243 win with 75 grain HP suprise

[corbin9191]

Well I loaded some rounds up for my brothers 243 win with 41.2 grains of IMR 4064 (worked up the load very cautiously) and a Hornady 75 grain hollow point bullet for varmint. Well we were getting good groups but we didnt know what the velocity was going. We expected it to be going around 3400 with a 22 inch barrel. So we put five rounds through the crony and to our surprise we were getting 3849 fps on average!!! I could not believe the speed so We waited a day and put a new battery in the crony just to be sure and went and put 5 more rounds through the crony and it showed the same average number for the five shot string. There is no pressure signs what so ever, not even a cratered primer. Is this even possible or is there something going on. The rifle is a savage model 110 in the 243 Winchester. I even shot a couple other guns through the crony just to see if the crony was giving us false readings and they were the same velocity as before. The crony was set up at 15 feet from the end of the muzzle.

 

[remingtonman_25_06]

I dont think theres any way to get that velocity without being way over pressure, and you would see those signs.

Dont really know what else to tell you other then to do some actual shooting drop data.

Sight in at 100 yards and shoot at say 500 and see how much it drops. You should be able to tell the velocity by the drop, or close to it.

Let us know what happens.

 

[corbin9191]

I dont think theres any way to get that velocity without being way over pressure, and you would see those signs.

Dont really know what else to tell you other then to do some actual shooting drop data.

Sight in at 100 yards and shoot at say 500 and see how much it drops. You should be able to tell the velocity by the drop, or close to it.

Let us know what happens.

Yeah I thought that was very strange that they were going that fast and there was not pressure signs (primer was looking great, no extractor mark, easy bolt lift, and the brass didnt even expand more than usuall.) But I will do the 500 yard test and see were it is hitting. I will also run some more rounds through the crony and see what they are running now that the temps are around 30 degrees instead of 63 like they were on that day.

 

[R Flowers]

For starters, you load is a good deal over the maximum listed in the Hornady Reloading Manual. However, I still doubt that the velocity readings are correct.

Chrony's are notorious for giving high readings when they are not set up properly. Several people I know have had this problem.

I would suggest trying to find someone who has another brand of chronograph and see what the speeds are over that one.

It is highly unlikely that you are getting that kind of speed from a .243 Winchester with a 22 inch barrel.

 

[jmad_81]

Seems pretty dang fast to me...Don't see how that couldn't be over preasuring :? . Maybe you have a very special .243, but I can't even get those that fast out of my 26" tube.

 

[DrMike]

Check to make certain your Chrony is fully extended. Sometimes, it will appear to be fully opened, but opening it on a flat surface will reveal that it failed to open fully. The velocity is excessive, which points to pressure as excessive, unless the chronograph is faulty.

 

[corbin9191]

Thank you for all the reply's, I am pretty sure that the crony is at fault here for giving the faulty readings. I went through my strings last night and found out that one of the bullets from my 9mmx19 was reading 4217 fps that same night. So I am going to change the battery once again and try some more bullets through it and see, and I will make sure that the crony is laid out flat just like is always is while I am shooting through it but it could have folded up a little bit. Plus I will make sure there is plenty of light when I am shooting through the crony, because I know that will through it off quite a bit as well and it was getting to that point where is could through off false readings. But on two different days... :?:

 

[DrMike]

Insufficient light should not give an exaggerated velocity. Rather, it would fail to give a reading if anything at all happened (failure to register a shadow). It is always possible that a photoelectric cell is faulty, or that there is dust/dirt on the lens which moves, giving a false reading. Make certain the lens are clear and that there are no droplets of moisture obscuring the lens. Check your readings against other cartridges with a known velocity. You can always send the unit back to Shooting Chrony for a check-up and to calibrate the system.

 

[Richracer1]

I feel your pain, I "supposedly" have a 30-06 that will shoot 180ABs at an average 2922FPS. I have yet to retest, but the 180ET had an avg of 2750fps. So..........

 

[cold_hunter]

i can only say this, my savage 25-06 is a faster than what the book claims not thaty fast but up to 200 fps over book. so do the 500yd test and go with it. people dont need to believe you

 

[corbin9191]

Check your readings against other cartridges with a known velocity.

That same night I tested my 25-06 and it was giving the same reading as the previous 2 weeks.

 

[R Flowers]

Corbin, as a clinical scientist, I can tell you that repeating an answer and getting the same results does NOT mean it is correct.

