BOAT-TAILED Gas Check Update/Teaser

[RoyEllis]

I'd like to know what they believe was the cause of the short-comings in their efforts. It may give me an idea what to look out for as I move forward with this project.

At the moment the only thing that might hinder my progress is the fact that I'm working with machinery that isn't as accurate as I'd like it to be. In order to get optimum results from a project like this, It's critically important that everything be aligned and concentric.

HollowPoint

I'll gladly share what I found & theories I have for the unsuccessful attempt I had.
First off, you're perfectly correct that concentricity is of paramount importance and inaccurate machining will eat your lunch (was the largest problem for me at least). Too long of a boat-tail will amplify imbalance/concentricity issues, a problem I discovered only after spending the time to cut mold blocks for the bare slug. This done with a D bit and drill press, I think lathe bored blocks would've gotten me past40 to 50% of the problems. Unlike your design, my boat tail check was designed to be almost a 1/4 jacket as I deleted the bottom lube groove and extended the check/jacket up to attempt a gain in grip surface parallel to the bore for check retention both in the bore and throughout boolit flight (trying to eliminate flyers due to checks blowing off in flight).
In theory it should've worked, and may well do so if manufactured to design specs (and this is where Pat Marlin may be invaluable to collaborate with) my checks were made from .020 soft copper sheet stock in a "check-maker" I made. They came out looking quite good to visual inspection but in actuality they had thin & thick spots in the walls from my home made swaging die. I fell certain the problem was forming too thick stock and forming in one stroke from flat to finished check. These added to the slightly unconcentric boolit produced a wobbling boolit flight that was out of control. Wild flyers in groups shot in excess of 500M finally led me to track down the keyholing boolits. Enlisting the help of a friend who's a surveyor, I was able to post targets from 100 to 900M out. All targets were carefully placed so as to retain the same point of aim and allow one shot sent @ POA 100 yds to strike every paper back stock. This showed me the flyers were keyholing, but weren't consistent, the tail tears from 500 to 900M looked like clock hands.
This effect I believe was induced by imbalances as they were negligible with moderate loads (1800 to 2300fps) but as speed climbed, so did the violence of the wobble, finally reaching a point where the wobble increased air resistance enough to decrease the trans-sonic range to where I saw tears that told me the boolits were tumbling and/or spinning sideways and flyers jumped from 4 to 7 inches out of group area to landing up to 3ft out of group area.
Your shorter check should help with the erratic forming issues I had, so if you can get a concentric slug to start with I think you'll be halfway there at the very least. Should I think of anything I missed telling you about my experiment, I'll post that up also.
Best of luck brother, I'm pulling for ya to succeed!

[texassako]

I will be watching this develop since I always wondered why a gas check had to be flat.

[HollowPoint]

This is one of those, "Good News/Bad News" posts.

The Good News? I was able to cast some bullets using my NOE mold with the Extension Plates attached. Once I got past the fifth or sixth pour the bullets were looking real good.

The Bad News? Those "Metal Flaps" that I milled off after I'd machined those Extension Plates would have helped eliminate the "Bad News." Duh!

These bullets don't just drop right out of the mold like some cast bullets do. They need a little persuading; in the form of a wooden banging stick to jar them out of the cavities.

This Bang-Stick method always works for me; as it did this time around too. The bad thing was that I kept hitting the edge of my Extension Plate which caused them to shuffle over and out of alignment with the bullet-mold cavities.

After a while, I didn't even have to make contact with the Extension Plates. The jarring that my wooden stick imparted onto my mold was enough to make the plates go out of alignment.

This meant that the Ridges that I'd deliberately fashioned into the Extension Plates were no longer identically aligned on all the bullets. Some were so far off as to show on one side of the bullet while the other side of the bullet mated flat with the factory Gas-Check Shank.

I decided to eliminate that "Ridge" all together. I found that on the bullets that I cast with these Ridges perfectly symmetrical, the Boat-Tailed Gas-Checks wouldn't slide on without having to apply excessive force; which tended to damage the check when it was run through the sizing die.

More Good News: I was able to cast about twenty really good bullets. The rest of them will go back into the melting pot for the next casting session.

On a side note: After looking at these Boat-Tailed cast bullet, they look like they may be a good candidate for the sub-sonic 300 BLK-Out cartridge that's all the rage right now.

I've already fixed the "Ridges" problem so I'm still on track for another casting session this weekend.

Here's a pic with some weights and measurement info on these modified bullets and Gas-Checks.

HollowPoint

[geraldsd]

Very interesting. A lot of work! I hope that things work. I'll be watching, too.

