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 Post subject: NOE .217 cal 30 gr BBTs
PostPosted: Wed Dec 14, 2016 9:03 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8988
Location: Coalmont BC
I found some time today to cast some of the new .22 cal Bob's Boattails from NOE.... I used 1% tin in pure lead, and a temperature of about 840*F because of the tiny size of these bullets.... I have found the smaller the bullet, the hotter the temperature the lead needs to be, to properly fill out the mould.... They looked pretty good while I was casting them, no wrinkles on the body, but when it came time to sort them I found that over 2/3rds of the HollowPoints had a couple of small wrinkles so that the nose was not perfect.... Since some were fine, this is not a mould problem, but not quite enough temperature in the melt.... probably another 10*F would have made most of them perfect.... Alternately, a bit more tin might make the difference, but at over 800*F, the tin tends to burn out of the alloy, so just more heat might be the best answer.... Here are what they look like....

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If you look at the HP on the upper right, you can see a couple of small divots in the HP rim.... compared to the perfect HP on the upper left.... In two hours of actual casting time (not including setup, melting the lead, and preheating the mould) I cast about 600 bullets, half were solids and the other half HPs.... Here is a photo of them....

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The 2nd quality HPs are on the left (over 200), the solids are in the middle (nearly 300), and the perfect HPs are on the right (about 90).... The solids weighed 29.6 gr. in this alloy, and the HPs were 27.4 gr.... and you couldn't weigh any diference between the perfect ones and the seconds.... so I can use the seconds for Chrono testing and possibly target work, depending on how accurate they are, and I will save the first quality HPs for hunting.... As cast, the bullets were very close to the design size, which was 0.217" at the back of the nose, 0.211" in the middle, and 0.219" at the rear band.... They were pretty good for being round, within about 0.0005", and the diameters varied about 0.0005" from bullet to bullet, just due to temperature and technique I am sure.... That's what sizing dies are for, right?.... Here are photos of the beautiful NOE Moulds....

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There is a Lyman style HP pin in one cavity, and this mould is for the smaller size that is available.... The larger one is 0.220"/0.222".... ie 0.003" larger in diameter....

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The barrel for my Regulated Disco Double project gun is a TJ's designed by Sean Pero and I, and supplied by Mike for airgun use.... The designed dimensions are 0.217" groove, 0.213" land, with a 16" twist, and I have to say, it's very close to those dimensions.... I pushed through an oversized (.257) bullet and got a groove diameter of 0.2168".... I purchased an NOE Sizing Die Body and some of their new airgun size bushings, so this was a good chance to try them out.... As part of the initial testing I will be seeing if there is any difference in velocity between differently sized rounds, so I ran some solids and (2nd quality) HPs through my new NOE Sizing Die, using bushings of 0.218", 0.217" and 0.216".... This is the first time I have used the NOE sizing bushings, so I was curious as to how close they were to the size stamped on them.... It turns out that when I sized my bullets, at least with this alloy, they came out exactly 0.0002" smaller than the marked size.... Here are the sized bullets, both Solids and HPs, and the bushings.... It is a great feature to be able to try different sizes at a cost of less than $10 per bushing.... As expected, the 0.218" bushing didn't touch the nose and gently sized the driving band.... the 0.217" bushing just touched the nose in some areas on some bullets and sized the band.... and the 0.216" bullet sized about a 1mm long ring at the back of the nose, and sized the entire band but without dragging any lead aft onto the boattail.... I wouldn't want to size more than 0.003" in one step, there was a fair resistance with the smallest bushing....

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I took a few of the unsized solids and pushed them through some different .22 cal barrels I have here.... Now remember, the back of the nose is 0.217" and the driving band is 0.219".... The Disco barrel I had here required no effort at all to push the bullet through.... In fact, it FELL through the bore, from end to end, under it's own weight.... So now I know that standard Crosman barrels can be pretty big!.... I pushed one into the barrel I will be using on my Regulated Disco Double (which at present is unchambered and unchoked) about an inch, and then back out the same end.... I had an MRod .22 cal barrel here, so I pushed three bullets into/through that.... one just past the port, one about 1/2 of the way through (both of those back out through the breech), and the other one right through from breech to muzzle.... There was a noticeable increase in resistance about 3" from the muzzle, so it appears that the .22 cal MRod barrel is choked.... Here are the bullets....

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The MRod bullets are on top, from L to R, through the choke, 1/2 way through the barrel, and just past the port.... My TJ's barrel is the one on the bottom.... In the TJ's barrel, as expected, the 0.213" rifling engraved both the nose and driving band, pretty much missed the middle (as intended, to reduce drag), and the 0.217" grooves shaved off a bit of the drive band, which was 0.219".... In the MRod, the bullet (on the right) slid into the chamber right up to having the drive band just past the barrel port and then stopped and required a bit of force to chamber it past the port.... not a lot, you should be able to chamber it with the bolt.... In both that bullet, and the next one, which was pushed about halfway through the barrel, you can see rifling marks on the drive band, but none on the nose.... There are no marks from the grooves of the barrel on the one just chambered, but there are a few on the middle bullet, which indicates that the groove diameter of my MRod barrel is about 0.219".... On the bullet that was pushed through the choke, you can see a few marks from the rifling on the back of the nose, and the driving band is deeply engraved, and in fact it is sized down by the choke, and now measures 0.218".... This means that the riflng in the MRod barrel is only about 0.001" deep, with the barrel being 0.216" land and 0.218" groove at the muzzle, about 0.001" larger than that throughout the bore, and about 0.218" land and 0.220" groove just in front of the port.... I would think that these bullets, as cast, might work pretty good in a MRod, chambering without too much effort, sealing OK in the bore, and not losing too much going through the choke.... However, that is for someone with an MRod to test....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
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Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Thu Dec 15, 2016 10:28 am 
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Joined: Sat Nov 26, 2011 9:35 am
Posts: 96
Location: Eastern Ontario
Have you tried heating the mold(s)?
Used to do this when casting parts years ago.
Grunt


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PostPosted: Thu Dec 15, 2016 11:38 am 
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Location: Coalmont BC
Yes, I preheat the mold on a hotplate.... If the lead is not hot enough, small bullets are problematic.... there is simply not enough heat in the small amount of lead to heat up the much larger aluminum mould block and keep it up to temperature.... The bigger the bullet, the cooler you can run the pot and not get wrinkles....

Bob

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Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


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PostPosted: Thu Dec 15, 2016 1:43 pm 
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Joined: Wed Jan 05, 2011 12:35 pm
Posts: 6077
Location: P.G. B.C.
I rest my moulds on the top edge of the pot to heat them up as the lead is melting. With HP moulds, the stem must be heated separately as it sticks out the bottom of the mould. A cooling HP stem is usually the worse problem for casting. A spray with moly will help on the stem, however having a propane torch running with a semi-soft flame to stick the HP stem into before replacing it into the mould. A too-cool stem will cause casting defects on the rim of the HP hole due to too-quick shrinkage of the lead at that area - from the too-cool stem. If the stem is slightly too-hot, the mould blocks themselves will quickly moderate it's heat, however if the stem is too cool, it will draw heat from the mould and the result will be more defective bullets. When casting in cooler weather, keeping the moulds hot enough, especially with small bullets, is a tough chore. Having a HP mould makes it even more tricky.

They look great, Bob. I haven't tried my new 4-cavity .25NOE FP mould yet. -23 last few days - too cold for casting, as I cast in the car port.

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Daryl


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