I'm using Yew Tree 80.5 and 46grains of N160
Help - Quickload Data - .243 Win + N140
- Thread starter Sampo
- Start date
Sampo
Well-Known Member
I am curious about this as well.
Steve, have you had much chance to test the load with bigger fallow bucks? I'm yet to use a copper .243 on live quarry. Appreciate you are full time at this so would really appreciate your thoughts? Have you changed your shot placement at all?
ChesterP
Well-Known Member
Unsuitable powder choice. As said, you're looking for trouble using a powder charge that high. Vhit have correctly listed their max recommended charge as 37.2gr N140 for that bullet weight and whilst there will be some deviations between bullet types, loading a full 4 grains over what they recommend to achieve the MVs you want is the wrong way of going about it when you really need to consider another more suitable powder such as N160.
GRT for your case volume would suggest that your sensible max pressure loading is close to 38 gr for close on 55Kpsi which gives you a little leaway on pressures to account for batch to batch variations and temperature rise. Vhit suggest 37.2 which sensibly puts you at PMax-15%. They've done this for a reason.
Using that lightweight bullet and N140 doesn't even get you close to 1700ft-lbs. Loading to 38gr gives you 1514 ft-lbs so there's a clue here that really you need to change powder and bullet to something more suitable rather than try and aim for what some bloke on another forum reckoned. Anyone remotely considering using 40.5gr needs their heads examined as this is a 66,000 psi loading.
The advice above is pretty clear. For a deer load perhaps start considering a heavier bullet and different powder?
I shot factory barnes last season with no complaints but caused a lot of damage to the carcass. Only started on the yew tree this season but so far so good everything has gone done within 20 yards out to 200m shots. Headshots very effective. Damage to carcass looks more favourable than the barnes.
No QL isn't always correct, it seems to work very well with Lead, but some results for LF are out.
Using Barnes and Neilsen which have grooves or bore rider bands, my experience has been that QL overestimates velocity and presumably pressure, so some tests have given speeds 100fps+ less than predicted, but no signs of pressure.
Using Nosler E Tips, the results were the opposite, they were going faster than predicted and pressure signs appeared before I was expecting to see them.
ChesterP
Well-Known Member
The advantage with GRT is that the bullet database includes LF, so the derived pressures are based on the actual bullet bearing dimensions and mass which obviously differ between lead and LF. QL has also thrown up a few question marks over the accuracy of some of their assumed powder burn rates, notably I think RS52?
As always, these things are only a guide and working up loads and using a chrony to test MVs is the only reliable way of evaluating what might be safe pressures.
As always, these things are only a guide and working up loads and using a chrony to test MVs is the only reliable way of evaluating what might be safe pressures.
Not sure what you mean by this CP, QL also has a wide range of LF in the database and you can download the latest data sets from the bullet manufacturers if they make them available?
There are certainly some question marks about some burn rates in QL, but isn't this the same in GRT, though there is a confidence rating based upon user feedback, and on some powders this is minimal?
I tend to think that this is mainly down to the different algorithms that the two programs use.
Comparing the same load in GRT and QL can often give very different results until the real world data is fed in and then they both produce predictions that closely correlate.
Whilst I find both useful, I wouldn't have implicit faith in either at the top end of loads until test results in the field have been used to tweak the mathematical models that they use.
Loler UK
Well-Known Member
Having actually pressure tested 100s of cartridges to cip standards let me assure you QL and other software is crap at estimating pressure, especially when it comes to lead free bullets.
Don't take short cuts, ladder up, stay safe.
Study the vit data and see how wildly start and max loads vary for the same weight bullets by different manufacturers, there's a reason for that.
Don't take short cuts, ladder up, stay safe.
Study the vit data and see how wildly start and max loads vary for the same weight bullets by different manufacturers, there's a reason for that.
How so ? For roe and anything bigger in England/Wales you need 1700 ft lbs. For big deer in Scotland its 1750. Though their Roe only need 1000.
As we all surely know, the 243 is just about the bare minimum chambering to be all deer legal. That is assuming that the ammo used is delivering the required muzzle energy. Which does seem rather unlikely if trying to do it with N140.
BTW, in much of Europe the minimum calibre is 6.5mm. Not 6mm. They have their reasons for that.
To be precise:
UK CALIBRE LAW
England & Wales
For muntjac and Chinese water deer only, a rifle with a minimum calibre of not less than .220" and muzzle energy of not less than 1,000 ft/lb and a bullet weight of not less than 50gr may be used. For all deer of any species, a minimum calibre of .240 and minimum muzzle energy of 1,700 ft lb is the legal requirement.
Scotland
For roe deer, the bullet must weigh at least 50gr AND have a minimum muzzle velocity of 2,450 fps AND a minimum muzzle energy of 1,000 ft lb. For all deer of any species, the bullet must weigh at least 100gr AND have a minimum muzzle velocity of 2,450 fps AND a minimum muzzle energy of 1,750 ft lb.
