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I think I know the answer to this one but I'm not 100% sure.
I'm loading 77gn TMKs for a .223 Wylde bolt action. Right now I'm loading 24gn of TAC at 2.415" & getting +/- 2800fps from a 20" barrel.
It's too hot. I'm getting cratered primers, flowing along the firing pin & I need to reduce my load. Obvious first option is to drop my powder load & work back up.
But.....
Would loading the rounds longer (I can go out to 2.54") reduce the pressure? I'd really like to stay between 2750 & 2800 if possible.
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Joined: Jun 2004
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Campfire Outfitter
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It depends on the length of your chamber. If you are still well off the lands, the extra COL will reduce pressure. If you're at the lands, or close, it may increase pressure. Of course, reducing pressure will also reduce MV.
What primer are you using? If not one of the thick cup varieties, it is possible that it's just a primer problem.
I haven't looked up your load or run it through QL, but the above is generally true.
Edited to add: Ramshot says the maximum charge for 77 grains is 23.4 grains of TAC.
Last edited by denton; 06/19/22.
Be not weary in well doing.
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It depends on the length of your chamber. If you are still well off the lands, the extra COL will reduce pressure. If you're at the lands, or close, it may increase pressure. Of course, reducing pressure will also reduce MV.
What primer are you using? If not one of the thick cup varieties, it is possible that it's just a primer problem.
I haven't looked up your load or run it through QL, but the above is generally true.
Edited to add: Ramshot says the maximum charge for 77 grains is 23.4 grains of TAC. I'm still jumping 0.003 at 2.54" (I had the throat cut long on purpose) I'm using cci 400 primers, so I'm guessing I'm just waaaay over pressure. My goal is to produce a load that's still carrying 2000fps at a minimum of 300yds. I tried Varget, but the fastest I could see with that was a very disappointing 2350.
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Campfire Outfitter
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I just took a look at QuickLOAD to see what's what. Based on what I see there, I personally wouldn't push beyond about 2700 fps (about 59 kpsi) or maybe allow up to 2725 or so. QL isn't always precise, but it has helped me stay out of trouble. Sometimes I do push just a little more not for the velocity gain, but to home in on accuracy. YMMV.
Don't be the darkness.
America will perish while those who should be standing guard are satisfying their lusts.
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Joined: Dec 2004
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Campfire Outfitter
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I'm still jumping 0.003 at 2.54" (I had the throat cut long on purpose)
I'm using cci 400 primers, so I'm guessing I'm just waaaay over pressure.
My goal is to produce a load that's still carrying 2000fps at a minimum of 300yds. I tried Varget, but the fastest I could see with that was a very disappointing 2350. QL suggests your pressure is about 66,500 psi or more.
Don't be the darkness.
America will perish while those who should be standing guard are satisfying their lusts.
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Campfire 'Bwana
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Campfire 'Bwana
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The CCI 400 isn't the best for stiff loads.
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Joined: Jun 2004
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Campfire Outfitter
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The CCI 400 isn't the best for stiff loads. Correct amundo. .003 off the lands will, by itself, increase pressure. Back off to .030 to .050. Get an appropriate primer like #41 or CCI450. Back your charge down. That should fix it. You will probably not safely reach your velocity goal. Good luck with your search.
Be not weary in well doing.
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The CCI 400 isn't the best for stiff loads. Unfortunately, I'm not spoiled for choice right now! It's those or Winchester.
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Joined: Aug 2010
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Campfire 'Bwana
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Campfire 'Bwana
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The CCI 400 isn't the best for stiff loads. Unfortunately, I'm not spoiled for choice right now! It's those or Winchester. Keep your eye out for CCI450's to be on the shelves. A LGS here has them, but they are $85/1,000. I'd suspect it's your CCI400 primer and the load is too stiff. I ran in to a similar issue with a new 204 Ruger I am loading for. Switched to CCI450's, reduced the charge and no issues now..
I try to stick with the basics, they do so well. Nothing fancy mind you, just plain jane will get it done with style. You want to see an animal drop right now? Shoot him in the ear hole. BSA MAGA
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Campfire Regular
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Campfire Regular
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If it’s a Remington action / bolt, then cratered primers might not be a sign of excess pressure - just a lose fitting firing pin.
Any heavy bolt lift or ejector marks / swiping on the case head?
Last edited by Stammster; 06/19/22.
