Hall 30br first range trip 125grain acting strange

Discussion in '6BR, 6BR Improved & Wildcats' started by joshb, Dec 19, 2017.

  1. joshb

    joshb Gold $$ Contributor

    Joined:
    Oct 5, 2014
    Messages:
    3,689
    I bought this gun a while ago. I finally dug it out and hit the range with it's 30 br barrel installed. I haven't even measured the twist yet. A friend called me Sunday and said he was off on Monday and suggested a range trip. I barely had time to load some test rounds Sunday evening. I bought some 115 grain "custom" bullets for this gun and segregated them by weight into 3 batches. I shot some of the lightest bullets first. Set at touching the lands, they shot fairly well over H4198 in the primed brass that came with the gun. Primer unknown. Best group was at 35 grains, just where the previous owner said it would. The flier on 34.4 was me. I sneezed and touched the trigger. :rolleyes: I adjusted the scope after the first group. I also wanted to try some "really cheap" 125 SMK in the gun to see how they would do. Also set to touch, I got some strange results. I half expected some key holing but the 33.5 grain group has me scratching my head. Sweet spot or fluke?
    IMG_1492.JPG
    IMG_1493.JPG
     
    Last edited: Dec 20, 2017
  2. BenPerfected

    BenPerfected Gold $$ Contributor

    Joined:
    Nov 24, 2009
    Messages:
    823
    My 30BR results with 112 gn custom bullets are very similar to your 33.5gn group with 33.4gn of 4198.
    Ben
     
  3. RGRobinett

    RGRobinett

    Joined:
    Sep 13, 2005
    Messages:
    342
    Josh, how long are the 125 Gr. Sierra? It would also be good to know the twist rate, and the temperature. ;)RG
     
  4. GSPV

    GSPV A failure to plan is a plan for failure. Gold $$ Contributor

    Joined:
    May 2, 2006
    Messages:
    2,031
    With normal benchrest bullets, at least, I would jam the bullets further. You’ll usually need more neck tension than you are accustomed to. I’d also recommend CCI BR4 primers.

    All three are commonly recommended to somewhat mitigate the marginal pressure curve of H4198.
     
    Last edited: Dec 21, 2017
  5. North Fork

    North Fork

    Joined:
    Oct 29, 2009
    Messages:
    228
    Try some 125 gr TNT you will be surprised how well they shoot
     
  6. JimPag

    JimPag Silver $$ Contributor

    Joined:
    Dec 6, 2013
    Messages:
    988
    I think Greg meant BR4's. I have never had good luck with those primers in any of my dozen or so barrels chambered in 30BR but my 30x46 just loves those primers with N133. The Federals didn't even come close to the BR 4's in that chambering. IMO a 17TW seems to shoot well in all temps, but an 18tw once the temp is below 50 degrees you have to put more powder in the case to make it shoot. I use Speer 125gr TNT's to fireform cases and they shoot ever better if you sort them out. I don't know why I just don't shoot real match bullets when I fireform since I have in excess of 75K of them. I 'll be dead and buried before I ever shoot that many.
     
    Last edited: Dec 21, 2017
    Damfino likes this.
  7. RGRobinett

    RGRobinett

    Joined:
    Sep 13, 2005
    Messages:
    342
    If those are the "tipped" Sierra MK, there is likely the problem - they are likely too long - especially for 1:18" twist . . and, possibly, depending upon length, even 1:17" twist. :eek:RG
     
  8. BenPerfected

    BenPerfected Gold $$ Contributor

    Joined:
    Nov 24, 2009
    Messages:
    823
    Randy, These bullets were made by Mike Stinnet.
     
  9. joshb

    joshb Gold $$ Contributor

    Joined:
    Oct 5, 2014
    Messages:
    3,689
    Hello Mr Robinette:
    I just measured the twist 3 times.
    Twist: 1-17
    Temp: 50 degrees
    The 125 loads were compressed pretty hard.
    Bullet length: 1.14 .432 from base to ogive by my Hornady tool.
    My customs are .931 long and .273 to ogive.
    I paid around 15 cents/each for the 125 Sierra HP. I was hoping they would be good for practice. Would a 15 twist stabilize them?
    I noticed the markings on the barrel, tho very faint. Shaw Rifles
    IMG_1496.JPG
    IMG_1497.JPG
    IMG_1495.JPG
     
  10. RGRobinett

    RGRobinett

    Joined:
    Sep 13, 2005
    Messages:
    342
    Josh, at this OAL, without entering all of the geometry, the Sierra 125 is, as suspected, too long, even for a 1:17" twist rate: at 1.140", the gyroscopic stability factor will be less than 1.4 and probably less than 1.3.

