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Lane's: jtallen83 inspired 21.750" 300 AAC Blackouts


Lane

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INCOMING!

Well not quite yet... I got an email today from Compass Lake Engineering; and they want more money for shipping. The barrels are both complete and ready to ship. I can't really complain about the added cost, considering their custom fabrication price was only $125.

I had to go make a deposit once I saw that; but I should be able to call them back in the morning, pay for additional shipping costs; and get both custom barrels heading this way. 

That means I'll have lots of new projects running sometime next week. And I already had a lot of projects on the table; so I'm going to have to get serious about buttoning things up around here. 

I honestly haven't even begun to break down the order of operations on these 300 Blackout builds. Chamber casting seems like a logical first step. Headspace check; and making some ammo. I've got powder and projectiles in spades for these new builds; and a small handful of factory loads...

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2 hours ago, 98Z5V said:

You literally have alot of irons in the fire, man...   :laffs::thumbup:

Not sure which kind of "irons" you mean here. I have a lot of metals in the fire these days. The element Fe is just one component in the mix; and I can't remember the last time I even welded steel for fun. Coming soon though; there is a casting furnace going in this year. Should be capable of around 30 pounds of aluminum, or 90 pounds of bronze; give or take...  I do still need to forge a few tools to make that a seamless operation. 

Who wants .308 silver projos?

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Decided to go back to my roots on this next aluminum lower. I inspected the blueprints and took the important numbers down on paper. Did a few calculations, and planning to scribe the FCG pocket layout in the coating this time. That is; as opposed to using any kind of jig, or applied template. I'll just start measuring with calipers as I get close, and try to get a nice interior finish with my final passes.

This will be the lower for the 21.750" barrel build. I'm planning to start the 24.000" on the polymer lower, but will have to swap those around at some point. I'm still considering my options for upper configuration differences; especially early on. There are some constraints that cannot be understated in these builds. The strain gages may require a modified barrel nut (quite likely with a 300 Blackout chamber length). That also may prevent future barrel removal without removing or ruining the strain gages. It may also mean no handguards with strain gages installed. So; it's either a do it once process; or a calculated effort to take measurements at exactly the right time in the experiments. Haven't come to any conclusions here; but it may pay to wait on that part, and experiment on some other build short term.

I took case measurements with micrometers and haven't really decided on a path forward yet. I may still drop back to neck only sizing soon if it functions at all; that means more new dies. I also don't have scopes for the 300 Blackouts yet, so that's going to be a constraint early on. My final build concern at the moment is the strength of the rear charging handles. With a gas free straight pull build; that may become a problem. The heaviest weight handle available would be ideal, without any ambidextrous features (or pivots that reduce overall strength).

Don't want to be too optimistic on delivery date; but both barrels are a few hours drive away from here already...  Not sure if they require finishing; if I do have to blue them, that takes a solid day all by itself. 

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Not quite finished milling out the (black) aluminum lower; but getting pretty close. I spent some time calculating and testing the feeds and speeds that work in my setup. That got me pretty excited unfortunately, and I created a few tiny flaws I would prefer didn't exist. The cost of a replacement is low enough that it's worth the effort to make one look superior. I'm sure if I place this one in a box, hidden inside a drawer; that something good will come of it later on. It also allows me to mill the next one when I'm not pressed for time, rushing, or getting overly excited by my progress. I also need one or two replacement end mills, because I've been working these hard from time to time. I do plan to shoot this lower in the short term; but it's not the gem I wanted.

I also started working on the purple lower. Despite seeing reports it wouldn't work, I tried painting on the dye cold. Even with a heat gun, the application seemed lackluster at best. Multiple coats and sitting overnight produced something with a few dark splotches, and a slightly darker overall hue. So I put the whole thing in a pot of boiling dye as recommended. I waiting a bit more than 30 minutes; but the results I achieved were almost exactly what I wanted. I might have taken it out five minutes sooner had I been paying more attention; but it's better this way. It appears black as any factory black polymer lower; until you see it in bright sunlight. If you look very closely you can see a violet glow emanating from the texture of the surface. It is actually a bit brighter inside (mag well and FCG) where I didn't brush on the dye the first time. Truly stunning; midnight blueberry.

Looked over the numbers I can get in terms of FPS to projectile weight between 7.62x39 and 300 Blackout in long barrels. Adjusting for everything; it appears they are nearly a 1:1 comparison. I may have to use a different powder in one cartridge or there other; but FPS number are almost exactly the same for any given projectile weight between the two calibers with long barrels in use. This is good!

