Reduced Volume Cases for Better Burn

[stephen m weiss]

I have been toying with an idea to shoot cast bullets cheaply, and efficiently, which is a lot of the point of casting your own. The known fixes are:
* dacron to hold the powder to the back for reliable ignition.
* fast fluffy pistol powders, with dacron.
* inert filler such as cream of wheat to reduce chamber volume.

So: what if I use silicone pourable casting compound and a waxed dowel pin down the center of some dedicated brass to convert my 5cc 308 win cases to ~2 cc with a ~.25 hole to the primer hole clear and the case neck clear?

For reference, I can either use 23 grains of alliant 2495 with a 155 grain bullet to get 1500 fps, or 17 grains powder and 26 grains of filler, or 12 gr powder with a reduced volume case. So the reduced volume case saves me 48% on powder cost, or about 3 cents a shot. The round costs 10.5 cents each, and is quicker to build than using dacron or filler, but takes making the custom cases, which add about 15 cents per case. Cases are re-used many times, so this is a few cents per round. Other less expensive casting compounds may work, such as polyester resin, vulcanizing rubber, polysufide,or epoxy, or wax might work, but 2 part silicone would be my first guess.

I have searched at least 10 times trying to get pistol powders, nope. And they are expensive. Whats the point in using 9 grains of pistol powder that costs as much as 15 grains of something else? Loading dacron is slow, and still results in low efficiency burns, so you pay 50% more for your powder than you should. Filler, ie Cream of wheat is still not ideal because its so airy that pressure still stays low, it has weight which must be accelerated, wasting powder, but does nothing for bullet energy on target, and gets everywhere, in my barrel, on my crony, and on my shop floor.

Now, I like the idea of a rifle that can load a fast long distance round if I want, or an energetic round to penetrate elk or moose. But I want to be able to fire 10 cent quiet shots at targets or squirrels as well, preferably with the same gun.

I have designed for elastomers and adhesives for years, and was a machinery stress analysist so let's assume I get the engineering part right. If not.. I will fix it or shelve it. Also, I have been developing internal ballistic calculations which seem to be working fairly well, so I am close to having accurate predictive ability of burn rates, pressures and such. Assume I also know how to safely test by creeping up on a design limit using failsafe precautions during testing.

My real question is about usability of such custom cases, methods of marking and handling so they dont get mixed into standard cases, and what capabilities would be best made. See, a case that efficiently burns my 2495 and will fire a 120 grain bare base at 1500 fps will not be able to fire a gas checked round at 2200 fps. You couldnt get that much powder in there.
So, if I became interested in firing 180 grain bullets at 2200 fps, I would have to either use a standard case with any of the above methods, or make a different custom case. Would etching the case with the usable volume on the low stress area of the base make sense? Paint comes off during forming. Small filed notches on the extractor rim would be easy, but wouldnt indicate volume, that would have to be known or measured.

Who else is interested in having custom low volume cases for their favorite rifle?

It should be mentioned that not having any kind of packing creates its own problems with hot explosive gas attacking the rear driving bands of the bullet. Either a small amount of filler, a gas check, a paint coating on the bullet, or some other idea would be required to address this.

[Bigslug]

I think you're onto a workable concept. The ideal way - I think - to approach this would be to manufacture one of those polymer cartridge cases with the steel head. Make with reduced internal dimensions that stop the bullet at the base of the neck, and sell a depriming setup. Would not require any resizing and could probably seat bullets by hand. Initial marketing in the big Wal Mart calibers of .223, .270, 7 Rem, .30-30, .308, .30-06, and .300 Win. Specify a working burn rate range that allows the user to fill to the base of the neck with a dipper with a wide range of options.

[Bjornb]

Stephen,
If you are proposing to make up a quantity of cases as described above, I would be very interested ordering both 308W and also a number of cases for the XCB rifle.
Bjorn

[wlc]

IIRC someone in the not so distant past had made reduced volume cases for the 308. They were lathe turned of solid brass. I personally think it would be cool to be able to get reduced capacity cases for several different rounds I have.

