If one were to shoot for zero in a tunnel, would it result in a true zero or would there be a pressure wave that would disturb the trajectory? If it's size dependant, how big would the tunnel have to be to negate standard rifle cartridges (6.5cm, .308, 30-06, not .338LM or .50BMG)
Theoretical question for a "no wind" zero
- Thread starter ShortShooter1908
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That’s a Litz question, but my guess would be a supersonic bullet is moving so fast it could be a pretty small tunnel without affecting it...
D
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Seems like the biggest factor would be whether you're seated or prone vs what you're going to use afterwards. i.e. if you zero sitting, it might affect you if you shoot prone regularly, or vice versa. The differences would seem to be secondary to both setup (bipod on hard bench while seated vs bipod in soft grass while prone causing a POI-shift type thing), as well as a velocity variation between seated vs prone that doesn't get corrected for. Most tunnels I've seen use a bench/seated firing position.
Doesn't seem like the pressure aspect would affect much until you approach a caliber-level tunnel, i.e. what you see in suppressors. If so, it'd seem to be a POI-shift secondary to velocity variance. Independent of a harmonic POI shift, anyway, which doesn't apply to the closed tunnel-pressure system.
Pure thought experiment though. I'd be curious to hear Mr. Litz's response, too.
Doesn't seem like the pressure aspect would affect much until you approach a caliber-level tunnel, i.e. what you see in suppressors. If so, it'd seem to be a POI-shift secondary to velocity variance. Independent of a harmonic POI shift, anyway, which doesn't apply to the closed tunnel-pressure system.
Pure thought experiment though. I'd be curious to hear Mr. Litz's response, too.
I agree that tunnel would not effect bullet. Problem is that I like my no wind zero at 750 M.
I would need not only length but huge diameter due to trajectory.
I have found best way to establish no wind zero is to set up range, target, rifle etc. in the evening and shoot at first light. Otherwise I place a flashlight in a box to hold it on the target and shoot well after dark when wind stops if possible.
I would need not only length but huge diameter due to trajectory.
I have found best way to establish no wind zero is to set up range, target, rifle etc. in the evening and shoot at first light. Otherwise I place a flashlight in a box to hold it on the target and shoot well after dark when wind stops if possible.
No effect, and it's been done; in Texas several decades ago.
Funny, I guess being a fossil still has some value around this place...
FWIW, I had a few of my own articles published in PS (and TS-Tactical Shooter) around the same time (pre2K)...
Also, FWIW, I did my own experimentation re: annealing and neck tension. I applied an even older BR neck prep technique (from back in the days before bushing dies were employed) and had considerable success that came near to equaling the benefit of annealing. I adjusted neck tension by backing off the F/L Die and only resizing a part of the neck, I.e. the end portion; so more length resized equals more neck tension, and vice-versa. Since only the resized portion undergoes work hardening, this approach nearly, but not completely, supersedes the mandate for annealing.
To this day, I still do this. For my .260 loads, I start with 7-08 brass, and run it through the .260 die adjusted so only about 1/3 of the neck length gets resized down to 6.5mm. I leave it there, and watch my groups. As firings mount up, I back off the die so slightly less is resized. On that reloading not much happens but the next time, the neck tension falls back (it gets tighter as the brass hardens) to roughly where it was when we started. FWIW, the 7mm size portion of the neck will fit into the SAAMI Chamber/Neck without any appreciable resistance, and the soot ring stops precisely where the 7mm portion of the neck begins).
It's not the preferred method, but it at least allows a bit more management of neck tension than doing nothing at all..., and the soot delineation likely means that the narrow portion of the neck rather effectively centers the case/base of the bullet in the chamber during launch, possibly negating potential runout, and possibly compensating for the looseness of the SAAMI neck spec. Let's also bear in mind that the case sidewall does not get resized so far down, and may remain a better fit in the base end of the chamber, thus aligning case center axis better with the chamber center axis.
...And maybe the Moon really is made of green cheese, but it's still a fun thought experiment.
Finally, I keep my .308 die (and the Savage .260 headspace) adjusted so the brass from each (.260 and .308) fits to the same depth in the same .308 case gauge. Then, I can use the .308 die as a bump die for the .260, so it never disturbs the .260 neck setup.
I suppose this technique could also work for other chamberings that share parent cases. So far, I only do this for brass used in bolt guns.
Greg
PS Apology for the Thread Hijack.
Funny, I guess being a fossil still has some value around this place...
FWIW, I had a few of my own articles published in PS (and TS-Tactical Shooter) around the same time (pre2K)...
Also, FWIW, I did my own experimentation re: annealing and neck tension. I applied an even older BR neck prep technique (from back in the days before bushing dies were employed) and had considerable success that came near to equaling the benefit of annealing. I adjusted neck tension by backing off the F/L Die and only resizing a part of the neck, I.e. the end portion; so more length resized equals more neck tension, and vice-versa. Since only the resized portion undergoes work hardening, this approach nearly, but not completely, supersedes the mandate for annealing.
To this day, I still do this. For my .260 loads, I start with 7-08 brass, and run it through the .260 die adjusted so only about 1/3 of the neck length gets resized down to 6.5mm. I leave it there, and watch my groups. As firings mount up, I back off the die so slightly less is resized. On that reloading not much happens but the next time, the neck tension falls back (it gets tighter as the brass hardens) to roughly where it was when we started. FWIW, the 7mm size portion of the neck will fit into the SAAMI Chamber/Neck without any appreciable resistance, and the soot ring stops precisely where the 7mm portion of the neck begins).
