How much Runout is acceptable ?

Discussion in 'Main Message Board' started by short range, May 8, 2010.

  1. short range

    short range

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    How much runout is acceptable ? I bought a used 30BR, and 100 Lapua brass. 72 of the brass were loaded, and the rest were fireformed, resized and primed, none of the necks are turned. The rifle has a .330 bore, Al ( the guy I bought the rifle from) told me to buy a .325 bushing. I don't have a micrometer to measure the neck wall thickness, I just have a caliper. I'm using ReddingType S Neck sizing Die, and a Redding Competition Bullet Seating Die. I have been sizing about 2/3 of the neck. I bought a Sinclair concentricity gauge, and I took some readings on 20 brass at three different stages of reloading: fired brass, after neck sizing, and bullet runout. I checked the brass neck runout at about 1/8 th of an inch from the end of the neck, and the bullet runout at about a 1/4 inch from the end of the neck. these are the results on ten of them:

    Fired brass After neck sizing Bullet runout

    11. .001 .00125 .00225
    12. .001 .001 .00125
    13. .001 .0013 .00225
    14. .001 .0012 .0025
    15. .0015 .0015 .002
    16. .001 .001 .0015
    17. .001 .001 .003
    18. .00075 .00075 .00275
    19. .00125 .001 .00225
    20. .0015 .001 .003

    It looks like I'm getting too much runout from my seating die. What should I do to correct this problem ?
     
    47WillysGuy likes this.
  2. whiskey08

    whiskey08

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    im also using a redding seater, I honed out the stem so it would seat using the ogive instead of towards the meplat. I didnt check runout before i honed but now i have an average of .003 runout on each round. I thought that it was my hone job but if your seeing the same thing...

    I was talking to an guy the other day at the range, he mentioned that they would test loads at a 1000 yds with different runout. what they found was that a batch of ammo with no runout and a batch with lots of runout. (dont remember how much, but it was significantly more than .003) printed the same at 1000 yds. Im sure there will be lots of opinions, but per his test it didnt matter.

    so on monday im gonna find out for myself. Ill let you know how they shoot.
     
  3. camac

    camac

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    Shortrange, Now you have the gauge you can sort on runout for yourself and fire a few groups to see if it makes a difference to you. Some rifles it matters. Others it doesn't seem to - there will definately be different opinions here. Looking at your figures I would suggest your runout is quite normal and it is also not necessarily all the seating die but also to do with the distance away from bend in neck. Your figures show basically 1.5-2 x the runout at bullet than at neck. This is normal as you are measuring further away from the point of bending and hence, runout measurements are larger.

    There is a bit of information on accurising the neck bushing dies and seating dies in the last few threads on concentricity and runout if you want to wade through them.
    First step on a reddiing is to make sure the neck of shell is centralised in the seating die. It must push the collet up from cone of shoulder, not shellholder. This helps centre the neck in line with bullet. This is done by grinding a bit from the bottom of the collet so that shell holder doesn't touch collet when seating.
    Second, as suggested above you can lap in your seating stem. Although the redding bullet "bore" is made to pretty exactng tolerances and seating stems are pretty good so not as big an issue. Also ensure you place shell in shell holder exactly the same every time you seat a bullet.
    Also Ensure you have squared (trimmed) and chamfered necks.
     
  4. fdshuster

    fdshuster

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    short range: Your runouts are not all that bad, not far from my average. I also use the Sinclair gauge with the pointer at the ogive location of contact with the leade. My "standard" is .002" and less used for "serious" match firing, and all distances beyond 200 yd. More than .002" to around .004" for practice, first round foulers, basic scope adjustment, and 100 yd. Anything over .004" gets a magic marker ident & if the R/O continues after another reload & firing, the case will be set aside for uses that do not involve accuracy/ I write the case off as being defective from when it was formed. I do inside taper neck ream all my brass using the K&M inside taper neck reamer. It gives a smooth non resistant start to bullet seating. I also sometimes seat the bullet in 3 "steps". Seat about 1/3, rotate case 120 degrees, seat 1/3, rotate for final seating. I'm also using the Redding Type S bushing die, but with the Forster Ultra micrometer benchrest seaters, a close "twin" to your Redding. I'm curious: how do you measure to 5 decimal places ( for that matter to 4), with the Sinclair dial indicator? 3 decimal's with maybe the nearest 5/10,000" is close enough for me. When using my dial calipers, (Starrett,Mitutoyo, and a cheap digital) I can vary the readings to 4 decimal places just by how much pressure I put on the adjustment wheel. :)
     
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  5. LHSmith

    LHSmith

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    Run-out is NOT a priority that short-range competitors concern themselves with. I'll bet most top competitors couldn't tell what runout their getting from their set-up......most use a Wilson in-line seater.
    How well the rifle performs on the target is paramount. Learning how to tune to different conditions, learning how to throw consistent powder charges, learning what bag set-up and holding technique your rifle likes, finding a properly matched sizing die for your specific chamber,learning how to read and adjust for wind and mirage, ALL of which are more important factors in the short-range accuracy equation.
    If your are planning to use your 30 BR beyond 300 yds, then it may become an issue to address.
     
  6. BoydAllen

    BoydAllen

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    LH,
    All your points are very good, but you might want to have a chat with Billy Stevens before you proclaim that short range Benchrest shooters are unconcerned with loaded round runout.
    Boyd
     
  7. short range

    short range

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    Hi fdshuster, thanks for the info. As far as getting readings out 4 and 5 decimal points on the Sinclair, If it looks like it was 1/4 of the way between .001 and .002, I put .00125. I wasn't really sure how precise to enter my readings.
     
