Downloading a .243

Tamar

Well-Known Member
I've been planning to load up some 65g vmax rounds for foxing and thought that I may try to load some with a bit less 'oomph' and so reduce recoil. I don't think that I need the extra 600fps or uberflat trajectory, given that most of my foxing is over the small fields of Devon where a 100m shot is long range. I've currently got some N160, and usually load 100g softpoints. The min load for N160 given in the Lee Manual (for a 70g bullet) is 49.1g compressed, whereas the min load for a 100g bullet is 34.4g. I read that the danger of down loading is that of flashover, if insufficient case space is used, with the suggestion that 80% of case be filled to avoid this. My calculation is that for a .243 case of 3.4cc, 80% is ~2.75, making a minimum load in N160 of 37.5g

Can anyone suggest any problems that I may encounter if I use this lower 'minimum load' of 37.5g as opposed to the Lee recommendation of 49.1g. I usually stay well within the recommendations, so this is (may be) my first foray into more exploratory reloading:)
 
2014-05-25 16.11.06.jpgI loaded some 75grn v max just for muntie .3400 fps ish no recoil at all four shots in finger nail at 100yrd I shot two cubs yesterday afternoon was not much left of them .they were 40gr imr 4895 20 tho of the lans cci primer and vmax heads I have be told never to go out of your comfort zone ,stay safe:cool:
 
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Thanks for those comments. Downloading in small steps is clearly sensible. Roll on a sunny day to get out on a range!
 
The problem with going down in small stages is the first sign of a problem could be a detonation. I've done a fair bit of testing with reduced loads and subs but I wouldn't risk what you're planning. If you really want to do some reduced loads try and get some h4895 you can safely download it. Data is on hodgdons site. There is also trailboss but that may give you less than you want speed wise.
 
Get a .222!

That's one answer, but you could just say always use a calibre/round appropriate to the task. As the .243win was designed for varmint shooting originally I would suggest that there's really no need to download. Recoil is only minimal with this cartridge anyway, and as rabbit fingers says you could have problems if downloading beyond recommended load data from a manual. In any case you have to ask yourself will the bullet expand reliably at the reduced velocity.
Seriously if you think that the .243w is too much gun for you in your particular circumstances then Mungo is on the right track and get yourself a .222rem you will never regret it.
 
Yes detonations have occurred in pistols calibres, I don't know if it has ever happened in rifles. I don't think that anyone has ever been able to reproduce them though when they have deliberately tried.
 
Yes detonations have occurred in pistols calibres, I don't know if it has ever happened in rifles. I don't think that anyone has ever been able to reproduce them though when they have deliberately tried.

you seem sure ? but also nobody seems to have reproduced it ? I'm still not convinced?
 
Yes I am fairly sure, going back years ago when Nobel of Glasgow produced pistol and shotgun powders (also rifle powders) they did some research into the subject following a couple of incidents involving their powders. They however failed to reproduce a detonation in their tests but came to the conclusion that it was possible.
 
That's one answer, but you could just say always use a calibre/round appropriate to the task. As the .243win was designed for varmint shooting originally I would suggest that there's really no need to download. Recoil is only minimal with this cartridge anyway, and as rabbit fingers says you could have problems if downloading beyond recommended load data from a manual. In any case you have to ask yourself will the bullet expand reliably at the reduced velocity.
Seriously if you think that the .243w is too much gun for you in your particular circumstances then Mungo is on the right track and get yourself a .222rem you will never regret it.

I think that Mungo is just trying to ferment domestic strife:D His wife and mine compare notes regularly and I suspect he's trying to shift bounds of perceived normality on rifle ownership.....

As I understand, flashover is a POSSIBILITY when case fill falls below 80% capacity. My point in the first post is that the recommended minimum load for N160 behind a 100g bullet is 34.4g or 2.52cc. The case capacity of the .243 is 3.42cc, thus the recommended starting load is 73% of case capacity. My question - why would say 37g (~80% case capacity) of N160 behind a 100g bullet be less of a flashover risk than the same load behind a 65g bullet. Perhaps naively, I guess that the lighter bullet would lead to lower pressures over the same charge (less inertia to overcome), hence another facet of risk (overpressure) is removed.

