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meplate uniforming

 
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  #8  
Old 06-29-2006, 01:57 PM
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Join Date: Oct 2005
Location: Alberta, Canada
Posts: 16
Re: meplate uniforming

How do you properly measue bearing surface area? Is it the same as base to ogive length using a comparator and a set of calipers? I'm trying to improve my consistency with the 300gr SMK @ 800-1200 yards I seem to have sporatic high "flyers" as much as a foot at around 1000 yrds. Also, goodgrouper, I thought I might ask you, I'm having trouble with run-out on my loaded 338 rum rounds. I've tried
squaring the die, the expander ball(I have not bought a set of bushing dies yet as I may get a different 338). I've tried different shell holders(loose and snug), sharp angle- chamfering, 2 sets of dies (hornady and RCBS) and case neck turning. I know that the Rem. brass I'm using is bad but i've neving had this much trouble getting straight ammo. Out of 50 rounds I'll get 15 rounds @ +/- .001, 15 round @ +/- .003 and the rest vary up to .008! Is this normal with Rem brass, or is the long 300 SMK a tough bullet to seat straight. I realize that my dies put me at a disadvantage but I've used non-redding standard dies before that are set up properly and gave got reasonable results. Does a guy have to buy 300 rounds of REM. brass to get 100 good ones? Any advice or ideas would be very valued as I'm ready to toss my dies and brass in the garbage.

andy
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  #9  
Old 06-30-2006, 08:05 AM
 
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Re: meplate uniforming

Might want to give the Lee Collet Neck Die a try. Much less than a bushing die and works as good or better than a bushing die. And you don't have to turn necks or use lube.
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  #10  
Old 06-30-2006, 08:33 AM
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Join Date: Sep 2004
Location: on the rifle range in Utah
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Re: meplate uniforming

Andy,

Got to run off to work now but I'll post back tonight on your questions.
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  #11  
Old 06-30-2006, 05:44 PM
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Re: meplate uniforming

Andy,

Unfortunately, you are trying to shoot one of the most inconsistent bullets for bearing surface on the market. Taking a Stoney Point bullet comparator and measuring from the ogive to the base won't cut it.

There are several ways to measure the bearing surface or as close to the bearing surface as we can actually measure. None actually measure just the shank of the bullet. They also get a little of the boat tail in there too. The cheapest and still my favorite is to use two SP comparators (one on each blade of the caliper) and it works great. I marked one of my comparator bodies as "top" and then also marked my second set of inserts as "top". This way I can always be consistent on my measuring.
The second method is the Tubb tool which I believe to be way overpriced and I know to be no better than the SP way.

Using the SP method, I can say that on my last batch of 300 grain MK's, I had .013" variation in measurement. Most of that came from the front half of the shank to the ogive but there were a fair amount that had error in the last half of the shank to the boat tail. Interestingly enough, a few of these latter bullets showed no variation from base to ogive measure! This tells you that there IS inconsistencies in the boat tails of bullets. So it helps to measure from base to ogive but you might miss a few pills that will certainly give you fliers at long range.


As for your concentricity issues, it sounds like you have a real head scratcher.

Ok, I assume you are running the dial on both the fired, unloaded case (and finding straight cases) and the loaded ammo and the problem is truly coming from the loading process. I also assume that you are running a dial indicator on the loaded bullet from the tip to the case mouth, and on the neck of a turned case.

If this is so, then it could be a few things.

The first thing I would try is a bushing die with the correct bushing. The 300 grain MK bullet has a long bearing surface and usually measures .3385 diameter. Neither of these things help when trying to stuff it down a piece of brass that has been squeezed way down by a standard die that gives the brass very much bullet grip. Your expander ball should bring it back to the proper diameter but the brass may have tons of spring back and the die could be taking it down to .243 diameter for all we know.

75% of the time, concentricity issues come about from the dies than any other thing. Brass usually makes up the last 25%. But brass is an easy thing to trouble shoot. Select a piece of brass that runs good concentricity one time and then check it again after firing and reloading it. If it is still good then take a bad one and run the same test. If the good stays good and the bad stays bad, then you have brass issues that your dies probably won't solve.

If you determine it is the dies that are causing it, you will need to determine if it is the sizing die or the seating die. This is easy. Just run the dial over the sized case before seating the bullet. This will tell you what to do next-get a new sizer or a new seater. If it is the seater that is causing it, before you replace it, load a different bullet (preferably a shorter one) and see if the runout is still there. If it is, pitch that die!

If it is the sizer causing it, try a bushing die or a different FL sizer.


I had custom dies made for my 338 thunder (which is on the ultra mag case) and they run less than .001" runout even on my culls. My culls are straight but they were off in weight tolerances.

And yes, it is a good rule of thumb to buy at least one more bag of Remmy brass from the same lot than what you think you need just to have some extra in case you have to cull out a few. [img]/ubbthreads/images/graemlins/wink.gif[/img]

Hope this helps.
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  #12  
Old 07-04-2006, 02:37 PM
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Join Date: Oct 2005
Location: Alberta, Canada
Posts: 16
Re: meplate uniforming

Thanks for everyone's input. Thanks goodgrouper for taking the time to lay-out a good troubleshooting plan and lending your experience. It is very hlepful to have good advice when involved with such a potentially frustrating hobby.

andy
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