    As noted by North Fork, above, the much shorter Speer 125 Gr. TNT may surprise you.;)
    They usually perform much better via 17/18" twist barrels than they do via the commercial
    norm of 1:10", or sometimes, 1:12", which will show the imbalance/center of gravity off-set, which the 17.18" twist will "hide", while still delivering Sg in excess of 1.4.:eek:
    Thirty Cal. bullets in excess of 1.10" long usually need a 1:16", or faster to reach Sg 1.4. RG
     
    Damfino and joshb like this.
  11. RGRobinett

    RGRobinett

    Joined:
    Sep 13, 2005
    Messages:
    342
    Sorry, BenPerfected - I had intended to refer to the Sierra bullet, from OP.:DRG
     
  12. RGRobinett

    RGRobinett

    Joined:
    Sep 13, 2005
    Messages:
    342
    At 1.14” long,, the Sierra 125 Match in a long bullet!:eek: In the accompanying comparisons, though I had to guess at the geometry (nose radius, etc.) the guesses are close enough to display just how this affects the required twist rate (differences due to jacket thickness, core alloy, etc., would be insignificant).

    This begs the question: was the 1.14” length correct, or, did you mean 1.014. or, even 1.041? o_O If correct, it also displays why the apparent yaw angle was so great as to cause , what appears to be, at least, one “key-hole” . . . Sg at sea-level, + (slightly denser) conditions, is a measly 1.0 - or, not quite tumbling!:eek: It’s surprising that all of them did not display significant pitch & yaw.

    The first comparison is of your custom [115Gr.] bullet, at OAL of 0.931”, vs. a [125 Gr.] 10.0 ogive bullet at 1.14”OAL. In the far right column(bold black), note the SG (here, specific gravity of construction), which enables the program to calculate the CG & over-turning moment, based upon the geometry. The last digits, line #4 (in red) is the twist rate required to produce Sg 1.5.

    The second example compares a custom [125 Gr.] bullet (right hand column), at 1.01” OAL, to another [125GR.] bullet, at 1.14 OAL. Again, note the specific gravity of construction line, and the much lower value required to make the longer bullet weight equal to the shorter bullet, of the same geometry [nose, me'plat, base], just shorter in length. Here, the shorter bullet, even via 1:18” twist will exit the muzzle with Sg slightly better than the minimum 1.4, deemed, by the gurus, necessary to completely damp pitch& yaw.

    A graphic example of why precision seekers should check the length of bullets, as opposed to the weight, which, “may be [mostly] along for the ride”!:eek: If we made the last comparison with bullets of equal specific gravity, the 1.14" long bullet would weigh in at 150 Gr., and need a twist rate of 1:14.9” to attain Sg 1.5: over 1.5” slower twist than its 125 Gr. sibling (1st comparison, above).;) RG
    IMG_0522.JPG IMG_0523.JPG

    Addendum: This is in no way intended to disparage Sierra, or, anyone else! If, indeed,
    there was no misplacing of digits/decimal points, we should not forget that Sierra and their competitors are primarily focused on making bullets which will, very likely, be fired through the default 1:10" to 1:12" twist barrels used for the vast majority of mass produced rifles. Via the commonly twisted (factory) barrels, bullets of 1.140" OAL, are more than adequately stabilized. RG
     
    Last edited: Dec 21, 2017
    Damfino, joshb and Jet like this.
  13. GSPV

    GSPV A failure to plan is a plan for failure. Gold $$ Contributor

    Joined:
    May 2, 2006
    Messages:
    2,031
    Yep. Sorry. I’ll go back and correct it.

    I’ve had better luck with the CCI in the 30 BR in cooler weather. Especially early in the day, in the first shots. No matter what, I learned to shoot 2/3 sighters before going to my record target...even if it was a long delay between shots.

    My 30 Major with N120 liked the 205M no matter what.
     
    Last edited: Dec 21, 2017
    RGRobinett likes this.
  14. joshb

    joshb Gold $$ Contributor

    Joined:
    Oct 5, 2014
    Messages:
    3,689
    Thank you! Pure gold. Do you know of any success with 12 and 14 twist barrels in the 30br with longer bullets? Merry Christmas! Josh
     
    Last edited: Dec 23, 2017
  15. RGRobinett

    RGRobinett

    Joined:
    Sep 13, 2005
    Messages:
    342
    There is no reason longer, and relatively light for length, bullets would not work via 12-14" twist barrels. It appears that the 125 Sierra would fall into this category - nothing "wrong" with it, just not what has become the 'norm' for custom, domesticat/wildcat chambered barrels, shooting custom bullets. The biggest probable issue would be the "throating": in order to get all of the goodies out of the combo, that would need to be determined.