I took a picture of the epoxy filled area of the trigger hole to prove it was the same lower. Bonus; the plastic epoxy was all black with just the cold brush application of dye; it was only the lower itself that needed the full on hot bath treatment. I hope this still qualifies as a black rifle...

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Since it's a quiet night; so here is a slightly better color comparison. I really can't tell the difference if I weren't looking at it from 3" away under a bright light. 

After closer inspection of the aluminum lower; I think it's pretty nice... But still want one that has a flawless interior finish for this particular build. Since I'm free-styling the milling on this lower; I'm rethinking the rear cutting constraints (outside of the blueprint). I think I only need a slot wide enough for a trigger. Also; Polymer80 recommends leaving a bridge behind that for strength; apply that to an aluminum lower... And given the laws here; it's not any kind of problem to block that area out.

That MIGHT change resonance enough to notice in testing; though at this point, I don't even know if the polymer lower will make a barrel react differently... That's why I need more than one for all this fun.

Aluminum lower still needs quite a few thou taken off the walls, more off the front; and whatever I decide on the rear pocket. Then of course the pin holes; but those are fast if setup correctly. After turning the dials for hours; I think I could install some heavy duty servos on the jog wheels to drive this rig CNC. If I can run it slow enough, it should be highly capable. I've been cutting at 0.1mm per second in many cases, and would like to go even slower for fine detail work. 

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Can't stop thinking about the charging handle. I have a new design in mind (read: five or more), but haven't fully worked out the details. Not sure whether to call it the tickler, stripper, or... the ripper. The idea is, it needs to do the work of the gas system all by itself. Can't really show off any pictures or drawings here. There are many possible solutions; more so if you are able to remove the gas key (aka UK build)...

This may be the first bronze casting I do here. I have a small crucible that would be perfect for casting about 5-10 charging handles. Cast them a bit fat, and mill them down to specs. It's MUCH smaller than the 90 pound crucible I'll be running later on; so it's a perfect experiment in this case. I already have a furnace capable of doing exactly that once I work out an alloy blend. I try to recycle as much as possible, and might need to buy an ingot or two to make that just right. I also advocate for silver in a good bronze for many reasons. Never much; but just enough makes everything right...

If you didn't figure this out yet; there is a re-introduction of the ambidextrous charging handle design here. It needs to actuate upstream via some kind of control. And some other things. Pretty sure a few of you could beat me to this if you tried.

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no one works at your speed bro! You are miles ahead. I have to wait and see picks to understand some of your hard work! I could blow your mind at my end,  but I cant explain it so you could understand it. Its too simple. I like where your thoughts are and will wait to see the prototype! carry on bro! 👍

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So Lane, are you thinking along the lines of a side charging handle to move the bolt carrier to unlock the bolt? If you made the handle long enough, you could get a lot of leverage on it.

Or, is that cute brain of yours envisioning something similar to a pump action?

Nope. You’ll come up with something unique, patent that sucker, make a fortune and move out of that anti-liberty state you currently call home  

Whatever it is, I can’t wait to see it. 

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The biggest concern left is tempering my expectations in terms of speed. I'm going to need to plan a barrel removal/swap every month or so; maybe even every two weeks. Barrels arrived yesterday, though I didn't even unwrap them right away. Just now got around to bluing them both, and finished the lower assembly for the 24". Can't show the barrels off quite yet because they are in a heat bath for 24 hours. Then I clean off the leftover bluing solution; and oil them. Also need a new buttstock (on the way), because of the resonance concerns with an adjustable stock. It was neat to play with a reduced size AR like that though; I can certainly see why you all like your pistol builds.

Had to order the second upper receiver BCG combo. While I had earlier considered a side; or dual charging upper, I don't think that offers a great side by side comparison of the 21.750" barrel. I found an Aero Precision upper on sale with Toolcraft BCG; so that's going to be for the 21.750 when it arrives (it has already shipped). That gives me a pretty straight comparison between standard upper receivers with different forge marks. I'll be sure to weigh both first, and note any physical differences. Close to the last thing on my list is a pair of scopes. I haven't ordered them yet; but may have the funds soon. Looks like a bunch of rainy days coming up; so that gives me time for mold making, test assembly, chamber casting, etc. I also still need to finish milling the aluminum lower; carefully of course... 

