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> why is my barrel so slow
why is my barrel so slow
@ 04:39 am (GMT) |
G DogHi guys (and girls),Ive just done some load testing with my new (old) tang safety ruger in 7x57 and I couldn't believe the speeds (lack off) I was getting. Powder AR2209 projectiles are 162 amax, 160gr accubonds and 154gr sst. Power charge weights from 45gr up to 46.5. Speeds were 2250avg to 2450avg, this is a good 150fps slower than I anticipted. Is it just s case of the barrel being slow? Barrel is in very good condition. any ideas, I can maybe load 1 grain more. cheers |
Replies
@ 08:27 am (GMT) |
Thomas KitchenRe: why is my barrel so slowhi grantjust after few more details how long is the barrel? do you no how much freebore / jump you have to rifling you have? are you seeing any pressure signs? |
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@ 08:46 am (GMT) |
G DogRe: why is my barrel so slowHi Thomas,-22" -160 thou jump from memory there abouts anyway. I think the amaxs were closer to 200 thou. Projectiles are seated .284 (caliber) depth. Twist rate should be 1:8.75. I dont mind slower loads, but Ive never had a barrel this slow before. Grant |
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@ 08:48 am (GMT) |
G DogRe: why is my barrel so slowForgot to add, no pressure signs at all. New norma brass and cci primers. |
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@ 09:13 am (GMT) |
Thomas KitchenRe: why is my barrel so slowok hopefully someone can be of more help then me.few things spring to mind. you might have a short throat. new brass has slightly less capacity then once fired brass. if you run out of room before you see any pressure signs you might have to go to quicker burning powder like 2208/varget. how the accuracy even if its bit slower then you would like? |
@ 09:41 am (GMT) |
Jacob JensenRe: why is my barrel so slowTo rule your cronograph out sight in at 100 meters/yards and then go to 600 meters/yards and sight in again (Take note of your actual drop and put the data into the ballistic app "Shooter" wich has a velocity calculator. That way you get the true Vo of your load. Please ignore the horizontal spread since you only look at the drop!If the barrel still turns out slow, try with 2-3mm jump 0,098 - 0,118 inch. I see the 7X57 much like the 6.5x55 Swede. The swede generates lots of its velocity because of the large jump. Jacob |
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@ 10:39 am (GMT) |
Jacob JensenRe: why is my barrel so slowJust ran your load data thrugh Quickload.Your problem is the long COAL vs. powderload. My program calculates the exact same velocitys as you display in your first post. With a seating depth of 0,284 inch your COAL with 162gr Amax will be aprox 85mm or more. As Nathan describes in his book (cartridge research) the Optimal COAL for the Amax is 78,5mm (3,091 inch). If i put that data into QL you will get 2450 - 2550 fps with 45 - 46,5 gr AR2209. If you dont have pressuresigns work your way up in 0,5gr increaments. My guess is you end up near 48gr. But please work up the load!!! 48gr will theoretical give you a Vo of 2630 fps. Jacob |
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@ 04:46 pm (GMT) |
G DogRe: why is my barrel so slow1 load out of each of the 3 projectiles tested shot less than an ". Unfortunately it 2as on the lower side of the velocity scale for the amax and sst. The Accubond shot greater velocity at the highedt charge, but still to slow I believe for a 300yd in my opinion. Good point Thomas re shooting at a longer range and seeing the actual drop.Hi Jacob, thanks for the good info. Should have put my coal in at the start. My current coal is 80.30mm. Thanks for the QL data, very interesting. Yes I'll load some more up in .5 increments, as above, I think ill only be able to get another grain in the case. I'll give it crack and in the next day or 2 and see how it goes and report back. Thanks for tge responses :) |
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@ 04:49 pm (GMT) |
G DogRe: why is my barrel so slowSorry for some of the confusing statements above, what i meant re the accubonds was the best aaccuracy was at the highest charge weight. |
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@ 12:17 am (GMT) |
G DogRe: why is my barrel so slowWell I went out and some some more testing yesterday, just quickly though as I didn't have much time up my sleeve. I bought some test pack projectiles - 139gr sst and 139gr softpoints. I wasn't overly hopeful of good groups due to the twist rate, but was wanting to see what speeds I could get with these. Velocity was not good again. 49grs of 2209 with either projectile produced 2730fps. I think I just have a really slow barrel and will just have to live with it. I can't fit any more powder in unless I seat the projectiles further out.I loaded up some 162 amaxs and 160gr accubonds with a charge weight of 48gr. I was a bit naughty and went straight to 48 from my previous testing of 46.5. I was confident there would be no pressure signs and once again it's as much powder as I can fit in the case. I could maybe go half a grain more with the accubonds, but because the amax has such a massive boat tale, 48 is the absolute. Pretty much got the speeds Jacob said I would. 2654 avg with the amax and 2602 with the accubonds. the coals for the loads were Amax - 3.187"/80.94mm Accubond - 3.205"/81.44mm Happy enough with the amaxs for the range I shoot too, but I think the accubonds will become a bush load only - better accuracy but too slow for the 300yd shots. Will have to do some more testing though, and on the next set of test I'll load some 154gr SSTs and see if they'll shoot any better and or faster. I could try different powder, maybe go to 2208, but from the research done, 2209(H4350,imr4350) is the more popular choice for this caliber and projectile weight, plus the gunsmith said it'll be more stable in pressure than 2208 if it's at full (or near) capacity. Grant |
@ 01:09 am (GMT) |
Nathan FosterRe: why is my barrel so slowHi Grant, the velocity of 2650fps is generally about right as far as accuracy sweet spots go in the 7x57 - without pushing pressures too high.I see no reason why you should not also experiment with 2208 if you want to run the 139gr SST as well as for further experimentation with the 162gr A-MAX if your current load work does not prove fruitful in the accuracy department. I have had no problems with 2208 in the 7x57 in the past. |
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@ 10:34 pm (GMT) |
G DogRe: why is my barrel so slowCheers Nathan. |
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