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January 5, 2015, 12:08 PM | #26 | |
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Quote:
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January 5, 2015, 02:02 PM | #27 |
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Clark,
3) full length sizing dies with necks opened up to a couple thousandths less than loaded round neck diameter produces case necks straightest on the rest of the case parts axis. They're the only sizing die type that holds all of the fired case aligned on the same axis while its being sized down a tiny bit. Full length bushing dies are darned near almost as good. If their bushing could be shimmed center in its chamber above the die shoulder, it wouldn't shift sideways a tiny amount as it sized the case neck down. |
January 5, 2015, 03:13 PM | #28 |
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Thanks unclenick, I'm not sure what to do with this info now :-). By that I mean what is an acceptable range? RO is generally acceptable at .003 or less but I don't know or how that translates to bullet tilt. Obviously zero would be best.
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January 5, 2015, 05:39 PM | #29 |
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Bart,
I know your groups are 10x smaller than mine, but I also have sent full length dies back to Forster to have them honed out to my specs on their Hardinge collet lathes: 1) 6mmBR .265" 2) 257 Roberts Ackley Improved .284" 3) 30-30 .326" 4) 308 .330" 5) 30-06 .330" 6) 8x57mm .344" 7) 338 Win Mag .362" 8) 223 .245" 9) etc I have honed out RCBS dies on my big lathe after dialing them in with a pin gauge in the neck. I have made dies with necks a couple thousands under loaded size with a shoulder and a part of the body length. I have done tests on dies with populations with random large selections of brass dedicated long term to a combination of dies. I have compared concentricity and case length growth. 1) The worst dies are Redding FL bushing neck. 2) There a lot of dies in between. 3) The best by a big margin is Lee Collet neck dies. I think it is because of neck thickness runout. The LCND nulls that out by sizing with respect to the inside of the neck instead of the outside.
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The word 'forum" does not mean "not criticizing books." "Ad hominem fallacy" is not the same as point by point criticism of books. If you bought the book, and believe it all, it may FEEL like an ad hominem attack, but you might strive to accept other points of view may exist. Are we a nation of competing ideas, or a nation of forced conformity of thought? |
January 5, 2015, 06:17 PM | #30 |
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Clark, my very straight cases have been made with such honed out dies with a .0015" spread in neck wall thickness.
We must be doing something different if your collet die makes straighter necks on cases. Damned details mask so darned much good info these days. |
January 5, 2015, 06:51 PM | #31 |
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Are you saying you have brass with a neck 0.0015" thicker on one side than the other, you neck down from the outside, making the inside of the neck offset by ~ 0.0015", you seat a bullet in the case, and then measure bullet run out at 0.0000" with respect to the case? as good as Lee collet neck dies?
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The word 'forum" does not mean "not criticizing books." "Ad hominem fallacy" is not the same as point by point criticism of books. If you bought the book, and believe it all, it may FEEL like an ad hominem attack, but you might strive to accept other points of view may exist. Are we a nation of competing ideas, or a nation of forced conformity of thought? |
January 5, 2015, 07:20 PM | #32 |
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No, because a case mouth .00075" off center of the neck's outside diameter means the neck wall's that much thinner on one side and that much thicker on the other. Which makes neck wall thickness vary twice that much; .00150". Bullets can be very parallel to the case axis and have .00075" runout while the neck's outside has virtually zero runout.
