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long as I don't exceed 46.8gr with the new bullet then i should be fine - over 46.5gr the pressure is over 60k (which quickload has set to over max pressure) - But i think I'll stick with 46.5 as suggested. have it jump 0.020" so an OAL of around 2.900" (or as close as i can get consistently) - should be pretty good... my only beef is i have no idea how to zero it.... hopefully putting in the zero i had for 300 yards with my last batch of factory ammo will see me on target at 300 yards with this ammo, atleast enough so i can sight in.

Some thoughts and observations...

Your previous jump was 110 thou (2.920 - 2.810).
You are now proposing 20 thou (2.920 - 2.900).
Your previous rounds were up to 9 thou above your average length (2.819 - 2.810).
This could reduce your 20 thou jump to 11 thou.

I'm not sure how accurate your chamber measurements were - you did use the words 'seems to be about', so I'm guessing you may not be using a Stoney point gauge and a bullet comparator. So, throw in some measurement error for your chamber and OAL values and that 11 thou could disappear pretty quickly, or at least be down to single figures. This is a very dangerous recipe. Here are some quotes from a sticky thread on OAL over at the snipershide.com forums

"NEVER start jumping and move towards jammed when near or at MAX loads, no,no, no."

[One manual gives the max Varget load for the 2155 as 44.8 grains - your 46.5 grains definitely qualify you for the above statement]

"if we were to (think we) learn(ed) what max charge was without our bullet jammed and then jam it into the riflings, coupled with a max powder charge in search of a most accurate bullet setting we could blow up our rifle, loose both our eyes, our hearing a good portion of our face and destroy the rifle- that is if we come out of it alive. That all sounds scary, which is a good thing."

You need to be very confident in your measurements, your measurement process and have the right tools, before moving towards to the lands, and if you reduce the jump significantly, or start to jam, you should work up again from a safe starting point. Conventional wisdom is that if you change anything about your load you should work up again - you're changing the bullet, and (importantly) reducing the jump significantly.

The old Sierra (2155) is very tolerant of different amounts of jump - you don't need to go to great lengths experimenting with different lengths to get it to shoot well. I don't know if the same goes for the 2156 - I would guess that it might possibly be very slightly more fussy, but not to the extent of many other bullets.

TattooedGun wrote:I don't have chance to get to a 100yard range

Bear in mind that, depending on your twist, the SMK may not be well stabilised by 100 yards (remember the post with the Litz video). For your fine tuning you are probably better off at 200.

TattooedGun wrote:my only beef is i have no idea how to zero it.... hopefully putting in the zero i had for 300 yards with my last batch of factory ammo will see me on target at 300 yards with this ammo, atleast enough so i can sight in.

You should find very little difference at this distance. I'd be surprised if you are much more than 1 or 2 minutes out, assuming no other changes. A 6 foot frame gives you a lot of minutes to work with - I think it's 12 each side of the waterline.

TattooedGun wrote:how do i figure out how much powder i should use for this jump...

Personally, I would keep everything - particularly the jump - the same as your previous load. It is essential to get an accurate chamber measurement, so I would try to get an experienced third party to verify your measurements for confirmation and piece of mind - maybe someone can do this at your next shoot - take a few of your 2156's along for this purpose.

You really don't need big velocities for 300 yard work. For last year's CSF Commonwealth Championships I reduced my long range load by 2 grains for the 300m events - it proved quite successful.

Enjoy your loading and your shooting, and stay safe.

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TattooedGun wrote:Okay, so to follow on form my last load development thread, i recently went to pick up some more reloading bits...

I got 3 lb of hodgden Varget and 500 bullet heads...

but this time i got 2156 - the new palma match bullets instead of the 2155's i did my load development on...

I know, that means my load development will be out... but any idea how much?

can I use the same load with the new bullet and expect similar results?

I don't have chance to get to a 100yard range in order to do some load development before my next shoot (always leaving things to the last minute!)...

I made up the last 40 rounds of the 2155's but i was going to let the future MIL use those and I would use the new ones... although if the load development isnt right, I could be left off the target after my sighters, which would mean no full shoot for me :(

any tips?

load that worked before was 2.800" - will get a digital vernier caliper shortly to get exact measurement
46.5gr varget
federal primer
sierra 2155 HPBT bullet
RWS once fired FL Sized brass...

everything will be the same except the bullet head...

anyone with some sophisticated software care to help out?

rox wrote:Some thoughts and observations...

