NEW LOAD CARTRIDGE LENGTH HELP. (.243win)

[mike243]

Apologies if this is a bit of a long question/expIanation.

I have finally got to a stage where I can start some load development, rifle all shiney clean, once fired brass all resized to my chamber length minus .002 to .003" all primed and trimmed and the necks expanded to bullet Ø-.002", I have measured to the lands which gives me a CBTO length of 2.298" that gives a COAL of 2.724" which is 14thou longer than the max lenght of 2.710 for .243w, I am initially proposing to load batches of 3 with 0.3gn increases in powder, starting at 38.5gns of H414 upto max charge of 40gns for a 100gn bullet, hopefully finding a string of powder weights that will all group before fiddling with seating depth.
I'm unsure as to what CBTO length to start at, should I start short and work longer or the opposite, any help will be greatly appreciated, the bullets are regular flat base soft points, not the long pointy things
Mike

 

[Cottis]

Save yourself the trouble and use the powder or bullet makers data in terms of COAL. If you want to measure what the max COAL is for your rifle then just seat the bullets between 25-30 thou shorter than the max length. That will be pretty close to a lot of powder/bullet makers data but there are exceptions. I use 70grain noslers in a .243win for fox and I load them to 2.680 inches from memory. The max COAL for the bullet in my rifle is close to 2.740 inches which i was quite surprised at. I normally seat bullet 25 thou back but that would have had very little of the shank of the bullet in the neck. It could well be fine but the book data says 2.680 and they know plenty.

What bullet are you using?

Lastly, is H414 on the reach list of banned powders? If it is, might you struggle to get more of it when you exhaust your supply? Viht N160 is a brilliant powder for heavy for calibre bullets like 100g soft points in the .243

Best of luck with your reloading.

 

[mike243]

Save yourself the trouble and use the powder or bullet makers data in terms of COAL. If you want to measure what the max COAL is for your rifle then just seat the bullets between 25-30 thou shorter than the max length. That will be pretty close to a lot of powder/bullet makers data but there are exceptions. I use 70grain noslers in a .243win for fox and I load them to 2.680 inches from memory. The max COAL for the bullet in my rifle is close to 2.740 inches which i was quite surprised at. I normally seat bullet 25 thou back but that would have had very little of the shank of the bullet in the neck. It could well be fine but the book data says 2.680 and they know plenty.

What bullet are you using?

Lastly, is H414 on the reach list of banned powders? If it is, might you struggle to get more of it when you exhaust your supply? Viht N160 is a brilliant powder for heavy for calibre bullets like 100g soft points in the .243

Best of luck with your reloading.

thanks for the reply Cottis, the bullets are Nosler Partitions, I have almost 3lbs of H414 so should last me out, I have a 1kg bottle of N160 that I got incase I couldnt find any H414, I have been loading my fire forming rounds with it under some 95gn Match kings I had in a drawer, I have 50 fire forming round to shoot off this week, I think I will reload a few dummy rounds with some of that brass to make sure they will fit in the magazine and feed properly and start at that length, the 2.724 cartridge did look ridiculous though

 

[Foxyboy43]

Hmmm. When I started reloading, just after the last Ice Age, I was told to seat the bullet by calibre depth which I did with good results. Then I got interested in what the ‘Merican target shooters were doing - “chasing the lands” i.e. chamber length and backing off only 1 or 2 thou or heaven forefend actually touching the lands but I never quite managed to summon the courage to load them for fear of lack of jump causing a pressure spike. Then I bought a 6.5x55SE and after some experimentation chose Sierra Prohunters as my bullet of choice - brilliantly accurate in my .308 and drops everything in it’s tracks so a great result. However this was when I also discovered that chasing the lands with my initial test rounds resulted in the bullet simply falling out of the case - something to do with the chambering being designed to accommodate much heavier bullets for the Swedes etc. to shoot very large hairy things which sadly and despite global warming we don’t get in the UK.
Soooo the compromise was much shallower seating, a decent crimp and a moderate jump - I then copied this approach to my .308 Prohunters with no impact on measured velocities but a very accurate round as a result - some may disagree (Wot - on SD?) but it works for me - simples!

.308

6.5x55SE (Prohunter on rhs)

 

[timbrayford]

I stick to the SAAMI dimensions and ammunition company reload data, it seems to work fine for clover leaf groups!

 

[25 Sharps]

Apologies if this is a bit of a long question/expIanation.

