Month: November 2005

Bullet Moulds

Posted by on November 26, 2005

A buddy turned up at my house this morning with a bullet mould to show me. Actually a round ball mould. He’s good at making things. Same guy who makes 375 rifle bullets from fired 5.56 and 38 Spl cases in dies he made himself.He has a muzzle loading 12G double shotgun and wondered how it would perform with slugs, or more precisely patched round balls. The idea being a short range weapon either for hunting or whatever else. More like a smoothbore double rifle really.But where to get the balls ? As we have played around with ideas of how best to make bullet moulds he figured this would be a good place to start. He first made a pair of blocks from aluminium. He ground a twist drill of suitable diameter so the point was more or less half round and used it to drill each half of the cavity. Having found a ball bearing of roughly suitable diameter, he closed the two blocks around the ball bearing and pressed them together with 30 tonnes of pressure. The bearing finished the rough cavity very nicely. Then, leaving the bearing in place to keep the two blocks aligned, he drilled and fitted a pair of alignment pins and machined the outside surfaces of the mould.It cast some very nice lead balls. Not perfect, he had drilled one half of the cavities a little too deep, so one side of each cast ball is slightly high and shows the shape and tool marks left by the drill where the ball bearing had not pressed deep enough to remove them. But the cast balls are perfectly usable. It is not considered a fault at this stage. The exercise was not to get perfection, it was to prove the method, which it did handsomely.He got the idea from Lee’s round ball moulds which are finished by pressing with a carbide ball. It has proved that the drilling and pressing are easy, and that it can be done with a ball bearing. Lee uses a carbide ball because it’s worthwhile for the number of moulds they make.It makes sense to drill the cavities close to final size to minimise the amount of metal that must re-arranged by pressing. A very accurate cavity could be drilled with a ball end mill. As they are available in 1mm increments it shouldn’t be too dificult to get one the right size. If that’s not close enough, they are easy to make. Getting a ball race with exactly the right diameter balls might be more difficult, and will need some research. But a ball can be made from tool steel if necessary. Quite tricky but not impossible.So, if round ball moulds become difficult to obtain, they can be made, to any desired size.We then got to figuring whether this pressing technique could be used for bullet moulds. The only practical method of cutting cavities for the amateur is lathe boring. But the difficulty of following the profile of a cast bullet is practically insurmountable because of the lube grooves. Theoretically, the body of the cavity could be reamed, and the grooves, or in reverse the lands, could be cut with a single point side cutting tool. But that would leave the lube grooves only four or five thou deep which is too shallow. It is the need for bullet diameter to be smallest in the lube grooves that makes it so difficult.If most of the cavity could be reamed, maybe it could be finished by pressing on to a suitably dimensioned tool steel bullet. We are sure it can be done. As with lathe boring, however, the difficulty will be in the lube grooves. That is, can aluminium be made to “flow” into the grooves ? If it can, mould making will become practical for the amateur. But it remains to be seen, and I don’t know when we will get around to testing it.There are also other unanswered questions, the main one being how much pressure will aluminium take without distortion. That is, enough pressure must be applied to cold form the cavity without compressing the blocks under load. It is not critical for round balls as they don’t have to be perfectly round to function acceptably. There is no such latitude with bullets. Does Lee use oversize carbide balls to allow for some spring back of the aluminium, or does it stay where it is pressed ? That will only be shown by trial and error.Making rifle bullet moulds, particularly in the big calibres like 458, is easier if only small quantities of bullets are required. The cavity can be drilled and reamed with a home made reamer the same profile as the bullet. The lube grooves can then be cut with a form tool in the lathe. Needs a simple fixture to hold the bullets dead on centre repeatably. Easy to make.The gas check shoulder can be cut at the same time. But why bother ? Get the same results with polywads. Gas checks are expensive, are already not easy to come by, and might be all but unobtainable the way things are going. For that matter, paper patching is another low cost alternative, for which moulds can easily be made because no lube grooves are needed.[Originally posted to SATalkGuns -- Admin]