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If it’s a Remington action / bolt, then cratered primers might not be a sign of excess pressure - just a lose fitting firing pin.
Any heavy bolt lift or ejector marks / swiping on the case head? It's a Ruger American. I'm not seeing any ejector marks or bolt swipes, just the primer. Oddly, they're still rounded on the edges, not at all flattened or sharp edged. Someone on another forum mentioned temp sensitivity & I feel stupid for not considering that. When I initially developed the load (long story short, after working up a very accurate load, I discovered that the chamber had been badly cut & the throat was so short, I couldn't even load to spec. 2.26" without making the lands. Iirc, my MAX coal worth this bullet was 2.15"!) it was mid February & in the 40s. Last week when I tested these, we were in the high 90s.
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Joined: Mar 2010
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Campfire Regular
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Lots going on here, high velocity for a short barrel, poor choice of primer for the job, Ruger lottery, brass capacity varies between brands.
Good luck.
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Campfire Tracker
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TAC is one of the better powders for temp stability, 40 to 90 shouldn't be a problem.
Less powder, less pressure.
'Four legs good, two legs baaaad."
----------------------------------------------
"Jimmy, some of it's magic,
Some of it's tragic,
But I had a good life all the way."
(Jimmy Buffett)
SotG
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Campfire Tracker
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It has been said on here many times that the primer is not a good teller of pressure.
If we live long enough, we all have regrets. But the ones that nag at us the most are the ones in which we know we had a choice.
Doug
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Campfire Regular
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There are some CCI 450's floating around right now, I think either midway or brownells has them.
But if your primers are still super round might just be firing pin vs firing pin hole size relationship.
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Campfire 'Bwana
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Campfire 'Bwana
Joined: Nov 2011
Posts: 30,903 |
Yep, probably a little hot:
Cartridge : 5.56 mm NATO - 5.56 x 45 mm
Bullet : .224, 77, Sierra TMK #7177
Useable Case Capaci: 23.086 grain H2O = 1.499 cm³
Cartridge O.A.L. L6: 2.260 inch = 57.40 mm
Barrel Length : 20.0 inch = 508.0 mm
Powder : Ramshot TAC *C
Predicted data by increasing and decreasing the given charge,
incremented in steps of 2.083% of nominal charge.
CAUTION: Figures exceed maximum and minimum recommended loads !
Step Fill. Charge Vel. Energy Pmax Pmuz Prop.Burnt B_Time
% % Grains fps ft.lbs psi psi % ms
-20.8 83 19.00 2180 813 31823 6304 82.7 1.305
-18.8 85 19.50 2238 856 34121 6532 84.1 1.268
-16.7 87 20.00 2296 901 36594 6755 85.5 1.232
-14.6 89 20.50 2355 948 39256 6975 86.8 1.194
-12.5 92 21.00 2413 996 42124 7189 88.1 1.156
-10.4 94 21.50 2472 1045 45215 7397 89.4 1.119
-08.3 96 22.00 2531 1096 48551 7599 90.5 1.083
-06.2 98 22.50 2591 1148 52155 7792 91.7 1.049
-04.2 100 23.00 2650 1201 56052 7978 92.7 1.017 ! Near Maximum !
-02.1 102 23.50 2710 1256 60273 8154 93.7 0.985 ! Near Maximum !
+00.0 105 24.00 2770 1312 64853 8320 94.7 0.954 !DANGEROUS LOAD-DO NOT USE!
+02.1 107 24.50 2831 1370 69831 8475 95.5 0.925 !DANGEROUS LOAD-DO NOT USE!
+04.2 109 25.00 2891 1429 75252 8618 96.3 0.896 !DANGEROUS LOAD-DO NOT USE!
+06.2 111 25.50 2952 1490 81170 8748 97.0 0.869 !DANGEROUS LOAD-DO NOT USE!
+08.3 113 26.00 3013 1552 87646 8863 97.7 0.842 !DANGEROUS LOAD-DO NOT USE!
+10.4 115 26.50 3074 1615 94753 8965 98.3 0.816 !DANGEROUS LOAD-DO NOT USE!
Results caused by ± 3% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 3% relative to nominal value:
+Ba 105 24.00 2815 1355 68365 8383 96.2 0.933 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 3% relative to nominal value:
-Ba 105 24.00 2723 1267 61384 8226 92.8 0.977 ! Near Maximum !
You didn't use logic or reason to get into this opinion, I cannot use logic or reason to get you out of it.
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