|
|
Post by edge on Dec 29, 2008 18:00:24 GMT -5
Personally I am amazed how quickly folks give up on accuracy. IMO, most folks would not be happy with their first range visit with a 4 MOA group. However I am a stubborn SOB when it comes to making my bullet of choice shoot. This will be my personal journey with a particular bullet/sabot. This started a while back when I decided that I wanted a long range bullet with plenty of energy when it arrived, whether I ever use it on game is another matter. I have one field where I can set up targets at very specific distances from two shooting locations. I shot a buck a while back at about 325 yds with the 308 accubond and from that location I can set a target at 416 yards. That same target can be shot from a second vantage at 622 yards. That location can also shoot 90 degrees to a target at 805 yards. So here is my goal: Hit an Elk kill zone at the 805 target with 2,000 foot pounds ( 1500 foot pounds @ 1,000 yards. ). Now I will probably never hunt Elk, but it is fun to know that if the opportunity came up, that I could do it  So to back up a bit, I asked for some .338 250 grain Accubonds for Christmas...which Santa brought The good/bad news is that I am off work from Christmas til after New Years...good for hunting, but bad for making sabots. I made a guess as to the sabot design and came up a bit short  As you can see the bullet shank is about 0.200 longer than the sabot:  Since I don't have access to a lathe at home I decided to shoot a few anyway to see if they would stabilize and whether there was any possibility of getting these to shoot. I went hunting this morning and after not seeing any bucks went to the range and shot out my 0.308 Accubond load. I decided to start with a 3 shot group with a baseline load ( FOR MY SETUP ONLY ) The bullet/sabot/fiber wad weigh in at 287 grains and I decided on 80 grains of 10X powder. I expect to shoot more of a slower powder for speed, but this was the first test for stability. As you can see, the holes are round, and as a bonus the group center is only about 1/4 inch from my 0.308 bullet hole, and all shots were at the center diamond target!  Thank you rossman40 for the Target Analyzing software: dougva.proboards.com/index.cgi?board=Savage&action=display&thread=10401I will make some new sabots after I return to work and do some load experimentation. Hopefully I can find a sub MOA load for this bullet, and if I can I hope that it will make those of you that gave up when your favorite bullet wasn't 1 or 2 MOA on your first range visit. Either way, I will let you know of the successes and failures along the way. edge. |
|
rexxer
Eight Pointer
Posts: 184
|
Post by rexxer on Dec 29, 2008 19:03:31 GMT -5
and if I can I hope that it will make those of you that gave up when your favorite bullet wasn't 1 or 2 MOA on your first range visit.
Edge- your kinda cheating in that statement because you already said your sabots were .200 short! I would have to go back and try the longer ones too!!! ;D
Interesting concept on your homemade sabots. Did you make your own mold? Sabot base looks like its not round.what kind of sub-base are you using?
Accubonds look awesome!!
|
|
|
|
Post by DW on Dec 29, 2008 19:09:35 GMT -5
This will be interesting, look forward to seeing some more results.
|
|
|
|
Post by bigmoose on Dec 29, 2008 19:19:04 GMT -5
Friend Edge, Did you say you planning to shoot at 805 yards..WOW
Shades of Carlos Hathcock.
I don't like to brag, but I will, I think I could hit a target at 806 inches away, if you give me 5 or 6 shot, make it ten
I'm glad you seem to agree with me, that testing is half the fun.
Good Luch, though I doubt you need luck.
Marty
|
|
|
|
Post by edge on Dec 29, 2008 19:46:08 GMT -5
SNIP Interesting concept on your homemade sabots. Did you make your own mold? Sabot base looks like its not round.what kind of sub-base are you using? Accubonds look awesome!! The sabots are machined one at a time from PVC-II bar stock. They are essentially round but they are rifled for my 1:14 twist barrel. The rifling angle is most obvious on the center sabot. If you look at the groove at the top of the sabot it is almost centered, but at the bottom it is almost 1/8 inch to the left side. We will see the results together 805 yards is the goal, but it remains to be seem if I can get there....first test is sub MOA at 100  edge. |
|
|
|
Post by SW on Dec 29, 2008 19:50:06 GMT -5
Edge,
What's the cal you are using now - 45? Twist? Twist calculated to stabilize this bullet at the velocity you are shooting or planning to shoot? BC of that bullet at the velocity you are shooting? I continue to be impressed with your work.
