I don't think I could sell a rifle that wasn't acccurate!
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All optical chronographs can be affected by light conditions. Except maybe infra red back lit ones.
Litz also suggests that wind can set up resonance in the sensor arms which can affect results.
As far as not getting on target I have the view that, particularly with for eg hot 7mm throat burners, that every shot fired is one shot closer to a buggered barrel so I try to minimize firing extra shots for any reason. As such, I would have used your first shots fired when doing your ES and SD testing to at least get hits on a target. Maybe EC's method of not firing anything resembling a group at the ES and SD stage is valid with kinder calibres?
Quite right, even when testing charge weights in the future I will make sure that I am at least on paper, this rifle and scope are new to me and maybe I should have put a bit more time and effort into getting it sighted first.
I have now got it pretty close to right so lesson learned and at least it's a 270win and not a WSM or big magnum.
Oh.....just seen you were testing a poo 70? Might have to reneg on the offer of the radar[emoji1787]
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Hopefully this will sort it. Will do a quick thread about what I have done but hopefully I can now stick to using my magnetospeed
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cool, looks like you've converted your 270 to a muzzle loader. :thumbsup:
that photo looks like you trying method I suggested to find max overall length....LOL
It's very hard to argue with Eric's results. I watched his video about neck sizing vs full length sizing and thought, alright I'll give it a go. It made a bit of a difference. These are two 3 shot groups shot about a month (possibly longer) apart, from the same rifle ( Howa 1500 308), same
type of projectiles from the same box, same powder from the same bottle, etc.
What I'm getting at is the only difference was I full length sized the brass and the group size halved. I know 3 shots is only indicative and maybe Jupiter was fully aligned with Uranus for the second group on the left, but...I'm converted. I'll be full length sizing for this rifle from now on. Attachment 150656
I've always full length sized so your ^ results are good news!
Any of you guys watch Mark and Sam ?
https://www.youtube.com/watch?v=Dn1pRTvmP8k
I have watchEd a few of their videos, am currently trialling their cleaning regime to try and avoid a fouling shot. I’ve only tried this once - shot at a rock at 500 From a clean barrel. Height was good but was about 5 inches right, was very windy though but seems promising. Also far easier than my normal cleaning regime.
I nearly always partial length resize....BECAUSE my first rifle the mighty poohseventy.hates necksized rounds,there is suspicion chamber is slightly offcentre of bore.
full length resize and brass last 3 firings...partial length resize and 6-8
for those who arent familiar with method..screw in full length resizer till it touches base then UNSCREW 1/2 a turn NOT screw in more....it bumps walls of case a little and does most of neck....its in my nosler #2 manual.
@dannyb you havent explained the above photo yet???
clear as mud now thankyou....
Ironically he's just swapped one "moving target" for another. Because what is 'jam'? One case with its own neck tension and runout will never leave the bullet in the exact location as any other case on earth.
Might as well use the 'just touch' method and take an average if you're looking to be super precise.
No, that is incorrect. For the purposes of getting started with load testing, 'jam' is the point beyond which a projectile will stick in the rifling and stay behind if a loaded round is removed from the chamber. He never references this point after an initial measurement. It is a practical safety step to avoid a problematic situation.
The take away message of the video is not to try to measure where the lands are as this is futile (this is a moving target for sure). The whole point of the video is to show a methodology to let the target tell you what seating depth is best. By identifying the closest point to the rifling at which there is a 'tiny group node' to use as your initial length, you maximise your time shooting groups in that window.
After you've shot a bunch of rounds you load 5 rounds at the accurate length plus 3 thousandths to see if the window of accurate lengths has moved. There is no more measuring. Shoot a group to see if the lands have moved.
The only absolute is the base to ogive of a loaded round - this is easily measured.
With the neck tension, bullets, and chamber leades where I've tried this, there has been 1mm of base-to-ogive difference in length between jammed and just touching. Backing off 20 thou (0.5mm) from jammed seems quite a large safety margin for range shooting, and would halve the available length settings I have to experiment with if wanting to keep the bullet in the lands. At the other end I also try to avoid getting too close to the just-touching position because I've found the pressure jumps throw the ES out, and accuracy also showed day-to-day inconsistency. So my preference is to keep the bullet engaged with the rifling and then my adjustment increments are from 0.2mm engaged through to 0.7mm engaged in 0.1mm steps, so 6 steps, hoping to shoot some smaller groups somewhere within those settings. As noted in the previous posts the reference point from where I take these measurements is arbitrary provided I know roughly where the two end points (jam and touch) lie, and can just be the CBTO gauge readings.
On a related but different topic, what are members using for their CBTO measurements please, and how sensitive to clamping force are the measurements if using vernier calipers, ie does the contact surface on the gauge have a tendency to bite into the bullet jacket?
Not having a micrometer seater myself, only verniers to measure, I have sometimes used a set of feeler gauges to accurately increase seating depth from my base measurement. Is this sensible or am I making a laughing stock of myself by even mentioning it ?
