

jonp
07-30-2013, 08:24 PM
Are you sure it's 1:7? Most come in at 1:8 or 9. You might have to go with a heavier boolit near 200gr to get this to work. Just an idea I read on another forum about the Blackout as I am thinking of getting 2 barrels myself

swheeler
07-30-2013, 10:50 PM
I don't think the size should be a problem; 300 Blackout has a nominal bore diameter of 0.308", and since this is a new production gun I can't see it being off by much. Commercial cast bullet companies that produce bullets for 300 Blackout usually size to 0.309". I suppose I could slug the bore...but is that a common practice for brand new guns? I always thought it was more of an issue with milsurps.

The neck dimension is something that I put A LOT of thought into. I made a number of expander plugs before I settled on one that I felt was just right. Currently I'm expanding with a 0.309" plug with a step (like the Lyman M die) to help guide the bullet in straight. The seating plug that I'm using is shaped specifically for this boolit. My brass is also annealed. I've pulled loaded bullets to check for any reduction in size and found that the bottom driving band can get squeezed down by a mere 0.0005", while the middle and top driving bands remain at 0.310".

Most 300 Blackout barrels come in 1:8 or 1:7 twist these days, as they are designed to stabilize 200-240gr bullets at subsonic velocities. Mine is 1:7. How fast did you push your boolits? I didn't think 1200 fps was very fast, and the gun won't cycle with the bullets going slower than that, at least not with this powder. I'll definitely try lower velocities though, just to be sure. I can't heat treat the boolits because I'm using Hi-Tek coating, which requires heat to cure. I've found that that heat will anneal heat treated bullets.

read thishttp://castboolits.gunloads.com/showthread.php?208186-RPM-Threshold-barrel-twist-velocity-chart

popper
07-30-2013, 11:25 PM
You can heat treat and then do the HiTek. 10 min at 300F really only gives 2 min at at that temp, won't anneal the lead. I started shooting cast in AR10 with 50/50 pure/#2 from a 1:10, 170 gr. no problem. Your Sb is pretty high. You really have to make sure the bases are really crisp. Lots of 9mm users using HT at 1100 GPS without problem. IMHO you still need a slower powder with the plain base. You are hitting a heavy weight hard alloy fast.

swheeler
07-30-2013, 11:52 PM
30-40 moa, probably at 195K+rpm

Jumbopanda
07-31-2013, 04:53 AM
read thishttp://castboolits.gunloads.com/showthread.php?208186-RPM-Threshold-barrel-twist-velocity-chart

Interesting, thanks.

popper
07-31-2013, 03:08 PM
Look at the chart. A 30-30 or 308 1:10 will do the same as your 300 1:7, RPM limit. Most use 50/50 WW/Pb. Use a slower powder. The Hodgdon loads are for jacketed! A 9 gr. l'gun 220 gr. load gets 25K pressure. Way lower than AR (or brass) limit.

Jumbopanda
07-31-2013, 05:34 PM
Look at the chart. A 30-30 or 308 1:10 will do the same as your 300 1:7, RPM limit. Most use 50/50 WW/Pb. Use a slower powder. The Hodgdon loads are for jacketed! A 9 gr. l'gun 220 gr. load gets 25K pressure. Way lower than AR (or brass) limit.

There is no data for any powder slower than Reloader 7 for 300 Blackout (and the Reloader 7 data I used wasn't even published). And I'm already filling what little case capacity there is.

http://www.reloadbench.com/burn.html

According to this, Lil' Gun is #69, while Reloader 7 is all the way down at #93. The other powders used for 300 Blackout are all in between the two.

I've fired a few rounds with a 220gr boolit over 9.0gr Lil' Gun and the action didn't even come close to cycling.

blikseme300
07-31-2013, 09:58 PM
There is no data for any powder slower than Reloader 7 for 300 Blackout (and the Reloader 7 data I used wasn't even published). And I'm already filling what little case capacity there is.

http://www.reloadbench.com/burn.html


According to this, Lil' Gun is #69, while Reloader 7 is all the way down at #93. The other powders used for 300 Blackout are all in between the two.

I've fired a few rounds with a 220gr boolit over 9.0gr Lil' Gun and the action didn't even come close to cycling.

I run Reloder 7 at effectively 100% case capacity with 17gn under 155gn cast and this is by far the most accurate cast from both my AR-15's in 300blk. The longer dwell time than Lil Gun ensures good action cycling and accuracy matches expensive j-words at 100yards. I also use RL7 under the Lee 230gn boolit but reduced to 14.5gn to allow the boolit to be seated. I do fit these boolits with GC's as without their accuracy was nonexistent. My experience with cast in the 300blk showed that slower powder works better than the favored powders used for j-words. Reloder 10X also works but not as clean as RL7. YMMV.

BTW - I have used powders slower than RL7 and some showed promise but in the AR platform they were way to dirty to consider keepers.