Testing two rifles, identical chambers ...different barrels

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Black Diamond 408, Jun 1, 2006.

  1. Black Diamond 408

    Black Diamond 408 Well-Known Member

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    Both of these rifles are chambered for the 338 Snipe-Tac caliber. 338-408imp for those just reading the post for the first time.

    Rifle (one) is a Stainless repeater action with a stainless
    Barney Lawton barrel, 33" long twist rate 11.25 groove dia is .3295 (bbl is fluted)

    <font color="blue"> </font> Rifle (Two) is a Titanium repeater action with a Mike Rock 5R bbl-ABS carbon fiber system 33" long 9.25 twist rate. Groove dia .329

    <font color="green"> </font> I tested the same loads in both guns to see how much the speed changes with tighter bores.

    300MK 141grns H-BMG50 powder
    gun one: 3395
    gun two: 3305

    250MK 149.5grns WC 873 powder
    gun one: 3438
    gun two: 3360

    <font color="black"> </font> I set up some targets at 100, 400 and 500yds to test some loads in both guns.

    Gun one at 400yds with 300MK bullet WC 873 145.5grns 3400fps ave. Group 1.2"
    [image][​IMG][/image]

    Gun two at the same range, 400yards, with a different load,
    300MK 141grns H-BMG50 3305fps average. group size .352

    [image][​IMG][/image]

    I then fired gun two at 512yards with same load, 300MK
    141grns H-BMG50 powder 3305fps group size .540

    [image][​IMG][/image]

    I shot some 350grn wildcat bullets for comparison, 141grns WC873 powder...3060fps (starting load) 100yds These shot right at 1" Didn't do much load testing as i only have about 20 left. In gun one several weeks ago the same tests were no good with the 11.25 twist. 3250fps

    It appears there is about 90fps difference between the two barrels, the tighter bbl is a bit slower. It is hard to say what the accuracy difference is between both guns, the triggers are not the same, Gun Two has a Shilen trigger set nice and crisp, gun one has a factory Remington trigger and it needs work or replacement. Both guns will cut a bug hole at 100yds. Due to trigger issues with gun one, i didn't do any 500 yard testing, just pulling the trigger on the 400yd target i could see the crosshairs moving back and forth across the target before the sear would drop. I am so use to a 2 ounce trigger that a 3# pull is a nightmare!
    Both of these rifles are carry hunting guns and are set up accordingly.

    Both chambers are identical.
    Barrel lenths are 33"... with brake, 35.5"
    Both guns have the same carbon fiber Lone Wolf stocks.
    gun one has a IOR 6-24 with 35mm tube
    gun two has a Nightforce 5.5x22 30mm tube
    both guns have a 40moa picatinny base

    Gun one weighs 16.7#
    Gun two weighs 15.2#

    both guns shot from sandbags on my special shakey bench!
     
  2. goodgrouper

    goodgrouper Well-Known Member

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    From looking at the very dirty rings around your bullet at 400 yards and from the speeds you got, I would venture to say that the powders you are trying might be a tad on the slow side for your guns.

    I typically do not see as dark of rings around the holes at 100 yard BR matches and your target was 4 times further out and jet black. That tells me the powder is burning dirty and/or inefficiently or it is a hot day or both.

    COnsider this:
    96 grains of RL25 shoots 300 grain MK's at 3075 from a 36" barrel in a 338 lapua improved over my oehler 35 on a 4' rod. You are dumping in roughly 50 more grains of powder and only getting only 225 fps more with a 3" shorter barrel. That has got to be "sandblasting" your throat with oodles of unburned powder.

    This might be one of those cartridges that will shoot a slightly faster burning powder at unreal velocities. I would try VV170 or Retumbo and see if it likes them. I'd be willing to bet it shoots faster (although it may or may not shoot as good as you're getting now with H50bmg-those are great groups!) with a slightly faster pressure curve.

    It might be like the 30-378 wby. The powder everyone seems to use is H50bmg and 180-200 grain bullets and they never go faster than a 300 ultra will using 20 grains less of a faster powder! Then you run RL25 or Retumbo in the 30-378 and they will shoot 180's about 3500 fps and best the ultra by 100 feet or so. The gap gets even wider when heavier bullets are used.

    ANyhow, looks like a very fun project and it should keep you busy for awhile for sure! Enjoy that monster! /ubbthreads/images/graemlins/cool.gif
     

  3. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    GG,

    Not sure with Daves 338 but with my 338 AM I will top out in pressure before I top out the case capacity with a 300 gr pill and H-50BMG. That said, I do load up to 149.0 gr H-50BMG with my top end load. This is a 98 to 99% load density in my 338 AM.