[xs11jack]

Jack again, in your reply to me, you spoke(wrote) of a short attention span makes you work quickly. I too, have suffered with a short attention span and it is to the point that my wife quiped one time that I have the attention span of a demented squirrel. She's right.
Jack

[fcvan]

I saw one post of a mold modification where the poster made a gas check boolit mold from a mold by affixing the new section of the mold directly to the top of the mold block. I think he used counter sunk set screws. That might hold your pieces in place

[HollowPoint]

I saw one post of a mold modification where the poster made a gas check boolit mold from a mold by affixing the new section of the mold directly to the top of the mold block. I think he used counter sunk set screws. That might hold your pieces in place

I've done this very thing before. In fact, it may have been me you're referring to. It was back when I was making bullet molds for my then newly acquired 45 caliber air rifle. At the time, I posted pics of the whole process. Or maybe it wasn't me.

On this particular bullet mold I don't want to permanently attach these plates until or unless I get this Boat-Tailed Gas-Check thing to work out as I'd hoped. No sense in altering a perfectly good bullet mold just yet.

As it is, the only affects of putting those Extension Plates on are some small divots on the sides of the mold-halves where the set-screws press against the sides.

HollowPoint

[HollowPoint]

More Bad News: For me, I mean.

It doesn't directly affect this project.

I'm not sure what brought it about but, on Thursday afternoon I bent over to pick up a dirty sock and when I went to straighten back up my lower back started shooting lightning bolts of searing pain up my spine.

I feel a whole lot better now but for the last couple of days I've been gingerly walking around like a Real-Old-Man with a sahuaro cactus up his butt. I hurt my back when I was around 35 years old and every now and then that injury comes back to visit.

When this old injury comes in for a visit, there's no position I can get in that doesn't involve some degree of pain. Only someone who's been there and done that can really relate to what I'm saying.

I've mentioned all of this to let those of you that are following this project know that for the next couple of days these Boat-Tailed Gas-Checks are being put on the back burner. (at least any machining elements of this project anyway)

Since I'll be spending the next couple of days in the sitting or laying down position and my fingers on the computer key board feel no pain, I thought I'd take advantage of the sitution by going back into my CAD software and tweaking my drawings some more.

If you'll notice in the last image I posted of my completed bullets, the Boat-Tailed Gas-Checks sit pretty far back from the last Driving-Band. I was concerned that even though I'll be crimping these Gas-Checks down, the overly-wide lube groove between the mouth of the Gas-Check and the last driving band may make it somewhat easier for the Gas-Check to maybe come off somehow.

I'd have to test several of these bullets to be sure but, since I have the time now I can go ahead and address this problem before it happens.

By comparing the Boat-Tailed Gas-Checked bullets in the last image with the Flat-Based Gas-Checked bullet in that same photo, you can see that the Flat-Base Gas-Check is up close enough to the last Driving-Band so that it creates a Lube-Groove that's pretty close to the same width as all the other Lube-Grooves.

I'm wanting the last Lube-Groove on the Boat-Tailed Gas-Checked bullets to have that last Lube-Groove be about the same width as the others.

I don't know if this is the case or not but, in my mind's eye, I can picture an Air-Vortex being created in the area of that last Lube-Groove as the bullet sails through the air with that Lube-Groove being as wide as it is now.

I'm more than likely over-thinging the whole thing but, when you're laying around or sitting around and trying not to move around to much, changing the width of that last lube groove isn't going to hurt anything.

With that last Lube-Goove not quite so wide, it should mitigate any turbulance that may have othewise occured. (if it occured at all)

The new Extension Plates are already laid out and mounted on my mill. It's just a matter of turning on the machine and pressing a few buttons.

I'll be back.

HollowPoint

[Doc Highwall]

HollowPoint, get some traction for that back. I have 2 lower back surgeries along with my neck, plus 5 other operations and I know what it feels like.

[HollowPoint]

Hi Doc:

I'm not sure exactly what you mean by "traction." Fortunately, these occurrences are rare for me now days but the memory of them last a long time.

I generally just put on the widest leather belt I own and cinch it down as tightly as I can. (it acts kind of like a weight-lifting belt) It doesn't completely stop the pain, it just makes it bearable. As long as I follow a certain precautionary protocol whenever this happens the pain normally subsides to nothing in about two days.

I used to go right back to work as soon as I could stand up without to much pain. I learned the hard way to just let it run its course with a minimum of exertion and I can put it behind me pretty quickly.

The initial shooting pain is equivalent to having a root-canal with no anesthetic. For the females in the audience; the pain is equivalent to giving birth to triplets with no epidural, all coming out at the same time and all three coming out side-ways.

It's OUCH to the third-power.

Only another back-pain sufferer could really understand the pain.