[Jack Stanley]

It may not reduce volume as much as you'd like but once upon a time I rounded the head of a .223 Remington case , cut the neck off an aught six case and expanded it slightly . Then put the small case inside the big case and ran the whole mess into a .308 trim die and went after it from there . It worked pretty well as I remember .

The castable stuff may work better at getting the volume to what you want . As long as it stays in the case you're good I bet . As for volume if you are starting with unmarked cases you could stamp the internal volume on the head . Anyone fooling around with this sort of thing probably would know what the case is for .

Jack

[williamwaco]

I have one word for you that will solve all your problems.

Unique!

[ColColt]

If I feel the need to go to dacron to fill my cases I need another hobby.

[Yodogsandman]

I have one word for you that will solve all your problems.

Unique!

+ 1 and switch to an appropriate caliber pistol boolit for plinking or small game.

[Artful]

In my search for subsonic 308 rounds - I found certain powder combination that would work in
some circumstances but not in others - I tried Unique, Red Dot, Trailboss and others.

In the end I bought machined 308 brass cases with smaller internal volume so that I had 100% or close too it loading density so that I could take shots at any angle without having it effect velocity of my subsonic loadings. - I think it was about $8 per case back then. So I would be interested in what you have to produce for at least a trial compared to my other cases.

[Mohillbilly]

I think you might befit using a chamber insert that would allow you to shoot .32 caliber cartridges in your .308 , 30-06 ,.303 brit , 7.62 x 54 r .

[stephen m weiss]

Haha, there are always the posters that say get expensive unavailable powder and use lots of it or just quit shooting...I struggle for a polite response. ...er, I guess thats what they do, so I thank them for that. Heck I know people that just buy boxes of $3 rounds and fire them out of $4000 guns and just love their hobby. So, it takes all kinds. I know folks that use a 12 ga shotgun to hunt 1/2 lb squirrels. Not for me! I take a third of my squirrels with .177 silenced pellets, when there is no threat that something bigger needs killin.

The chamber insert sounds interesting. I would worry that it would be slow to switch back to a full power round if a buck got in my way, and that the rounds would not feed in my magazine. And of course my reloading equipment doesnt work on pistol rounds, and finally, I still have no pistol powder.

[ohland]

I have one word for you that will solve all your problems. Unique!

Mmm, so is Unique in gel tabs?

From my futzing around, Unique is pretty much position insensitive (8.0 gr in a 7-30 w/285129 boolits) and other than weighing charges (my OCD shows...) its a dependable reduced charge. When throwing in my Uniflow w/small mic, the charges are usually within -.1 grain. Good enough for just about everything.

I want to take another try with the 280468 in the 6.8 SPC. The reduced case and Unique seem to be a good fit, but accuracy was not on the same level as the 7-30. It is entirely possible that the problem with accuracy was the loose nut behind the trigger.

[ohland]

Wow, this reduced stuff is interesting. I know of the use of flash tubes to convey the primer flash to the front of the case. Suppose a flash tube held in with a mandrel thru the flash hole would keep it centered while the case filling material is added.

Oops, after some thought, the original ideal of a waxed dowel that is removed eliminates the potential problem of securing a flash tube so that it is not being blown out the barrel. Or worse.

Another (obviously defective) thought came to me, turning an insert to fit in a 38-55 case that will work after the case is resized to a 7-30. Think of the old .303 cases loaded with strings of cordite, then necked.

[Airman Basic]

I was thinking: 300 BLK?

[Three44s]

What about lead?

A member here, mroliver77 ...... I believe wrote on this forum about using lead poured into cases to reduce volume. He drilled down to the flash hole from the mouth of the case and also cleaned out the flash hole from the primer pocket side but had few issues with that in general.

Just a thought

Three 44s

[NoAngel]

Brass cased 308 blanks will get reduced capacity. You'll probably have to do some neck turning and/or reaming.

[Malamute]

I have searched at least 10 times trying to get pistol powders, nope. And they are expensive. Whats the point in using 9 grains of pistol powder that costs as much as 15 grains of something else?

Pistol powder costs that much more than rifle powder? It may be regional, which isn't helping you where you are, but pistol powder doesn't cost much different than rifle powder here, and has been on the shelf intermittently.

I may be doing it wrong. I use Dacron for some extra-light loads. It slows down the process some, but not a lot. The results have been worthwhile for me in ignition consistency.

