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Thread: Deburring Flash Hole Question

  1. #1
    Boolit Master Avenger442's Avatar
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    Deburring Flash Hole Question

    I am trying a set of Remington cases that I have uniformed the primer pockets and deburred flash holes. Trying to get rid of some higher standard deviation numbers and maybe a quarter inch closer grouping. These were loaded with a Lee C309 same loading that produces typical 1 1/2" groups with this bullet in this gun. For some reason the groups were more in the 2 1/2 - 3" range after the deburring. I think I'm going to have to adjust the load after deburring the flash hole. Standard deviation were lower, so speeds were closer to the same. Does anyone have experience with this? Is it common for the flaring of the deburred flash hole to cause a change in the burn of the powder, pressure, (or as Glenn would say the RPM) etc causing the groups to spread?
    While I work at it, it is by God's grace that it happens..

  2. #2
    Boolit Master reed1911's Avatar
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    Not unless there was a significant amount of material removed. I would look to either the powder weight or bullet weight (% drift) as the suspect before I considered it the DB of the flash hole. Anything of course is possible, but I have not seen only a DB cause that much change.
    Ron Reed
    Oklahoma City, OK
    info@reedsammo.com

  3. #3
    Boolit Master Avenger442's Avatar
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    Understand that everything is the same for the two rounds except the flash hole deburr and pocket uniforming. Bullets the same all weighed and segregated. Powder and charge same even same lot and weighed within one tenth grain, primer, OAL, rifle all the same. Even loaded on the same setup of dies. Shot from a weighted lead sled to take most of the me out of it. Several five round groups. But instead of 1 1/2 they are 2 1/2 - 3.

    I'm thinking that the flaring of the flash hole has changed the ignition of the powder enough to spread the groups. I'm getting groups now that I was getting with one more grain of powder. But might be thinking wrong. May have to do more testing. I have never tried the uniforming and deburring before so I'm kind of happy that the SD was more uniform. Now if I can get the group to shrink.......... The original hope.
    While I work at it, it is by God's grace that it happens..

  4. #4
    Boolit Master reed1911's Avatar
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    What caliber is this? What brass? What primer? What powder and load?

    When you say de-burr, did you simply cut the primer punch burr out of the inside of the inside of the brass? Cut flush and level right?

    The only thing I can think that would cause this, and this is a stretch, is that by DB the brass you've allowed the primer to ignite the powder column better and are getting slightly higher pressure. Did the velocity change with the decrease of the over all SD?

    Another thought to consider is to not chase the SD. I understand why you are, and yes generally more accurate loads will show a lower SD but that is not always the case. I think you are already on the right track and you are really chasing the group size like you should, just don't get too wrapped up in the SD.

    The only thing I would suggest is the drop back a little on the load and go from there, but I don't know what you are shooing so I cannot really suggest that without the data.
    Ron Reed
    Oklahoma City, OK
    info@reedsammo.com

  5. #5
    Boolit Master
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    Same lot of cases? How many times fired? Case weight after uniforming? Sometimes new cases do better annealed. So many variables... Full-length sized? Neck-sized?

  6. #6
    Boolit Master
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    do you still have some shells loaded that did the 1 1/2 "" ??

    If so shoot them to see if the gun still groups well
    may be something else has change with the gun

  7. #7
    Boolit Master


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    The hanging tags of brass from the punching of the flash hole, act just like a damaged crown in deflecting the flame into the powder. I thought everyone removed the production carp when working for precision.
    Information not shared. is wasted.

  8. #8
    Boolit Master Avenger442's Avatar
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    OK More information: Caliber .308, Remington brass, CCI primer, Powder is H4895 load is 41.5 grains, bullet is the Lee C309-160R average weight as cast is 161 grain.

    I'm using a Hornady deburring tool on the cases. It leaves a slight bevel on the inside of the case at the flash hole as it cuts away the burrs. This tool was suggested to me by a guy who, I understand, wins high power rifle matches on a regular basis.

    This was a recent range trip so all of my data is not transposed into my load data record sheet. I have just, in the last three months, been using something to measure the speed of my bullets. So data is a little sparse. But I got the records together and looks like there is not much difference in the speed. Probably about 20 fps. What is interesting is that the speed is a little faster before deburring. Which would seem to indicate that what I thought at first about lowering the charge may be the wrong direction to go. SD went down from average of 18 to 9. Which means I'm getting more consistent speed. Still having some 15 SDs but before some of them were around 27. This is probably still something to be worked on in the loading process. Have not started measuring concentric yet. Something to be done. As there always is.