I have finally got to a stage where I can start some load development, rifle all shiney clean, once fired brass all resized to my chamber length minus .002 to .003" all primed and trimmed and the necks expanded to bullet Ø-.002", I have measured to the lands which gives me a CBTO length of 2.298" that gives a COAL of 2.724" which is 14thou longer than the max lenght of 2.710 for .243w, I am initially proposing to load batches of 3 with 0.3gn increases in powder, starting at 38.5gns of H414 upto max charge of 40gns for a 100gn bullet, hopefully finding a string of powder weights that will all group before fiddling with seating depth.
I'm unsure as to what CBTO length to start at, should I start short and work longer or the opposite, any help will be greatly appreciated, the bullets are regular flat base soft points, not the long pointy things
Mike

Use the length suggested in the data, it really is that simple

 

[sikadog]

Just seat the bullet so it's base is level with the shoulder, if using boat tails just seat to the base of the parallel sides.

 

[sauer]

1. go with COAL in load data for that bullet ... won't go far wrong and I've had bug hole groups doing same
example ...vhit data app... for 53grn vmax & N133 is 2.256" to tip and group was best i ever did

or

2. you can measure with a bullet & comparator say over a 5X measure.... take average then seat 20 thou or whatever you choose off the lands..
do your various powder charges & once you got a charge you like...can tweak again with seating depths .


depends how far down rabbit hole you wan t to go chasing that elusive "one hole gorup"


Paul

 

[mike243]

1. go with COAL in load data for that bullet ... won't go far wrong and I've had bug hole groups doing same
example ...vhit data app... for 53grn vmax & N133 is 2.256" to tip and group was best i ever did

or

2. you can measure with a bullet & comparator say over a 5X measure.... take average then seat 20 thou or whatever you choose off the lands..
do your various powder charges & once you got a charge you like...can tweak again with seating depths .


depends how far down rabbit hole you wan t to go chasing that elusive "one hole gorup"


Paul

Cheers Paul

in the end I loaded a dummy round right out to the lands and then tried it in the mag, I had to shorten it a few times before it would feed easily into the mag and out into the breech, the final starting length is 15thou shorter than the 2.710 max COAL which if my sums are right .029 out from the rifling, lets see where that leads

 

[Foxyboy43]

 

[Cottis]

Apologies if this is a bit of a long question/expIanation.

I have finally got to a stage where I can start some load development, rifle all shiney clean, once fired brass all resized to my chamber length minus .002 to .003" all primed and trimmed and the necks expanded to bullet Ø-.002", I have measured to the lands which gives me a CBTO length of 2.298" that gives a COAL of 2.724" which is 14thou longer than the max lenght of 2.710 for .243w, I am initially proposing to load batches of 3 with 0.3gn increases in powder, starting at 38.5gns of H414 upto max charge of 40gns for a 100gn bullet, hopefully finding a string of powder weights that will all group before fiddling with seating depth.
I'm unsure as to what CBTO length to start at, should I start short and work longer or the opposite, any help will be greatly appreciated, the bullets are regular flat base soft points, not the long pointy things
Mike

Sorry, I got my figures wrong when I replied to your initial post. I need to put some more fox rounds together, so I was just checking my notes. The book data cartridge length I quoted was for 100grain bullets and sounds very similar to the measurements you are quoting. Which makes sense as most .243 chambers are probably cut in a very similar way from factory and 100g bullets will be longer than lighter bullets, mostly.

Try not to quote figures like CBTO. That is just an ambiguous number relevant only to you and the tool you are using. Remember that a comparator as such is comparing. Unless someone has exactly the same tool as you, it is just a spurious number that is meaningless to anyone else. It is a number that you personally can alway relate back to. Calipers on the other hand do not lie and the measurement of COAL is what it is and will be the same for everyone who has a working set of calipers (assuming cases and bullets etc are equal)

Back to my 70grain noslers. They are not seated at book depth as that would have well north of 60 thou jump and although I cannot recall (it was some years back), I expect I would have tried book data first and I imagine they did not shoot that well so I would have shortened it to around the 25 thou mark, which is an area that I tend to find most accuracy, whilst not risking jamming bullets and potentially causing pressure issues.

Anyhow, sounds like you have found a length which fits in your mag and sounds very close to book data from a COAL point of view. I imagine it will shoot fine. Sorry for the confusion in my earlier post.

 

[mike243]

this afternoons load test results shot at 50yds from sand bags on the bonnet of my truck, I fired 6 fouling/fire forming rounds first, the top 2 goups show 3 holes but the very top left and top right holes are where I pegged the paper to the backing, the 3rd bullet in both those groups went high just off the paper, the 39.7gn group is only 2 shots, the 3rd round was tight to chamber so I didnt fire it, i'll strip it down and rezise the case again, I am proper chuffed with the 40.0 group, I will load another 3 of those along with 3 more 39.7 and 3x 40.3

40.0gn is max load for the bullet weight and powder but there was no sticky bolt or super flat primers, if the 40.3gn first shot shows any pressure signs I wont fire the other two

 

[fizzbangwhallop]

Evening Mike,
Just looked up my load for the 70gn Nosler Baltips and H414 which I’ve personally been using since 2001 having been recommended it and I know of various rifles in which it’s been successful…. Sako A11, RWS, 2 Tikkas, 2 Blasers.

