Lathes and bumping. Machinists?

[Nardoo]

Can anyone tell me if it is possible to enlarge a cast bullet by lathe cutting the driving bands in the mould to a larger diameter? I have thought about lapping but I am worried about the result.
You see, I have traded my reliable old Marlin 45/70 for a cute little Ruger #1 of similar calibre. My wife insists I am having a mid life crisis but I think she is content that I am only obsessed with to sexy rifles. I have found, like many glamorous types, this Ruger is a high maintenance gal and seems very fussy. She is being difficult about her bedding and I am working on that. I will not mention a nasty roughness and some tight spots as these problems have been cured. But her biggest problem is she demands bullets of .460” diameter minimum otherwise she gives a great imitation of a shotgun and throws patterns instead of groups.
The trouble is, all my moulds drop bullets no larger than 458” in diameter. I have experimented some, bumping bullets to .460” in a rather inexact way, and got some half decent results and some poor results. The RCBS 405gn GC proved best, though this group is closer to 1” than the ¾” that my son wrote. And 50 metres is not far.
http://i131.photobucket.com/albums/p317/nardoo/uu.jpg
I think the RCBS mould bumped up best because it of its shorter nose section. But I had fliers in nearly every group. Overall I have little control over what parts of the bullet expand or contract during bumping which I assume contributes to my lack of consistent accuracy.
I would prefer to have the bullets drop .460” or .461” from the mould rather than bump them. Is it possible to enlarge the driving bands of this RCBS mould with a purpose made cutting tool in a lathe? Or will this burr the point where the two halves of the mould meet? Will it be necessary to enlarge the troughs of the lube grooves as well?
I have an old machinist friend who is prepared to do the work. He is good and does exact work. He even made an inside dial indicator to centre a mould in a four jaw chuck when he hollow pointed my Lyman 457124. All I did was show him Buckshot’s pics and away he went.
http://i131.photobucket.com/albums/p317/nardoo/100_0211.jpg
Weighing 380 grains these hollow points were very accurate out of my Marlin but not in the Ruger.
I have ordered a .462-500GC from Jim at CBE but it will not be delivered for another month.
Can anyone help this poor confused man?

Nardoo

[Willbird]

I think Buckshot can do them and has done them, the setup would be the toughest from the way he described it. Lapping will round it up and as a result may make it bigger.

Did you try Beagling it ??


Bill

[dragonrider]

Yes it is doable, done it myself on a Lyman 457122 that was given to me by a guy that said it was junk, and it was, it cast an hour glass shaped boolit that was .025" small at the waist. In the lathe I used an inside necking tool just a bit smaller than the grooves in the mold, 8 of them in this mold, using and indicator as a stop for max diameter and when reached moved the carriage back and forth to finish the width of each groove. first and only time I did this and only because the mold was junk as it was and I had nothing to lose. Tell your freind to use as sharp a tool as he can.

[Buckshot]

.............Yes it can be done, and that's how lathe cut moulds are done anyway.

http://www.fototime.com/B14C8C7293C3501/standard.jpg

I cut drive bands in a 12 ga Lyman slug mould for a member here, and it was VERY scary :-). I also tried opening up the bands and nose on a Saeco 30 cal RG4 and it didn't turn out so shiny, but that was earlier in my career, ha! In fact it has soured me on doing anything more in a mould cavity then boring out a BB. I don't need that kind of stress.

"Is it possible to enlarge the driving bands of this RCBS mould with a purpose made cutting tool in a lathe? Or will this burr the point where the two halves of the mould meet?"

Just cut a tool to match the drive bands and take very carefull measurements of the cavity. You might have a bit of a burr across the parting lines but it's no big deal. I'd say most mould cavities do but they're so small the first few castings remove them. On a microscopic level a lathe tool or any other metal cutting tool that scrapes, compresses the metal ahead of it (no matter how sharp). The metal finally fractures to one degree or another.

This is what determines machinability as a feature in various metals and alloys. You're going to be working in a very fine grained cast iron, and it crumbles into fine powder so there should be no issue. I'm sure your old machinist friend knows that all setups and cutting tools are rubber, so use the shortest and largest OD possible for the tool.

.................Buckshot

[9.3X62AL]

Nardoo, you've bumped up against (no pun intended) one of the more common pet peeves of MANY 45-70 shooters, that being the insistence of Lyman and RCBS upon making 45 caliber rifle mold cavities that correspond to .457" grooves--which are not real common in mass-produced or surplus rifles. My Ruger #1 has a .459" groove, and a number of Trapdoors run larger yet. If I can get my Lee and RCBS molds to cast that big through Beagling, temp control, or alloy cooperation--things go well downrange. The real answer is a purpose-built mold that casts boolits reliably at the proper diameter--without the gymnastics and incantations described above. One of these days.