    Not sure about the lot all were once fired. And have not to this point started weighing cases (another thing to do). It also occurred to me that I might have some cases that needed the necks to be annealed. But went back and looked at cases, I mark mine with number of firings, and it is the same with the deburred and not. So neck tension is probably not the problem. I sometimes shoot in different guns so all of my cases are full length sized. This one is the Weatherby Vanguard. Which will give me under an inch at 100 yards with Federal Gold Match ammo. Also sometimes use a Remington 700 with a bull barrel. It was my first test mule. It will also give me (average) 1 1/2" with this load. And I don't have to be concerned as much about the barrel temp.

    I agree with you on the SD. While it is something to work on to make a more consistent load/group. Which is the thought behind the deburr. It is not the only thing that can impact group size.

    Yes still have about 80 of the 1 1/2" case not deburred and will shoot some to check that. May be a while. Usually only get a range trip about twice a month. And it has been raining here almost every day. Will probably load some of the deburred cases with loads on either side of the 41.5 grains and see what that does.

    Was just interested if there was any information out there on how deburring impacts the same load in a case.
    While I work at it, it is by God's grace that it happens..

  9. #9
    Boolit Master
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    All of the flash hole deburrers that I know of are a center drill on a longer shaft. It will enlarge your flash hole. I was working with my R77 in 280 trying to get better than 1.5" with jacketed. I found that the rifle's max loading changed. Trying different loads, I hit max, hard bolt lift, about 1 or 2 grains before Sierra said I should with their bullets.

  10. #10
    Boolit Master

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    How do the velocities compare between the uniformed load and in uniformed loads? I found uniforming deburing to give better ignition and slightly higher average velocities. If you were on the upper end of velocity for your bullet, alloy, or harmonics the slightly higher velocity may be putting you over the threshold. Try backing down a couple grains and working back up to where you were velocity wise and or to the accurate point. I also believe the uniformed pocket gives a better surface for the pirmer anvil and better faster transfer of the flame and hot particles.

  11. #11
    Boolit Master Avenger442's Avatar
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    Quote Originally Posted by country gent View Post
    How do the velocities compare between the uniformed load and in uniformed loads? I found uniforming deburing to give better ignition and slightly higher average velocities. If you were on the upper end of velocity for your bullet, alloy, or harmonics the slightly higher velocity may be putting you over the threshold. Try backing down a couple grains and working back up to where you were velocity wise and or to the accurate point. I also believe the uniformed pocket gives a better surface for the pirmer anvil and better faster transfer of the flame and hot particles.
    Velocity averages are close to the same in the prepped and non prepped cases. I do not have an enormous amount of data but the non deburred flash holes are showing an average of 20 fps over the deburred with the data I have. Which doesn't make a lot of sense to me. I thought that I might get higher velocities with the deburred flash hole just because the hole is flared to the inside of the case. The one positive so far is that SD has dropped. If I can get back to a loading that will work I'm thinking I can maybe get 1" and under sometimes.

    I'm going to go back to the range with some different loads in the uniformed/deburred cases and see if that tightens the groups. Needed to know if I need to go up or down on the loading because of the deburr. Will also take some of the known 1 1/2 loads to shoot at the same time. But it is going to be a while.

    And I was wondering if there was any knowledge out there on impact to the same loading by deburring the flash hole. Sounds like, so far, it might impact loads in either direction higher or lower velocities.

    AggieEE
    If I read you right you were increasing the load headed toward a closer grouping. Did it look like groups were tightening as you increased the load?
    While I work at it, it is by God's grace that it happens..

  12. #12
    Boolit Master
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    Avenger, That Ruger is a 1.5" gun period. The plus side is almost any load will do between 1.75 and 1.25 and do it all day every day. I couldn't find a magic sub minute load. But there was no load that it really hated either. I just thought that it was strange that I was finding a max load in the deburred cases before finding one in the non deburred cases. Uniforming the primer pockets might have something to do also don't know. Just found a load that worked and went with it.

  13. #13
    Boolit Master

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    AggieEE, the improved ignition may have been part of the reason. A faster more complete burn may be the reason

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    Is this 2.5 - 3.0" group/s from one range visit?

    Some days, we just have an 'off' day...at least I do.
    with the SD tightening up, the 'off' day seems more likely than anything else, IMHO.