    With the 350 gr ULD RBBT, I have a significant amount of air in the case. I would say topping out at around 90% load density with H-50BMG.

    I would be a bit on the nervous side to try Retumbo in my 338 AM at least with a 300 gr pill or heavier. H-50BMG seems about right for the 300 gr SMK and I am loaded up and ready to test VV 20N29 in the 300 and 350 gr loads as well here soon as I get out to the range.

    I am pretty sure BD408 can go up quite a bit in powder charge and would also increase velocity some as well and get a cleaner burn out of his 338 ST.

    On the dark bullet hole thing, you may be onto something but also consider that the 300 gr SMK has nearly the same meplat as most 22 and 6mm caliber match bullets. Only difference there is a whole lot more bullet diameter so there will be similiar initial paper tear from the meplat but much more paper stretching around the larger diameter bullet resulting in more paper to bullet contact. I suspect this is the reason for the larger black areas on the target more then anything.

    If you look at an expansion ratio comparision, this class of 338 rounds has a lower expansion ratio then even my 7mm AM.

    The only problem with case capacities this large and bullets this heavy is that things can get serious real quick. That is where the slow burning powders give a bit extra cushion in safety margin as they give you a bit more warning when your getting to the top.

    Maybe Retumbo would get some more fps but I suspect it would be a bit tricky getting it to shoot consistantly well at these top end velocities. Just what I have seen with the really big 338s.

    Now a 250 gr pill, I would say that would be a very practical powder choice.

    Good Shooting!!

    Kirby Allen(50)
     
  4. Black Diamond 408

    Black Diamond 408 Well-Known Member

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    Goodgrouper:

    The main reason for this test was to see what the difference was between both barrels. I used starting loads while fire forming the brass, for this test, it was a hot day and basicly was all that i had loaded up. I have tried faster powders, the case is too big and you will have all kinds of pressure problems. BMG50 powder seems to be one of the best for this cartridge. 141 is a starting load i use for fire forming the cases. i use 147 for my rifle, that puts it just under 3500fps with the 300MK bullet. You can go with a quicker powder with the 250gr bullets, 3700+ fps.

    I tested some WC873 powder, its a bit dirtier than the BMG but shoots rather well and lower pressure. Like kirby's gun and mine, both are about the same. I used a loading of 145.5 WC873 with the 300mk, 100yd, bug hole. 400yds, 1"

    Just for testing purposes, 149.5 WC873 with the 250MK, 3/8" group 100yds. 3495fps. Low pressure load, i could bump this up to 152 or more. I will test this one later.

    There is a big difference between 3075 and 3450, it takes powder to make velocity. 3450 with a 300grn bullet flat out hauls butt. Bug hole groups at 100yds, 400-500yard groupings are under 1"

    33" bbl burns 99% of the powder according to Quick load,
    150grns of BMG50 powder. The bbl was 35" to start with, no change in velocity after cutting off 2". Kirby is getting almost the same velocity in his 40" tube over my 33" job. His larger action and bbl seems to run a bit lower pressures than my lighter carry rifle. I can get 3520, but the case life will be short. 3450 seems to be about right in my particular rifle. I have 4-5 loadings on 12 pieces of brass i have been testing with, lost none of them. Pockets still hold primers. I did however blow a few pockets working up to see where it tops out at.
     
  5. ewallace

    ewallace Well-Known Member

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    Are you using WC 872 I have not seen WC 873 /ubbthreads/images/graemlins/confused.gif
     
  6. Black Diamond 408

    Black Diamond 408 Well-Known Member

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    Yea its WC872, my forgetter is working overtime today. /ubbthreads/images/graemlins/confused.gif
     
  7. goodgrouper

    goodgrouper Well-Known Member

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    [ QUOTE ]
    On the dark bullet hole thing, you may be onto something but also consider that the 300 gr SMK has nearly the same meplat as most 22 and 6mm caliber match bullets. Only difference there is a whole lot more bullet diameter so there will be similiar initial paper tear from the meplat but much more paper stretching around the larger diameter bullet resulting in more paper to bullet contact. I suspect this is the reason for the larger black areas on the target more then anything.