To answer some other questions; yes, I've seen a bolt action BCG, but didn't like the arm. Seemed way too long to use in this project because of the resonance questions at play. It also didn't seem to actuate the bolt directly (though I may have missed something). 

In terms of charging handles; I've made some progress. If everything works out, I may be able to modify a 7075 handle. While inspecting these clearance issues I came across a roller cam pin (again). That alone might be enough to satisfy my desire to reduce friction (and force required), to manually remove cases. They are typically used in piston builds; which is relatively similar in terms of function to a gas free build. For all I know, the reduced surface area of these 300 Blackouts will make it a null issue; but there are other builds where I want this.

I have melted some modeling wax for casting. Found a tube of silicone to make molds; the fun part here will be moving the handles enough to make the mold oversize. Shrinkage is a serious consideration when making copies this way. Then on to modify waxes, gate, and invest for casting. There is little sense in pouring just one part if I'm going to melt metal. Might as well iterate a few designs in the same batch that can be modified later for various reasons. I'm not pouring aluminum for this because I don't have the ability to temper aluminum parts of that size at the moment... 

 

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Some things have come up here which have kept me away. I also needed a bit of a break to catch my breath...

Things are about to get very serious with these builds. The bluing on the barrels looks amazing, but keeps accumulating red iron oxide even after repeated oiling with numerous products (and numerous extra washing steps). The difference this time around was a had to buy a bottle of cold blue solution that wasn't Birchwood Casey brand. It appears to have a different chemistry, and I may need to take some other steps to make it right. It may also mean that I need to polish the barrels more, and blue them both all over again... The last thing I'm willing to try is: CRC brake cleaner, boiling water wash, and another attempt to oil. If that doesn't work, it's back to the beginning. I also still have to cast the chambers, and while inspecting things, I'm beginning to wonder about some differences I've already noticed between the two. This isn't meant to be a complete update; so I'll let that slide until I know more. I may need to call Compass Lake Engineering and ask a few specific questions before I can move forward.

Both scopes are here already. The only thing lacking to build a functional pair; is the scope rings, which are still a few days out still. I'm currently re-reading Vaughn's Rifle Accuracy Facts cover to cover. This time I'm taking more detailed notes on some of things I glossed over earlier. In his introduction, Vaughn clearly states there are some things he doesn't fully understand; so those points will be of specific importance to me. I also want to know more about this idea of monitoring barrel movement. I still have numerous options in that regard, and I'm shooting for 2D minimum; 3D would be ideal.

I probably should have asked this question first; but I need to know more about small rifle magnum primers. I stopped by the local shop recently and they are; of course... Out of stock. They said it will be a few months before the come back in stock; so I need to make some other arrangements. Again; I just hate wasting $35 on shipping for a box that costs $35. I can likely find some other way if I have to get some in the short term. The real question is; does EVERYONE use magnum primers with H110 powder in 300 Blackout (supersonic)? Will Federal Premium Gold Metal AR Match small rifle primers be fine if I adjust my loads properly? Is this an issue of having a full case of powder REQUIRING me to use magnums? I simply don't have enough experience in this particular configuration to know for sure. I've certainly read a lot about it elsewhere; and I still don't know what to think. 

I have yet to order new end mills though; and need to finish the aluminum lower with what I have. Still planning to mill another one sometime soon that will have an immaculate FCG pocket, and built exactly to blueprint spec; it's just this first one is not going to be that animal. 

Aero Precision upper combo showed up a few days ago; but I haven't even had a chance to compare any details. The new charging handle is here; and waiting for me to make a silicone mold. I had an idea about that though... What if I carefully cover the entire component with painters tape? What about two layers? I simply need the final castings to be slightly oversize so I can mill them down. Too small; and I will absolutely NOT be welding them for thickness (make new silicone mold, start over, melt down the old metal with a new pour). So again; it pays to fix these issues on the front end to save huge amounts of time later. I haven't pulled enough parts to be 100% sure of my modified charging handle design; but everything I've seen so far says it's a go.

Edited by Lane
word missing a letter; clarity
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6 minutes ago, Lane said:

I probably should have asked this question first; but I need to know more about small rifle magnum primers. I stopped by the local shop recently and they are; of course... Out of stock. They said it will be a few months before the come back in stock; so I need to make some other arrangements. Again; I just hate wasting $35 on shipping for a box that costs $35. I can likely find some other way if I have to get some in the short term. The real question is; does EVERYONE use magnum primers with H110 powder in 300 Blackout (supersonic)? Will Federal Premium Gold Metal AR Match small rifle primers be fine if I adjust my loads properly? Is this an issue of having a full case of powder REQUIRING me to use magnums? I simply don't have enough experience in this particular configuration to know for sure. I've certainly read a lot about it elsewhere; and I still don't know what to think.