Thank God the worst is now past. I feel a whole lot better. A couple of ibuprofen and some asper-cream and I can't even tell it ever happened. I'm still taking it easy though.

Doc, I just have to ask you; have you ever been in the depths of this kind of back-pain and feel a sneeze coming on? You know there's not a darn thing you can do but brace the torrents of pain that are about to hit you. It's humorous after the fact but, DAMN; when it hits it hurts like hell.

Ok; I'll quit for now because I've drifted way off subject. Boat-Tailed Gas-Checks, Boat-Tailed Gas-Checks,
Boat-Tailed Gas-Checks.

HollowPoint

[HollowPoint]

I went back in and tweaked my drawings of the Extension Plates I made up earlier.

The Boat-Tailed Gas-Checks now ride up a little closer to the last driving bands on these
bullets.

An added benefit is that I was able to reduce the weight of these cast bullets (including the Gas-Check) to a respectable 220 grains.

This is a good thing for me because I was having trouble tracking down load data for the 240 grain bullets I was casting earlier.

After doing a little research online I found that I could use the minimum starting loads from the 30-06 cartridge for my load work up. I just need to drop the charge weight a little as an added precaution.

I want to stay around the 1900-2000 FPS range with these. (accuracy permitting) I'm not sure how fast I have to push them in order for them to remain stabilized beyond three hundred yards. Any of your ideas on this would be helpful.

I have twenty bullets sized and lubed. I'll load them up within the next few days and pray for some free time to get to the range to see how they perform.

This first time around I just want to see if they'll fly true with no key-holing or any other unwanted surprises.

I posted an inquiry in the "Favorite Loads" section of this site asking for input on a good starting load for the then 240 grain bullets I came up with. I got absolutely no responses whatsoever. That's the first time that's ever happened since joining this forum. No Responses.

Oh well; there's a first time for everything.

Here are a few of the latest pics I've taken of this project. I'll be back after I've gotten to the range.

HollowPoint

[Oreo]

FYI, supersonic fluid dynamics are very different then subsonic. Lube grooves, or any other irregularity will produce shock waves but not turbulance / vortecies.

[HollowPoint]

That's good to know.

This type of useful information tends to show up after you've put in the time to change
things that appear not to have needed changing in the first place.

Oh well; some good did come of it. I reduced the overall weight and length of the bullet.
As a flat base, this bullet already had to be seated pretty deeply down into the brass.
Now with the Boat-Tailed Gas-Check in place, it's not to much farther down in the case as
before.

I also went back in and tweaked my forming-rod and I intend to make another forming-cup as well.
The reason for this is that although the Boat-Tailed Gas-Checks are coming out usable, the beveled
part of the Gas-Check has a slight outward curve to it.

I believe that the pressure generated by the burning powder should compress that "Slight Outward Curve"
so that they hug the Beveled/Boat-Tailed end of the bullet before they leave the barrel. I just want them
to come out of the forming-cup already to the correct shape.

HollowPoint

[HDS]

I remember reading that schutzen cast bullet shooters that shoot at a 1000 yards with bullets that definitely drop through the sound barrier on their flight towards the target, are in fact aided by their lube grooves, they prevent the bullet from destabilizing whereas a modern smooth surfaced bullet doing the same would become unstable.

So in that respect maybe a cast bullet can have an advantage here?

[HollowPoint]

I remember reading that schutzen cast bullet shooters that shoot at a 1000 yards with bullets that definitely drop through the sound barrier on their flight towards the target, are in fact aided by their lube grooves, they prevent the bullet from destabilizing whereas a modern smooth surfaced bullet doing the same would become unstable.

So in that respect maybe a cast bullet can have an advantage here?

I have a hard time visualizing how that would work unless -judging from the image that Oreo posted- the lube grooves imparted enough drag that it kept the bullet flying true. Kind of like the fletchings on an arrow as it flies through the air.

If you'll note on Oreo's pic, you can see the crimping groove on the bullet silhouette. There is a small trace of a "Shock Wave" in that area.

HollowPoint

[oldpara]

OK;

I'm not going to have time to post pics tomorrow so I thought I'd get it out of the way.

I took some quick pics but the ones of my prototype dies came out all blurry. I'll do those later. For now, here's enough to whet your appetite.

I installed a couple onto the NOE 200 grain spitzer flat base gas checked bullets. Although I haven't added the beveled tail to the bullet yet, you can see what I'm trying to accomplish with these Boat-Tailed Gas-Checks.

These are already some of my most accurate cast bullets out of my K31. I'm hoping that the Boat-Tails will give me better long range performance.

HollowPoint

That is a great design !
You're doing some excellent work.
I have a 30cal 225gr spitzer BTGC mold I cut but yours is a more thourghly thought out piece.
I love this stuff, a great hobby and you have impressive skills.

