F
frwillia
Guest
Hypothetically, if all the vertical components are eliminated, which doesn't seem likely, I'd think the system wouldn't need tuning.
Fitch
Hypothetically, if all the vertical components are eliminated, which doesn't seem likely, I'd think the system wouldn't need tuning.
Fitch
Boyd Allen
Active member
Al,
Exactly what bends? As far as I am aware, the bolt raises until stopped by the underside of the rear bridge, and in the process the lug engagement is reduced to a line at the end of the bottom lug. As soon as the trigger releases the cocking piece the bolt starts to fall. If the case is fire formed and shoulder setback from sizing minimal, this acts as a limit as to how far the lugs can be angled off of their seats. The current 200 yd.record for a sporter class short range benchrest rifle, is .086 (Tom Libby). This was shot with an action that has no Borden bumps. It is one thing to guess about limiting factors, it is another to accurately assign magnitude of importance. If there is a design flaw, it should cause a problem all the time. Last Saturday, a friend broke a range record at Visalia, shooting a .105 at 200 with a 10 1/2 # rifle, a plain old, angled interface, Panda. Modern equipment has a lot a potential, and if one is not seeing these sort of results, and the bolt fit is benchrest typical, I would look somewhere else for the problem.
Boyd
Boyd
Exactly what bends? As far as I am aware, the bolt raises until stopped by the underside of the rear bridge, and in the process the lug engagement is reduced to a line at the end of the bottom lug. As soon as the trigger releases the cocking piece the bolt starts to fall. If the case is fire formed and shoulder setback from sizing minimal, this acts as a limit as to how far the lugs can be angled off of their seats. The current 200 yd.record for a sporter class short range benchrest rifle, is .086 (Tom Libby). This was shot with an action that has no Borden bumps. It is one thing to guess about limiting factors, it is another to accurately assign magnitude of importance. If there is a design flaw, it should cause a problem all the time. Last Saturday, a friend broke a range record at Visalia, shooting a .105 at 200 with a 10 1/2 # rifle, a plain old, angled interface, Panda. Modern equipment has a lot a potential, and if one is not seeing these sort of results, and the bolt fit is benchrest typical, I would look somewhere else for the problem.
Boyd
Boyd
It's not a design flaw, it's a good design. It's proven to work. It HAS an overriding vertical component which Libby used to tune his rifle to perfection.
"I believe that eliminating or mitigating certain of these vertical components leads to an un-tunable system."
That's me in the quote, from this thread........ ummm, yeahhh, Libby's gun works.... it's all good.....
Nobody is hearing what I'm saying, so I'll stop.
al
"I believe that eliminating or mitigating certain of these vertical components leads to an un-tunable system."
That's me in the quote, from this thread........ ummm, yeahhh, Libby's gun works.... it's all good.....
Nobody is hearing what I'm saying, so I'll stop.
al
M
mks
Guest
No, you need vertical in the system to compensate for the unavoidable vertical caused by variation in muzzle velocity within a group. This is a very important concept that is nicely explained in the Border Barrels link.
Cheers,
Keith
M
mks
Guest
Now this I can agree with. But the vertical from the cocking piece, barrel droop, recoil lug and stock are all driven by and/or secondary to (and smaller than) the moment created by the force of the chamber pressure above the center of gravity of the typical BR rifle. 10,500 lbs bolt thrust times 1-2 inches moment arm equals 875-1750 ft lbs of torque. (Good thing it only lasts for a millisecond or so.) We need that torque to whip the barrel upward to have a chance for tuning. Now lower the boreline to the CG and it is a different story. The other effects you mentioned could still be active, but in my opinion, would have little chance of being able to accomplish tuning because they are so much smaller.
Cheers,
Keith
Boyd Allen
Active member
Al, I read you. My question referred to this."the cocked system is not only biased upward but actually bent." BTW how does trigger timing come into this?
Boyd
Boyd
The "trigger timing" you're referring to has to do with where in the cocking stroke the sear picks up. This timing as ref'd by Jim Borden or Jerry Stiller, or yourself, is different than the timing referred to by Bill Calfee in his "just relax" articles. Bill contends (and I don't disagree) that one way to skin the vibrational cat is to time the system to where the bolt is floating dead center (both lugs seated) when the pressure hits.
al
So why do electronically initiated rifles shoot round sloppy groups?