I use CCI 400 primers in all my 300BLK loads, and have never, ever used a magnum primer.  There is zero need for that, at all.

There is also no way you will ever get close to a full-case capacity on a 300BLK load, for supers.  That's why the basis of the cartridge is pistol powders.  Pistol powders are what it take to run this type of load, due to the specific case capacity, and the projectile.  

This is just .30 Carbine, reinvented.  Same powders, same projectiles if you're comparing the lowest weights - 100~110 grain.  The biggest difference between those two is the case itself.

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20 minutes ago, 98Z5V said:

There is zero need for that, at all.

Thank you for that information and advice sir. I'm going to run with this; though I am planning to walk up pretty high in terms of projectile weight fairly soon. 

The one interesting thing I saw somewhere else was; a claim of slightly higher FPS (less than +10); along with vastly reduced chamber pressure with magnum primers. So; when I get a chance and have strain gages attached, that will be a question I need to ask again (of myself). 

I'm also planning to standardize on 4198 & 1680 somewhere down the road; so by the time magnum primers are here, there will be plenty of variation to examine. Reason being; is they both cross with 7.62x39, and I need that data for some other projects.

I'm sure you want to see the barrels and all that; but I'm not quite ready. I don't want to attach anything to the uppers before a weigh in. I also don't want to lube the barrel nuts. And, if I HAVE to re-blue the barrels; it's just a tease how black they are now. I'm hoping the settle in with some kind of heat treatment; maybe I need to try and find some MSDS information to compare chemical contents. Heat does work to drive out nitric acid; not sure what's in this solution... Still might be an issue with pitting, or tooling marks holding out on me at this point.

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3 minutes ago, Lane said:

The one interesting thing I saw somewhere else was; a claim of slightly higher FPS (less than +10); along with vastly reduced chamber pressure with magnum primers.

That's a strong possibility, right there.  I only run CCI 41s in my heavy 5.56 loads, just for that reason.  It gives those 75s a little bit more velocity, and gets them over 2750fps.  That's where the magic happens on those projectiles.  You don't need to use them in any 300BLK loads, but that might be a benefit, if it works the same...  :thumbup:

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3 minutes ago, 98Z5V said:

I only run CCI 41s in my heavy 5.56 loads

Are CCI 41s a true magnum primer? I saw them available in a plain white box. Even asked specifically; and was told they didn't have magnums. A quick search showed CCI #41 was a mil-spec primer; but I didn't know what that meant off hand. I saw quite a range of primers specified anecdotally, and simply haven't looked up every single one yet. I can go get some CCI 41s this week if it's worth trying above the Federal Match.

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20 hours ago, 98Z5V said:

Yes, they are. 

Thanks to you Sir!

I actually drove by that place today because I didn't see your message. The reason I asked in the store was because of that odd packaging; and knowing it was a mil-spec thing to begin with (from prior reading). 

I'll take care of that later this week. I only got 303 caliber projectiles in the mail today; but that's a good indication that scope rings will be here soon...

Sadly the barrels are still totally @#$%^&*. They continue to rub off a sick red/brown... I don't need my barrels giving blood every day. I also can't withstand the tiny variables that might be created later on down the road in this process. Total stainless steel scrubber polish, and re-do the bluing (after cleaning). I have a pile of oily rust covered towels from this project; and it's not alright in my mind. Birchwood Casey, or screw around with chemistry all day; wonder which is easier? ...

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I've unfortunately hit a partial work stoppage because it's so late... I can't seem to get the forward assist roll pin in on the Aero Precision upper. It's 3/4 of the way; and holding the forward assist. It just hasn't crossed into the other hole in the upper. First thing in the morning though...

Finished re-bluing the barrels after a substantial amount of polishing. It appears there was some kind of odd lathe marks allowing them to hold or grow rust underneath ledges. After a few more cleanings the bluing went ok. There are also some (newly visible) markings on each barrel; from their turning process of course... At first I was disappointed because they still looked silvery. But after a hot water wash, heat gun treatment, and hot oil; they look almost as dark as before. I'm pretty sure those extra lathe marks also made shadows that allowed them look amazing the first time; but just not something that would last. I spent days oiling and cleaning them before I finally gave up...