[HollowPoint]

oldpara: Thanks for the positive feedback.

I'm thinking that eventually I'll be making up a new bullet mold that incorporates the Beveled tail end to accommodate these new Boat-Tailed Gas-Checks. The setup I have now is good enough for testing but, it would be better to have a dedicated bullet mold rather than just adding that Beveled Tail section. That way I'd be certain that everything was aligned.

As it is now, if I look real close I can see that the Beveled-Additions are just ever-so slightly misaligned with the existing Gas-Check Shanks on these bullets. I'm just hoping that the sizing process with the Boat-Tailed Gas-Checks in place will bring everything into alignment. Time will tell.

I'd like for any new bullet mold I come up with to drop a bullet in the 150-160 grain weight category if I can.

I went back and I attempted to ream out my existing Forming-Cup yesterday. I wanted it to have the exact interior contour as the exterior contour of my Forming-Rod so that my Boat-Tailed Gas-Checks came out with a more defined Boat-Tail shape.

I ended up just totally screwing it up; so, I'll have to make another one from scrtatch; and I'm now out of metal stock so I'm going to have to order some more.

This time around I'll be using some 12L14 round stock. It's much easier for me to work with and my home made reamers don't have to be as hard in order to ream the shapes I'm wanting.

I'll be back later.

HollowPoint

[HDS]

I have a hard time visualizing how that would work unless -judging from the image that Oreo posted- the lube grooves imparted enough drag that it kept the bullet flying true. Kind of like the fletchings on an arrow as it flies through the air.

If you'll note on Oreo's pic, you can see the crimping groove on the bullet silhouette. There is a small trace of a "Shock Wave" in that area.

HollowPoint

I found where I read it originally, see chapter Aerodynamics:
http://www.lasc.us/Fryxell_Book_Chap...ouldDesign.htm

There is a detailed explanation inside, I don't have the knowledge in aerodynamics to say yay or nay about it though.

[HollowPoint]

Interesting read.

Back when I was first considering trying to make my own bullet mold for my then newly purchased 45 caliber air rifle, I scoured the internet in search of an online wind-tunnel software that I might be able to use to fashion the profiles of my bullets. I was trying to find a way to shape the profiles of my bullets in order to get the optimum BC for the given velocities I was hoping to attain.

In this day and age of simple software applications there must be such a software out there somewhere, I just didn't happen to find it at the time.

The software used by Heating and cooling contractors to visualize the air flow from air vents placed at certain positions inside a given room can be used to loosely simulate what one can expect in the way that a powder burns inside your cartridge case at ignition. It could be used to generally confirm that the shorter fatter cartridge cases burn powder more efficiently than long straight powder-columned cartridges do. (that type of thing)

I was hoping that by finding a simple software online that I could simulate the aerodynamics of given bullet profile I could forego the trial and error of different bullet designs and thereby save myself alot of time. I ended up just making a bullet mold with four adjustable cavities that would drop bullets from 150 to 240 grains depending on how I had them dialed in. (ended up selling the air rifle and dropping the project)

I ordered some more metal stock yesterday. Due to my work schedule I won't be doing anything more on this Boat-Tailed Gas-Checks project until I get my income-producing work finished and that metal stock comes in. I should be able to get back at it next week some time.

HollowPoint

[HollowPoint]

It's been a while since I posted anything new on this thread. I hope you all didn't think I'd abandoned this project.

The metal stock I ordered finally came in. It's a whole lot easier and quicker working with this type of metal than the stuff I was salvaging off my junk pile.

I re-made a couple of the components of my Boat-Tailed Gas-Check dies; including a new component I'll be using to final-form the bevel on the Gas-Check rather than relying on powder-burn-pressure to final-form the Gas-Checks. I think it's pretty well taken care of now. I'm getting some decently uniform Gas-Checks out of it now.

I can see now that I am going to have to break down and make that dedicated bullet mold for these new Boat-Tailed Gas-Checks. To that end I've been lathe-turning possible candidate bullet shapes to accommodate these new Checks.

There's one last component of my existing die set that I'm considering re-doing as well. It's the first-stage sleeve of the three-stage set. It's presently made of aluminum and I'm wanting to make it out of the 12L14 steel that the rest of the dies are made of.

Here's a pic to give you an idea what I'm referring to. Bare in mind that these are just prototype components. Once I get everything working right I can then go in and refine and re-shape the dies.

I've already laid out my mold blocks for the upcoming Beveled-Tailed bullet mold that will wear these new Boat-Tailed Gas-Checks. Now I just got to find the time to set up the mill to machine the parts.

I'll be back.

HollowPoint