It was posted on a thread on a Facebook post by someone else. I uploaded it from that post. From the looks of it, it came from 65grendel.com
Vihtavuori N140
- Thread starter Tony1320
- Start date
memilanuk
Gold $$ Contributor
Looks like it came from this thread here....
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My gut reaction is that chart needs a lot of work. I don't buy all the temp sensitivity values. $0.02 please!
memilanuk
Gold $$ Contributor
I kind of had the same reaction... like I said, I've used a *lot* of N150, and it behaved much like Varget w/ regards to temps. That said, I didn't chronograph religiously back then (due to optical chronographs being kind of hit-or-miss in the PNW) so I can't say that with absolute certainty. Either way, it gives people a ball park idea. But yes, I would recommend against treating it as 'gospel'... for one, you have no idea what equipment they tested with (how accurate was their chrono) or how wide the temperature span was that they tested across... or whether the response was even linear. Plus I've seen some weird fluctuations even with Hodgdon 'Extreme' powders that seemed to change with the *primer*... so how much of the temp stability of the powder is confounded with the stability of the primer?
Having used N150 and N550 for 20 plus years, I too found those sensitivity results difficult to accept - they look the wrong way round to me.
Frankly, I distrust any MV readings (or conclusions that are based on them) from shooter chronograph readings pre the MagnetoSpeed era, except for those which come from a really careful user of the Oehler 3P and other professional models ......... and that includes my own records the older ones of which I treat simply as guide figures now.
Even with the likes of the 3P, 100% correct alignment and levelling are essential - and for a typical two sensor unit with them 12 to 24 inches apart, consistent / accurate results are rarer still. I notice from Bryan Litz's Modern Advancement books that prior to switching to a Labradar, the professional quality device skyscreens in his test range set up are held in a wooden framework set up to get the bullet path absolutely central and at a common height across them - and he mounts two sets in tandem too so that any error should appear as mismatched results. In his typically detailed and scientific look at chronographs in Volume I, Bryan goes into the error effects that even small amounts of misalignment produce on simple models.
......... and that (distrusting most optical chrono results) is before ambient light intensity levels change which I've watched destroy results on many an occasion! Living in the British Isles where the cloud cover and thickness changes every few minutes on most days, you soon learn all about the effect of changing light levels. Not that I needed chronograph problems to tell me this having been a keen photographer in the days of hand held light meters and manual camera shutter / aperture settings.
Frankly, I distrust any MV readings (or conclusions that are based on them) from shooter chronograph readings pre the MagnetoSpeed era, except for those which come from a really careful user of the Oehler 3P and other professional models ......... and that includes my own records the older ones of which I treat simply as guide figures now.
Even with the likes of the 3P, 100% correct alignment and levelling are essential - and for a typical two sensor unit with them 12 to 24 inches apart, consistent / accurate results are rarer still. I notice from Bryan Litz's Modern Advancement books that prior to switching to a Labradar, the professional quality device skyscreens in his test range set up are held in a wooden framework set up to get the bullet path absolutely central and at a common height across them - and he mounts two sets in tandem too so that any error should appear as mismatched results. In his typically detailed and scientific look at chronographs in Volume I, Bryan goes into the error effects that even small amounts of misalignment produce on simple models.
......... and that (distrusting most optical chrono results) is before ambient light intensity levels change which I've watched destroy results on many an occasion! Living in the British Isles where the cloud cover and thickness changes every few minutes on most days, you soon learn all about the effect of changing light levels. Not that I needed chronograph problems to tell me this having been a keen photographer in the days of hand held light meters and manual camera shutter / aperture settings.
Brian, what brass and primers you are using, neck tension ? And what charge weight for new(not formed) brass ? I had some pressure issues on new non-formed lapua(LR) brass and 42.5 vv140 with 200.20x at 35F.
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Lapua Palma brass and Fed 205m primers. I am still fire forming brass, so the 43.2 is what I have been using.
I have ran .001 and .002 neck tension. That being said, I have just ran a .308 mandrel thru them in order to turn the necks down about .0005 or 80-90% shaving off. When I went to the .002 tension, I did notice a firmer seating pressure to seat the bullets on a few of the rounds (about 10-15%) compared to the rest.