Scope rings are here. Charging handle is wrapped in two layers of painters tape for mold making. One layer was right on the edge in terms of thickness required; so I decided to stay on the safe side. Just need to whip up a silicone mold. Half thinking about doing the same with a .308 charging handle in the same mold; and one other thing...

Both uppers were weighed out; and are about 3 grams different. I consider that negligible; and will do it again after the UPKs are installed to see how that makes a difference. I also need to measure the inside where the barrel connects to see how different they are.

I've got everything set out for the chamber castings. Just trying to figure out how much heat I want in the barrel before I pour. I'm still considering what kind of container to use too. I might be best off with a plastic beaker; apparent this alloy wets glass. Another option is a cut aluminum can though; so we'll see how it works out when I start trying to melt. I have a small ladle for pouring projectiles; but that seems too small for this particular job; also have no plans to cut the ingot. Should be able to melt off what I need, and pull the rest back out when I have enough liquid. I do need to make up some quick ingot molds for the excess; but at less than 200 degrees F; even cardboard is good enough. Seems like it will be almost as fun as casting gallium; though the latter can literally scream as it cools. 

Got a .936" gas block that almost slides on these .940" barrels. Seems like a bit of lapping on the inside the remove the coating would fix the difference. It was much cheaper than any .940" gas block I've ever seen. Also seems like aluminum as opposed to steel; so I'm not sure I'll try to tap threads to make it adjustable; it will be installed on the 21.750" barrel down the road when I've finished my testing. 

The weather is decent; I might be able to fire a few factory loads this week if I can keep up with things.

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7 minutes ago, 98Z5V said:

They erode quite quickly, due to the gas pressures

Very much appreciated sir. I will toss that one in the spare parts pile and order up a real one when the time comes. That part of the build is easily months away at this point... And hey; who doesn't need an extra gas tube roll pin?!

I split and cracked the Aero Precision forward assist roll pin. I only had one more extra in stock; so I chucked it up in the drill press to sand down a bit; and it flew out. Took me a solid hour to find that thing... But both uppers are fully built now. Quite a few things left on the list before they are both ready to fire; but getting closer.

I did a test assembly of the 24" and found yet another problem. The screws for the handguard are a hair too long. I even pulled one out of another AR-15 to measure. Worst part is I torqued one down hard enough to gouge the chamber area on my new barrel before I figured out how bad it was! They are only 0.015" longer than some others I have. I'm not sure if the handguards are different or what yet; looks like the only way to use them is to put a washer under each of them (or trim the screws).

Almost ready to mold the charging handle, and I'm glad I waited this long. With the Primary Arms FFP scope mounted, I can barely actuate the stock charging handle. I'm going to need some huge arms on these to get a grip. The last thing I need to do is add the pour spout and vent tubes with wax to the charging handle before making that mold. It's going to be tough to fill the thin part of the charging handle without the wax freezing up and creating a plug; I may need to pour into an unusually warm mold for these components. 

Side by side of the 21.5" 7.62x39 with the 24" 300 Blackout. The stocks are still different; so that's why they appear the same length. Those new buttstocks just arrived today, and aren't a 5 minute install. 

IMG_4247.JPG

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10 minutes ago, Lane said:

 And hey; who doesn't need an extra gas tube roll pin?!

I split and cracked the Aero Precision forward assist roll pin. I only had one more extra in stock; so I chucked it up in the drill press to sand down a bit; and it flew out. Took me a solid hour to find that thing... But both uppers are fully built now. Quite a few things left on the list before they are both ready to fire; but getting closer.

Be careful with gas tube roll pins!...   :banana:

What you described was my exact psychosis with an extra gas tube roll pin.  I know they're tricky little bastards, and I know they can't be left alone - or they'll disappear.  They do that when you try to install them.  I lost one, one time. I had to wait a week to get the next one it - then I smashed that one.  I ordered TWO more.  The first one (of the two) went in, with a chamfer on it's end.   Then, I had a spare...   I chamfer the end on them now, and use that chamfered end right against the gas block - and smash that little unruly bastard in there with a good mini-hammer whack.  Once it's started, it's over, for it.  It's going in.

So, in fear of losing that spare, I had to order a gas block to put it in - WAY harder to lose a gas block, right?!  I figured, with the gas block in the cart - why not just get a midlength AR15 gas tube with that block?  Pin them together at the same time - NO WAY to lose a gas block with a midlength gas tube hanging out of it...  