(pretend for a moment that you've heard they do.....
)BTW, IME railguns set to below cg of the tracking system still 'tune.' Many high cg setups have been tried. In fact it's not at all hard to bed conventional stocks with enough upward bias that they recoil downward. Or redistribute parts. Shucks.... I put a big ol' hawg Schmidt and Bender on tall mounts above a Stiller action in a light stock a while back........ you stick a 3lb scope 2-1/2 inches above the bore....
BTW, why do you use the term "bolt thrust?" I've fired many rounds which exhibit zero actual bolt thrust, the head of the case doesn't even touch the boltface on firing.
al
Boyd Allen
Active member
Al,
I know what trigger timing is. How does it come into what is being discussed, and again what bends?
Boyd
I know what trigger timing is. How does it come into what is being discussed, and again what bends?
Boyd
Boyd, trigger timing as you're referring to it affects the cycle because moving the pickup point fore and aft changes where the bolt is (how far it's dropped) when the rifle fires. Trigger timing be it Borden style or Calfee style affects bolt slap. IMO bolt slap is a major player in the generation of vertical vibration.
IMO the receiver bends.
IMO the receiver bends from upward pressure exerted by the angled cocking piece engagement. Is it meaningful??? I dunno. In the interest of science I did just go down and run a lever indicator on a couple receivers. Very crude, very jerry rigged but I did do it.
I stuck a mag base on the front rec ring, stylus bearing on the rear,
And I stuck a mag base on the rear, stylus bearing on the front.
And I stuck a mag base on the barrel, stylus bearing on the rear.
I waggled the rear of the receiver up and down with my fingers.
I inserted the bolt and carefully cocked the action in each of these situations.
I did this with an open bottomed 700 and with an XP100. The 700 is Borden Bumped which greatly lengthens the lever arm. The rear rec ring on the XP is short so I had to build a standoff.
In my test I did find repeatable deflection, I would call it a tenth on the XP and a half thou on the 700.
Was my test flawed? Yes.
But in my opinion it it did show deflection. And that the deflection produced by the tension in the system is 'similar' to the deflection produced by waggling with fingers.
A waste of time? Probably..... useful??? Probably not....
But I'm just sharing my opinion
al
IMO the receiver bends.
IMO the receiver bends from upward pressure exerted by the angled cocking piece engagement. Is it meaningful??? I dunno. In the interest of science I did just go down and run a lever indicator on a couple receivers. Very crude, very jerry rigged but I did do it.
I stuck a mag base on the front rec ring, stylus bearing on the rear,
And I stuck a mag base on the rear, stylus bearing on the front.
And I stuck a mag base on the barrel, stylus bearing on the rear.
I waggled the rear of the receiver up and down with my fingers.
I inserted the bolt and carefully cocked the action in each of these situations.
I did this with an open bottomed 700 and with an XP100. The 700 is Borden Bumped which greatly lengthens the lever arm. The rear rec ring on the XP is short so I had to build a standoff.
In my test I did find repeatable deflection, I would call it a tenth on the XP and a half thou on the 700.
Was my test flawed? Yes.
But in my opinion it it did show deflection. And that the deflection produced by the tension in the system is 'similar' to the deflection produced by waggling with fingers.
A waste of time? Probably..... useful??? Probably not....
But I'm just sharing my opinion
al
M
mks
Guest
So why do electronically initiated rifles shoot round sloppy groups?
(pretend for a moment that you've heard they do.....
BTW, IME railguns set to below cg of the tracking system still 'tune.' Many high cg setups have been tried. In fact it's not at all hard to bed conventional stocks with enough upward bias that they recoil downward. Or redistribute parts. Shucks.... I put a big ol' hawg Schmidt and Bender on tall mounts above a Stiller action in a light stock a while back........ you stick a 3lb scope 2-1/2 inches above the bore....
