Overpressure differences. Where to next?

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groundrush

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I recently started reloading for my .223 and am trying to determine a good load for my rifle. The pressure signs I seen one day didn't match the next trip?
Rifle = Savage Axis 2 Precision
Bullet = Hornady Match 68gr BTHP
Primer = CCI BR-4
COL = 2.235" (.02" off the lands)
Powder = Hogdon BLC-2 (min 24.5-max 26.5 as per published data)

First time out I worked up through the loads in 0.2gr increments. Starting at 24.5 gr and watching for signs of pressure increase. Each increase would show ever so slight flattening of the primer but the edges were still rounded. I stopped at 25.9gr as the flattening as the primer was flattening out pretty good and the groups started spreading out beyond 2”. No other signs of overpressure though.
Based on the grouping I decided to focus on the 24.7 - 25.3 range and bring out the chronograph. Loaded up some more test rounds and went to the indoor range a couple days later.
With this second batch, the primers at 24.7 were much flatter than the 25.9 that I stopped at earlier! The recent loads at 24.7gr averaged 2883 fps with deviation of 17.5fps. The 25.3gr loads yesterday were averaging 3050 fps.
Where do I go from here? Explore charge weights below the minimum? Work on best accuracy and ignore flat primers?
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You should factor in that your barrel is getting dirtier with each shot, which tends to increase pressure even if the load is constant.
 
Do you weight sort your brass? Have you tried other cases? Some heavy cases (less volume) will produce pressure signs faster than lighter weight cases.
 
OP, each rifle is an entity unto itself for a number of reasons.

Tight/loose bore, free bore, tight/loose chamber to start, then it moves on such things as powder lot, primer manufacturer, case capacity etc.

BLC2 is a very popular powder for the 223rem and an overall good choice.

24.5 grains is a mid range load with 55 grain bullets and most milsurp cartridges I've pulled apart to measure the charge weight is within half of a grain with this type of powder.

You're well within the parameters listed in the manuals so there may be an issue with the material the primer cup is made from.

Your loads may be quite safe and the issue may be "soft" primers.

CCI550 are SMALL PISTOL MAGNUM primers and IMHO, they're doing a pretty good job handling the pressures your charge is generating.

There are no other signs of pressure on the cartridge face, like smear marks from case expansion, etc, so I think pressures are fine.

Likely it's the material the primer cup is manufactured from is softer to ensure ignition with lighter hammer/striker hits from handguns.

I've used those primers in the 223rem as well, with the same designation powder, in milsurp IVI cases, which are heavier than most commercial brands.

I've had almost identical results with those primers as your photos show.

My rifle is a Tikka T3X, with a very tight chamber.

IMHO, you shouldn't be exceeding 24.5 grains of BLC2 with your case/powder/primer/bullet combination.

PMC cases tend to have more material in them, closer to or the same as Milspec, and your powder charge should take this into account.
 
If you are using CCI 550 Magnum pistol primers in your 223 , the flow / flattening of the primers is an indication you are approaching a catastrophic failure. The variance in results for the two days may be attributed to changing ambient temperatures , case dimensions , charge weight ,barrel fouling etc.
A more pressing matter is the use of a primer that is not intended for the high pressures you are subjecting it to.
This article may help explain some of the issues you are experiencing.
https://www.accurateshooter.com/technical-articles/primers-and-pressure-analysis/
 
bearhunter said:
OP, each rifle is an entity unto itself for a number of reasons.

Tight/loose bore, free bore, tight/loose chamber to start, then it moves on such things as powder lot, primer manufacturer, case capacity etc.

BLC2 is a very popular powder for the 223rem and an overall good choice.

24.5 grains is a mid range load with 55 grain bullets and most milsurp cartridges I've pulled apart to measure the charge weight is within half of a grain with this type of powder.

You're well within the parameters listed in the manuals so there may be an issue with the material the primer cup is made from.

Your loads may be quite safe and the issue may be "soft" primers.

CCI550 are SMALL PISTOL MAGNUM primers and IMHO, they're doing a pretty good job handling the pressures your charge is generating.

There are no other signs of pressure on the cartridge face, like smear marks from case expansion, etc, so I think pressures are fine.

Likely it's the material the primer cup is manufactured from is softer to ensure ignition with lighter hammer/striker hits from handguns.

I've used those primers in the 223rem as well, with the same designation powder, in milsurp IVI cases, which are heavier than most commercial brands.

I've had almost identical results with those primers as your photos show.

My rifle is a Tikka T3X, with a very tight chamber.

IMHO, you shouldn't be exceeding 24.5 grains of BLC2 with your case/powder/primer/bullet combination.

PMC cases tend to have more material in them, closer to or the same as Milspec, and your powder charge should take this into account.
Click to expand...

I made a mistake in my original post (since corrected). The primers I used are CCI BR-4 small rifle primers. Not sure why I wrote CCI550.
 
257Wby said:
If you are using CCI 550 Magnum pistol primers in your 223 , the flow / flattening of the primers is an indication you are approaching a catastrophic failure. The variance in results for the two days may be attributed to changing ambient temperatures , case dimensions , charge weight ,barrel fouling etc.
A more pressing matter is the use of a primer that is not intended for the high pressures you are subjecting it to.
This article may help explain some of the issues you are experiencing.
https://www.accurateshooter.com/technical-articles/primers-and-pressure-analysis/
Click to expand...