That gas system ended up being a midlength-gas 16" AR15 precision gun in no time flat. 

That extra gas tube roll pin cost me about $1.5k...   Little bastard.

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29 minutes ago, 98Z5V said:

I chamfer the end on them now, and use that chamfered end right against the gas block

That first Aero Precision supplied roll pin I had was also chamfered. Apparently though, I did not do it well enough. I think it was the coating thickness inside the hole that was a problem (maybe hardness, or scraping off in this case?). I ran a drill bit through it and it seemed fine (even loose), I measured it; also seemed fine. No idea why that first one blew up on me.

I find that gas blocks are the same way though. It's a whole lot easier after one pin has been driven through the block; so what if you destroy that pin in the process. The hole forms enough during that procedure to make the next one go in far more easily. I haven't tried oversizing holes for pins; seems better to make the roll pin work since it's the disposable part anyway (and cheap). 

33 minutes ago, 98Z5V said:

That extra gas tube roll pin cost me about $1.5k...

I dare not calculate how much this project has cost me.

All in good fun though; I wouldn't be doing this if it wasn't interesting to me. These ideas of obtaining stupid accuracy, measuring barrel movement, charge accuracy, shot placement patters, etc. are all very important. And I don't think anyone else has inspected resonance this way in the AR platform. Everyone I've read so far has been testing bolt actions on wood stocks. I'm personally fond of this platform as a "bolt" gun just the same as semi-auto. It's a trivial matter to step up with a gas block, gas tube, and a roll pin (after drilling the barrel port). 

Going to take my time with the superior @jtallen83 21.750" build. Probably a few more days best case. I sure do want it to be presentable visually and functionally. No other way to play this 21.750" number.

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I tried to move this project forward last week; but when I sat down to make the silicone mold of the stock charging handle, I found both I had were fully cured in the tube. Not even a gooey center... So that had to wait; and the mold suffered a bit for that. I should have made up some new hot water to work with; and next time I'm going to use a soap off the approved list. Honestly; who cares if this one is a waste though. They cost a mere $5 to make; and this one works fairly well out of the box. 

While I haven't measured the copies; I will say they look totally useable already (slightly oversize in every dimension). Even if I have to modify them (which I was planning to do anyway); it's not too much wasted time. Yes; the first one was an under-fill. I pulled it out still warm to pour another ASAP. I suspect moisture still in the mold cooled the wax too quickly.

I did learn some other lessons along the way. Painters tape comes loose in the silicone when it cures. It also oozes blue dye which will readily stain your skin. Otherwise it did hold up to add thickness to the part in a non-destructive way. I should have used hot water, and kneaded the silicone in said hot soapy water. I didn't realize that process was actually removing some of the acidic acid for faster curing. Without doing that, there ends up being uncured lumps here and there; which would take at least a few extra days to cure. I would also block out the mold frame more tightly so as not to waste silicone, and leave uniform thickness walls around the part. This one takes some mold heating to pour; though it might be possible cold with two people, two pour spouts, and another vent. Still tons cheaper than platinum or tin curing silicone; and easy to find on the shelf.

After making a few waxes, I decided it was time to do chamber castings. Turned out to be pretty easy; though my second one was a failure. A few minutes later I tried again and it went just fine. I had under-heated the alloy on that run thinking it had already overheated (looked chunky). No problem using a rice cooker and aluminum can for the melt (same rice cooker I use for wax). I was also able to break a half pound ingot in a vise with a good shove. Made it a lot easier to get it into the cut off aluminum can for melting. Apparently a heat gun works great for that process too (I only used that to warm my chambers this time). I didn't even bother with the 1 hour measurements; the final size can be calculated easily; and I will likely pour both again to get a better look before initial assembly. It really only takes about 10 minutes each if you are wasting time and unprepared.

All the official parts are here for this project; but I've decided to wait on reloading until I have a scale capable of 0.1mg resolution (0.0015 grain). That is my next order; thought it will take some days or weeks to arrive. I have some fresh ideas about how to collect more, and more useful data at the beginning of this project. It will allow me to make some direct comparisons down the road that I hadn't previously considered. And honestly; I just want my loads to be tight, for somewhat obvious reasons. 

Little sense rushing to assemble both rifles only to shoot the two whole boxes of factory ammo I have on hand. I'm starting a notebook on this project, and want to record a number of measurements before they go back together. Page 1...

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