This is a re-post. I mistakenly posted this in the Paper-patch section yesterday and I want to get this in the correct section for comment.
I have been working with different alloys for the target rifle matches for fifteen to twenty years now.
None of the following applies to Paper-Patch bullets or some may, I just have not spent as much time experimenting with them and I would like to limit any discussion to the Grease Groove bullet in this thread. And a good discussion I would enjoy having! PP alloy requirements are a somewhat different animal and can be discussed elsewhere, please. I hope to not turn this into a GG/PP compare and contrast.
Thanks!
The suitability of the long time Lead/Tin alloys used for BPCR have been worked over by everyone.
50/1, 40/1, 30/1, 25,1 and 20/1 were the main stay. 16/1 has been the new darling for the long nosed high Bc target bullets as of late and for good reason. Though only slightly harder than 20/1, the 16/1 has been tested to show more resistance to nose slumping than its close alloy - 20/1.
I've shot a lot or 16/1 and have had great success with it. Although, the 16/1 bullets are not magic bullets and the full range of problems can still be had with it too.
By my experience, there is no need to use the high tin alloys to shoot the more traditional short radius nose profiles. Their short nosed geometry proves strong enough and stable with the lesser alloys. But, in the target rifle-BPCR match shooting world, like anything else, competitors use every advantage available to them. One of them is the long, unsupported, low drag bullet nose. The so called "money bullet" is one example but there are many more. Especially when the targets are 600y distant or with Creedmoor shooting, the distance is 800, 900 and 1000 yards, then the small improvements to the bullet's nose add up over the 30 shot or 60 shot final scores. In other words, if you are shooting blunt bullets or bullets made blunt and off center by soft alloy in long-range matches, you are suffering death by a thousand cuts.
This would be a good place for a picture of bullet nose examples but I can not pot pic's just now. I will work on that. anyway....
I've taken to shooting various Lead-Tin-Antimony alloys in Match shooting. Years ago, common knowledge, received wisdom and wives tails stated that shooting the widely available wheel-weight alloy and/or any amount of Antimony in your BPCR alloy would grow hair on your hands. Or more to the point, leave lead in the barrel and produce poor accuracy. I never found this to be true. Not one little bit. When leading occurs and it does often when shooting GG bullets under a hot sun like in a Long-range match, I have never found Antimony to be the sole source of leading. Other reasons can and do cause leading and jumping to conclusions is the easy way out but not the helpful solution.
You will notice I have avoided the mention of BHN values because of the differing values produced by the various brands of testing devices available to us at our price point. BHN can be covered but elsewhere too. As long as YOU know what your hardness values are on your tester and can reproduce it - your good!
My best accuracy-least leading bullets to date are made of something close to but not an exact alloy of 97.5PB-1Sn-1.5Pb. I make my alloy in large batches of 200+ lbs and have had nothing to complain about. If you are faint of heart and need to have "certified metals" to sleep at night, the following alloys can be constructed by ordering metal from the likes of Rotometals, a sponsor here or others and come to exact ratios. I have found that close is fine and the least of the big picture.
A useful alloy for the big target guns:
Lead-Tin-Antimony or Pb-Sn-Sb by percent
97.5 - 1 - 1.5
This can be made by mixing 50%-50% wheelweight-soft lead and adding 1% tin to that. Easy- yes? I do not recommend adding 2% tin to the mix. This results in a greater amount of Tin than Antimony. Not good. Adding 2% tin, as often suggested does not help cast-ability much and has the unwanted effect of produces hardness changes in the alloy over time. In other words, in my experience, the addition of the second 1% of Sn in the mix produces an alloy that is not time stable. The stated 1% tin alloy is time stable and casts fine. Keeping the Sn equal to or less than the amount of Sb in the alloy seams to result in a stable hardness.
I have used many small variations of this. I used to mix (in small batch) 30 lb wheelweight with 45lb soft lead and add 1% tin and this worked well and really great for the lighter loads used in 45-70, 40-60 Maynard, 38-55 but was lacking in big charges used in L-R loads, the 45-90, 45-100 and such.
Next week I am going to batch up a ratio of 100lbs WW with 60 lbs soft lead and 1% tin added; a mix I have shot before. It is useful to BPCR and shoots very well. This should produce a mix that is close to 96.5 Pb – 1.25 Sn – 2.25 Sb. I want to test this alloy some more but it may not be needed to meet the desired goal and there for not a good use of the extra antimony base metal. I can re-blend it with more soft lead if there is no clear advantage.
I would be interested in anyone’s experience using this for BPCR.
Michael Rix