And:
With regards to some of the other popular calibres for deer stalking in the UK, Steve had some interesting things to say, particularly about the .243 Win, which, according to a recent survey of British Deer Society members, accounts for 70 per cent of all deer rifles in the UK. Launched in 1955, the .243 Win is simply a .308 case necked down to accommodate the .243 bullet. The calibre was designed as a vermin calibre in the States, with the optimal bullet weights being 70 to 85gr. It is possible to load heavier bullets into the cartridge, up to 105gr, making them more suitable for deer. In fact, it is only legal to shoot deer (apart from roe) in Scotland with bullets of 100gr or heavier at over 2,450fps. Steve agreed that the .243 is a highly versatile round, but only in the hands of a competent shooter. “There is little margin of error on larger species,” he said. “For foxes, roe, muntjac and Chinese water deer, you couldn't get a better cartridge than a .243 as it is flat flying and accurate, but for larger species, a slight miscalculation on the shot is likely to lead to wounding issues.”
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Already corrected this previously that I blended a few rules in that comment there, none of which related at all to what I should of said. Dont have the 1700ft/lb requirement as I'm not using that calibre and round for deer.
ChesterP
Well-Known Member
I hadn't realised QL had a wide range of LF but haven't used it in a while.
Yes, different programmes may use slightly different methods and algorithms and no one version is infallible. The confidence levels expressed are very useful because the way GRT was set up, the feedback was used to refine each model so the high confidence ones will have been tweaked to be as representative as it's possible to get using modelling. At least to the point where their predictions are in the ballpark. Just where the tweaks have been made is unknown as it can be anywhere from altering friction coefficients for the bullet, to coefficients of ignition, to energy to primer energy etc. The trick is in finding the things which are most likely the cause which takes thought and care in order to produce the best educated guess which is as good as you can do.
It's rarely purely the energy figures that are out. That's urban myth, as these are often taken from manufacturer's data themselves unless that itself is wrong. It's other detail areas which are subject to variability impossible to model consistently, such as variability in uniformity of ignition between different loads, variations affecting coefficients of combustion and a host of other things which cannot be precisely calculated by any model. One obvious one is barrel differences. Take two different rifles of the same calibre and put the same bullet down them. The friction needed to overcome initial movement and the swaging resistance as that bullet is forced down the barrel will vary from barrel to barrel and that affects pressure, barrel time and MV. Anyone expecting any model to predict exact outcomes misses the point and usefulness of modelling.
Whilst there will always invariably be such variations and unknowns, impossible to guess the right answers to, I refute any suggestion which says such modelling cannot predict pressures with any accuracy at all. That's simply untrue. If what is modelled doesn't reflect what's tested, then it's just as likely that the input data somewhere is wrong. Nonsense in = nonsense out every time. I also refute it on the basis of inputting years worth of data and tailoring GRT with calibration based on this data which now has it for me, predicting very closely actual outcomes. Never exact but in many cases very close indeed. That though has involved considerable time spent in refining models, in getting to grips with intricacies if internal ballistics and the realisation the the more you learn, the more you realise you don't know! It's not one to approach with a simplistic view and expecting miracles. It doesn't work that way.
So how do we know that pressures can be modelled to be within the ballpark? Because there is a proven relationship between pressure and MV for every barrel length/cal/bullet type & weight. It can never be exact for all the variables mentioned above but that doesn't make it useless nor close otherwise powder makers themselves as well as bullet manufacturers wouldn't use modelling and many do.
This is a topic which will always spark differences of opinion but my advice would be to all the budding reloaders approaching modelling solutions, do so only if 1) you understand how to use the model properly and 2) consider it as a guide to getting into the ballpark and not as gospel.
I would always put more faith in actual shooting and testing of loads but for me, modelling is a way to circumvent a lot of wasted ammo and undertake my reloading and development steps more efficiently. It also has been a tremendous help in getting a better understanding of internal ballistics. For most stalkers, this will be a meaningless waste of their time and I can fully understand and appreciate that. For people like myself who are both stalkers, target shooters and someone who does have a keen interest in internal and external ballistics, it's also something I enjoy learning and using.
ChesterP
Well-Known Member
I agree up to a point and would always recommend careful ladder testing. However one reason min and max loads for the same bullet weights varies so much is bullet weight itself is not anywhere near accurate enough to be used to judge safe loads. Bullet form factor determines bearing pressure (due to bearing area variation) along with jacket material and thickness, rifling type and twist etc so you will get and should expect to get large variations between the same weights using different bullets and barrels. I appreciate you already know this but for those unwary and delving into it for the first time it's a point worth highlighting.
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