It is comforting that your 25-06 gave the same results as previously tested, but they could be just as wrong.

 

[DrMike]

It is comforting that your 25-06 gave the same results as previously tested, but they could be just as wrong.

+1

You still need to check against "a known velocity." This provides a rough calibration of your unit.

 

[corbin9191]

Corbin, as a clinical scientist, I can tell you that repeating an answer and getting the same results does NOT mean it is correct.

It is comforting that your 25-06 gave the same results as previously tested, but they could be just as wrong.

I know by repeating an answer and geting the same results does not mean it is correct. But DrMike wrote a suggestion and I was just letting him know that I did try that already. :grin:

 

[cold_hunter]

dr mike has the best point find someone with a 308 that shoots 168gr match ammo that knows the load and try that if u can. the first time my 25-o6 showed 3800 with a 75gr VMAX i was real pleased and its true. the thing is that kind of fps is hard on things, like barrel throats

 

[corbin9191]

dr mike has the best point find someone with a 308 that shoots 168gr match ammo that knows the load and try that if u can. the first time my 25-o6 showed 3800 with a 75gr VMAX i was real pleased and its true. the thing is that kind of fps is hard on things, like barrel throats

Oh, Ok I see what he is saying. Sorry I took it a different way. I will do that then. Thank you everyone for all the help.

 

[FOTIS]

Ensure the chrony is unfolded all the way.

I once chrono'ed a 200 grain nosler at 3400 fps from a 308 Norma!!!! The chrony was not extended all the way

Cartridge : .243 Win.
Bullet : .243, 75, Hornady HP 2420
Cartridge O.A.L. L6: 2.710 inch or 68.83 mm
Barrel Length : 22.0 inch or 558.8 mm
Powder : IMR 4064

Predicted data by increasing and decreasing the given charge,
incremented in steps of 3.0% 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

-30.0 64 28.84 2354 923 23267 7503 85.8 1.467
-27.0 67 30.08 2445 995 25521 7926 87.9 1.418
-24.0 70 31.31 2535 1070 27974 8337 89.9 1.372
-21.0 73 32.55 2625 1148 30639 8734 91.7 1.326
-18.0 75 33.78 2715 1228 33532 9113 93.4 1.283
-15.0 78 35.02 2804 1310 36669 9472 94.9 1.242
-12.0 81 36.26 2893 1394 40067 9807 96.2 1.192
-09.0 84 37.49 2980 1479 43747 10115 97.3 1.144
-06.0 86 38.73 3067 1566 47732 10395 98.3 1.098
-03.0 89 39.96 3152 1655 52046 10643 99.0 1.056 ! Near Maximum !
+00.0 92 41.20 3237 1745 56720 10857 99.5 1.015 ! Near Maximum !
+03.0 95 42.44 3319 1835 61784 11035 99.9 0.977 !DANGEROUS LOAD-DO NOT USE!
+06.0 97 43.67 3401 1926 67276 11175 100.0 0.941 !DANGEROUS LOAD-DO NOT USE!
+09.0 100 44.91 3481 2018 73236 11290 100.0 0.906 !DANGEROUS LOAD-DO NOT USE!
+12.0 103 46.14 3559 2110 79713 11399 100.0 0.874 !DANGEROUS LOAD-DO NOT USE!
+15.0 106 47.38 3636 2202 86760 11502 100.0 0.843 !DANGEROUS LOAD-DO NOT USE!

Results caused by ± 10% powder lot-to-lot burning rate variation using nominal charge
Data for burning rate increased by 10% relative to nominal value:
+Ba 92 41.20 3356 1876 65736 10560 100.0 0.949 !DANGEROUS LOAD-DO NOT USE!
Data for burning rate decreased by 10% relative to nominal value:
-Ba 92 41.20 3069 1569 47701 10729 95.6 1.102

 

[remingtonman_25_06]

I usually check with a 22 LR.

Make sure the crony is laid straight, new battery and check again.

If I remember correctly, crony's dont work all that well below 32F.

 

[FOTIS]

Ditto!

 

[corbin9191]

I usually check with a 22 LR.

Make sure the crony is laid straight, new battery and check again.

If I remember correctly, crony's dont work all that well below 32F.

Thanks for your help with this. I will probably take the crony out tomorrow and put a couple rounds through it with my 22.