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Author Topic: Shooting the 310-165-FN (XCB), some observations  (Read 84153 times)

goodsteel

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #30 on: December 15, 2014, 08:42:15 AM »
Excellent work Bjorn, as usual. Just keep doing what you are doing. Run the spectrum with the BS, observe and record. When Larry gets it, and put's the Ohler lab on it, we may just have a very clear picture of what is going on.
The identical powder speeds are bugging me too. The reason I built the tool was to eliminate the engraving pressure from the pressure trace, and also eliminate any unconcentric damage to the bullet that the RPM can play havoc with. However, I really think that the back pressure created by the bullet engrave could have a dramatic effect on the way the powder burns.
I've already run into this with 44 Magnum loads where case neck tension can make or break a good load because it modifies the powder burn. I think this could be no different.

curmudgeon

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #31 on: December 15, 2014, 03:41:35 PM »
Bjornb,

Agreed. Settingup the MSV3 is Simple and easy as long as you have something to hold the rifle steady when switching from one rifle to another. Trying to juggle several pieces when all you have is a front and rear bag to hold things from squirming around is a pain At least that's been my experience.

Other than that it's a great outfit and I reccomend it to any one who asks. In these parts we have to deal with winds high enuf that it will blow a regular unit over unless you put some wgt. on the tripod. Gas checks tend to imbed in the front reader of a regular chrono unless you put up some kind of shield. Then of course with regular unit there's always the chance of putting a bullet hole thru it.  Ask me how I know about these things? :) 50 years of playing with chronographs of one kind or another and I've done them all. The MSV3 is the greatest thing to come along for shooting in a LONG time.

Pete

sgt.mike

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #32 on: December 15, 2014, 11:38:39 PM »
...... However, I really think that the back pressure created by the bullet engrave could have a dramatic effect on the way the powder burns. .......
Might be as good as any to explain I thought of case volume fill ratio would be close with those powder that gave close to what Bjornb experienced. I do not have a definitive answer off the top of my head for Bjronb

goodsteel

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #33 on: December 24, 2014, 12:10:39 PM »
I will be adding a little to the testing shortly.
It has been said that linotype is too hard to hunt with, and that it will shatter upon impact etc etc etc. First, I don't think it will shatter. Second, while it may be too hard to hunt with at 1900FPS, I don't know anybody who has tried it at jacketed speeds. I think that it may do quite well, but I don't know, so I will fire bullets into wet phonebooks/unvulcanized rubber etc etc and see what happens.
I have been assembling a rifle for myself on the side, and it's almost finished. I'm naming this one "Felix".





Action: 1909 Argentine
Trigger: Timney
Bedding: Devcon 10-110
Stock: Arkansas Native black walnut/South American Kingwood/Black micarta
Barrel: 1-14 twist 27" long, 1.220 cyl.
Caliber:30 XCB

I will use this rifle for the bullet trials backing up Bjornb's results as I can, and pretty much just so I can enjoy a little of this HV accuracy without a thought in the world except punching little groups in paper at big velocities. 
« Last Edit: December 24, 2014, 12:22:10 PM by goodsteel »

swheeler

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #34 on: December 24, 2014, 02:36:16 PM »
Felix would be pleased!

goodsteel

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #35 on: December 26, 2014, 05:07:29 PM »
OK, it's pretty much finished. Still waiting on the Brux barrel to arrive, but this one will work to put a few bullets in a phonebook or two. LOL!







« Last Edit: December 26, 2014, 05:09:40 PM by goodsteel »

detox

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #36 on: December 26, 2014, 07:50:51 PM »
That is a very nice and sturdy test bed to iron out loads. What brand and twist is the barrel? Have you worked on taper bumping the 30 XCB bullet? Show grouping test before vs. after taper bumping.  ;) The shorter taper of this bullet will be easier to bump and get more centered.

This bullet shows lots of potential. I was thinking of purchasing a .310 diameter  x 1.22 taper reamer to lengthen free bore for test and to cut bump die.


I wish there was such thing as a cheap CNC machine to cut hard lead bullets into any shape. It would pump bullets out at the rate of 10 per minute.
https://www.youtube.com/watch?v=gNG0dFCN4Ts
« Last Edit: December 26, 2014, 08:13:25 PM by detox »

goodsteel

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #37 on: December 26, 2014, 09:40:56 PM »
The barrel is a mystery. This is the takoff barrel from Bjornb's target rifle (the one with the bulge). Probably not suitable for target work, but certainly able to shoot some bullets into test media for some observation of hard alloys at these blistering speeds. The critical dimentions are .300/.308, 1-14 twist, 27" long.