|
|
|
|
Post by edge on Dec 29, 2008 20:09:39 GMT -5
SW this is still the same 45 caliber 1:14 twist Shilen barrel that I have used for the last couple of seasons. The 150 grain Accubond 30 ( cal ) is 1.22 long The 250 grain Accubond 338 ( cal ) is 1.57 long Without having chronographed the 338 I am not sure of the minimum stability, but expect to add a bit more fuel so as long as I can burn it all it will only get better as the velocity climbs. Goal velocity is 3k fps but if 2900 is more accurate I will settle there. The rifle is in the 13 pound range so recoil should not be too bad, but for shooting prone I'll bring along some band-aids for the forehead edge. |
|
|
|
Post by hillbill on Dec 29, 2008 21:07:09 GMT -5
You the man Edge, good luck with your load development & by the way GOOD SHOOTING.
Bill
|
|
|
|
Post by CraigF on Dec 29, 2008 21:21:21 GMT -5
Edge, if anyone can get something like this to work, you can! Good look and I look forward seeing the results.
|
|
rexxer
Eight Pointer
Posts: 184
|
Post by rexxer on Dec 29, 2008 22:10:59 GMT -5
The sabots are machined one at a time from PVC-II bar stock.
Edge. I bet alot of people don't realize the machine work involved making those sabots. Adding rifleing to the sabot should make them seal even better. (pretty clever thinking).Most everything I tried to machined, plastic related seem to push away from cutter. Yours look to be clean.
Are them splines or threads and are they single cut? Were the sabots finished on cnc mill? I'm amazed at the time in each sabot. I would think this design is about as close to the perfect sabot. Extremely nice work!
|
|
|
|
Post by edge on Dec 30, 2008 7:58:04 GMT -5
SNIP Are them splines or threads and are they single cut? Were the sabots finished on cnc mill? I'm amazed at the time in each sabot. I would think this design is about as close to the perfect sabot. Extremely nice work! The rifling is an 8 start 14 inch lead thread. I use a Manchester style grooving tool rotated 90 degrees and shimmed to be on center. Since plastic does tend to push away the "thread" is tapered in the machine to take this into account, and depends on how long the sabot is. On these sabots which are 0.850 long the CNC cut starts at the base and cuts 0.005 deeper toward the end away from the spindle which makes for a uniform depth. A shorter/longer sabot requires a different compensation. Since I am a bit anal , I actually machine with a 9 start thread. There are 8 threads in 45 degree increments to match the rifling. Number 9 is @ 5 degrees. After machining I find the 5 degree groove and mark it with magic marker and always make my sawcut in that groove, and also load it into the same Land in the barrel. Someday I may do away with it, but for now I know that the sabot is loaded as consistently possible. The sawcut is just done with a hacksaw. I start it in the groove with the black line. I then insert the sabot into an EC spring collet which keeps the sawcut in perfect alignment. Then rotate 90 degrees for the second cut. Deburring is done by hand and is the longest single operation. Machining is just over 1 minute ( the rifling takes the most time since it slows down to 30 RPM to do that ). Sawcutting takes about 30 seconds and deburring probably about another 45 seconds to a minute. The plastic is about $1.45 per foot + shipping from Mc Master and comes in 5 foot lengths. With setup and machining losses I get 55-60 sabots per length depending on the sabot. That will drop to about 45 for the 338 sabots since they need to be longer. edge. The OD tolerance I try to hold 0.0003 and the ID 0.0005 Any sabots that falls out of that gets marked either Loose or Tight. The same for those at the extremes, ( like a sabot that is minus on the OD and plus on the ID ). |
|
Al
Spike
Posts: 41
|
Post by Al on Dec 31, 2008 4:59:21 GMT -5
Edge, so how far up on the bullet should that sabot go? close to the ojive?
Multipul start threads, I haven't cut them in eons. May just go into work tomorrow and play thou :>)
|
|
|
|
Post by edge on Dec 31, 2008 7:39:11 GMT -5
I would go the length of the bearing surface of the bullet using plastic. If you had a near infinitely rigid lightweight materiel then the sabot should probably be the entire length of the bullet. PVC is a fairly heavy plastic so weight is a consideration. If you molded the sabot for a particular bullet then molding in the ogive would certainly add to alignment. Many years ago I was molding inner sabot halves for use inside regular sabots. Since those 35 caliber bullets were short I molded in a portion of the ogive. The material was polycarbonate and was somewhat lighter than the PVC. Here is a sample in which I coated the inside with whiteout so that the interior shape could be seen:  ,  edge. |
|
|
|
Post by dave d. on Dec 31, 2008 15:40:56 GMT -5
:)bud you never cease to amaze me .goodluck |
|
|
|
Post by CraigF on Dec 31, 2008 17:23:06 GMT -5
Edge, you are the master!