[versifier]

Any .45 GB's that have tried to deal with this issue? I know it's common in smaller bores and the fat .30's have done wonderfulness.

[Nardoo]

Thankyou all for the advice. Much to think about know.

Nardoo

[Frank46]

Nardoo, welcome to the club regarding the care and feeding of ruger #1's in 45/70. Like yours I have a .459 throat and this rifle demands .461 or bigger to shoot well. You may also find two constrictions (spelling?). The first and probably worst is where tyhe barrel mounted sling swivel is located. The second is where the front sight assembly is. Both can be located with patches and a jag. I have spoken to veral smith of LBT about this and he concurs. Fire lapping will help to lessen these problems. He also said that about 80% of the shooters who have 45/70's all wanted oversized 45 cal rifle molds because of this. I fully intend to persue the fire lapping and then purchase a larger diameter 45 cal real rifle bullet mold from him. Most if not all my 45 cal rifle bullet molds rarely cast over .458 and I have only one 45 cal mold that will cast .459. Hope this helps. The ruger is a nice rifle but with the shorty barrel looks more like a carbine. They would have been better off with at least a 26" long bbl. Frank

[KCSO]

Quick answer yes, but you would be better off buying a mould. The set up and tool grinding needed to bump up a mould will cost more than a new mould if you hire it done. If you do it yourself expect to ruin a couple of moulds before you get it 100% right. My druthers would be a new mould from Mountain Moulds for $60.

[Nardoo]

Hi Frank,
I can recommend the fire lapping route. I discovered the tightness (and roughness) of the barrel beneath both the barrel band and the fore sight when I slugged the bore for its dimensions. I am sure they were partly to blame for my early problems with inaccuracy.
I went for firelapping as I had nothing to lose as I was contemplating a new barrel anyway. After 30 rounds the tooling marks in the bore at the muzzle were beginning to disappear so I stopped. Then 100 double strokes with a tight patch soaked in lapping compound and another 100 with metal polish and I was done. The first two things I noticed were the beautiful shiny bore and the absence of the previous steep beginning of the rifling in the throat (do not know the technical name for this). I was worried I had a long free bore section ahead of the chamber but it does not appear so as I can only seat the bullets about .020" further out than before.
The tightness under the barrel band has gone but there is still a very slight constriction at the bore which is a good thing for cast I believe. After slugging the bore I can detect no change in its dimensions, so I guess I have not done a great deal of damage.
Anyway, the ultimate test is in the shooting and after two trials with bullets unscientifically bumped to .460" I am on to a winner. A few groups around 1" at 50 metres at 1700fps and I am confident it can do better. Here is a picture of the worst group. These little hollow points should do better. It is a pity I did not take a pic of the groups I got before firelapping with .458" boolets. I would have needed a wide angle camera as the bullets that did hit the target were often keyholing.
http://i131.photobucket.com/albums/p317/nardoo/100_0169.jpg
I love the 22" barrel as it is a hunting rifle. Thanks for the advice and let me know how you get on with yours.
KCSO,
I have ordered a .462-500GC from Jim at CBE as it is far easier to buy a local product here in Australia than try to import a mold. Customs can be a bit funny. It should be here in February and I am hopeful it will be OK. Regarding turning out the driving bands of my mold I am up to the stage of having had a tool made to do the cut but no lathe with the tolerance to do it. I have one more possible chance as another retired machinist I know has a better lathe but he is on holiday. The local machine shops want more than the cost of a new mold to do it. The retired guys are happy with beer!
I have experimented with beagling today but as I can not find high temperature adhesive I have found it a bit tedious placing two tiny metal strips in the mold with a pait of tweezers each time I mold a bullet. Anyway I have been able to drop some bullets at .460" and some others at .462"; and with some pretty consistant roundness. I will attempt to load these and trial them in the next day or two but with 105 degree F weather forecast and bushfires everywhere I may have to wait. I have heard a little about Mountain Moulds. Are they good?

Thanks Nardoo

[lar45]

Have you tried Beagleing?
shimming the mold halves apart with a couple small strips of Aluminum Ducting style tape?

[drinks]

If it is an aluminum mold, a mild steel reamer will easily enlarge the grooves, for brass or iron, just make the reamer from a high speed tool steel drill bit shank, a carbide tool turns them as easily as mild steel, chuck the reamer in a drill press, align the reamer with a band and slowly turn the reamer while closing the mold.
Easy to get exact diameter and thickness of band, use cutting oil when doing iron molds, make a touch of relief on the edge, so you do not wind up with a square corner and a sticky mold.

[Ken O]

Check the goup buy section of this forum, there have been quite a few 460 molds. I picked up a TL type a little while back, I have never been a fan of them, but this one shoots a house a fire.