[stephen m weiss]

Lead as casting agent... Physically it would work. How to build it? I was going to pour through the neck, start the dowel, the flip it over and home the dowel plugging the primer hole, letting the air out the primer hole, then curing. I can't do that with lead.

Oh, just fill to the neck with lead and then drill out to the primer hole? I could poke a toothpick into the primer hole to keep lead out. Hmm.. I hate drilling lead. I break so many drill bits. I need to take small pecks to break the chip... but it grabs so fast and sucks in....

[Nueces]

Bet you know how to stone a twist drill for brass - put a small flat on the cutting lip to steepen the cutting angle. I haven't tried it on lead, but I will.

[country gent]

For reduced loads and possibly better consistency instead of a .125 hole for the flash to travel thru and added distance posibly filled with powder diffrently from shot to shot, flash possibly being slowed by this also. Figure the amount of reduction needed an make the hole the ppropriate size to hold the charge to the base of the bullet and make aquire the manderel. I would turn up several mandrels with a .250 X .060 pin on the end to center in flash hole. a dia as needed to reduce case capacity, and a caliber dia shoulder to center in the case mouth. A measured amount of epoxy deposited in the case the waxed mandrel inserted to deepth and set aside to cure. With the curing time of most good epoxies I would make 15-20 mandrells so a batch of cases would only take a few days to make up. This would be very similar to the card board tubes used in 45-70 carbine loads to redue capacity used years ago. A syringe filled with a long cure epoxy and read closely would allow you to measure the amount of epoxy dropped into the case, the wax mandrel would position it fairly evenly and gravity during curing time would even it out even more. Clean cases good with solvent and brush inside to get a clean surface for adhesion also,

[stephen m weiss]

Yeah, changing the cutting angle would fix it. And worth it if I am gonna do 50 cases or 100. Hah, and you can tell by feel it's not a standard case because it's so heavy.

[stephen m weiss]

country, yeah that is what I was wanting to do. But I dont have a lathe so would just plug the primer hole with the cut off dowel tip. I can drill out the primer hole later if some leaks in. The only issue with epoxy is the case expansion may fatigue the epoxy if it is not tough enough. Also, the force required to form it might be substantial, but that is true with lead as well.

[Alan in Vermont]

How would you eliminate any chance of the silicone filler being dislodged and a piece of it ending up lodged in the bore? That would have the possibility of the next round doing bad things.

Other than that it's a great idea and one I would like to see developed.

Somewhere I have seen the inserted .223 case idea, that Jack Stanley mentioned, documented in a printed article with pictures. Maybe Handloader, anyone else remember seeing it? If it was the full blown cabin fever time of winter I might be tempted to browse my magazine collection in search of it.

[wmitty]

I have also seen the article concerning placing a .223 case inside a larger (.30-06 case, I think) round to reduce internal volume. The author sectioned the case within a case lengthwise to illustrate the volume reduction. If I remember right, the mouth of the larger case was expanded to .375" or so to allow positioning the smaller case inside. The .223 case had been cut at the extractor groove and at the neck/shoulder juncture. If lead or lead alloy were used to reduce volume, would the heat involved reduce the hardness (strength) of the case head to a significant degree?

[303Guy]

Who else is interested in having custom low volume cases for their favorite rifle? I am. I have actually made such a case modification for a 303. I used epoxy and a mandrel. The mandrel had a pin to fit the flash hole and was smaller than the neck so that it left a shoulder at the neck base for seating the boolit against. I don't recall having any problems with it but I opened the cavity to the neck diameter. The epoxy doesn't hold out well to flame cutting. I'm thinking of setting a brass or stainless tube into the cavity. If I make the fill to neck size then setting the tube in place would be easy. I'm wondering whether I could preset the tube then filling the outer cavity with epoxy or similar through a hole at the shoulder.

[tomme boy]

30 BR or a 7.62x39 is what you want to do. Both have reduced capacity and both can be run up to 2200 fps.

[Artful]

country, yeah that is what I was wanting to do. But I dont have a lathe so would just plug the primer hole with the cut off dowel tip. I can drill out the primer hole later if some leaks in. The only issue with epoxy is the case expansion may fatigue the epoxy if it is not tough enough. Also, the force required to form it might be substantial, but that is true with lead as well.