    The 30BR case, matched with the appropriate barrel twist will do very well with bullets up to, at least, 150 Gr. This, however, is counter to the reasoning behind the adoption of the 30BR, which we teamed with the "just right" twist rates (1:17" & 1:18") and short/light for caliber bullets, specifically for the developed for precision benchrest work. The objective was minimizing 30 caliber recoil, thus reducing the cumulative fatigue factor over the course of a full Grand Aggregate - time has proven the concept/combination productive.


    I'll probably get some of this incorrect, but, way back, "in the day" (over 50 years ago), the 308Barnes (1.5" long .308) - not to be confused with Barnes bullets, of monolithic fame - enjoyed some success, but was intended for other uses, and teamed with twist rates contemporary to the time, and the heavier bullet weights then preferred. While it was close to the 30BR capacity wise, it was employed more as a small capacity, light(er) recoiling hunting round (as compared to the .308 Win. & 30/06), launching cast bullets, and/or jackets bullets of 150 to 180 GR.

    But I'm rambling - with the variety of bullet types today, we should look first at the length, and lastly at the weight.:eek: To achieve equal stability, the polymer tipped bullets, almost across the caliber spectrum, will need almost 2" faster twist rate than their, 'old school' HP/SP siblings!;)

    Merry Christmas!:) RG
     
  16. joshb

    joshb Gold $$ Contributor

    Joined:
    Oct 5, 2014
    Messages:
    3,689
    Thank you again, Randy! I love it when you "ramble". I'll give you a little info on my situation. I just shoot for fun. I take as many kids and friends as are willing to go. I usually provide the guns and ammo. I'm doing my part to help promote the shooting sports and get them interested. Right now I have 2 guns set up in 30br, with a new 17 twist barrel ready for chambering. These 2 seem to be chambered correctly for the short custom bullets and they shoot well. I'm having a lot of fun with the cartridge but shooting those $.40 pills for fun seems a waste. Looking for a cheaper alternative, I purchased a bulk quantity of the 125 Sierras. I also own many 308s, so I can use the bullets in them, too. I have a Kodiak RBLP that needs a new barrel so now I'm gathering as much info as I can to figure out what twist would be best for those Sierras. I don't expect to get record breaking groups out of them. Just a moderately accurate "fun gun". Thanks for all your help and Merry Christmas. Josh
     
    RGRobinett likes this.
  17. JimPag

    JimPag Silver $$ Contributor

    Joined:
    Dec 6, 2013
    Messages:
    988
    Josh. If your running 17TW barrels, your best bet would be to find bulk boxes (500ct) of Speer 125gr TNT's. Usually they are around 95 bucks for 500 plus shipping, so around 23 cents apiece which a true match bullet with shipping would cost you around 42 cents each.
     
    Last edited: Dec 24, 2017
    joshb and RGRobinett like this.
  18. joshb

    joshb Gold $$ Contributor

    Joined:
    Oct 5, 2014
    Messages:
    3,689
    Hi Jim: Thanks for the sugggestion. I'll do that for the 17 twisters. It looks like I'll be getting a 12 or 13 twist for these 125s. Occasionally, I do the "cart before the horse". I bought 7K of these Sierras. I can easily shoot them in my 308s for short range plinking but I started to think about using them in a 30br to lower the powder consumption a little. I invite a lot of kids and friends to shoot and they're really chewing up the ammo. Also, handing them "something different" piques thier interest. Merry Christmas, Josh
     
  19. rangertim

    rangertim

    Joined:
    Jan 2, 2005
    Messages:
    253
    TNT 125 sorted are Great 30BR & 30x47 Bullets ! I have shot a bunch of them fouling & practice they usually would shoot in the same hole mixing them with custom 118, But that PAC-Nor 1-18 Twist 30x47 Barrel was a hummer !
     
  20. AlNyhus

    AlNyhus

    Joined:
    Nov 25, 2004
    Messages:
    500
    The Sierra 125 MK measures 1.108-1.111. At 3,000 fps, you'll need a 14 twist barrel to get to a safe 1.3 Sg. A 13 twist gets you almost 1.5 Sg. -Al
     
    LA50SHOOTER likes this.

Share This Page