Sub .0010" bullet runout's not worth fixing. Does your collet die do that? If so, then you and it are doing all the right stuff. Last edited by Bart B.; January 5, 2015 at 07:27 PM. |
January 5, 2015, 09:35 PM | #33 |
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I need to measure some more neck run out
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The word 'forum" does not mean "not criticizing books." "Ad hominem fallacy" is not the same as point by point criticism of books. If you bought the book, and believe it all, it may FEEL like an ad hominem attack, but you might strive to accept other points of view may exist. Are we a nation of competing ideas, or a nation of forced conformity of thought? |
January 6, 2015, 12:50 PM | #34 |
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1stmar,
Go back and look at the image in post 12. If, like Abbatiello, you had group dispersion of 3.49 moa per degree of tilt, with 0.174° tilt, you would have 3.49×0.174=0.6 moa dispersion added by that much tilt. But I don't know what your bullets have or how they'll behave. The point of the angle is just to have a consistent way to compare runout measured with different tools by different people to see how much tilt they find matters and how well their tool setup is producing straightness as compared to your own. If you want to see how much difference tilt in a particular bullet makes in a particular rifle, you can test as follows: Drill a bullet size hole in your bench. Select 24 of your worst cases so you don't mind abusing them, and put them together with your best load with your bullet you want to test. Stick the noses of each round into the hole and bend them from the case head to an intentional 0.010" total indicated runout. Mark the each case head at the high spot of the runout with with a magic marker as you measure them. Load a few extra rounds normally for fouling shots—however many fouling shots your gun needs to settle. Just be sure it's the exact same load so the fouling pattern is identical. Gather up your sandbags and three identical targets and the bent ammunition and fouling rounds and rifle and go to the range. Fire fouling shots and check sight zero on the first target. Then set up the two other targets side by side. You will fire the targets alternately to share temperature and fouling changes evenly between the rounds put into them. The difference will be that on the first target you will always load the gun so the index mark on the case head is at 12:00 in the chamber before closing the bolt. On the second target, each time you shoot you will index the round 90° clockwise. So, the sequence is this: Code:
Shot Target Index Mark 1 1 12:00 2 2 12:00 3 1 12:00 4 2 3:00 5 1 12:00 6 2 6:00 7 1 12:00 8 2 9:00 9 1 12:00 10 2 12:00 11 1 12:00 12 2 3:00 13 1 12:00 14 2 6:00 15 1 12:00 16 2 9:00 17 1 12:00 18 2 12:00 19 1 12:00 20 2 3:00 21 1 12:00 22 2 6:00 23 1 12:00 24 2 9:00
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January 7, 2015, 07:56 PM | #35 |
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Nick would the first step be to identify what the moa per 0 degree is? Then I would have a baseline, then run through the steps you outlined below. You mention the purpose is for comparison, in your experience is.174 on the higher end? Frankly I get about 80% of my loads with a tir of between .001-.003. Btw it's a 3006 load w 168 smk.
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January 10, 2015, 09:19 AM | #36 |
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Once I dumped the formula in a spreadsheet I got curious and here is what I found for my reloads:
3006 loads: 168gr SMK Win Brass 80% of the reloads had a BTA of .1711 or less Rem Brass 80% of the reloads had a BTA of .1748 or less 22-250: Factory winchester- 60% had a BTA of .2036 Winchester brass Sierra 1390 70% had a BTA of .0881 223: HRNDY 55FMJ LC Brass 70% had a BTA .1762 308: 168 SMK LC Brass 70% had a BTA of .1246 The only high quality rifle I currently have is my 3006 bolt, it has a hart barrel/McMillan stock and easily shoots sub .5moa 5 shot groups. I use the Winchester brass for that. I use Remington brass in my M1's. Both shoot good for what they are 2" 5 shot groups. My 22-250 is being rebarreled, that will be a good test My 223 is a 16" barrel ar (1.5" groups) and a mini14 (2.5"-3" groups) My 308 is an M1A that shoots 1.5-2" groups Thought I would post some numbers so if anyone else was interested for comparison they would have some info. RO is pretty commonly accepted at .003 or better for decent ammo. It seems like it is easier to get a BTA with a shorter bullet/case/neck. For 3006 and 22-250 I use Redding body dies and Lee Collet dies, for 223 and 308 they are standard RCBS 2 die set. |
January 10, 2015, 09:47 AM | #37 |
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If you're shooting reloaded cases in your M1A, the case head out of square issues will probably mask any bullet runout changes.
It's my experience with 30 caliber ammo that runout up to .003", and sometimes .004", regardless of how it's measured, has little impact on accuracy. One would have to shoot 50- to 75-shot test groups to see any significant difference between ammo with .001" runout to that with .003" runout. How much does your own repeatability in holding and aiming your rifle contribute to the ammo's inaccurate performance? Shoot some groups with zero runout ammo and maximum runout ammo; what's the difference? 'Tis also my opinion that if the shooting system comprising rifle, ammo and shooter, cannot discriminate between zero and a few thousandths of bullet runout in the ammo, bullet runout extremes are not the weakest link in the system. Fix the bigger problems first. |
January 10, 2015, 10:24 AM | #38 |
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Bart once the weather breaks that's the plan... Take some loads with zero ro and compare them with those with max ro. I also want to compare against some loads I have "fixed" (had high ro and have adjusted to reduce ro). For the semi's (m1, m1a, ar, mini 14) I don't think they rifles systems I have are capable of shooting much better. That includes the shooter, I use mostly irons with those, with rare exception. It would be pretty unusual for these to shoot much better then they do, they are all pretty much stock. This exercise was as much about comparing my reloads against others in this forum as well as improving my shooting results.
