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Extreme spread / Standard Deviation

 
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  #8  
Old 02-11-2002, 03:26 PM
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Re: Extreme spread / Standard Deviation

If I can throw in my two cents, I have had some experience with moly. You DEFINATELY have to condition the bore to use the coated bullets (Brownell's Moly Paste works pretty well for this). Switching between coated and uncoated bullets tends to cause a problem also.

I have pretty much gotten away from Moly bullets, a lot of the BR guys I know have to. One of the big problems they were having, was the Moly was trapping moisture in the barrels. Not a good thing.

These are just my experiences, I'm sure people have had others, just wanted to throw my two cents in.

Jim
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  #9  
Old 02-11-2002, 03:29 PM
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Re: Extreme spread / Standard Deviation

When you want to get your rounds to be within 20 fps, the Chrony simply won't cut it. I own one and can tell you it's a joke. It will put you in the ballpark but it's just not capable of reading as accurately as is needed by many shooters.
It is also extremely fickle about light conditions. Mine was a waste of money pure and simple.
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  #10  
Old 02-11-2002, 04:50 PM
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Re: Extreme spread / Standard Deviation

Hmmm... Not the best of news... moly bad... chrony bad... [img]images/icons/frown.gif[/img]

Oh, well. Truth hurts sometimes!!

As far as the max. loads w/ moly, I don't think I said they didn't show pressure signs. There were pressure signs, just not as much as I would have thought. Very slight cratering of the primer, though still had the curved edges, shiny spots from the ejector, and a very noticeable extractor mark, though FWIW, even w/ the lighter fire-forming loads I'm using, I still can see a slight mark from the extractor on the new brass. Maybe the Winchester brass isn't as tough as the Hornady (the Hornady had been fired several times and was probably getting a bit harder, I'd guess).

I'll have to step back and decide what I want to go w/ for bullets, and whether I plan to stay w/ the moly coating. Like I said, I have about 500 moly BlitzKings sitting here, and they aren't going anywhere on their own. I may end up shooting different bullets yet, as the Swift has a bit different feeding requirements since it has a Score-Hi single-shot block installed in the magazine, vs. my .223 stuff which has to feed thru a Contender Super 14, a Rem. 700 VS, and a Bushmaster 16" V-Match carbine, and still make a suitable impression on the target out to 250-300 yds.

Another question here, related to the new brass: When I started out w/ the once-fired Hornady brass, I think I had to trim almost every piece I had. Set them all back to the minimum trim length, 2.195". Even after 6-7 firings, only a few were getting to where they would probably need trimmed in the next loading cycle. The new Winchester brass, by comparison, is *short*!!. Average length is 2.185", w/ some below, and some close but not actually up to the min. trim length. What do I do w/ these critters? Here I'm trying to make every little thing about the brass consistent, but I don't want to trim the brass to something _less_ than the minimum spec already!! Expecially since this 40X seems to have a very long throat as it is. Seating the bullets ~5 thousandths or less off the rifling doesn't leave much grippable surface of a boat tail bullet actually inside the case. That was why I intially started trying the Berger MEFs, since they were supposed to have a slightly longer bearing surface. Unfortunately, the local dealer has had enough of dealing w/ Berger since they were bought out (long shipping times, incomplete orders, quality issues), so they are no longer stocking any new Berger bullets. Any suggestions here?

Thanks,

Monte
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  #11  
Old 02-11-2002, 08:01 PM
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Re: Extreme spread / Standard Deviation

Monte,
Well moly isn't all bad..... it's just a horse of a different color that takes different TLC. With many larger caliber rifles there has been adverse things it causes. But I must admit that I still use moly in my 223 Remington VS without any problems. But a rifle shot with moly has to be cleaned differently and has different charactieristics than a bare bullet barrel does. wwheew say that 3 times real fast. There's many varminter shooters out there shooting smaller case capacities and have gone several hundred rounds without cleaning and no adverse affects of moly. My 223 is one of them. I get done shooting and push a very lightly oiled patch down the bore with Kroil and that's it. Takes 2-3 shots to settle it down and we're off and running again. But if I give it a good scrubbing with a brush, JB compound, soak, patch it out, soak, patch it out, etc..... It takes 8-10 rounds at least to settle it down to get it to group consistantly. This rifle is so predictable that my first shot out of a slightly olied bore is going to be 5/8-3/4" low and the others start going into the same group. I can usually hold for the first shot and put it somewhat into the group.

