Reduced Volume Cases for Better Burn

[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.