The secret behind JSB accuracy
I think I made a huge discovery, I think I found the secret behind one of the most accurate pellets.
It all started when I was playing with a JSB pellet and going nuts asking it why are you so straight? It then jumped out of my hand and fell hitting the floor, hard.
I picked it up and to my amazement I found the skirt on the pellet bent it’s strange how soft these pellets are, a bit too strange. I did a finger nail test on the pellet and I can scratch it pretty easily, I tested other cheap pellets and they were alot harder than the JSB.
I tested some pure lead that I had and it was harder than the JSB pellets.
I think that the JSB are made of a lead-tin alloy, just like the alloys they use for soldering.
Sure the pellet dimensions are important for determining accuracy, but I think that’s what makes JSB pellets unique.
What do you guys think?
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RC, you surprise me. Have you not heard the story of Archimedes? The king had a crown made of gold. Later he became suspicious that the goldsmith had stolen some of the gold by mixing in another less precious metal. He summoned Archimedes and ordered him to determine whether or not the goldsmith had cheated him. Archimedes left baffled. How was he to determine such a thing? He went to the baths and pondered this question. While he was soaking, he noticed that everytime someone entered, or left the bath, the water would rise and lower. He noticed that the amount of rise and fall coincided with that person’s girth. He realized that materials have a specific density…and that the amount of different materials can be calculated by how much they displace. Hence, Archimedes law of bouyancy. It is said that he leaped out of the bath and run through the streets yelling, “Eureka!”, when he figured this out.
For the moment, I will revel in the satisfaction that I may have known something that RC doesn’t. However, I am certain that within the hour, RC will set me straight. I am hoping that Uncle Hoot will chime in with his charming witt and that WOK will change his avatar to something that will mock me without mercy. 😉
Quoted from WIKIPEDIA:
“Pure lead is undesirably soft for casting bullets not requiring such expansion. [Tin is a common alloying element. “Lead alloyed with a small amount of tin fills out moulds more uniformly than pure lead. Tin also increases the hardness of cast bullets up to a maximum at about eight to ten percent tin.” Tin is relatively expensive, so many modern alloys rely upon antimony to increase hardness while retaining the casting advantages of a minimal addition of tin. Linotype metal is a eutectic alloy………………..
I have shot PURE TIN PELLETS and they are super light and SUPER HARD.
No amount of testing on your part is necessary, TIN is HARDER than Lead. That is just a fact.
Why do you think in the HISTORY of ammo making that no manufacturer has made a TIN cored bullet or even a TIN bullet. Its always LEAD for expansion and NEVER “TIN” for expansion.
GOOGLE IS EVERYONES FRIEND YET NO ONE USES IT ❓
David
I am sorry, but I doubt your ability to test lead to tin by a “density” test.
Even a lead hardener test will only tell you the hardness of the lead, but not the alloys to get there.
Tests are available, but the equipment is pretty far out there.
Now something new in testing lead alloys may have happened in the 40 years I have been doing this, but I have to call bullshit, like I did with your comments on the BSA scope being clearer than the Ziess.
You continue to “entertain” me.
RC
OG (The Midnight Threadjacker). 😆
My HW barrel is forged with a tapered bore. The process seems to produce the least pellet picky barrel. I’m not sure HW still makes barrels.
I brought up the choked bore because it seems to be the most pellet picky type of barrel of the four techniques (granted I haven’t used the smooth twist type). I would imagine that push cut and button pulled are end choked, have you noticed a difference between pushed and pulled rifling barrels that have been chocked in terms of them being pellet picky?
Squeezing the end of the rifled barrel to create a choke sounds right. It was late and I couldn’t remember which technique was used.
Interesting to hear you are having the same issues with the larger JSB pellets. Thanks for mentioning that even though they are not in 17 caliber… 😉 Have you been having issues within tins or just from tin to tin?
JSB has really dropped the ball recently on their pellet manufacturing processes. The good tins are good but I have to buy twice as many and then hope there are some good tins in the batch… 👿
I would sure love to return the 3000+ bad pellets I am currently holding. :banghead:
So far they have become my chrony testing pellets. Considering the new EdGun gets over 150 shots per fill I go through a bunch for each speed session.
Oh and OG, if you get a chance can you take a quick look at my velocity report in the Matador 177 post in the EdGun section? I could really use and appreciate your thoughts on the results. Thanks!
Instead of doing a chemical test, I can do a density test and may be determin the exact ratio of tin present if any.
I have choked some barrels myself and it seems to work no matter how bad the choke is. Even a choke that is not concentrinc or perfectly round, works pretty good, on a B21 (springer) the gun groups at half inch at 20 meters.
I have a theory of my own on how the smooth tiwst is made, and I would like to hear what you think your goatness on this one.
Imagin a hexagonal bar that is gun drilled (i.e has a very smooth un rifled .22 hole through it) and instead for compressing it from the outside, it is rotated (spinned/twisted) at one end and being a hexagonal bar means that the thicker parts are rotating at a higher speed than the thinner parts.
It also means that the inner hole is getting thinner (i.e it is getting compressed) now if the spun part is only 10 cm (I think in metric units so pardon my French), the middle part of the 10 cm will have a higher twist rate than the ends.