Now I used moly quite extensively in my 300 Win Mag Sendero also. Again it shot really good for awhile, but then the wheels fell off it. Couldn't shoot 1.5" groups at 100yds and my very last group shot in competition with it was at the 2000 PA World Open match. The first day I shot a 27" group that was litterly all over the paper and didn't get all shots on paper the second day after much cleaning that night. The week before in VA I shot a 13" group with 1 out. And jsut before that it shot (2) 7" and (1) 9" group in a row. So the rifle would shoot. But it got a buildup of a very hard residue about 3-5" in front of the throat. NO bore solvent that I used on it would touch it. I eventually took a tight patch with 600 grit lapping compound to get it out. Recrowned the barrel and the next (2) 100yd groups out of that barrel were 1/2" 5 shot groups. I had to sell that rifle and the guy that has it is still busting clay birds and milk jugs out past 500yds with it today.... (without moly).
Yes I do believe the accuracy of that Chrony is part of this equation also. You need more than 1' spacing between your screens to get a good reading.
So your 220 Swift may do very well with moly. I don't have any eperience with a Swift and moly. But you need to use it on all bullets or none at all. You didn't say if you were mixing bare and moly bullets or not. If you do use it, experiement with different cleaning techniques. Walt Berger has his method posted on his web page that alot of folks have used successfully.
As for the pressure signs, sorry about the assumption there. Yes, I've seen new cases have ejector marks in them at the first firing, but go on to use that load many times over in the same case without a problem for many loadings.
As for the case length issue, keep them as long as possible and miniumum trim them for now. You won't be able to tell much difference with a variation of a couple of thousands in case OAL. The neck has opened up and released that bullet long before the boattail passes the case mouth. I wouldn't read to much it this. Keep firing until they trim up evenly.

Not trying to throw more monkey wrenches at you but I wonder if seating your bullets out that far is there really is enough case neck support of the bullet. I had this "problem" in my 223 mentioned above. Eventually seated them back to maintain some case/bullet concentricty and jump the bullets about .040". Not the best accuracy and not like it use to be 10yrs ago, but it does shoot consistantly .4-.5" group now rather than the flyers I got when try to seat the bullet out to touch the lands. It prefered to be .005" into the lands in it's better day. But that was years ago.

Keep us updated,
Steve

[ 02-11-2002: Message edited by: Steve Shelp ]
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  #12  
Old 02-11-2002, 10:45 PM
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Re: Extreme spread / Standard Deviation

Steve,

How could you tell the hard build up was there, could you see it or feel it or what?
Just curious how I'll notice it in my own if it shows up.

Later
Brent
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  #13  
Old 02-12-2002, 07:18 AM
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Re: Extreme spread / Standard Deviation

Brent,
Take a good cleaning rod that has a handle that rotates easily, stick it through your bore, attach a good fitting bore brush on the end and slowly and as evenly as possible, pull it backward through the bore. You'll been able to feel a lot.
Also listen to the sound of the brush rubbing in the bore. You'll hear a difference also.
Once I noticed it with the brush and started looking for it with my naked eye I could see it somewhat also. But only by looking backward through the bore at a certain angle. It even had some buidlup near the muzzle also and is where you could clearly see it and it was hard. I couldn't chip it with a sewing pin.

Steve
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  #14  
Old 02-13-2002, 12:06 AM
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Re: Extreme spread / Standard Deviation

Thanks alot Steve.
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