  15. #15
    Boolit Master
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    Quote Originally Posted by Avenger442 View Post
    Snip I'm going to go back to the range with some different loads in the uniformed/deburred cases and see if that tightens the groups. Needed to know if I need to go up or down on the loading because of the deburr. Will also take some of the known 1 1/2 loads to shoot at the same time. But it is going to be a while.

    And I was wondering if there was any knowledge out there on impact to the same loading by deburring the flash hole. Sounds like, so far, it might impact loads in either direction higher or lower velocities. Snip
    When making a change in any component, ALWAYS start low and work your way back up.

  16. #16
    Boolit Master
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    OK More information: Caliber .308, Remington brass, CCI primer, Powder is H4895 load is 41.5 grains, bullet is the Lee C309-160R average weight as cast is 161 grain.

    That is pretty fast I'm betting 2600 fps and near 50k psi with that Lee bullet. Now if it was me I'd be starting at 25 grs plus some dacron and working up for best accuracy. Your 1.5 inch groups are at 100 yds with the same load, very good I'd say!
    Hell, I was there!

  17. #17
    Boolit Master
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    Were the groups shot on the same day? How much coffee before the test firing?
    Aaron

  18. #18
    Boolit Master Avenger442's Avatar
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    swheeler
    Your right, around 2600 fps average. And I did start back lower than the suggested minimum loading in the manual, forgot how much, and worked my way up.

    BHN of this bullet is about 16 and has a gas check. It is coated with three coats of Hi Tek. Leaves no lead in the barrel as long as you use good sense when doing the loads. In other words you can't shoot 8 BHN and no gas check in the gun and shoot it at 2600 with no leading. I tried some 12 BHN and no checks about the same loading and had to use the Chore Boy. I started out working for a hunting load that could be shot out to 200 yards and still mushroom. Somehow I got stuck on this got to have it 1" or under thing. I'm not one of those 300 to 1000 yard shooters. Eyes too bad for that even with a sniper scope.

    joatmon
    Test with the prepped cases (deburred) were done on the same day. The load in an unprepped case is one of my pet loads and I have had some bad days with it grouping out to 2"+ as JohnB noted. I could have just gotten off a couple of bad groups. But most of the time this is a 1 1/2" load at 100 yards.
    Don't drink much coffee these days. And it could have been I just hadn't woke up yet

    JohnB in Glencoe
    Could have been some me but shot from weighted lead sled to take most of my faults out of it. Slight breeze from behind me as I remember. Just a few rounds down the road from these shot another bullet with a different loading unprepped cases four into just under an inch and as usual a flyer that took group out to 1 1/2". It wasn't flyer that was making these 2 1/2 - 3" groups. They were spread out.

    One of the things I am trying to eliminate is the flyer that occasionally ruins a good grouping. Deburring the flash hole and uniforming the primer pocket were suggested as a start. I really need to start weighing cases and using a concentric gauge. Or maybe weighing the completed round as some do. And I know there are other things I could be doing to help make the loadings more consistent. And things that I'm already doing that I could do better. Always room for improvement.

    I think another range trip is definitely in order for more data. Just thought there might be a "yeah they always shoot different after you deburr the flash hole" answer out there somewhere with a "always faster or slower" to go with it. But it looks like the range and more testing may be the answer.

    Thanks everyone for helping with the suggestions. The more I load and shoot the more I find that my answer in my set of conditions might not be the same for someone in the conditions they are in. Of course there are always the basic things we must all do to get it right. But sometimes it's just you the gun the round and the target at the range that holds the answer for you. This site is a gold mine of information for all of us that cast and handload. Glad I found it when I started handloading.
    Last edited by Avenger442; 07-15-2017 at 12:39 AM. Reason: correction
    While I work at it, it is by God's grace that it happens..

  19. #19
    Boolit Master
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    Another factor, were the debuured cartridges fired on the same day under the same conditions? Alternating targets using the different loads might be different than results from two different range trips shooting different variables on different days. Temperature, humidity, barrel condition(clean, dirty, different solvent/oil), wind, sunny, cloudy, happy, annoyed, hurried can all make a difference.

  20. #20
    Boolit Master
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    The only thing I can think that would cause this, and this is a stretch, is that by DB the brass you've allowed the primer to ignite the powder column better and are getting slightly higher pressure.
    my guess is that's it. I found by deburring the flash holes on the magtech 24 gauge shotshell brass I use for the 577 snider, I get MUCH better ignition and burn of the powder, along with way more consistent loads. should prove to be true in this case as well.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check