I’m using Viht n160 on a .243 100gn Sierra pro hunter in a 1in 10 barrel. Now after multiple searches looking for load data on Viht there are conflicting data it appears some time in the past the Vhit reload data dramatically reduced the max load however several people they used N160 for years and ysed there original load that exceeded the latest data with new powder and not seen a difference. I looked at an article posted oct 2013 http://roestalker.co.uk/large-deer-legal-243-win-load/. Taking the same principle starting at 39 gr and moving up in increments to 43 gr. Well I started to shoot starting at the 39g when I shot the 41 gr their looks to be start of pressure signs on primer. Primer flatens out ok but on the firing pin indentation there is a ridge forming on the outside edge. I should know what the technical term is however I don’t sorry. So I have not gone further to 42 gr and 43 gr. Coming back to my question I have two conclusions possibly false conclusions. The first is that the latest load data is correct and I need to keep within those guidelines. My second is a another question that I can’t really find an answer to. I used a neck size bushing of .268 , this was probably my second choice as I was would have preferred .269 it was only down to a guy having one for the right price. So does neck size have an impact to pressure, I would imagine it would and I don’t have the information to substantiate my thoughts. If id does could this be the reason that pressure signs are starting to show. I have not chronographer the loads yet. I was going to test the group size then pick a load and test speed. Anyway this has been a bit of a ramble , however thoughts anyone is it powder max load data, or possibly neck Size adding to Pressure signs.
powder max load data, or possibly neck Size what do you think ?
- Thread starter patrol01
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Neck tension has a huge effect on pressure! its like holding a pen gently in your hand so that a light tap will force it through your hand. This is low pressure. Now hold it tight. You would have to use a lot more force to get the pen to go through your grip. This would be high pressure! if you get what I mean.
If you change the neck tension then I would recommend retesting your max loads as in most cases you would have to drop your load.
If your seeing your primer flatten out and a ridge around the fireing in I wouldn't go any higher! as the next step is blown primers!
If you change the neck tension then I would recommend retesting your max loads as in most cases you would have to drop your load.
If your seeing your primer flatten out and a ridge around the fireing in I wouldn't go any higher! as the next step is blown primers!
deeangeo
Well-Known Member
The ridge around the firing pin indent is called 'cratering'. It's a probable indication of high pressure.
Personally, I would revert to F/L resizing and ensure consistent case dimesions. Neck resizing only, will result anyway in eventually having to f/L resize and along the way is more than likely to cause difficulty chambering after a few firings. This means the case shoulder dimensions have 'grown' to the point where the cartridge cannot be chambered freely, therefore max level load pressure could increase beyond what was established and reaching undesireable levels. ATB
Personally, I would revert to F/L resizing and ensure consistent case dimesions. Neck resizing only, will result anyway in eventually having to f/L resize and along the way is more than likely to cause difficulty chambering after a few firings. This means the case shoulder dimensions have 'grown' to the point where the cartridge cannot be chambered freely, therefore max level load pressure could increase beyond what was established and reaching undesireable levels. ATB
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otisthedog
Well-Known Member
I had the same confusion recently re Viht data, using the same powder and bullet as yourself. Loading at VV data's OAL of 2.689, I started at 38gr and worked up in 0.5gr increments. I stopped at 42gr as I was getting extractor marks, cratered primers and stiff bolt lift. I backed off and found the most accurate load at 40.6gr. Chronographed, these are going 2915fps average, out of a 24in barrel. I am using a Lee Loader to load, which neck sizes only. Hope this helps!
bewsher500
Well-Known Member
#1 - max loads are not like speed limits.
one rifle may show pressure signs at 39gr, one may not see them until a compressed load
brass brand/size/volume/condition
primer brand/lot number
chamber size
powder brand/lot number
chamber dimensions/ barrel/bore/throat condition and dimensions
temperature and what day of the week you fire them all impact pressure and EVERY GUN AND LOAD COMBO IS DIFFERENT
Simple rule: use the book as a guide...that is all it is. find your limits carefully and back off, or just find the most accurate load and stick with it
#2 Yes it does.
but in simple terms if you under size the case neck the bullet will size it correctly for you!
The tension is not just a component of neck size
neck thickness, brass elasticity, surface of neck and bullet, chamber size...etc etc all come into play
#1 - Not quite
It is a possible indication of high pressure
It is a probable indication of a firing pin to bolt face hole clearance issue (bushing is an option)
I have a .222 BRNO that does this with every load no matter how weak
it is not an issue until it becomes one
if you are worried try a primer with a thicker shell.. IIRC federal are thicker than CCI. google will help you there
#2 - I ONLY neck sized my .243 N160 100gr loads (Norma Brass)
they were moderate loads I used for roe so ME was not a concern
Even in .243 the case never grew past max
The cases never failed to chamber
Load level and brass condition is fundamental in neck sizing being repeatable and not requiring FL sizing
I have 300WM brass (Norma again) that are on their 4th or 5th firing with a book max load of 78gr of H1000 that have only ever been neck sized
still chamber freely
#3 - not sure I understand what you mean here.
a case that is so large it does not chamber freely with all other things remaining constant will have a nominally larger internal volume and therefore demonstrate a slightly lower pressure than the same load in a FL sized case.