Corrected my initial mistake in the post. I am using CCI BR-4 small rifle primers.
 
ambient temp may be the issue, how much warmer is the indoor range?

I read that 3000 fps should be achievable with 69 gr'ers but stopped near 2850 in mine due to finding accuracy
targets trump chronographs imo
 
There was an atmospheric pressure difference between the different days. Sunny (shooting line is shaded) and +17C first day and rainy day but inside a range at close to same temperature on the second day.
From my measurements, the base of the bullet is likely just touching the top of the powder in the case after it first drops. Any shaking of the case settles the powder slightly below the bullet base. Can't extend the OAL with this bullet profile and not press into the lands.
I think I will try a little below minimums and keep an eye on the pressure signs and velocities. From what I can find, 3000+ fps is a little fast for 68gr bullets, but not a lot of info to verify this. I tried factory Remington 62gr match ammo and it averaged 2980fps on the same day. Bulk 55gr ammo was about 3250fps.
Mostly, I was taken aback a little when load range I first settled on gave me good grouping and was at the lower end of the published range. Having the same loads show greater pressure signs threw a wrench in my thinking.
 
How's your velocity compared to what the book says they should be, taking barrel length into consideration. Velocity = pressure. I tend to use velocity more than what my primers look for a pressure gauge.
 
bcsteve said:
How's your velocity compared to what the book says they should be, taking barrel length into consideration. Velocity = pressure. I tend to use velocity more than what my primers look for a pressure gauge.
Click to expand...

I'm not too much faster at the lower end. The 24.5 minimum at 2883fps vs my 24.7 at 2883 fps. However mine ramps up a lot quicker. The 26.5 max lists 3029fps and I hit that mark at 25.3 grn. Wish I had the chrony set up for the first day.
 
Did you use the same brass from the first run? Full length resizing? Crush fit on bolt close, or no resistance when you close the bolt on a loaded round?
 
KodiakHntr said:
Did you use the same brass from the first run? Full length resizing? Crush fit on bolt close, or no resistance when you close the bolt on a loaded round?
Click to expand...

I'm using a batch of brass that was processed all at the same time. Full length resized. Bolt closes easily, feels the same with loaded round as it does empty.
 
some info from Quickload

Cartridge : .223 Rem
Bullet : .224, 68, Hornady BTHP M 2278
Useable Case Capaci: 26.663 grain H2O = 1.731 cm³
Cartridge O.A.L. L6: 2.235 inch = 56.77 mm
Barrel Length : 22.0 inch = 558.8 mm
Powder : Hodgdon BL-C2

Predicted data by increasing and decreasing the given charge,
incremented in steps of 1.0% 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

-10.0 83 22.23 2615 1033 41664 7058 93.7 1.137
-09.0 84 22.48 2642 1054 42772 7139 94.1 1.125
-08.0 85 22.72 2669 1075 43917 7219 94.5 1.114
-07.0 86 22.97 2695 1097 45099 7298 94.9 1.102
-06.0 87 23.22 2722 1119 46316 7374 95.3 1.091
-05.0 87 23.47 2749 1141 47568 7449 95.7 1.079 ! Near Maximum !
-04.0 88 23.71 2776 1163 48857 7523 96.0 1.068 ! Near Maximum !
-03.0 89 23.96 2802 1186 50183 7594 96.4 1.057 ! Near Maximum !
-02.0 90 24.21 2829 1208 51550 7663 96.7 1.046 ! Near Maximum !
-01.0 91 24.45 2856 1231 52957 7731 97.1 1.035 ! Near Maximum !
+00.0 92 24.70 2883 1255 54407 7796 97.4 1.024 !DANGEROUS LOAD-DO NOT USE!
+01.0 93 24.95 2909 1278 55901 7859 97.7 1.013 !DANGEROUS LOAD-DO NOT USE!
+02.0 94 25.19 2936 1302 57441 7919 97.9 1.002 !DANGEROUS LOAD-DO NOT USE!
+03.0 95 25.44 2963 1325 59028 7978 98.2 0.992 !DANGEROUS LOAD-DO NOT USE!
+04.0 96 25.69 2990 1349 60665 8034 98.4 0.981 !DANGEROUS LOAD-DO NOT USE!
+05.0 97 25.94 3016 1374 62360 8087 98.7 0.971 !DANGEROUS LOAD-DO NOT USE!
Click to expand...
 
groundrush said:
No extractor marks. Easy clean ejection. Headspace is 0.02" from the lands.
Click to expand...

Do you mean you have 2/100ths headspace, or your bullet jump is 2/100ths, because these aren't the same thing. 2/100ths headspace is a problem.

Anyway, the temperature outside, neck tension, bullet jump, fouling in the barrel, etc etc. can all affect pressures.

You're nowhere near the max for that load - my guess is seating depth, or maybe an over-pour. Did they all look like that, or just the one in the picture?
 
Canuck65 said:
quote_icon.png
Originally Posted by groundrush

No extractor marks. Easy clean ejection. Headspace is 0.02" from the lands.



Do you mean you have 2/100ths headspace, or your bullet jump is 2/100ths, because these aren't the same thing. 2/100ths headspace is a problem.
Click to expand...

.020 is 20 thou, .002 is 2 thou
 
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