Even with a micrometer die adjustment you still have to deal with the contact point of the seating stem being some way up the ogive from where the bullet will make contact with the rifling, and the possible variation in CBTO that that could introduce.
The Hornady gauge is inexpensive, and contacts closer to a more appropriate diameter on the bullet.
Attachment 150794
Anyone got a homemade gauge that they can post a photo of, with details on the construction, and of course of the huge improvements in accuracy that have accrued from its usage ?
RCBS make a calibre specific seating guage. Bos had a .270 win one for sale here recently. The hornady system above is more flexible if you shoot multiple calibres and you can thread your own cases for a custom chamber fit (and save a few dollars). Calibre specific collars are not expensive.
Moa there is a bit of variation in projectile length due to tip condition etc. So if you looking to make small adjustments it might not be so accurate working off total length. Working off the shoulder / contact point (ogive?) should be more accurate.
Just a note on the above, #69: threaded "modified" cases are for the OAL gauge, a measurement that M. Cortina is at pains to emphasize is not required for his method. The stock photo I posted is misleading. Please disregard the equipment on the left that appears to be the end of the OAL gauge and a modified case, and - at the risk of stating the obvious - the process instead being that each loaded (loose) round is measured with the bullet comparator, the part clamped to the caliper jaw on the right, and then returned to the seating die as required to get the CBTO all the same for a given number of rounds that will be shot as a group.
For F Class, I, like most, batch my projectiles. Even with the better brands like Berger you can end up with 3 batches in a box of say 500. Hornady are the worst with some extreme outlyers. Although having said that my last lot of 7mm ELDMs weren't as bad as previous lots.
20 years ago Sierra used to be very bad box to box. It is the outcome of many projectile machines running in parallel with dies at various states of wear.
If you load into the lands you must check any newly acquired projectiles to avoid any surprises.
Some of the top Ozzies are also measuring the boat tails as well.
For hunting, not so important.
I have for years used the Stoney Point (now Hornady) ogive inserts. They do a reasonable job. I also have Sinclairs version of ogive inserts. They actually give a different reading to the Hornady ones. Either the Hornady or the Sinclair contact further up the "ogive", I can't remember which way round. IIRC the Sinclair gives a truer reading. For 30 cal I have a Redback ogive insert (Australian). It is the most accurate of all. It is made out of a section of rifled barrel (unfortunately not a section of my own barrel). It is cut with the same lead angle as my barrel.
Interested to hear of this. I had discounted the option of using a chamber reamer for a home-made bullet comparator, my thinking being that the edge of the ring of contact on a gauge should be as sharp as possible - or at least, not of a shallow taper.
Understood that having a leade that matches the chamber has the advantage of contacting the bullet to give the true base-to-ogive distance.
My concern was that replicating the shallow leade angle in the gauge would make the measurement that much more subject to variation in the pressure applied by the caliper - forcing engagement to some extent with the gauge, and throwing the measurements about.
Any such issues ?
Just a quick update, this is all on hold whilst I sort out a few things, I have sold my Lyman powder dispenser and will be replacing it with a RCBS chargemaster lite.
I have had a change of heart on projectile and powder choice also.
So will take me a few weeks to save some tokens and buy all the bits I need.
Basically I will start the process again and outline progress here.
I'm going to work up 150gn berger VLDH with ADI 2217 in my 270win
And Berger 168gn VLDH and ADI 2217 in my rem mag
All this in the hope of being able to use the one powder for both.
And just cause I'm a bit of a BC slut, I just like that the Berger pills are a lot more consistent
Will be selling off some 2225 and superformance in the hope of recouping some cost towards new stuff.
Will report back here when I'm ready to start again.
When I posted earlier about the feeler gauges, I should have said that I used them with my comparator inserts and calipers. As calipers are not accurate like micrometers are, I figured 3 thou of feeler gauge is a real 3 thou. So leaving the calipers fixed at one setting and measuring the increases in seat depth with feeler-gauges
Measuring the desired length is one thing. Getting the same length from your seating die less the 10-20 thou etc consistently can also be a challenge.
finally picked up the Winchester mod 70 today after waiting weeks for a replacement firing pin.
Will be re starting this process in the next week.
I have a box of 140gn berger VLDH
and 1 box of 140gn Nolser partitions
I may seat the partitions to sammi spec, but the Berger VLDH I will be doing the full seating depth test after finding the most consistent speed charge weight.
I also have a box of sako gamehead ammo to run through it for shits and giggles just for comparison. :cool:
If i were examining this i would be thinking the group on the right just had slightly too much pull into the shoulder. Note how your vertical dispersion is almost identical.
Howa 308s are like this with light projectiles flat base. Its hard to shoot em badly at 100m.
Right after a bit of hiatus this is back on.
I did the jam measurements and got 2.858" with 140gn Berger VLDH
My mag in the mod 70 allows for 2.843" which just happens to be 15thou off my jam and seems like a great place to do my charge ladder.
All above measurements are ogive length not COAL.
After cleaning, annealing, prepping and priming 150 cases yesterday I'm ready for a range session.
I have 18 rounds loaded for my charge ladder, hoping to get to the range in the next day or so.
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