Your previous jump was 110 thou (2.920 - 2.810).
You are now proposing 20 thou (2.920 - 2.900).
Your previous rounds were up to 9 thou above your average length (2.819 - 2.810).
This could reduce your 20 thou jump to 11 thou.

20 thou seems to be the "industry standard" for full bore TR shooting, it will be more attainable as I now have the use of a digital vernier caliper - something i was lacking when i made the last batch of rounds (leading to a good part of the variation) so i can try to keep consistency moreso than before.

rox wrote: I'm not sure how accurate your chamber measurements were - you did use the words 'seems to be about', so I'm guessing you may not be using a Stoney point gauge and a bullet comparator. So, throw in some measurement error for your chamber and OAL values and that 11 thou could disappear pretty quickly, or at least be down to single figures. This is a very dangerous recipe. Here are some quotes from a sticky thread on OAL over at the snipershide.com forums

Well the way i did it was a tried and tested method seen around the net (and suggested to me by Ovenpaa).

I cut a case down the neck, sized it and placed the bullet in at a big OAL - about 3", then put it in the breech and closed the bolt, reopened the bolt and pulled out the cartridge and measured it (so when the bullet touches the lands it gets seated further back by the pressure of the bolt)


I did this a few times and came back with the same results (or damn close, within a few thou) which gave me the distance to touching the lands - so if i take it back 20 thou - I should have a 20 thou jump.

rox wrote: "NEVER start jumping and move towards jammed when near or at MAX loads, no,no, no."

[One manual gives the max Varget load for the 2155 as 44.8 grains - your 46.5 grains definitely qualify you for the above statement]

"if we were to (think we) learn(ed) what max charge was without our bullet jammed and then jam it into the riflings, coupled with a max powder charge in search of a most accurate bullet setting we could blow up our rifle, loose both our eyes, our hearing a good portion of our face and destroy the rifle- that is if we come out of it alive. That all sounds scary, which is a good thing."

You need to be very confident in your measurements, your measurement process and have the right tools, before moving towards to the lands, and if you reduce the jump significantly, or start to jam, you should work up again from a safe starting point. Conventional wisdom is that if you change anything about your load you should work up again - you're changing the bullet, and (importantly) reducing the jump significantly.

Hmm, point made i guess, I have read on other loading pages around the web of people using over 48gr with these bullets - and indeed when I bought the first batch the guy behind the counter said 48gr was roughly where to start - ofcourse after reading up and being pointed to quickload data for it on these pages it was shown that max loads were around 47gr - but there must be some truth to the 48gr quoted around the net and the load the guy at the shop pointed me to (he got it out of a reloading guide he had behind the counter).

definately around 46.5 the groups tightened up on my rifle and my girlfriends mom's rifle (which by the way I have not changed the jump for as i havent had chance to try and find out what the max OAL to touching the lands would be), but I didnt try any more powders - I would say theres a few more grains before i start seeing signs of overpressure, and whilst I wouldn't want to try anything that would be unsafe - i still feel that the proposed round I have is still well within safe limits.

rox wrote: The old Sierra (2155) is very tolerant of different amounts of jump - you don't need to go to great lengths experimenting with different lengths to get it to shoot well. I don't know if the same goes for the 2156 - I would guess that it might possibly be very slightly more fussy, but not to the extent of many other bullets.

TattooedGun wrote:I don't have chance to get to a 100yard range

Bear in mind that, depending on your twist, the SMK may not be well stabilised by 100 yards (remember the post with the Litz video). For your fine tuning you are probably better off at 200.

This is nice to hear - especially as i'll be down Bisley for the small-bore meeting next week and theres space on the 200yard short siberia range from what i've heard, i was hoping to do a bit more load development...

rox wrote:

TattooedGun wrote:my only beef is i have no idea how to zero it.... hopefully putting in the zero i had for 300 yards with my last batch of factory ammo will see me on target at 300 yards with this ammo, atleast enough so i can sight in.

You should find very little difference at this distance. I'd be surprised if you are much more than 1 or 2 minutes out, assuming no other changes. A 6 foot frame gives you a lot of minutes to work with - I think it's 12 each side of the waterline.

waterline?

rox wrote:

TattooedGun wrote:how do i figure out how much powder i should use for this jump...

Personally, I would keep everything - particularly the jump - the same as your previous load. It is essential to get an accurate chamber measurement, so I would try to get an experienced third party to verify your measurements for confirmation and piece of mind - maybe someone can do this at your next shoot - take a few of your 2156's along for this purpose.