Cast Loads

Posted by on November 24, 2005

I’ve probably fired more cast bullets from my 308 Sako than jacketed. I am also interested in cast bullet performance in rifles but haven’t explored it in any depth beyond shooting them in my own rifle. It has crossed my mind that in certain possible scenarios that I won’t explore here, cast bullets might have some use for hunting for the pot, for example. While small calibres are not without value, for medium game and bigger, low velocity would need to be compensated by calibre and bullet weight for velocity retention.The other day I picked up a magazine that contained an account of the celebrated long shot by Billy Dixon at the battle of Adobe Walls, Texas, in 1874. He knocked an Indian from his horse at a range later measured at 1538 yards ( 1400 metres ) with a Big 50 Sharps. The writer of the article carried out some interesting tests with a replica rifle at the actual site of the battle, where Dixon’s position and that of his victim can still be identified.With a 425 Grain bullet, MV is 1475 FPS. That drops to 1000 FPS at 300 yards ( 270m ). At 1000 yards it is only 640 FPS, and at the range of Dixon’s shot, remaining velocity is less than 500 FPS, and energy a bit more than 200 foot pounds. Maximum height of trajectory would have been 168 feet ( 51m ). Time of flight was given as 2.50 seconds, but can’t be right, must be four seconds at least.A 425 Grain 50 cal bullet is pretty much the same shape as a handgun bullet, and a similarly poor ballistic coefficient. Lyman’s 425 grain 50 cal bullet has a BC of 0.25. Lyman’s 45 cal 490 grain bullet, being longer and slimmer, has a BC of 0.384, and not surprisingly, retains it’s velocity better than the 50 cal bullet. Fired at 1475 FPS, the 50 cal bullet retains 800 FPS at 600 yards. That’s 54% of MV. The 45 cal 490 grain bullet fired at 1500 FPS retains 940 FPS at 600 yards. That’s 63% of MV.By comparison the 30 cal 168 grain BTHP fired at 2600 FPS retains 1660 FPS at 600 yards. That’s 64% of MV, the same as the 45 cal cast bullet. The loss of velocity is a constant accross all weights and MVs of 30 cal bullets. They all retain about 64% of MV at 600 yards and 47% at 1000 yards. I don’t have figures for the cast bullets at 1000 yards, except for the 50 Sharps. But the data I have suggests the same 47%. That would be almost 750 FPS for the 45 cal 490 grain, fired at 1500 FPS.That’s a lot of performance for a cast bullet of RN or FP shape. And don’t forget that a 500 grain cast bullet can be fired at 2000 from a 458 Winmag. That would translate into 1000 FPS at 1000 yards and a hell of a lot of energy. I suspect that could be improved with a blunt pointed nose like my Lyman 311334 bullet, which, by the way, delivers sub MOA accuracy on a good day.The 30 cal Lyman 311334 gas check bullet ( 185 grains ) retains 50% of MV at 600 yards. That is consistent with it’s blunter profile compared with a jacketed spitzer. But note, that despite it’s superior ballistic shape, it retains less of it’s MV at 600 yards than the 45 cal 490 grain bullet ( 63% ). That demonstrates what we all know, that a heavy bullet will retain it’s velocity better all other things being equal.There are two other factors. The first is the greater velocity loss from high MVs. The 30 cal BTHP fired at 2600 reduces to 1200 FPS at 1000 yards. The 45 cal 490 grain fired at 1500 FPS reduces to a bit under 750FPS at that range. The velocity difference at 1000 yards is therefore much less than the difference in MV. The longer the range, the less the difference becomes. That is of course obvious, as all bullets would eventually decelerate to zero if they didn’t fall to earth first. What matters is the relationship between calibres and bullet types.The second factor is that velocity decay is greatest in the early part of the flight. The 30 cal BTHP, fired at 2600, loses 800FPS in the first 500 yards, and 600FPS from 500 to 1000 yards. Looked at in more detail, it loses 350FPS in the first 200 yards, but only 200FPS from 800 to 1000 yards. The Lyman 45 cal 490 grain bullet fired at 1500FPS loses 280FPS in the first 200 yards, but only about 100FPS from 800 to 1000 yards. Not only is the velocity loss less, but the loss in the last 200 yards compared with the first 200 yards, is proportionately less than the 30 cal BTHP. In other words, the decay is less in both absolute and proportional terms, and gets less as the range increases.Both are because air resistance and drag increase exponentially with velocity, with the result that velocity decay is greater at higher velocity, and also greatest at the first part of the flight when the velocity is highest. Therefore, comparison of muzzle velocities does not necessarily provide a reliable guide to long range performance, and the longer the range, the less reliable it is.This is of course all well known, and it could reasonably be argued that it is not important for most purposes. I just find it interesting, and it might possibly have some application in the unfolding scenario in SA. Consider light loads for example. I have mentioned BP loads in brass cases before. But similar or almost similar performance can be achieved with handgun powder. My 308 Win cast loads chrono 1600FPS with only 11 grains of MP200. The Lyman manual lists 1300FPS for a 480 grain bullet in the 458 Winmag with 21 grains of Unique, and a 385 grain bullet at 1500FPS with 23 grains. Unique is quite similar to MP200.I’m sure that higher velocities could be achieved with slightly slower powder like 2400, but still with economical powder charges. A 500 grain bullet at 1500FPS is not all that far behind factory ballistics in the 458 Winmag, and more than ample for medium game at any range at which game should be taken. Why would that matter ? Ordinarily, it wouldn’t. But in an increasingly restrictive scenario, powder might become hard to get, and should therefore be economically used. It will then also be useful for various calibres to be loaded with the same powder. That is, don’t stock lots of slow burning rifle powder that’s good for nothing but big charges in magnum calibres. Thin skinned game ( or human miscreants ) can easily be taken with light loads at short to moderateranges, with three or four times as many shots per can of powder.In case anyone thinks that the need to conserve powder in that way is unlikely, we all surely remember the seizing of NGA’s consignment of ammo at Durban docks. The ammo was seized on an invented excuse, and took NGA two years and a lot of money to sort out in court. Now, PMP is out of production, at least it’s 9mm ammo line is, on the say so of SAPS. It is astonishing that a big company with billions at stake and a substantial export market to serve, can be closed at the whim of a cop. But that’s what is happening. If you want 9mm ammo you have to load it, and for that you need components.And now that government is having such difficulty enforcing the FCA, what’s betting that the next line of attack will be stopping or limiting local production of ammo and components, and preventing import.I have no advice as to how to get around such a scenario. I’m just making the point that methods of conserving what one has might not be so wild, and that cast bullets, light loads and the like, might have a place.[Originally posted to SATalkGuns -- Admin]