|
|
|
|
Post by edge on Jan 2, 2009 20:15:50 GMT -5
Ten new sabots need to be split, but are closer to the correct length, ( inside view ) for comparison, the sabot is 1.050 long:  edge. |
|
|
|
Post by jims on Jan 2, 2009 21:40:25 GMT -5
Edge: I am impressed with that boattail sabot.
|
|
|
|
Post by DBinNY on Jan 2, 2009 21:47:31 GMT -5
That thing is so pretty it seems like a shame to shoot it. They would look good on the Christmas tree.
|
|
|
|
Post by DW on Jan 2, 2009 23:25:05 GMT -5
Edge: I am impressed with that boattail sabot. Ditto, you do some great work. |
|
Al
Spike
Posts: 41
|
Post by Al on Jan 3, 2009 7:10:26 GMT -5
Ten new sabots need to be split, but are closer to the correct length, ( inside view ) for comparison, the sabot is 1.050 long: edge. Edge, any scientific reason where to put the relief groove? I have some HDPE here, just not sure how nice it's going to cut with the small tooling thou. |
|
|
|
Post by edge on Jan 3, 2009 7:49:43 GMT -5
Edge, any scientific reason where to put the relief groove? I have some HDPE here, just not sure how nice it's going to cut with the small tooling thou. The groove is a matter of trial and error. With a regular jacketed bullet it must be in the base, not next to the bullet or the bullet will expand into the groove. With a copper or a thick copper base bullet like the Accubond you might be able to put the groove higher but I don't know it that is really better or not. My groove is 0.020 below the base of the bullet and 0.015 below the sawcut. Your material and bullet selection will probably require some adjustments. HDPE will probably be very much like a regular sabot and subject to the same limitations of bore/projectile diameter but I'll be interested in your findings since it would make for a very light sabot with a SG <1. As a last thought, I have many many hundreds of sabots that did not work. As tempting as it is to run off 50 or 100 sabots because they "look right", IMO, make 10 or 15 and shoot them all. Analyze the bullet holes and try to recover as many sabots and bullets as you can. I shot great groups and even shot deer before I found out that the groove needed to be below the base. It was not until I recovered a bullet from a deer that I realized that the bullet was expanding into the sabot groove. Here is the recovered bullet from a deer and a sabot similar to the one fired. Note the base of the bullet swelled into the sabot groove and made a near mirror image! :  edge. |
|
|
|
Post by wilmsmeyer on Jan 3, 2009 10:26:45 GMT -5
Edge,
Do you find it interesting that this bulged bullet flew straight and true? Were your holes in the targets indicating this by showing much bigger holes? hmmm
|
|
|
|
Post by wilmsmeyer on Jan 4, 2009 11:59:52 GMT -5
Edge,
Was hoping you would comment on this. I'm not sure that this rear bulge indicated that the bullet swelled in the sabot as paper punching would have showed this very obviosly before taking the load afield. Any comment?
|
|
|
|
Post by edge on Jan 4, 2009 12:18:52 GMT -5
Edge, Was hoping you would comment on this. I'm not sure that this rear bulge indicated that the bullet swelled in the sabot as paper punching would have showed this very obviosly before taking the load afield. Any comment? Actually it may have, but I did not notice it. When shooting sabots I am mainly looking for a , in this situation a 0.323 hole vs a 0.458 sabot hole. I suspect that if I looked more closely I might have seen a hole closer to 0.400 but I am not 100% sure. When I look at a hole, there is generally a small hole followed by a bore sized black ring and then tears in random directions. Would this base bulge make a separate ring...I don't know, but it is a good question. I have shot groups with oversize holes that I have attributed to the sabot but they seemed slightly undersized! If you look at my sabot, I normally thought that the sabot base stayed attached to the bullet and the cut section made the hole, but it may have been the bullet all along. My normal train of thought has been that if the sabot followed the bullet then the BC was reduced so I changed designs. Either way, I think that I have come up with a relatively good design. With unlimited time and funds I am sure that I can make it much better.....and the proverbial monkeys will eventually write Shakespeare...time will tell edge. |
|
