Yes, the H4350 Ba default is 0.5130 at the default 70 degrees. When I set the actual temperature to 44 degrees the Ba adjusts down to 0.5009. Perhaps ammo was not at ambient air temp. I'll rerun predictions at a warmer temperature.
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I reran the numbers at 70 degrees. It still takes an adjusted Ba of 0.5650 to get a MV of 2943.
waveslayer
Well-Known Member
QL needs to be adjusted. I often go over 10% for Ba.
One common error is measuring case capacity after firing. Measure after resizing and note the difference, it's more accurate what you will me reloading to. Using fired cases tells you what to bump back the reloading die to.
Ensure accurate temp, burn rates, OAL, barrel length, and you should be pretty good. Guys remember QL isn't a 100% it's a starting point.
PM with any questions
One common error is measuring case capacity after firing. Measure after resizing and note the difference, it's more accurate what you will me reloading to. Using fired cases tells you what to bump back the reloading die to.
Ensure accurate temp, burn rates, OAL, barrel length, and you should be pretty good. Guys remember QL isn't a 100% it's a starting point.
PM with any questions
If you have input all the parameters w great care, measuring your brass vol. in h20, using all the same headstamp brass, adjusting start press. for bullet type, examining the weighting factor for your powder, and seating depth and bbl. length,
then get the outdoor temperature conditions adjusted as that will affect and change your Ba.
One caveat. If you are doing mostly range shooting repetively, use only the first velocity to see what your Ba needs to be to match, because if you are not cooling the barrel, by the 5th shot, your chamber is likely 120 F plus. Ba is very sensitive even
with the Hodgdon extreme powders. Ba can does still vary
some even w those powders.
Powders like RL26 above 85 to 90 can be just crazy in variance of Ba.
It is not unreasonable lot to lot to have 10% Difference in Ba.
With temperature, its actually very likely. Work on all the other parameters. Then tune the Ba to match temp and conditions.
then get the outdoor temperature conditions adjusted as that will affect and change your Ba.
One caveat. If you are doing mostly range shooting repetively, use only the first velocity to see what your Ba needs to be to match, because if you are not cooling the barrel, by the 5th shot, your chamber is likely 120 F plus. Ba is very sensitive even
with the Hodgdon extreme powders. Ba can does still vary
some even w those powders.
Powders like RL26 above 85 to 90 can be just crazy in variance of Ba.
It is not unreasonable lot to lot to have 10% Difference in Ba.
With temperature, its actually very likely. Work on all the other parameters. Then tune the Ba to match temp and conditions.
Mikecr
Well-Known Member
Just pick other barrels of the same cal. They're in different cartridges, but that doesn't matter provided you enter H20 capacity for YOUR cartridge. Different barrels are often faster or slower, and powder lots vary as well, but the point here is to find out the TRUTH.
A lie is not a truth, and you should not just pick one attribute and lie big time about it, just to match a limited condition.
I believe instead of using a different caliber bbl., what you are trying to do is at the root, adjust for bullet friction. There is a friction adjustment in Quickload for the correct bbl. and caliber. Just use that friction adjustment to adjust velocity a little before playing w Ba.
I would think on a relatively new bbl,
without much wear, the friction could be a bit higher and the velocity actually lower.
As a bbl. is broken in and even wears out, it may speed up and you may get higher velocity than the Ba would or should predict in QL..
It could be its not Ba that is off but your bbl is fast because its worn and bbl friction is lower than assumed.
Where is this barrel friction parameter?
There are 2 or 3 places in Quickload to play with frictional parameters.
You can play with friction characteristics of the bullet itself, or the barrel.
Find this file in your Program Files under the Quickload Folder on your computer:
ql_eng.pdf
Search that file for friction and go to......you will see where in the program the adjustments are and what they cover and how they are used. I have never gone this far myself, but you can do it.
Looks like one of the adjustments is for extra long barrels where the friction QL assumes has to be adjusted because the barrel is just
so long, so much more friction to exit.
Have fun, enjoy.
Mikecr
Well-Known Member
I think friction adjustments are a funny idea that doesn't pass tests.
If you were to take an uncoated barrel, with uncoated bullets, and dry film coat them with Tungsten (WS2), you would find that MV does not change 1fps. This, while WS2 is possibly the slipperiest dry film lubricant in existence.