  8. short range

    short range

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    whiskey08, I'm interested in finding out how your groups come out. Now that I have my readings, I will go to the range and keep track of how the rounds that I measured group. Probably the best way to test them is to shoot the rounds with the least amount of runout together, and work up to the most runout. I will report back. If it makes a difference in groupings, I will start to address my options to correct the problem.
     
  9. camac

    camac

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    shortrange - the 30BR is almost the perfect rifle to test a lot of these theories. The barrel should almost never where out. Some people believe in runout others don't and you will get exactly those two answers every time you post the question. Best way to tell is to do your own trials. I would agree with Boyd though. A lot of the benchrest shooters I know do believe in runout. They believe in all the "little" things add up to the result. I certainly know a few of the top level long range shooters (whom I have a lot of respect for) over here don't give a hoot about runout but some do. Some of the limited testing I have done seemed to show significant improvement in some rifles but far less in others. It is really up to you to find out now but please do post your findings. I think if everyone posted we would have results for both sides of that arguement. and is all very interesting to me.
     
  10. whiskey08

    whiskey08

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    well no shooting today, I live in NM and winds were at 40mph by 9am. So next window wont be till weds. Im dying to try out my new nightforce scope, and my meticously loaded rounout ammo.
     
  11. short range

    short range

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    I didn't get to shoot today either, we have winds about 25 mph, and I think my next chance to shoot may be Wednesday also, but it might be windy or raining for the rest of the week until Saturday, but I will be gone on Saturday.
     
  12. short range

    short range

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    I went to the range today. It was 50 degrees and misting with a slight wind. I shot 4 three shot groups at 100 yards. these are my results:
    Group #1 3 shot group .157"
    they had bullet runouts of: .001, .001, .00125

    Group #2 3 shot group .222"
    they had bullet runouts of: .0015, .002, .002

    Group #3 3 shot group .186"
    they had bullet runout of: .00225, .00225, .002

    Group #4 3 shot group .331"
    they had bullet runout of: .003, .003, .003

    I was using 1' orange stick-on targets with a 1/2 ring and a center dot. All of the first 11 rounds were at ten to eleven o'clock touching the center dot, the last round on target #4, was at three o'clock touching the center dot, so I'm might have pulled that last shot a little, and that might have screwed up my test for the day. I also shot two rounds at an additional target,that was a .293" group one round had .004 bullet runout, and the other round had .00125 runout, but it was seated too deep. the round that was seated too deep was at ten o'clock touching the center dot, and the round with .004 bullet runout hit dead center. So because I think I may have pulled the last shot on target #4, I need to do more testing to see if bullet runout over .002 makes any difference.
     
  13. camac

    camac

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    Great shooting short range - nice to see that new project jump straight to some very decent grouping. A couple of tips from a statistical point of view so you can do a fair comparison. 3 shot groups are really hard to compare. Statistically speaking you would need to do a lot of replications before drawing a real conclusion. Your standard deviation (away from centre) may be in the order of .150 inches (including rifle and shooter error)meaning most 3 shot group sizes are in the 0.10-0.35 range purely by statistical probability. You will find them naturally occuring through this range and most people tend to try and ignore the 0.35 and only focus on the ones in the low 1's. 5 shot groups will be in the 0.25-0.40 range and 10 shots are larger again (roughly speaking). However from a comparison point of view you will need to do a lot 3 shot groups to draw a proper conclusion. This test (statistically speaking) so far is insignificant but keep it up and we will try and draw some conclusions over time. Good stuff.
     
  14. BoydAllen

    BoydAllen

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    Try this. Take your concentricity gauge to the range and after identifying your worst round (for runout) chamber the round fully, and then take it back out and remeasure it. If your bullet is seated into the rifling, there may be some straightening.
     
  15. camac

    camac

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    Hi Boyd,
    One of the things I am starting to wonder is if runout actually causes interference between neck and chamber and messes with neck tension etc. It certainly seems as though most chambers simply cannot have 3 or 4 thou runout when chambered (if shells fireformed) but larger runout can still have some effect on accuracy of some rifles. I am slowly piecing together some information but the more feedback the better. I believe there is some substantial interaction between thoat and neck dimensions of chamber and fireformed vs FL resized etc with regards to whether runout has an influence. I don't believe it is all to do with the "sleeping bullet" theory but a little more complex. Very interesting though. I just wish more people would post their findings to add to the pool of information.
    I am slowly working through all my rifles but it takes time - especially as I want to make all results statistically significant.....
     
  16. short range

    short range

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    Thanks guys, I will try chambering the round with the worst runout and take it out and remeasure it. I will also start shooting 5 shot groups, unless you think I should shoot more shots per group. I think I am measuring my groups correctly. I was told to measure the center of one bullet hole to the center of the farthest bullet hole. Do you think I should measure at each stage of reloading again, or just record bullet runout for my next few tests ?
     
  17. BoydAllen

    BoydAllen

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    Measure outside to outside at the widest part of the group and then subtract the actual measurement of a single bullet hole, which will be smaller than bullet diameter. Are you shooting over some sort of flags/
     
  18. short range

    short range

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    Thanks Boyd, That is a much more accurate way to measure groups, I didn't think the way I was measuring groups was very accurate. I will remeasure my groups. I'm not using any flags.
     
  19. short range

    short range

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    After remeasuring my 4 test groups the correct way, I used .276" as the size of the bullet hole. Here are the new measurements:

    group #1 .176"
    group #2 .216"
    group #3 .158"
    group #4 .376"
     
  20. johara1

    johara1

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    Short range,
    If you are not using at least 3 wind flags,you wii not get the answers. You have to shoot your group in the same condition
    If you have run out on a fired case somethings wrong,chambers crooked or the neck thickness is uneven.........jim
     

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