I have not changed loads between Neck and FL sized cases though as it is likely to be of no consequence unless at an absolute limit where a temp change could have a more significant effect
Patrol
It doesn't matter too much what data Vihtavuori publish - there are tolerances on all things & you must work in the real world with your own real components & the results you obtain. You started low & carefully worked up - That's the safe way to work.
You are getting reliable indications that you have reached the high pressure range in your tests so you need to do something to reduce it.
--- Alter one parameter at once & test the result.
Assuming that your cases are set at the correct headspace length and are all trimmed to the same length as stated in the SAAMI spec.
Firstly - Is the 100 grain bullet touching the bore lands on chambering the round? --- If so you need to seat the bullets deeper & have a jump to the lands.
(In 243 it is very easy to get excessively high pressures developed by ramming the bullet into the rifling) Bear in mind though that seating bullets deeper into the case will increase pressure so you need to work up the load powder charge again.
Your 100 grain bullet is a flat base design so I'd recomend setting it at a seating depth to make it just get full contact in the case neck bore whilst not touching the lands when chambered. This gives a good bullet guiding/concentricity condition that will leave a good case volume to start with.
At this COAL you should have no problems with overall length & magazine length.
With respect to neck tension, a quick way to give an indication is to measure a sized case neck outside diameter before & after loading the bullet. (it will be bigger after) 0.002" increase is often about right, but there is no single absolute rule on this.
Read the article :-
The Rifleman's Journal: Basics: Neck Tension
It may help you understand. It states:-
"Bullet grip is affected by many things, such as:
1. Neck-wall thickness
2. Amount of bearing surface (shank) in the neck
3. Surface condition inside of neck (carbon can act as a lubricant; ultrasonic cleaning makes necks "grabby")
4. The springiness of the brass (which is related to degree of work-hardening; # of firings; time between annealings)
5. Time during which the loaded round has sat prior to firing
--and there are others..."
It is possible to fiddle about with neck tension, but I have never needed to do it to alter pressure and feel that unless you have massively high neck tension it is a red herring. I suspect it is simply that you have found the max charge for your rifle with your components.
As long as you are getting appropriate velocities surely the important thing is to find the most accurate load for accuracy below the onset of pressure indication. - I use the OCW system to find the best load range then tweak it by seating the bullet deeper to fine tune it.
If you're not happy then you could always start again with another powder like Reloder 22.
Ian
It doesn't matter too much what data Vihtavuori publish - there are tolerances on all things & you must work in the real world with your own real components & the results you obtain. You started low & carefully worked up - That's the safe way to work.
You are getting reliable indications that you have reached the high pressure range in your tests so you need to do something to reduce it.
--- Alter one parameter at once & test the result.
Assuming that your cases are set at the correct headspace length and are all trimmed to the same length as stated in the SAAMI spec.
Firstly - Is the 100 grain bullet touching the bore lands on chambering the round? --- If so you need to seat the bullets deeper & have a jump to the lands.
(In 243 it is very easy to get excessively high pressures developed by ramming the bullet into the rifling) Bear in mind though that seating bullets deeper into the case will increase pressure so you need to work up the load powder charge again.
Your 100 grain bullet is a flat base design so I'd recomend setting it at a seating depth to make it just get full contact in the case neck bore whilst not touching the lands when chambered. This gives a good bullet guiding/concentricity condition that will leave a good case volume to start with.
At this COAL you should have no problems with overall length & magazine length.
With respect to neck tension, a quick way to give an indication is to measure a sized case neck outside diameter before & after loading the bullet. (it will be bigger after) 0.002" increase is often about right, but there is no single absolute rule on this.
Read the article :-
The Rifleman's Journal: Basics: Neck Tension
It may help you understand. It states:-
"Bullet grip is affected by many things, such as:
1. Neck-wall thickness
2. Amount of bearing surface (shank) in the neck
3. Surface condition inside of neck (carbon can act as a lubricant; ultrasonic cleaning makes necks "grabby")
4. The springiness of the brass (which is related to degree of work-hardening; # of firings; time between annealings)
5. Time during which the loaded round has sat prior to firing
--and there are others..."
It is possible to fiddle about with neck tension, but I have never needed to do it to alter pressure and feel that unless you have massively high neck tension it is a red herring. I suspect it is simply that you have found the max charge for your rifle with your components.
As long as you are getting appropriate velocities surely the important thing is to find the most accurate load for accuracy below the onset of pressure indication. - I use the OCW system to find the best load range then tweak it by seating the bullet deeper to fine tune it.
If you're not happy then you could always start again with another powder like Reloder 22.
Ian
One of the problems with Vhit powder data is that they list no pressures like Hodgdon does. Data is constantly updated so it is prudent to use the latest available data.
You could switch powders. Ii it were me I'd sell off that 243 and buying a rifle I didn't need to ride MAX pressures with to have it be legal.~Muir
You could switch powders. Ii it were me I'd sell off that 243 and buying a rifle I didn't need to ride MAX pressures with to have it be legal.~Muir
Sorry Muir i didn't realy understand what you said on the last line ?
Did I misunderstand? I was under the impression that you were running hot(ter) loads to keep it deer legal. My apologies if I misunderstood. If that was the case, I'd sell it and buy a harder hitting rifle.~Muir
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