Reducing loads and still overpressure

Discussion in 'Reloading' started by shawnb, Sep 7, 2018.

  1. shawnb

    shawnb Well-Known Member

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    Hey guys, i have been shooting my 30-375 ruger and i am having to reduce my loads to keep within the same pressure. My normal load was 80.5 gr of n570 and am now down to 78.5gr. Everything is the same, brass,powder lot, etc.

    Ive cleaned everything and still getting more overpressure. Last night i fired 4 rounds waiting in between a couple minutes. And on the 4th shot. My primer was completely flat and had to hit the bolt back with my hand. The first shot had absolutely no flattening and extracted very very smooth.

    Im puzzled? Never had this happen.
     
  2. shawnb

    shawnb Well-Known Member

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    I will add that bolt lift was perfectly smooth. It just couldnt pull the bolt back like normal.
     
  3. RockyMtnMT

    RockyMtnMT Official LRH Sponsor

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    May need to aneal the brass. Have you chronographed the load? Is the vel changing?

    Steve
     
  4. lancetkenyon

    lancetkenyon Well-Known Member

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    Have temps changed since you did load development? Some powders are temp sensitive once you hit a certain ambient temp. RL26 shows no pressure until you hit about 84°. So a round sitting in a hot chamber could be spiking pressure.
     
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  5. shawnb

    shawnb Well-Known Member

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    Brass is annealled, reduced loads are shooting to the same poi at past 1200 yds
     
  6. shawnb

    shawnb Well-Known Member

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    Temps are consistent. And i dont chamber until im ready to shoot.

    My one thought is a carbon ring? I noticed on my muzzlebreak that the holes are very fouled with carbon. So much that it flakes off like rust does. I cleaned with wipeout but not sure if that could get rid of a carbon ring?
     
  7. cjuve

    cjuve Well-Known Member

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    Might be worth a look with a bore scope
     
  8. NW Hunter

    NW Hunter Well-Known Member

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    I found my carbon ring by noticing my base to ogive measurement got shorter.
     
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  9. dok7mm

    dok7mm Well-Known Member

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    You can run your cleaning rod in the bore, then attach a new brush at the brake. Pull the brush, from muzzle to chamber slowly, but same amount of pressure. You should notice a tightness, that tells you where the carbon build-up is located.

    I would strongly suggest you have someone knowledgeable scope your barrel. Just because a patch comes out clean means nothing as to how clean the barrel is. It usually just means your solvent of choice isn't softening the carbon/copper enough to stick to a patch. JMO
     
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  10. tankgijohn72

    tankgijohn72 Well-Known Member

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    Barrels speed up over time, especially with a large overbore. You will likely see what looks somewhat looks like alligator skin in the throat area if you boroscope it. The larger the overbore, the faster the pressure/velocity climbs. I haven't ever worked with a 30-375, but spent a lot of time with the 300 Norma Mag. Pressure/velocity climb can continue into well into the hundreds of rounds. So, the approach you have taken by dropping back your powder charge is pretty much the only thing you can do.
     
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  11. phorwath

    phorwath Well-Known Member

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    Hornady brass?
    Is the barrel melonite treated?
     
  12. Lefty7mmstw

    Lefty7mmstw Well-Known Member

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    I'd guess you are getting carbon buildup, whether a "ring" or simply filling the grooves in the throat is a moot point. You've got to scrub the dogcrap out of the overbores once in a while to get the carbon out if you don't keep up on it. I've had a few rifles start running over pressure like you are stating; every time it's been a throat issue and usually carbon. You may even have to go to JB's bore paste to scrub the crap out.
     
  13. gohring3006

    gohring3006 Well-Known Member

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    I’m in the carbon ring camp.
     
  14. tankgijohn72

    tankgijohn72 Well-Known Member

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    It is possible that there is a carbon ring present. But barrels do increase in pressure/velocity over time. I JB borepasted (heavy scrubbing, tight fitting patch)a barrel every 100 rounds until 500 rounds. Pressure/velocity climbed continued throughout the duration. All same ammunition, no reloads.