I really have no plans to mess with bumping the bullet, as I am very happy with its performance so far, and I have been very pleased with the quality of the bullets as they drop from Al's molds. They fit the throat's of these rifles perfectly as dropped, and we are shooting faster than has ever been properly documented on the internet forums.
However, if you end up doing a test of using a bump die, please post the results. I would be very interested.

On that note, I keep thinking about you flatening your GC's by gluing them down and sanding the edges perfectly flat.
Seems to me that the other side of the check is the more important thing to focus on. Have you considered doing the same thing to the bottoms of the checks? I'm thinking about trying that.
« Last Edit: December 27, 2014, 05:40:09 AM by goodsteel »

detox

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #38 on: December 27, 2014, 08:38:08 AM »
I sanded skirts even to help balance the bullet and to grip shank better. Bumping will make the gas check base square without sanding base. A uniform edge at bullets base is important also.

I do not expect near perfect groups without a near perfect bullet.

goodsteel

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #39 on: December 27, 2014, 11:32:30 AM »
I sanded skirts even to help balance the bullet and to grip shank better. Bumping will make the gas check base square without sanding base. A uniform edge at bullets base is important also.

I do not expect near perfect groups without a near perfect bullet.

There is iron in your words for all to hear, and I agree completely, but perfection is a measured quantity.
I think we both agree that the trailing edge of the GC is much more important than the leading edge. The problem is that sanding the leading edge does practically nothing to square up the trailing edge. The GC's are formed through a bunting process where the disks are stamped out and a very heavy impression is made in them, after which , the cup is formed rendering the crimp on edge on the inside of the cup.
The material in the bottom of the check is of consistent thickness, but is bowed like a potato chip, which effects the outer edges (the trailing edges). The rim is very difficult to make a consistent hight from the bottom of the check, as material flows up one side of the punch more or less than the other side.
By sanding the leading edges of the checks, we correct one issue, but this has very little effect on the part that really matters: the trailing edge.
If we sand the check's leading edges and measure them with a .0001 indicator we can see how uneven the base of the checks really are:

In this case we have about .004-.005 variance across the base of the checks.

This is very easy to observe if we flip the checks over and apply some blue layout dye to the backs of the checks (you can literally see the odd and uneven curve of the bottom surface of the checks):


Then sand them lightly with the precision block and sandpaper:


I was just wondering if you had considered this as a possible way to make the trailing edge of the GC's more uniform and flat, and if you had measured the squareness to the bullet shank after installation? I intend to do so and observe any effect downrange.
Thoughts?
« Last Edit: December 27, 2014, 11:34:10 AM by goodsteel »

goodsteel

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #40 on: December 27, 2014, 12:15:12 PM »
So if we sand further and actually flatten the side that matters to groups, the warped, dished, and inconsistent base becomes flatter and flatter.


And measureing the check with the .0001 indicator shows near perfection with a TIR of less than .0002 (that's 1/40th the variance present just flattening the leading edge. Not too shabby.

cainttype

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #41 on: December 27, 2014, 12:52:06 PM »
 Veral recommended the cup-faced base punches to squarely seat gaschecks while sizing nose first through the Star years ago (I'm sure any well-aligned push-through sizer will work just as well). I haven't seen anything better.
 If a really sharp, square edge is desired, "heat treating" the checks to soften the temper and a closely matched punch-to-sizer die fit will show a marked improvement versus any other method I've used.

frnkeore

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #42 on: December 27, 2014, 12:58:03 PM »
Tim,
One thing to consider in doing them that way, is that the metal that they are made of is of uniform thickness and after you sand them, it no longer will be and that will leave a unbalanced GC.

I use a arbor press and a punch to both flatten the GC and open it to my size requirement.

Frank
« Last Edit: December 27, 2014, 12:59:58 PM by frnkeore »

DR Owl Creek

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #43 on: December 27, 2014, 01:01:22 PM »
Tim,

I never realized there was that much variation in the checks. Thanks for posting those photos. One more thing to consider now.

Dave

detox

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Re: Shooting the 310-165-FN (XCB), some observations
« Reply #44 on: December 27, 2014, 06:24:45 PM »
Tim,
Hornaday and all others do not have equal skirt length, skirt length can vary with each check (one side taller than the other). You can actually see the difference when sanding. This is why I sand all skirts LEADING EDGE equal length and square.  This MAY help balance bullet better when spinning. Some target shooters would actually spin each cast bullet  (I forget the device used) to see how well balanced the bullets were before loading.

It is a big mistake to sand the base of checks. DOH
« Last Edit: December 27, 2014, 07:05:43 PM by detox »

 



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