Been there done that - about the 3-5 firing every case lost some of the filler material - tried with several different fillers - and you want to use a neck size only die with your cases - I'm using the LEE collet.

[mozeppa]

how about plugging it with bondo then drilling it out?

[stephen m weiss]

Ah, awesome, some of you guys have tried it and found that casting compound shooting stress was an issue, as was sizing strain. Casting compound definatelty wont get 'stuck' in the bore at decent pressures, but a case that is missing some filler will have different volume, kind of hard to detect, and produce lower pressure and lower speed, so the grouping wont be as good. Not a huge deal at short ranges. The cases could easily be weighed to check for problems periodically...but that takes time. The problem with the 2 part silicone is that it is not very tear resistant. Polysulfide may be the ticket. It's cheap, high temperature, produces a super aggressive bond, stays soft and is tear resistant. It's the stuff they use to bond formed fighter cockpit shells into the aluminum frames for attachment hardware. The problem I had with it was that it was sold in 5 ga buckets.. haha and you have to weigh the activator very close or it doesnt set up. But reloaders weigh things very well. I just found 1.5 ga for $132. Still a lot of money but would make a ton of cases.. if it worked...It's probably best to start with the silicone for $20 and see if tearing is an issue. The 1.5 ga would make about 2000 308 cases.. a little more than I need, for 7 cents a piece, while saving 4 cents per shot. A good investment, if it works. Good cases cost $1 each anyway..

Oh.. my 7.62x39 is 3cc volume instead of the 2 I want, and the semi-auto action makes it intenally act like a 14" barrel, so it takes more powder anyway. For gas checked 2200 fps rounds it makes sense, except the brass is expensive and I dont want to lob it 15 foot in the forest because I will never find it. I could paint it pink.. haha. did that with my squirrel hunting brass. never lost any after that! But the hot brass still tunnels down in snow and cant be found.

[Cap'n Morgan]

I have done a lot of shooting with an old Martini Henry 577-450 using turned brass. The cases was turned from ordinary free-cutting brass stock and the capacity was reduced to match a 45-70 case almost exactly. All my shooting is done with smokeless powder and the reduced cases makes reloading much more manageable compared to full volume brass as it will facilitate the use of a wider range of powders

As long as the pressure is kept below 16.000 to 18.000 psi, the cases will last almost indefinitely and once they start to stick in the chamber it is only a matter of a few strokes with a fine file, followed by emery paper while the case is spun in a lathe. A distinct step inside the case keeps the boolit from moving backwards even with a loose fit.

[stephen m weiss]

Bondo is polyester resin filled with talc for good sanding. Neither has a sneeze of toughness. One shot and it would go to pieces and be rattling around in the case and falling out. Even just getting a big chunk of it very cold on a car will cause it to crack and fall off. Not good. I think that wood or cloth fibers would be a better filler (phenolic) but even that has really limited toughness. Dacron chopped as a filler might work, being polyester and pretty tough.. I know polyester-polycarbonate alloys get some insane toughness. Hmmmm.....

[wmitty]

I believe 303Guy is on the right track with the idea of placing a metal tube in position and surrounding it with an epoxy filler; it should protect the epoxy from gas erosion and allow for a consistent and easily calculated volume for the combustion chamber. (PI x radius squared x length ). I have some ancient Norma .375 brass which is too soft for use with normal loads which will be an ideal candidate for trying this idea.

[Jack Stanley]

Got get'um Stephen .... I can see the wheels turning in yer head !!;-)

Jack

[stephen m weiss]

Yeah the brass liner approach is a high road though expensive. I was thinking of using a bit of canvas as mold release and anti-tear wrapped around the wax dowel. Maybe t-shirt material would have enough give if cotton canvas failed under the strain.

LOL Jack.. polymer chemist is a bit out of my specialty.. I was hoping to bait some of the guys who know it better to comment!

[Echo]

George Nonte had a article many years ago regarding anodizing(?) brass for identifying modified cases. Made them red, green, &cetera. Sorry, I don't have the reference.