It implies to me that the speed of barrels is not about friction. I think it's about bullet sealing.
Now some of you may be inclined to counter about reduced MVs with moly.
Well here's the thing about moly: it reduces peak pressure through it's latent heat of vaporization.
That's a property of moly that is different from other friction coatings. The benefit of that can be longer barrel life, but only if managed with a lot of attention. Otherwise, it shortens accurate barrel life. Another benefit could be the allowance of more powder per pressure (better load density), if your chosen powder & load just doesn't fill the case well.
I've noticed past discussions where it seemed accepted that barrels speed up over the first 300rnds.
I have never seen my barrels do that.
The only thing I can guess about it is maybe it's due to less cleaning than I do.
If you were to take an uncoated barrel, with uncoated bullets, and dry film coat them with Tungsten (WS2), you would find that MV does not change 1fps. This, while WS2 is possibly the slipperiest dry film lubricant in existence.
It implies to me that the speed of barrels is not about friction. I think it's about bullet sealing.
Now some of you may be inclined to counter about reduced MVs with moly.
Well here's the thing about moly: it reduces peak pressure through it's latent heat of vaporization.
That's a property of moly that is different from other friction coatings. The benefit of that can be longer barrel life, but only if managed with a lot of attention. Otherwise, it shortens accurate barrel life. Another benefit could be the allowance of more powder per pressure (better load density), if your chosen powder & load just doesn't fill the case well.
I've noticed past discussions where it seemed accepted that barrels speed up over the first 300rnds.
I have never seen my barrels do that.
The only thing I can guess about it is maybe it's due to less cleaning than I do.
Carey Farmer
Well-Known Member
I shot a jump ladder today. 0.010" jump average 3051 fps. 0.030" jump averaged 3028 fps. 0.160" jump averaged 2979 fps. This is pretty typical. These changes in velocity are presumably the result of changes in chamber pressure, and it seems reasonable to assume that Ba and weighting factor don't change with jump. So yes, the higher shot start pressures associated with bullets right at the lands don't completely go away with a 0.030" jump.
If you have a well-seasoned barrel that "sped up" over the first couple hundred rounds, you also have to correct for that - since that increased speed is presumably associated with increased chamber pressure. It isn't reasonable to assume powder burn rate changed based on how many rounds were fired through your rifle, but I think it is reasonable to attribute any "speeding up" to increasing shot start pressure ... perhaps due to heat "roughening up" the lands. Increasing shot start pressure in QuickLoad will give you increased chamber pressure and increased muzzle velocity.
Nope increased velocity w bbl wear is due to less friction between the bullet and the rifling, ie, less surface engraving, therefore higher velocity.
Deeper bullet seating, ie, more jump
because you have less case volume increases start pressure and velocity. This affect in pressure is minor compared to jam though in the lands.
Seating into the lands can spike pressure 5000 psi for jam, and that may also increase velocity but for a different reason.
Carey Farmer
Well-Known Member
I guess we just see barrel "wear" differently. A copper jacket will polish a steel barrel for maybe 10 or 20 rounds and during that time (assuming no change in powder charge) chamber pressure and muzzle velocity typically drop a little. Watch your barrel's bore with a borescope. Particularly if loads are a little hot and powder is double-based, what you will see is heat checking progressing down the barrel. That heat checking sure doesn't look like it would reduce friction. When heat checking begins to be significant at the lands, that is when you will see muzzle velocity going up. That is because heat checking raises start pressure - which increases plasma temperature, powder burn rate, and chamber pressure.
Regarding deeper bullet seating, Mr. Weatherby saw things differently. Add jump to bring pressures down, then add more powder to bring pressure back up and keep the pressure high during the entirety of bullet travel down the bore. That will yield greater muzzle velocity. My 300 Weatherby Magnum says she agrees with Mr. Weatherby. So do the moose I shot with that rifle.
If you add copper fouling into the equation, yes I agree that will increase friction and reduce velocity, but if you keep the bore clean and the rifling begins wearing down over time, and there is less engraving of the bullet w the rifling, ie less friction, the barrel should speed up as it wears out.
I also agreed with you and Wearherby. Jammed in the lands is the highest pressure. Seating deeper with more jump is less pressure than jam. But lets say you are .02 off the lands and seat deeper .04 off the lands.
Less case volume for the explosion increases pressure going from .02 to .04 jump.
Hope that makes sense.