    [/ QUOTE ]

    Actually, bullet diameter has nothing to do with it at all. /ubbthreads/images/graemlins/shocked.gif I thought so too until I spent a day last year at a 100-200 yard NBRSA match helping score groups. I learned from a guy who has measured tens of thousands of targets that he could tell what powder each shooter was using by the amount, thickness, and color of the "ring" around the hole. He could tell when somebody was shooting 8208 a little mild, or when n133 was screaming, or when Scot was dialed in. I was then informed that some of the guys actually tailor their loads to "cheat the ring" so their groups look smaller! This was the case with the 22 ppcs and the .20 waldog variants too.

    So for the last year, I have been monitoring this phenomenon in my own shooting and by golly, it works!

    Some powders reverse the hot/cold thing so you have to know which ones do that or you could go the opposite direction with it.

    Very interesting stuff.

    I showed a picture of these holes to my scorer buddy today and he said that he had no experience judging H50bmg but that it looked too mild or shot in cool weather! On the other hand, it could be that H50bmg is one of those reverse powders and shows opposite traits. Sheesh, just when you think you've got things figured out, somebody tells you some new trick! /ubbthreads/images/graemlins/crazy.gif


    And you never know, Retumbo might just give a more gradual pressure curve down after a sharp peak and surprise you! I thought for sure that RL25 was going to be the powder of choice in my 338 thunder with the 250 grainers and it shocked me when RL22 was better in every regard across the board! Thanks to 7mmrhb for "forcing" me to just give RL22 a try with the 250's! I figured it would be the powder for the 225's and it worked for both! /ubbthreads/images/graemlins/cool.gif
     
  8. goodgrouper

    goodgrouper Well-Known Member

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    [ QUOTE ]
    I used starting loads while fire forming the brass, for this test, it was a hot day and basicly was all that i had loaded up

    [/ QUOTE ]


    Ahh, that explains it. So my scorer buddy and I guessed right on the mildness.


    Curious as to what other powders you've tried in that beast and the velos you obtained.
     
  9. Black Diamond 408

    Black Diamond 408 Well-Known Member

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    Goodgrouper;

    Well the only powder i havent tried yet is the VV20N29 cannon powder, I think Kirby is going to try it in his monster. US869 works if you run the pressures up to top.
    BMG50 powder is cleaner at 145 on up, I think Kirby is at 149 in his 338AM. The WC872 i have just started load development, 145.5 is a starting load i tried yesterday. I will bump up some incrementel loads to 150 and see where the pressures top out. I suspect it will be cleaner burning at higher pressures.

    US869
    142grns 3250fps
    144grns 3365fps
    147grns 3495fps

    HBMG50
    142grns 3350fps - fireforming load - 98% case form
    147grns 3505fps

    WC872
    142grns 3200fps
    146grns 3400fps
    150grns ? not tested yet

    These tests are from my original gun, not the carbon fiber bbl. There was some pressure signs at the top loads, then found out my neck was a little tight, shaved off .002 and all was fine. 3350-3495 is the operating range for this particular rifle.

    My case is just a bit smaller than Kirby's 338AM, i can fill the case with US869 and WC872 for top loads, BMG50 there is a little room left but the load has topped out pressure wise.

    This is new territory, takes a while to get all the powders checked out. /ubbthreads/images/graemlins/grin.gif

    From trigger pull to 500yard hit, less than 1/2 second with 300grn pill! .4783 of a sec to be exact.

    1 second to 1000yds.
    1.7 seconds to 1500yds
    2.69 seconds to 2000yds

    all at 3450fps bullet speed and 300MK bullet 1200ft elevation.

    Dave
     
  10. 7mmRHB

    7mmRHB Well-Known Member

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    B.D. 408 I believe a more valid test of barrel speed would be to shoot each gun with the exact same amount of pressure not just same amount of powder. You might find out the canted 5R Rock barrel reduces friction enough to reduce pressures as well. When you increase the powder until you have the same pressure as the other barrel you usually see a velocity advantage. The 5R rifling shows much less engraving on recovered bullet jackets than standard rifling.I suspect thats due to the fact that there is a grove opposite a land in this configuration reducing stress on the bullet.
    Looks like both will be shooters and your Smithing speaks for itself.------7mmrhb
     