It's not the preferred method, but it at least allows a bit more management of neck tension than doing nothing at all..., and the soot delineation likely means that the narrow portion of the neck rather effectively centers the case/base of the bullet in the chamber during launch, possibly negating potential runout, and possibly compensating for the looseness of the SAAMI neck spec. Let's also bear in mind that the case sidewall does not get resized so far down, and may remain a better fit in the base end of the chamber, thus aligning case center axis better with the chamber center axis.
...And maybe the Moon really is made of green cheese, but it's still a fun thought experiment.
Finally, I keep my .308 die (and the Savage .260 headspace) adjusted so the brass from each (.260 and .308) fits to the same depth in the same .308 case gauge. Then, I can use the .308 die as a bump die for the .260, so it never disturbs the .260 neck setup.
I suppose this technique could also work for other chamberings that share parent cases. So far, I only do this for brass used in bolt guns.
Greg
PS Apology for the Thread Hijack.
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Greg, I believe you are referring to the P.S. article 'Secrets of the Houston Warehouse.' It should be a mandatory read for anyone looking for precision in bolt actions. When I was shooting 1000yd BR with a factory Savage years ago, I employed a similar system as you described with your .260. It served me well with the sloppy factory chamber.
I do similar with mine as well. Great explanation, Greg. I still have a couple friends that ask me why I shoot a .243 when 6mm Creedmoor is the rage. Hmmmm.… since I own a 308 and a 260, with appropriate dies…
Ah, never mind - I still don’t think they would understand ;-)
Ah, never mind - I still don’t think they would understand ;-)
Maybe not, maybe they would.
I'd never pass up an opportunity to bring friends into the inner folds of accuracy shooting, showing them a concept is just ever so much more effective than attempting to explain it with nothing but hands for demo tools.
Personally, I believe the .308 Winchester-based family of cartridges provides a nearly unique opportunity to apply a bit of Elders' Ingenuity. It blends so well with the age of such great folks like Mike Walker, who made guns shoot danged well without all of the modern whiz-bang super tools and wonder gadgets. I've always admired the thought processes they used, and the successes they managed.
Me..., I don't think those days are dead; anything but. If anything, the new tools/toys serve as a stimulus to get that task done with far simpler means, the way the partial neck sizing methods get at least a moderate handle on neck tension without resorting to significant monetary outlays.
Time marches on, and we with it; but the rear view still holds gems of good worth.
Carry on, the Elder Fart will be out of the area for the remainder of this day... (I.e., the entire family is doing prep for my Wife's Pampered Chef demo this evening at the VFW.)
I'm happier these days, despite some transient old-age respiration issues. Our household is now up to 5 from 3. In addition to Granddaughter Elena, her Mom Jen and younger Brother Patrick arrived this Tuesday from NY, as permanent transferees. Two more delightful cases of Escape from New York.
Greg
I'd never pass up an opportunity to bring friends into the inner folds of accuracy shooting, showing them a concept is just ever so much more effective than attempting to explain it with nothing but hands for demo tools.
Personally, I believe the .308 Winchester-based family of cartridges provides a nearly unique opportunity to apply a bit of Elders' Ingenuity. It blends so well with the age of such great folks like Mike Walker, who made guns shoot danged well without all of the modern whiz-bang super tools and wonder gadgets. I've always admired the thought processes they used, and the successes they managed.
Me..., I don't think those days are dead; anything but. If anything, the new tools/toys serve as a stimulus to get that task done with far simpler means, the way the partial neck sizing methods get at least a moderate handle on neck tension without resorting to significant monetary outlays.
Time marches on, and we with it; but the rear view still holds gems of good worth.
Carry on, the Elder Fart will be out of the area for the remainder of this day... (I.e., the entire family is doing prep for my Wife's Pampered Chef demo this evening at the VFW.)
I'm happier these days, despite some transient old-age respiration issues. Our household is now up to 5 from 3. In addition to Granddaughter Elena, her Mom Jen and younger Brother Patrick arrived this Tuesday from NY, as permanent transferees. Two more delightful cases of Escape from New York.
Greg
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Difference, even if zeroing at 100 yards in a few MPH (unless its like a 22LR or something) is inconsequential.
Greg,
Thanks for that link to the article containing the full text and pictures of Secrets of the Houston Warehouse.
This^^^, because every one of my chambers is cut to SAAMI spec, much the same as was very likely the case way back yonder in the early BR days. I do it because my guns are my family legacy, and I have no plans for leaving firearms in their hands that require specially spec'd ammunition in order to shoot them safely. I offer, but so far, none have taken the bait leading to serious reloading. Our Grandson just arrived here in AZ and has expressed an interest in reloading, but for now, it's just talk. I will be following this up.
This technique may allow some compensation for those looser SAAMI chamber necks, and may also provide some manner for addressing runout. In any case, it's not a difficult technique; and I can't really see any drawbacks inherent in the process. It may even be a way to get better performance in "Factory Rifle" competition.
I think the Houston Warehouse article's comments about BR calibers (bores?) being over the hill at 1000, or even 700 shots may be colored by the tendency of BR shooters to push the pressure limits in the name of accuracy. I believe it's possible to effectively combine accuracy and saner pressure limits when reloading. If velocity's the thing, a longer barrel can get it without maxing out the pressure limits, and if it isn't, the velocity may hedge the bet somewhat when the winds pick up. My .260 runs in a 28" barrel, and my .308 and .223 precision rifles use 24" barrels.
Greg
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