I think I'm going to take this advice - atleast for the shoot I have on Sunday!

keep the load the same except for the different bullets and hope they hit the target atleast mostly in the area i want them to go (the middle!! haha)

and then make up some development loads for use at short siberia to try and hone in my load for my rifle... an afternoon on short siberia will be fun aswell regardless! :)

rox wrote: You really don't need big velocities for 300 yard work. For last year's CSF Commonwealth Championships I reduced my long range load by 2 grains for the 300m events - it proved quite successful.

Enjoy your loading and your shooting, and stay safe.

Yeah, i get that you can develop different loads for different ranges... although one of the things i havent yet done is long range work, and I'd love to have a load developed that works very well at the ranges I frequent (3-600yards) and still works great out to 1000!

I'm young and Niave and i want everything now... I don't want to have to wait... its a curse, but its what i have to live with

Thanks for your input though, I do appreciate it, and I hope I don't come across as arrogant/disrespectful - i realise you are looking out for my safety :)

TattooedGun wrote:Well the way i did it was a tried and tested method seen around the net (and suggested to me by Ovenpaa).

It's not a bad method (I guess it's the best if you don't have any other tools), but you'll get a more reliable and repeatable measurement with a Stoney Point gauge when you can really feel the contact onto the lands (especially when you also have a rod down from the muzzle end), and you've no risk of the bullet sticking at all (potentially giving you a longer reading). Ideally you should perform the chamber measurement with a bullet comparator attached to the callipers, and use the same comparator when you measure the length of your loaded rounds. That way you are (i) measuring close to the point that will contact the lands and (ii) measuring a more consistent part of the bullet.

If you combine these possible sources of error in the worst case they could significantly erode your 20 thou jump - that is my concern. I would definitely invest in a comparator if you don't have one (if you're at the NSRA meeting you could ask HPS to bring one up for you - if you can get hold of them before they arrive to set up their trade stand).

TattooedGun wrote:waterline?

The 'waterline' is an imaginary/invisible horizontal line through the centre of the aiming mark.

TattooedGun wrote:Yeah, i get that you can develop different loads for different ranges...

It's the only time I've ever loaded for a specific distance, and the idea was more about trying to slightly reduce the recoil battering when firing circa 75 shots of .308 in English match/ISSF conditions (in 47 degree heat). I doubt it had any real effect though. For routine TR work from 300 to 1000 I always use one standard load.

TattooedGun wrote:I hope I don't come across as arrogant/disrespectful -

Absolutely not.

..

Well, i spent saturday afternoon loading some rounds for use on sunday, and I split the difference between the OAL of what I wanted to put (0.020" jump (2.900" OAL)) and what rox suggested (keep the OAL the same (2.800")) and upon completing the rounds (yes, I left it until I'd finished the last one, 2 and a half hours later (or fairly close to) before seeing that the powder load was infact a little too hot according to Quick Load, because the 2156 is a longer projectile than the 2155, which meant that at 46.5gr in 2.850" OAL (the split difference i did) was infact a little compressed - according to Quickload, i was within .1 gr of being the "near maximum" - but i was the wrong side of it "dangerous load, do not use".

With just over 60k psi I thought it was worth the risk, as it was right on the pressure load and i was confident that I would'nt have a mishap.

But had I followed rox's advice to the letter the pressure inside the chamber would have been far more extreme, and I would have had to re-load all 40 rounds again :(

Just goes to show, check, check and double check the loads you are using - if you have a way of varifying loads (quickload for example) make sure you use it BEFORE loading too!

As it happens the loads I made up were spot on, there were no signs of over pressure on the spent cases/primers and they shot extremely well (without being able to call wind exactly the rounds went where i went everytime apart from bad calls - there were certainly no flyers!).

I'm off to short siberia (200yds this time) on Saturday to do a bit more load development

As there's only 1 type of case I'm using, it gives me a bit more scope to load different rounds...

I think I'm gonna start at 2.900" OAL for my rifle, and measure my G/F's mom's rifle chamber and see what her round will be.

start at about 46gr and move up in .2gr intervals to about 47gr

and do 3 shot groups, see what we get.

Wind I'm afraid will be the only limiting factor to plot our groups at 200 yards to see which ammo performs the best, as the wind will not be constant :( But It'll be fun to spend a morning on the range firing some boolits again

rox wrote:I would keep everything - particularly the jump - the same as your previous load.

TattooedGun wrote: and what rox suggested (keep the OAL the same (2.800"))

Actually, I said to keep the jump the same, not the OAL (and particularly, don't dramatically reduce the jump when already at or above max load).