Now imagin also that the 10 cm part is parted at the middle and the small 5 cm part thrown away and now you have a smooth barrel that has a .22 hole that is getting tappered and spun. It will genlty swage the pellet and spin it in a progressevly higher rate.
I made a reg with gears to test this theory out, but so far gun drilling is the main problem I am facing, can’t find a shop that gun drills.
I have noticed that in my pellet testing that the skirts fill out under high pressure and fully obturate. I am less uptight about dented skirts with the pellets that have thin skirts. I know that the thin skirt will open up and conform to the lands and grooves.
So far, my red tin .25 JSB Kings have been accurate, but then again I’m not a very good shot. 😉
I think that the choked barrels are just put in a press and the end of the barrel is squeezed down a little. RC knows a whole lot more about this than I but, I think that there are only 4 different kinds of barrels currently being made. All 4 of them have a somewhat bore sized hole drilled in them to start.
The conventional rifled barrels then have a cutter pushed thru the bore and it cuts the bore and grooves.
The button rifled barrels have a “button” pulled thru the barrel and it cuts the bore and grooves.
Hammer forged barrels have a mandrel, that is of the proper bore and groove dimensions inserted into the bore and it is then put into the hammer forge. The hammer forge beats the barrel down until it is “mashed” around the mandrel. The mandrel is then pulled out of the barrel. The mandrel has a slight taper on it, if it didn’t, it would be a tough bastard to pull out! BSA, CZ and TJ’s barrels are hammer forged.
The 4th kind of barrel is the FX Smooth Twist. It is just a hollow tube that has been put in a press and then had 6 rounded grooves squeezed into the last 3” or so of the muzzle end.
I am frequently wrong and this just might be another time!
I hope to be able to soon give up on JSB pellets. My last couple of 12 tin 25.4 JSB orders have been all over the place, head, skirt diameters and weights. I try to weigh sort them, keep the different head sizes separate and push all of them thru a .255 Lee sizing die. It takes a lot of time to do all of that. Even after doing all of the above, I can see some of them wobbling around before they get to the 100 yard target.
Wednesday, I got my Hart .257” barrels back from my machinist and I hope to be able to fire lap the one for my R3 25 long Matador and get it up and going this weekend. The Boss/.257” project needs to have the brass transfer port sleeve made and it is another week out. I will use my cast bullets in the Matador and the Boss. I really hope that it works out for me. Casting is also cheaper. My cast 55 grain bullets cost me 0.6 cents each and a 30 cal JSB pellet costs 8 cents each.
I sent some of my resized bullets to Knifemaker and they shot very well out of his crappy LW barrel. I just sent him a .257” TJs barrel that I wasn’t going to use and I also sent him an ass load of sized bullets for it. Can’t wait to see how Mike’s setup does!
Sorry for the thread hijack; I get off from work at midnight, have a few beers and tend to highjack threads! 😯 😆
I find the taste test works every time… 😉
And how are you going to do that?
Do you have a full metallurgy lab?
Regards,
Roachcreek
This is interesting and got me thinking…
Could the way barrels are choked explain a lot about why some pellets are accurate and some are not.
It is my understanding that the choke is made after the barrel is rifled?
Knowing that all steel isn’t totally homogenous or the same hardness throughout could it be possible that the chocked part isn’t as concentric or perfect as the original rifling?
When the choke is created what is to stop it from deforming at a non-continuous rate inside?
Do they put some type of reverse rifled insert in the end of the barrel to make sure the choked bore is a certain size and is uniform?
And does the deformation ability of softer lead pellets allow less than perfect chokes to impart less effect on the trajectory?
My LW barrel (muzzle choked) is somewhat pellet picky. My HW barrel (taper choked) is a lot less picky.
Interesting post David!
Oh, have you been using the new red label JSB heavies in 177? I have found that six out of twelve tins have been super accurate (3/8″ groups at 45 yards) and the bad tins are grouping at about 1 1/2″ at 45 yards…
When they come back in stock i’m going to order another batch of twelve and do the same tests again. Hopefully I don’t get twelve tins of bad ones… 😯
Don’t know about that but I have a tin solder that is 40/60 lead/tin and it is way too soft.
I’ll do a quick chemical test and check it out.
I believe JSB pellets ARE pure lead.
If its SOFTER than your pure lead block then your block isn’t pure lead. I have about 5 blocks at 18lbs apiece that are pure lead like the JSB’s. The solid 18lb block I have is “CHEWED UP GUM FRESH OUTTA YOUR MOUTH” SOFT. 😆 Drop it too the ground even on a corner and the block just about sticks to the ground while on edge.
Lead and Tin will NOT make a bullet or pellet SOFTER than PURE LEAD. Tin helps the bullet FILL THE MOLD better and more of it will actually make a bullet harder.
But your thinking is SPOT ON about the pellets skirt and head. Being as soft as pure lead is in pellet form, the pellet FORMS to the bore/grooves better upon FIRING. The skirt expands at the blast of air and obturation happens which helps seal the bore.
Just sayin
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Perhaps Steve, but I suppose history has hidden some facts, if not made up the story in the first place.
But how are you going to tell what specific alloy is in there by how far the water goes up? If that was the case, bullet casters would have used that test for centuries now.
It may tell you the specific gravity of the unknown materials by water displacement, but the actual metals in the alloy would remain unknown.
Nice try tho.
RC