Lathes

Posted by on November 11, 2005

A couple of tips about lathes that might be worth mentioning.  For handgun work and the related tool making they don’t need to be very big.  About the size of a Myford or Emco Compact 8 is good.  The Myford is 19″ ( 480mm ) between centres, overall length just over one metre, weight about 100 kg.Used lathes can be bought quite cheaply if you are prepared to make an effort looking, plus a bit more effort refurbishing.  A buddy of mine recently bought a South Bend of 4.5″ centre height x 33″ between centres for only R1500.  It needs some work but is in decent enough condition that it will be nicely serviceable when the work is done.  The work is within the ability of a hobbyist.  That is also quite big for a hobbyist, long enough to profile and chamber rifle barrels.There seems to be a fixation with high speed, but it is less important than low speed.  My little Unimat 3 runs up to 4000RPM.  I have never needed more than 1500 even for polishing.  1500RPM is useful for getting a good turned finish on firing pin noses which are about 2mm diameter.  Few things in gun work are smaller than that.  My old Myford has three direct speeds, 200, 350 and 640RPM.  It has three indirect speeds all slower than that, the slowest being 35RPM.  I seldom need more than 350 even for pins, screws, action screws, and lots of things around 5 or 6MM diameter.  The highest speed of 640 is slow for firing pins but enough for most anything else.  I use 200 RPM more than any other.   The low speeds are needed for large diameter work.I’m planning to make a little roller bearing headstock for mounting on the bed ahead of the main headstock.  It will be driven by the main headstock spindle but a pulley arrangement will allow up to 2000RPM for small parts.  It will use the existing saddle and tailstock.  It will be a cheap and easy way to get the high speeds needed occasionally for very thin work.I use free cutting steel for most of my work.  It has slightly more lead and sulphur and machines faster and to a better finish than ordinary mild steel.  It is also kinder to the lathe.  My lathe must see me through my time, so I must care for it, and free cutting steel reduces the load on the lathe and thus the wear and tear.  Don’t use construction reinforcing steel.  It is mostly high tensile ( heat treated ).  It is hard and tough, is difficult to machine and to get a good finish.  I wouldn’t touch it.  The apparently high cost of free cutting is nothing when looked at in terms of the cost per component or tool made.  6mm Costs about R5 per metre and 20mm about R30 per metre.If you find a lathe in respectable condition without a chuck or with a clapped out three jaw chuck don’t worry about it.  Buy a new four jaw chuck and use it for everything.  Three jaw chucks are nothing more than convenience tools.  Four jaw is hugely more versatile and permits precision work that can’t be approached by a three jaw.  Good Taiwanese four jaw chucks up to 150mm were available for about R1000 last time I looked.  It will mean you’ll have to make a backplate or get one made, but that’s neither difficult nor costly, and backplate mounting is the most accurate anyway.Lathes must be set up carefully, or they won’t turn parallel work.  That’s because the beds twist under their own weight, so the feet must be shimmed to get them level.  Mine turned way out of parallel before I set it up.  Can’t remember how much but it was a lot, somewhere around three thou in three inches ( 75 microns in 75mm ).  That would have been five or six times as much over it’s full turning length.  It isn’t noticeable over short lengths, but sooner or later you’ll need to turn something long and precise.  Longest thing I’ve made so far is a lapping rod for scope rings.  It’s 280mm long because that was the length of a piece of free cutting I had.  It tapers one half of one thousandth ( 12.5 microns ) from end to centre.  That’s diameter, so the lathe is out 6.25 microns in 280mm or 2.5 microns in 100mm.  I suppose some lathes are more accurate than that, but it’s more accurate than any gun work I can think of.  It took all day adjusting and testing to get it that good.Stand a lathe on a steel stand not a wood bench.  Wood benches move with the weather so you’ll be continually adjusting it.  Steel cabinet stands are not too hard to make.  Best is probably to get a sheet metal company to make one.  Don’t think it would be outrageously expensive.  Metal is not too thick, haven’t measured mine, but probably only one millimetre or so.  The drip tray should be thicker, 2.5 should be enough.  Then you need two mounting blocks, bright drawn would be OK, for mounting the lathe feet.  The feet and blocks should be bolted through the tray, and the whole stand bolted to the floor.  This makes excellent stability, so once levelled the lathe will stay level.[Originally posted to SATalkGuns -- Admin]