My throat is short compared to most running them. It is about .090 free bore in order to run some of the longer nosed bullets. I would think a deeper seating depth would only increase the pressure from what I understand (and per quickload).
Kinda of out of options why you are getting pressure signs. I have ran them up to 44.2 without pressure signs. The 43.2gr was ran this past weekend at 50 degrees F without any pressure signs
Yeah, the stop on that allows it to cut way too deep into the case head's inner surface. You DON'T want a COUNTERSINK cut, you just want to remove any burrs then leave behind a Very Narrow Flat @ 45° between case head and flash hole bore.
Now that weathers warming up to 68° I've been testing some more
44.3gr N140 with Virgin Palma brass and 450 primers is giving me
2666fps
ES 8
SD 3.0
I have them seated .015 off the lands
It was too windy last week to test for group size but I will be heading out tomorrow
Has anyone else got a chance to test some more with N140?
How do you guys have the 200.20x seated?
Next month once it really warms up I should be able to confirm how temperature stable N140 really is
44.3gr N140 with Virgin Palma brass and 450 primers is giving me
2666fps
ES 8
SD 3.0
I have them seated .015 off the lands
It was too windy last week to test for group size but I will be heading out tomorrow
Has anyone else got a chance to test some more with N140?
How do you guys have the 200.20x seated?
Next month once it really warms up I should be able to confirm how temperature stable N140 really is
N-150 VIHTA VUORI powder is considered one of our "temp stabile powders" right now. We are working on getting this feature on all of our powders and a de-coppering agent in the future also.
Hengehold
Silver $$ Contributor
I do not debur flashholes typically and am curious. What is wrong with a countersink cut As long as it is the same on all cases?
Thanks,
-T
Trevor it’s a question of ‘how much’ of a countersink, not that it’s consistent.
It should be consistent of course but IMHO it should be minimal.
Tool I use has a stop designed to limit the bevel cut to maybe 0.010”. Essentially all it does is remove the 90
° edge around the flash hole. Cutting too deep a bevel creates a reverse funnel effect that I believe disperses primer flash rather than doing anything to help focus it.
Too, I moved to using Palma brass because of the extra brass in the case heads that seems to improve case life over their large-primer brethren.
Even on Lapua’s Palma brass I’ve seen inconsistencies at the flash hole in new cases using my borescope. I view the operation not unlike chamfering case mouths in that regard but this operation need be done just once. I do it once I’ve ensured my new cases have uniformly round case necks by running cases into a bushing die then onto a sizing mandrel.
It should be consistent of course but IMHO it should be minimal.
Tool I use has a stop designed to limit the bevel cut to maybe 0.010”. Essentially all it does is remove the 90
° edge around the flash hole. Cutting too deep a bevel creates a reverse funnel effect that I believe disperses primer flash rather than doing anything to help focus it.
Too, I moved to using Palma brass because of the extra brass in the case heads that seems to improve case life over their large-primer brethren.
Even on Lapua’s Palma brass I’ve seen inconsistencies at the flash hole in new cases using my borescope. I view the operation not unlike chamfering case mouths in that regard but this operation need be done just once. I do it once I’ve ensured my new cases have uniformly round case necks by running cases into a bushing die then onto a sizing mandrel.
I found very accurate node of 200.20x for my rife and me - its 43.5 N140, 68F, 2620 fps, no turned lapua palma with s&b small rifle primer and 0.001 neck tension @ 32 inch 10 twist 4 groove heavy palma True Flite NZ barrel with .170 FB. My coal is 3.080-3.085 with 0.020 off the lands. I think the main gift of N140 is my ammo's SD of 3.08 and ES 7.
I have a CIP chamber with .345 NK and on 8 of 50 brass have hardly noticeable circle marks of remington bolt ejector (I think they was taken on fireforming process)
And for your statistics, at 53F mv was 2613.
Measurements were performed with magnetospeed and kestrel.
PS
Tried Varget(produced 2017) in same brass/primer combo in closed range with 64F
It gives me at:
43.0 - 2664fps
43.5 - 2680fps
43.8 - 2696fps
on all those varget try-outs I haven't received good accuracy, it was 0.7-1moa at 100meters.
Best,
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