The 2156 is about 0.085" longer than the 2155 (1.220 - 1.135), while the base to ogive length is pretty close (measured at within 0.004"). Consequently, by increasing your OAL from 2.800 to 2.850 with the 2156 you've actually increased your jump by 30 thou or so (and reduced case volume/increased compression). This is why I kept harping on about measuring with a comparator.

..

rox wrote:

rox wrote:I would keep everything - particularly the jump - the same as your previous load.

TattooedGun wrote: and what rox suggested (keep the OAL the same (2.800"))

Actually, I said to keep the jump the same, not the OAL (and particularly, don't dramatically reduce the jump when already at or above max load).

Ah, Sorry, I misinterpreted.
I didn't actually know the jump of the 2155 - I never measured it, just made it (as close as i could) to 2.800" OAL.

wouldn't it be more accurate to say don't INCREASE the jump when already at or above max load? then ur jamming the bullet into the cartridge and increasing the pressure (As I did), rather than lowering the pressure when you reduce the jump (seat shallower)?

rox wrote: The 2156 is about 0.085" longer than the 2155 (1.220 - 1.135), while the base to ogive length is pretty close (measured at within 0.004"). Consequently, by increasing your OAL from 2.800 to 2.850 with the 2156 you've actually increased your jump by 30 thou or so (and reduced case volume/increased compression). This is why I kept harping on about measuring with a comparator.
..

Ah, well, I can't use what I don't have unfortunately, so I measured with what I did have, and ended up with the load mentioned above.

I realise that the jump was increased as the bullet was more jammed into the cartridge - hence the higher pressure from the same load.

Had I loaded at 2.900" as I had planned, I would have only changed my jump by 20 thou - albeit decreased instead of increased.

I guess we both kind of assumed that the length of the bullets were the same when comparing them;

rox wrote: Your previous jump was 110 thou (2.920 - 2.810).
You are now proposing 20 thou (2.920 - 2.900).
Your previous rounds were up to 9 thou above your average length (2.819 - 2.810).
This could reduce your 20 thou jump to 11 thou.

Neither of us picked up on the fact that the jump would be different when basing the figures on the OAL of 2 different bullets....

TattooedGun wrote:wouldn't it be more accurate to say don't INCREASE the jump when already at or above max load? then ur jamming the bullet into the cartridge and increasing the pressure (As I did), rather than lowering the pressure when you reduce the jump (seat shallower)?

Both can increase pressure - loading longer can increase peak pressure due to reduced jump or jamming, loading shorter can increase pressure due to reduced case volume. Hence best practice is to work up from safe starting loads when changing any component or aspect of the load.

..

rox wrote:

TattooedGun wrote:wouldn't it be more accurate to say don't INCREASE the jump when already at or above max load? then ur jamming the bullet into the cartridge and increasing the pressure (As I did), rather than lowering the pressure when you reduce the jump (seat shallower)?

Both can increase pressure - loading longer can increase peak pressure due to reduced jump or jamming, loading shorter can increase pressure due to reduced case volume. Hence best practice is to work up from safe starting loads when changing any component or aspect of the load.

..

Surely if you have a maxiumum length (as I did, 2.920") before you get to the lands, then making sure none of your rounds touch that length is being safe as you are not jamming the rounds?

I'm not saying that you shouldnt work up, merely that working within the parameters of understanding that I have - I would think that aslong as you arent jamming the round and keeping the powder under a safe level then you should be fine? decreasing the OAL of the bullet however starts to make the cartridge pressure a bit twitchy...

Either way, I was only just above the pressure limit recommended from Quick Load, and I'm fine, Lesson learned, check the load prior to loading the cartridge!!

TattooedGun wrote:Surely if you have a maxiumum length (as I did, 2.920") before you get to the lands, then making sure none of your rounds touch that length is being safe as you are not jamming the rounds?

It's not purely a binary thing (jammed or not). The closer you get to the lands, the less chance the bullet has to get up speed and momentum before engraving into the rifling. It might not make much pressure difference reducing the jump from 0.070" to 0.050", but reducing it from 0.020" to 0.005" could be more significant (these figures are just for example). Combine some error in chamber measurements, some variation in seating depth and some bearing surface variation and a target jump of 0.020" could quickly erode when the errors combine to create the worst case. Hence, if you're going to work near to maximum loads (or exceed them), and you're going to load relatively close to the lands, then the measurements and process need to be appropriate, accurate and repeatable. I guess this is why the article I referenced suggests developing the load jammed, then any small variations or errors are only likely to make the situation safer, as far as this aspect of pressure is concerned.

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