I started off with once-fired FC cases but moved to Lapua.. with 46grns of H414, CCI Large Rifle Magnum primers (recommended to get a good burn of the H414’s ball powder) seated to 2.230”-2.233” using a Stoney Point comparator. The OAL of the 2.230” round in my hand is 2.7095”. In my Blaser Match barrel that was giving me c3463fps measured way back in 2010.

The difference in seating depths between batches haven’t ever made an appreciable difference to my zeroes.

My Hodgdon Book No26 shows the starting/max loads as 43.5 & 47.5. Ditto the Nosler 5th edition.

 

[fizzbangwhallop]

After realising you were talking 100gn bullets, I sent you a pm with the above and more….mean’t to delete the above but obviously didn’t get as far as that!

It was Cottis’s post mentioning 70gn that led me astray

cheers

fizz

 

[25 Sharps]

Sorry, I got my figures wrong when I replied to your initial post. I need to put some more fox rounds together, so I was just checking my notes. The book data cartridge length I quoted was for 100grain bullets and sounds very similar to the measurements you are quoting. Which makes sense as most .243 chambers are probably cut in a very similar way from factory and 100g bullets will be longer than lighter bullets, mostly.

Try not to quote figures like CBTO. That is just an ambiguous number relevant only to you and the tool you are using. Remember that a comparator as such is comparing. Unless someone has exactly the same tool as you, it is just a spurious number that is meaningless to anyone else. It is a number that you personally can alway relate back to. Calipers on the other hand do not lie and the measurement of COAL is what it is and will be the same for everyone who has a working set of calipers (assuming cases and bullets etc are equal)

Back to my 70grain noslers. They are not seated at book depth as that would have well north of 60 thou jump and although I cannot recall (it was some years back), I expect I would have tried book data first and I imagine they did not shoot that well so I would have shortened it to around the 25 thou mark, which is an area that I tend to find most accuracy, whilst not risking jamming bullets and potentially causing pressure issues.

Anyhow, sounds like you have found a length which fits in your mag and sounds very close to book data from a COAL point of view. I imagine it will shoot fine. Sorry for the confusion in my earlier post.

But bullets aren’t equal, particularly soft and plastic pointed bullets which can vary out of the same box.

 

[Cottis]

But bullets aren’t equal, particularly soft and plastic pointed bullets which can vary out of the same box.

I didn't say they are. I also use a comparator to compare my rounds but they do not necessarily provide a generic measurement that everyone can rely on (as in their machined comparators giving the same readings)

It sounds like the OP knows what he is doing to me.

 

[25 Sharps]

I didn't say they are. I also use a comparator to compare my rounds but they do not necessarily provide a generic measurement that everyone can rely on (as in their machined comparators giving the same readings)

It sounds like the OP knows what he is doing to me.

It’s was your statement ‘calipers on the other hand don’t lie’ as they can, in essence, if you are getting variation in bullet length you will get variations in COAL but the jump to the lands for the base of the ogive is constant.

 

[Cottis]

It’s was your statement ‘calipers on the other hand don’t lie’ as they can, in essence, if you are getting variation in bullet length you will get variations in COAL but the jump to the lands for the base of the ogive is constant.

What I meant is that calipers are a constant in terms of being a tool unlike some comparators. Some bullets clearly have differing QC and you are right that some will display more accurate readings when taking a measurement from base to ogive but the difference in base to tip measurements are not as large as some variations I have seen on comparator tools. The other thing is that if people are talking about the same bullet, we will be talking about differences of less than 10 thou in terms of variations between base and tip (base to ogive generally seems to be much less in low single figures of thous of an inch), which unless you are shooting comp benchrest etc, will not be too important for most. The differences I have observed in comparator measurements are more than that.

Nowt wrong with comparators. Useful tools for our own needs. Less useful to quote to others unless everyone has identically machined components.

 

[mike243]

Thanks for you input guys, most helpful, I do get the comparator thing, I put the cbto measurements because I thought the posts would be meaningless without posting what I was seeing, I dont use anything fancy, just the Hornady L and L, I do use the little flat faced piece that fits on the other caliper blade though, it seems to make it easier to position the case correctly, I have also maked the comparator and the holder so that they fit together the same each time, I dont know if it makes any difference, but it works in my head

 

[Cottis]

Thanks for you input guys, most helpful, I do get the comparator thing, I put the cbto measurements because I thought the posts would be meaningless without posting what I was seeing, I dont use anything fancy, just the Hornady L and L, I do use the little flat faced piece that fits on the other caliper blade though, it seems to make it easier to position the case correctly, I have also maked the comparator and the holder so that they fit together the same each time, I dont know if it makes any difference, but it works in my head

You clearly understand the process and looking at the results on paper, you can shoot too. A good combination. You are gonna have no issues.