  11. Black Diamond 408

    Black Diamond 408 Well-Known Member

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    I did some more load testing last weekend with the WC872 powder and 300MK's. I loaded up 148,149 and 150grns in some cases that have shot at least 3 loadings. 3350fps up to 3450 was the range between the loads, 150grn load was topped out for my gun, Signs of ejector marks on the brass.
    I shot targets from 100yds out to 700yds, various distances in between. I spent most of the morning lasering the entire range and putting out markers as to the distances. My range is my pasture so it has never been marked off, MOO cows seem to destroy things left lying around. Groups at 100yds were oblong holes on average between all loads, three shots ea. 300yd three shot groups were cloverleafs. 500 yard i completly cleaned and started over, groups were now .600 on average, 148grn load was the smallest at .552. 700yards the groups were right at 2", i also cleaned before starting this test distance. The wind came up and played havoc with my bench during this test. I have settled on 148grns of WC872 in my personal gun, 3395 was the average speed on this particular day. It was 90deg, sunny and 10-15mph wind into and from the left.
    I only did this test with my personal gun, gun one. The bbl was easy to clean, Very little copper, wiped out in one pass through with Outers foaming cleaner. I used Hoppes for the carbon residue.

    All loads were with the bullet just touching the riflings, 215 mag match primers, TTI armory and German brass was used.
    300mk bullets had the meplats uniformed, no weighing of cases or bullets was done. The runout of the necks or bullets was tested either. Powder was dropped by a Lyman measure, no individual weighing of powder was done. Basic style reloading, nothing match or benchrest was performed. Cases were trimmed, but not neck turned. The next round of tests will be more of a match quality situation. I will start a new thread for that test.

    Dave
     
  12. davewilson

    davewilson Well-Known Member

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    i guess the lack of brass prep and bullet sorting would explain the "poor" groups you were getting, especially at 500 yds! /ubbthreads/images/graemlins/grin.gif
     
  13. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Damn,

    Pushing 1/10 moa at 500 yards, thats most impressive. Hell I do not even think Black Sunshine will do that. How many three shot groups was that an average for?

    Looks like your looking at 3" groups at 1000 yards. Not to damn bad for a light weight 338 monster!!!!

    And with no case prep or anything at all, most impressive. I think you have a serious shooter on your hands!!!

    Kirby Allen(50)
     
  14. Black Diamond 408

    Black Diamond 408 Well-Known Member

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    Fifty,

    That group average was from three different loads, 148,149,150. They all shot about the same, speeds were real close, the 148 shows the least pressure signs. This gun is the one i personally fluted the barrel, very deep i may add, and thought maybe it would need to be stress relived and re-lapped. Groups were not this good from the start or even after 50 rounds or so. The bbl was copper fouling bad from the start, even with carful break in. I was in contact with several bbl makers and they thought i should re-lap the bbl as it maybe to smooth inside. Then after getting the ABS-Mike Rock bbl and talking with Mike about his process for break in i ordered a Moly Kit from Sentry Solutions and did the rock bbl. It broke in very fast! Very little copper at all using this system, i thought well lets give it a try on my gun. I completly cleaned my bbl, as well as i could, started the moly break in on my bbl, fired the 20 shots that is recomended, cleaned the gun and the groups shrunk in half. The last upgrade the rifle needed was a better trigger, fixed that problem and here we are. All i can say is the gun shoots way better than i can! There maybe lots of luck involved as the test didnt span a large number of shots. But this is just a carry hunting rifle and several shots is all i ever use for testing this type of rifle. The bbl will get hot fast, 148grns will really heat er' up! To say the least i am very happy with the gun /ubbthreads/images/graemlins/grin.gif It will prolly end up in some hunters gun cabinet.
    I only have one gun i will never sell, it was my dads Browning superposed he bought new in 59 and completly wore out hunting ducks and pheasants with. He gave it to me to do a sporting clays project, i cut off the bbls out of the breech block and completly re-barreled it similar to a Kreigof over and under, only i used my big bore system, it has twin 16ga tubes and chambered for 20ga. The bottom bbl is 60% high shooting and the top bbl is 0% (dead on) for the second shots in sporting clays, both bbls have long screw in choke tubes. I had the reciever nickel plated, put an adjustable comb on the stock, had the bbls engraved and blued. The gun is one of a kind. I gave it to my dad to shoot the 20 ga class, but he had a stroke and the gun was too heavy to use so he gave it too me. I used it in competion for several years until he no longer could compete, i only did so we could still shoot together. I use it occasionlly to hunt pheasants and quail. I should get it out and post a couple pics for the heck of it. Its the only custom o/u i ever will do. It was more work than building a rifle from scratch!

    I bet black sunshine will do that, just got to get out and shoooot her! 7" group at 1500yds is pretty damn impressive. There are guys that will give their left one for that at 1000yds, or closer.

    Dave