BTW, why do you use the term "bolt thrust?" I've fired many rounds which exhibit zero actual bolt thrust, the head of the case doesn't even touch the boltface on firing.
al
Al,
Actually, the first 3-shot group from my 243 Etronx was a half incher at 100 yards. It won't always repeat this, but it doesn't seem any worse than other factory guns. From a barrel vibration standpoint, I wouldn't expect the lack of a firing pin spring to make a big difference, and in my limited experience it hasn't.
In principle, high CG guns can be tuned the same as low CG guns. Just need to time barrel exit to rising muzzle angle, whether it is on the first cycle or the second (or third, etc ...). In general this means that low CG guns need to be either considerably stiffer or considerably more flexible than tuned high CG guns to hit the right vibration cycle.
No overriding reason for "bolt thrust," just trying to use common terminology. The force gets transfered from the chamber to the rest of the gun regardless.
Cheers,
Keith
4
4Mesh
Guest
Al,
I'd agree that maybe a Remington factory action would have measurable flex. Especially the ones with the bottom hardware (adl/bdl). But, for something like a 1.450" - 1.625" custom with no port in the bottom, theres not much flex. Boy, you better REALLY measure a while to find it if yer gonna look. But, guns built on those things can shoot vertical to beat all hell. So whats that say?
Maybe some rifles might have such a lock issue as to have measurable vertical due to what you suggest. But, I'd say it's a rare instance where that is the major contributor.
I'd say that unsprung weight, varying from above to below the bore line, is a much larger contributor to vertical. But still not the major ones when shooting long range. Those are on the reloading bench. imho... Should I have h in there?
I'd agree that maybe a Remington factory action would have measurable flex. Especially the ones with the bottom hardware (adl/bdl). But, for something like a 1.450" - 1.625" custom with no port in the bottom, theres not much flex. Boy, you better REALLY measure a while to find it if yer gonna look. But, guns built on those things can shoot vertical to beat all hell. So whats that say?
Maybe some rifles might have such a lock issue as to have measurable vertical due to what you suggest. But, I'd say it's a rare instance where that is the major contributor.
I'd say that unsprung weight, varying from above to below the bore line, is a much larger contributor to vertical. But still not the major ones when shooting long range. Those are on the reloading bench. imho... Should I have h in there?
Boyd Allen
Active member
Al,
I have shot a cute little sporter that used caseless ammunition that was electronically ignited. The original .22 cal. bullets had been pulled and Bergers substituted. It was the ballistic equivalent of something on the order of a .222, or a little smaller. I was amazed at how well it shot, especially given the overall design. I would have not expected groups even half as good with conventional ammunition and ignition system.
http://guns.wikia.com/wiki/Voere_VEC-91
I suppose that if someone wanted to test the potential of electronic ignition in combination with more conventional, cased ammunition, he could find a supply of the primers as set to work using one of the discontinued Remingtons that have that feature. As with anything, reductions in what you refer to as bolt slap, reach a point of diminishing accuracy returns, and other factors become more important.
Boyd
I have shot a cute little sporter that used caseless ammunition that was electronically ignited. The original .22 cal. bullets had been pulled and Bergers substituted. It was the ballistic equivalent of something on the order of a .222, or a little smaller. I was amazed at how well it shot, especially given the overall design. I would have not expected groups even half as good with conventional ammunition and ignition system.
http://guns.wikia.com/wiki/Voere_VEC-91
I suppose that if someone wanted to test the potential of electronic ignition in combination with more conventional, cased ammunition, he could find a supply of the primers as set to work using one of the discontinued Remingtons that have that feature. As with anything, reductions in what you refer to as bolt slap, reach a point of diminishing accuracy returns, and other factors become more important.
Boyd
Boyd Allen
Active member
Al,
Are you saying that 1/2" rifles do not show differences in accuracy depending on the specifications of their loads? It has been my experience that they do.
Boyd
Are you saying that 1/2" rifles do not show differences in accuracy depending on the specifications of their loads? It has been my experience that they do.
Boyd
W
Wildcatter
Guest
I disagree completely with this statement. 1-1/2" rifles are tunable.... Hell, even shotguns are tunable.