Can anyone recommend a text to read about downloading as it's got me fascinated?
 
Yes I am fairly sure, going back years ago when Nobel of Glasgow produced pistol and shotgun powders (also rifle powders) they did some research into the subject following a couple of incidents involving their powders. They however failed to reproduce a detonation in their tests but came to the conclusion that it was possible.

apparently it's POSSIBLE for me to dance well although despite extensive tests that all failed I came to the conclusion that it is possible.............
 
When a cartridge is designed, the case is supposed to be filled at least to the shoulder. This is for various reasons, it allows the powder to burn progressively from the primer forward But it also stops the powder kernels from abrading on each other and effectively creating a faster burning powder. I have seen a Ruger Blakhawk pistol , these were massively strong,let go when the owner only used 6 g of powder compared to the standard load of 24g. So yes detonation can and does occur.
 
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When a cartridge is designed, the case is supposed to be filled at least to the shoulder. This is for various reasons, it allows the powder to burn progressively from the primer forward But it also stops the powder kernels from abrading on each other and effectively creating a faster burning powder. I have seen a Ruger Blakhawk pistol let go when the owner only used 6 g of powder compared to the standard load of 24g. So yes detonation can and does occur.

can you reproduce your findings , or is it just a guess ?
 
Read Parker O Ackley's book: "Handbook for Shooter's and Reloading"

detailed descriptions of the phenomenon

Handbook for Shooters and Reloaders: Amazon.co.uk: Parker O Ackley: Books


To the OP
One of the issues with what you are suggesting is not the concept but the powder choice
using a faster powder whilst further reducing case fill is one option (subsonic loads use VERY fast powder in VERY small quantities)
using a magnum primer is another

Some light reading for you:




 
Bewsher500 - That is much appreciated and provides some of the evidence that others on the thread are looking for. Thanks for that.

However...... (and this is not directed specifically at Bewsher) although I fully appreciate that a substantial cut in powder (>50% as indicated in the examples in the photo-book above) can be catastrophic, I'm still left wondering how the min recommended load for (in this specific case) N160 with a 100g bullet is 34.4g, whereas for the 70g bullet in the same calibre it is 49.1g compressed. Sure, the bullet takes up a slightly smaller portion of the cartridge case, but not 15g worth. Thus - why should my rifle risk exploding if I place a load recommended for one bullet weight behind a lighter bullet? I'm not looking for someone to say 'Oh it'll be OK' and then I get on with it and blow my rifle up - I'm now genuinely interested in the science (and perhaps the mythology) behind downloading. If only I had the money, range and stupidity of the Mythbusters to tackle this question formally:)
 
I'm still left wondering how the min recommended load for (in this specific case) N160 with a 100g bullet is 34.4g, whereas for the 70g bullet in the same calibre it is 49.1g compressed.

not sure if this is the the question you mean but the reason the lighter bullet requires a larger load is down to the pressure required
less mass to shift = less pressure for a fixed charge

the detonation issue is usually put down to the way in which the charge burns and the concern that the volume of air for a specific burn rate of powder/primer combination leads to catastrophic consequences

I have a tub of blue dot (very fast) and a set of load data for subsonic and mildly supersonic loads using 87-100gr bullets.
Very light single figure Grain charges are enough

Rather than becoming a statistic for why you shouldn't try this at home I would be happy to provide you some to try.
much better using a proven/chrono'd download recipe
 
Read Parker O Ackley's book: "Handbook for Shooter's and Reloading"

detailed descriptions of the phenomenon

Handbook for Shooters and Reloaders: Amazon.co.uk: Parker O Ackley: Books


To the OP
One of the issues with what you are suggesting is not the concept but the powder choice
using a faster powder whilst further reducing case fill is one option (subsonic loads use VERY fast powder in VERY small quantities)
using a magnum primer is another

Some light reading for you:





Thanks for the Amazon reference - I went and bought the Kindle edition.
Now for some interesting reading.
 
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