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January 10, 2015, 11:22 AM | #39 |
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1stmar,
In the sequence I gave you, the target with only 12:00 orientation is your group size reference. You could also shoot perfectly straight rounds for reference if you prefer. I recommend the 12:00 tilted approach so that all other variables, including strain from neck stressing are matched. T A number of shooters have noted that even with variable runout, always putting the tilt's high side in one chamber orientation cuts the bullet tilt error in half. By doing it with bullets all tilted past the point the barrel will start to straighten them, you not only have the orientation the same, but also have the same degree of in-bore tilt for each shot. If you look at the illustration in my post #12, you see each hole has two bullets through it. That mechanism is why those holes are so tight. The above principle was also verified by Merrill Martin in Precision Shooting Magazine. He came across a gun with a factory chamber that had been reamed with the back end with 0.007" off axis (0.014' TIR). With new brass it shot bugholes. So, why bother making straight rounds if you can tilt them to best effect? There are several reasons I wouldn't go that route:
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January 10, 2015, 12:31 PM | #40 |
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Unclenick says a number of shooters have noted that even with variable runout, always putting the tilt's high side in one chamber orientation cuts the bullet tilt error in half. I'm one of them.
Oft times, I would spin 7.62 NATO M118 or M852 match ammo then mark all those with .004" or more runout at their high point with a felt tip pen putting a black dot on the case head at that point then indexing them at high noon in each slot in a box of 20 so they were easy to pull out indexed on my pointing finger. Loading them in a Garand chamber indexed at high noon (12 o'clock) then chambering them gave better accuracy at 600 yards. Some of those rounds had .008" runout and my tests showed they printed on target about 1/2 to 3/4 MOA away from where ammo with zero to .003" runout printed. That ammo jumped from .050" to .100" to the lands depending on how much erosion the bore had at the origin of the rifling. All my ammo with .003" or less runout was used in rapid fire matches as indexing them in an 8-round clip was meaningless. They would often roll around a bit being pushed up as the rifle cycled and how each one indexed in the chamber varied. Proved this to myself by indexing 8 rounds with .006" or more runout at a 12 o'clock position in an 8-round clip with the index end labeled "T" to me it's at the top when loaded in the Garand. Closed the bolt and shot all 8 rounds. Each one had a different orientation of their index mark on their heads to the firing pin's fingerprint reference; proof they twisted somewhat coming up through the clip and chambering. Last edited by Bart B.; January 10, 2015 at 12:38 PM. |
January 10, 2015, 12:44 PM | #41 |
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Sounds like a lot less work and better results then fighting to get .003 or less runout. When you were indexing garand loads in slow fire I assume you were loading 1 at a time and dropping the bolt on a loaded round. No risk of damage to the bolt ?
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January 10, 2015, 01:43 PM | #42 |
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A Garand's bolt has a little more impact force when single loading because no resistance of a clipped round against the clip is slowing down the bolt as it's chambered. AS far as I know, there's never been any instances of single loading a chambered round with its back end about half an inch sticking out of the chamber causing damage to the bolt. M14's and M1A's are the same.
The impact force of the case head against the bolt's face when the round's fired is a lot greater than what's caused by the bolt slamming home on a chambered round. Besides, when the round's chambered, the extractor slides out then over the case rim as the round's hard into the chamber shoulder from the ejector's force so there's no significant bolt face contact to the case head then and while the bolt closes into battery. As there's a few thousandths head clearance (space between the case head and bolt face), the case head doesn't touch the bolt face any significant amount until the round's fired. |
January 10, 2015, 04:47 PM | #43 |
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Ditto what Bart said. Also, letting Garand bolts go forward for dry firing doesn't seem to hurt them, either, and that's an even harder slam because the cushioning resistance of the extractor engaging a case is absent.
But I will mention that the higher bolt speed puts a little more inertia into the firing pin, so you want to double-check that your primers are properly seated below flush with the bottom of the case heads of your cartridges to avoid slamfires. For that purpose you can also use a primer pocket depth uniforming tool to let the primers set as deeply as they can for single loading. It also buys you a little more insurance to use one of the military sensitivity spec primers (CCI #34 or TulAmmo KVB762), which are less sensitive than standard commercial primers, but which the gun is designed to fire. Those suggestions are not required elements in a properly timed gun with the safety bridge in good shape and the firing pin protrusion within spec, but a pound of prevention and all that.
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January 10, 2015, 05:43 PM | #44 |
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Looking forward to getting out and testing. Thanks for the info guys. Appreciate it.
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