Bullet Length and Velocity in Spencers

[Herbert]

I was put onto this site(TMT Enterprises Priecision Ballistics and Records)to calculate twist rate,bullet lenth and muzzel velocity for optimum staybility.I found it very easey to use and explanes whey i am geting good acuracy with a ,975 inch long bullet and not with shorter bullets it suprised me ,aperently velocity or lack of it is the main reason for acuracy,with this information loads with shorter bullets can be worked out or if licke me you are planing to rebarell so you can youse a short bullet at around 1000fps you can get the right twist rate to suit

http://www.uslink.net/~tom1/

[.56/50 Iron]

Herbert:   I re-read your note but I guess you did not state what range you are shooting your Spencer at?  I have set a maximum accurate range of 75 yards on my Carbine although it probably would shoot pretty well at 100 yards. I just have no use for it at that range as I am not going to drive a crew away from a cannon! I am using Lyman #518145 bullet that weighs 350 grains using soft lead alloy. Length of this bullet (not entire cartridge) is .735" . I size this bullet to .512" and use 41 grains of Swiss FFg powder to get perhaps a bit over 1000 fps out of it. I generally get pretty nice accuracy out of this load. My carbine is currently at the Chiappa warranty station in Dayton, Ohio for some work as the barrel came loose after I tapped on the front sight base. Should not have come loose with this minimal tapping. I told Ron at the warranty station that I did not think that the barrel was tightened properly and wanted it tightened and then sealed in place with one of the grades of removeable Loctite (tm). Also told him that some of the guys on this list have not gotten what they felt was top accuracy and that barrel tightness, or lack of tightness, has everything to do with accuracy. I asked him on the phone yesterday if the the barrel had been Loctited and he said it had. The carbine is supposed to be sent back to me this week... I will see if there is a change in accuracy when it gets back. I had a couple of instances where the group of holes on the target would change where it hit on the target. What does your bullet weigh? I have looked in many places trying to find a use for bullets heavier than 350 grains in the .56/50 Spencer cartridge and could find only mention of one old factory load that used a bullet of 450 grains. All military loadings for the Spencer that I have found used 350 grains. If a bullet heavier than 350 grains  is used in the Spencer case, there is not much room for a powder charge that would shoot the bullet accurately. It would fly quite slowly and accuracy would not be very good. Accuracy at 75 yards may not be very good either. Another problem we have today is that we cannot use a bullet with the profile of the original Spencer bullet as that slug is too pointy  to be used in the buttstock magazine with a center fire primer. Some fear that the recoil of the carbine would shift the cartridges in the magazine enough to slam fire the cartridge ahead of it. The Lyman 518145 slug has a pretty  good bullet profile and a seating depth that is almost exactly the same as the oriiginal Spencer bullet was seated in the case. I can get 41 grains of Swiss FFg in the case behind the bullet with only a tiny bit of powder compression. The bullet has a broad, flat tip and should be fine in the magazine tube. The warrantly  center uses Ten-X factory .56/50 ammo to test fire the guns that come in for warranty work. My bet is that the bullet in that ammo is 350 grains in weight. I will try to find out. No way could I afford $144 dollars per box of 50 rounds of that stuff!!  So, I hope you keep working on your end with your Spencer. Sooner or later there will be a lot of good information out there for guys to draw on. This cartridge has not been worked with in over 140 years, so there is plenty of room for work!
Thanks,
.56/50 Iron

[Herbert]

the site shows that to get optimum staybility in the spencer for a given bullit lenth( you already know the twist rate and bullet lenth) for example in a armi sports carbine with a 1-26 inch twist rate .512 groove diameter and a .733 inch long bullit optimum stability ocures at 431fts,now this is opisit to what i thort( i thort faster would be beter)so i tested te theory in practice with a armi sports spencer rifle 1-20 twist rare with a .975 inch long bullit30 gr FF pouder.512 groove diameter,acording to the program the optimum stability is achived at 452fts very close to what i am geting with this combination and very acurate at 100 meters,i also tried the same program on two other original spencers,a Burncide carbine with a 1-34 inch twist rate and.520 groove diameter,bullit lenth is .775,optimum staybility is 775fts ,when i got closest to this velocity i got the best acuracy at 100meters,the other rifle is a sprinfield coverted carbine to rifle,twist rate 1-42 inch groove diameter .512 bullit lenth .733,optimum staybility achived at 1100fts yoused 41 gr Curtis & Harvy fine rifle pouder to achive this through the 32 1/2 inch long barell,it was the standout for acuracy,at 100, 200,300 meters with 10 shot groups at 100 meters being around the 2inch mark between cleanings,and constant out to 300meters,this rifle is a lot easer to shoot because it has beter sights the shooter was a army sniper who has won at bisley,much beter shot than me,all shooting was dun of the bench,my conclusion is this program shows you were the sweet spot is for a certain set of constants in any rifle and is a very good methord of tusing the best barell for a given bullit lenth and velocity you are after in my case the shotest bullit and the highest velocity i can get for the best acuracy,i have always belived that a rifle should be as acurate and powfull as the cartrige will alow