SMLE

Posted by on November 5, 2005

I’ve mentioned calibre conversion of the SMLE before.  The 303 British is a good calibre, so the only reason for conversion is the increasing obsolescence of the 303 and future availability of components.  Of course, if the barrel is good, cast bullets can be used, or factory ballistics can be duplicated by copper plated cast bullets.  That would need a custom mould but that can easily be made.But I have other ideas in mind.  In particular, the SMLE bolt head and extractor are right for belted magnums. Also, the method of extraction and ejection needs a case rim or belt of sufficient diameter as the rim slides along the left receiver wall before contacting the ejector.  A smaller rim doesn’t work too well because the extractor hook doesn’t reach far enough left to keep the rim against the left wall.  In other words, a smaller rim doesn’t fill the space between extractor and left wall, and is thus a loose fit and does not extract and eject reliably.I found that the 30-30 case works reasonably well but not quite well enough to use with a standard bolt head and extractor. I figure, though I haven’t tried, that a minor adjustment of the bolt head to allow the extractor to “bite” a bit deeper, would handle the 30-30 very nicely.  The Ackley Improved version of the 30-30 is practically up with the 308 Win ballistically.  The SMLE barrelled and chambered for the 30-30 Improved with a short barrel would make a very nice light rifle.Yes, I know the belted mags are too much pressure for the SMLE action.  But not with BP loads.  The 458 Winmag with a heavy cast bullet should work very well at not much more than shotgun pressures.  And don’t forget that belted magnums headspace in much the same way as rimmed.  OK, the 458 might be a bit short on capacity for BP loads.  Maybe it would be better with a smaller calibre bullet, say a heavy 30 cal or maybe a 458 necked down to 40 or 375.  The old 303 Lee Metford load was a compressed BP charge behind a 215 grain bullet at something like 1800 FPS.Sure, the ballistics are not impressive by modern standards, but a 500 grain 45 cal bullet at 1500 FPS is not to be sneezed at.At BP pressures brass is not a problem as cases can be lathe turned or fabricated.  A friend of mine fabricated a batch of twenty cases for a 50 BP Express rifle.  Because of pressure limits, velocity is limited to about 1350 FPS.  But believe me, a 50 cal cast bullet at that velocity is a reliable game getter at modest ranges.  And if the brass can be made so can the powder if push comes to shove.  That only leaves the primers.  Anybody know what the BP primer compound is ?  Potassium chlorate is the main ingredient I should think.  It was once readily available. Is it still ?  So who cares if it’s corrosive.  Barrels are easy to make so can be replaced anytime.The SMLE magazine would need to be modified, but the best is to make magazines to suit the desired cartridge.My enthusiasm for the SMLE doesn’t mean the same can’t be done with the 98 Mauser for example.  But if it is not to be limited to single shot, the mag lips must be modified.  Once modified they can’t be used for anything else.  Might be a better idea to alter the lips, but not to feed a particular cartridge, rather to make room for a detachable box mag.  The mags can be made for any cartridge.Why would that matter ?  Barrels don’t need to be screwed in very tight.  It is therefore easy to use one action for various cartridges.  Why ?  I’m just stretching my imagination to a possible scenario in which brass might be all but unobtainable.  That would mean using whatever is available, which could vary from time to time.  It’s a lot easier to make barrels than brass, except of course the lathe turned or fabricated variety.I don’t recommend opening the Mauser bolt face for the belted magnums.  It is case hardened and machining it removes the hardened surface at the edges at least.  Besides, once altered it can’t be reversed.  Rather leave it as is and rebate the case rims.  That’s easily done with a fixture in a lathe, and how many cases does one need to feed one rifle?There’s a lot to this, guys, the possibilities are unlimited with a bit of ingenuity.  Other opinions are welcome.  That’s why we have SAtalkguns, right ?  It’s surely why I write this stuff, to see what comes outa the woodwork![Originally posted to SATalkGuns -- Admin]