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Hoover Meplat Timmer and Pointing Die System .338 Lapua

 
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  #8  
Old 04-23-2013, 02:59 PM
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Re: Hoover Meplat Timmer and Pointing Die System .338 Lapua

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Originally Posted by Bart B View Post
So is every other rifle on this planet. The groups are all zero MOA at the muzzle.

I don't quite understand how removing metal from a meplat making its shape less pointed/aerodymamic will improve a bullet's BC. Please explain.

The second sentence carries the most weight of these two, in my opinion. Few folks are aware of the spread in BC caused by bullet imbalance. And the faster bullets spin leaving the muzzle, the more they will jump off the bore axis upon exit. From what I've been able to glean from the bullet makers is, bullet imbalance has a larger effect on accuracy than meplat shape or size variables. One, maybe two, folks I know of have measured bullet balance at high rpm rates and set aside only the perfectly balanced ones then tested them for accuracy compared to the rest that ain't so perfectly balanced. Results have been amazing.
How would one measure the bullet balance at high rpm rates? Is this something that requires very expensive machines or tools? Could you elaborate on the process?
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Old 04-23-2013, 04:24 PM
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Re: Hoover Meplat Timmer and Pointing Die System .338 Lapua

The thought behind trimming the meplat is not to make the BC higher, but rather more consistent. It is estimated a shooter will reduce the BC of a bullet by about 2% when trimming. This loss is offset by a more consistent bullet meplat shape, which in turn - should result in tighter groups. Several bench rest shooters have been doing this. Some swear that their groups have become more consiostent and tighter, while other have found no discernable difference. While the jury is still out on this practice, all invilved generally agree that were no negative consequences to uniforming the meplat.

Bench rest shooters have taken the next step of repointing the uniformed tip to either get back the BC lost during the first step, or improve the BC by closing up the meplat entirely.

I don't recall any specific studies being done on this meplat uniforming - just anecdotal response from shooters based on their own findings. Intuitively, it stands to reason that when a meplat is trimmed, it opens up the "hollowpoint" ever so slightly, which should start the expansion process a little sooner. There are a couple other threads on LRH dealing with berger bullets (specifically the 210 grain in 30 cal) that failed to open after hitting an animal.

Pics of Berger Bullets NOT Performing????

The evidence seems to be pointing to a plugged up hollowpoint in some of the bullets. I know I have found a few out of a box of 100 that were that way. But this doesn't seem to matter as much with the big 300 grainers in 338 cal.

Berger was going to do some testing, but it is unclear if that was/is the cause for the expansion failure. By trimming the meplat and the chamfering the rim to make it uniform, I believe expansion abilities are enhanced. This could be detrimantal at short range, but an advantage at longer ranges. In the end, better bullet consistency is what the shooter is striving for.
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  #10  
Old 04-23-2013, 04:44 PM
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Re: Hoover Meplat Timmer and Pointing Die System .338 Lapua

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Originally Posted by Arbogb06 View Post
How would one measure the bullet balance at high rpm rates? Is this something that requires very expensive machines or tools? Could you elaborate on the process?
The way a friend did it back in 1970 used simple tools, but well made ones.

First, a collet was made to hold the bullets point down into it. It was precision machined so the wall thickness around the hole in it was very uniform in thickness and shape. It had a shaft that fit a Dremel Moto Tool chuck.

Then an amp meter was connected to the Moto Tool's power cord and measured the current drawn when it was spinning at 30,000 rpm without a bullet in it. With a bullet in it, the current was a bit more.

The more bullets were out of balance, their centrufigual forces put more load on the tool's bearings and more current was drawn to keep it up to speed. Bullets needing minimum current were considered to be "perfectly balanced" and were set aside. The more unbalanced ones indicated by more current needed were segregated into groups and set aside. A few of the several hundred bullets spun were so much out of balance they flew out of the collet and bounced off the walls and ceiling of the room the tests were done in.
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  #11  
Old 04-23-2013, 04:51 PM
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Re: Hoover Meplat Timmer and Pointing Die System .338 Lapua

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Originally Posted by azsugarbear View Post
Bench rest shooters have taken the next step of repointing the uniformed tip to either get back the BC lost during the first step, or improve the BC by closing up the meplat entirely.
Federal Cartridge Company did exactly that making sniper ammo for the US Navy Seal Teams; possibly other services, too. 'Twas done to make the 30 caliber HPMK"s no longer a hollow point but instead a solid point bullet. The tool used to close their hollow points made them very well shaped and pointed; quite uniform, too. But the best shots testing them claim they never shot as accurate as the unaltered Sierra HPMK's. The general consensus was they were made more unbalanced by closing the meplat.
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  #12  
Old 04-23-2013, 07:37 PM
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Re: Hoover Meplat Timmer and Pointing Die System .338 Lapua

Quote:
Originally Posted by Bart B View Post
The way a friend did it back in 1970 used simple tools, but well made ones.

First, a collet was made to hold the bullets point down into it. It was precision machined so the wall thickness around the hole in it was very uniform in thickness and shape. It had a shaft that fit a Dremel Moto Tool chuck.

Then an amp meter was connected to the Moto Tool's power cord and measured the current drawn when it was spinning at 30,000 rpm without a bullet in it. With a bullet in it, the current was a bit more.

The more bullets were out of balance, their centrufigual forces put more load on the tool's bearings and more current was drawn to keep it up to speed. Bullets needing minimum current were considered to be "perfectly balanced" and were set aside. The more unbalanced ones indicated by more current needed were segregated into groups and set aside. A few of the several hundred bullets spun were so much out of balance they flew out of the collet and bounced off the walls and ceiling of the room the tests were done in.
That is pretty intuitive. I never thought about that. I imagine out of a box of 100 you'd only have 5-10 perfect ones. This would add a long drawn out step in my reloading process and still not sure how I could do it safely without bullets getting launched around the shop. Going to have to think about this and see how/if there is another way but I'm sure if there is it would've Ben brought to light by now

Thanks.
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  #13  
Old 04-24-2013, 11:46 AM
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Re: Hoover Meplat Timmer and Pointing Die System .338 Lapua

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Originally Posted by jfseaman View Post
Speak for your self..

So you can put 5-5 shot groups inside 6-1/4 inches at 1000 yards?
And you can do this on demand?
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  #14  
Old 04-24-2013, 07:18 PM
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Re: Hoover Meplat Timmer and Pointing Die System .338 Lapua

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Originally Posted by jfseaman View Post
Speak for your self.
Who else on this forum could I speak for?

Meanwhile, I'm not aware of any NBRSA 1000 yard benchrest aggregate group record with more than 4 groups that all of them are no larger than 5.000 inches. And the three 5-shot group agg record of 3.920 inches, its largest one may well be over 5 inches. Same for the six 5-shot group agg of 4.6042 inches.

As for the PA 1K yard benchrest club, only one of their 6 Match Group Aggregate is under 5 inches; 4.8813. And I'd bet at least one group was over 5 inches; probably two.

All these rifle and ammo and shooter systems at their very best drive tacks with heads at least 6 inches in diameter, in my opinion. Maybe 7 inches if the largest groups shot in too record agg's was easily available without having to read them on their bulletin board's results sheet. If someone knows of better 1K yard group agg's, let me know. I know of half a dozen or more 10-shot groups at 600 yards that were all no more than 1/4 MOA (1.5 inch or less) and the smallest were almost 1/10th MOA, testing bullets that had been sorted for perfect balance .
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