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Old November 29, 2008, 05:42 PM   #1
Major Dave (retired)
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What happens when you file a "flat" on a RN bullet?

I recently bought some 175 gr RN factory loads for my 7 X 57 Mauser, and discovered that they wouldn't cycle through my bolt action rifle. They were too long to fit in the magazine. I used my reloading caliper, and miked them at a COL of 3.011 inches.

Then I took a 10 inch mill file and filed the RN down until they miked 3.000 inches COL.

They fit the magazine just fine, and cycled perfectly.

The "flat" on the end of the RN (meplat is the correct term, I think) now measures 0.13 inch in diameter.

So, my question is, will there be any noticeable change in the performance of these rounds? Will the 100 yard zero change? Can I expect the rounds to group the same? Will there be enough exposed lead to "mushroom" properly?

I intend to go to the range Monday to check the zero and the group. Wednesday I will travel to a 5,000 acre Texas ranch and use these bullets to shoot deer over corn feeders at an average distance of 75 yards. (does weigh about 90 pounds, 2 1/2 year old bucks about 110 lbs).

I chose these 175 gr bullets over the 139/140 gr SP loadings because I knew the ranges would be short, and the 175 gr RN's exceed the muzzle velocity of 170 gr RN 30-30's by 240 fps. I see this 7 X 57mm 175 gr RN load as being a 170 gr RN 30-30 load on steroids!

30-30, 170 gr RN = 2,200 fps MV
7 X 57, 175 gr RN = 2,440 fps MV


Your comments, please.
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Last edited by Major Dave (retired); November 29, 2008 at 05:54 PM. Reason: Clarification
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Old November 29, 2008, 07:20 PM   #2
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G'day Major. Can you pull one of the projectiles and put it on some scales? Find out how much they weigh. Are you able to put any shots over a Chronograph? I suspect that 100 yards won't have a large influence on the effectiveness of the round on these large targets.
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Old November 29, 2008, 07:24 PM   #3
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I used to shoot squirrels with .22LR dum-dums (I believe that is the term for a DIY meplat) and I never noticed any accuracy changes. I imagine it will be a whole lot different with a projectile moving twice as fast though.

If I were you after I checked the grouping and POI vs. POA then I'd fire a few rounds into wetpacks or water jugs so I could recover the slugs and see how they expanded before I would consider shooting a real animal with them.

I did my .22LR dum-dum ballistic tests on grapefruits in my dad's basement when nobody was home! Left some nice craters in the basement wall that I "spackled" with some kind of toothpaste/wet toilet paper mixture IIRC. :P
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Old November 29, 2008, 07:24 PM   #4
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I believe the British executed Boers for doing that to their ammo in the Boer wars. If you ever expect the face Her Majesty's soldiers in guerilla warfare It would be in advisable, otherwise, have at it.
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Old November 29, 2008, 08:12 PM   #5
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You have lost a little weight in the bullet. That will cause a slight change in velocity ( faster) the B.C. will go down as it's not as aerodynamic. at 75 yards i doubt you would note much difference but I would check the zero anyway.
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Old November 29, 2008, 09:02 PM   #6
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Last century (I love that phrase...) there was a company called "The Hanned Line" that sold some bullet modification tools. I purchased a couple of their tools that you use with a file to to create "small game bullet" noses on .22LR and .22WMR bullets (flat nose = very effective). I wish I had purchased one in .22 Short as well...

They also sold a "Convert-A-Ball" tool that you used with your reloading press, a hacksaw, and a file to create a flat-nosed bullet in 7mm or .30 cal military cartridges. Supposedly the military ball ammo would then expand like a hunting bullet, but I never tried this one.

Just more useless stuff that I can't seem to forget (yet)...
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Old November 29, 2008, 09:10 PM   #7
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I doubt you'll see much difference if any at all. You didn't remove a significant amount of bullet weight (more copper than lead). FMJ rifle bullets typically have a pretty heavy jacket. I wouldn't expect much in the way of expansion.

The drawback as I see it is that you now have a lead core in a tube of copper. FMJ bullets are open at the base. There is a possibility, however slight, that you can push the lead core through the jacket leaving the jacket in the barrel as an obstruction for the next round. Made-for-purpose hollow and soft point bullets have jackets that fully cover the base to prevent this. If your RN bullets were already soft points then this isn't a concern.
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Old November 29, 2008, 09:50 PM   #8
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I have read stories in the past about folks filing or cutting off the noses of Military rounds for better expansion. The articles also cautioned about Military rounds with the lead at the rear exposed and the tip removed, that sometimes when fired the bullet would launch ok but the lead would shoot out of the jacket and leave it stuck in the barrel.
If you are a reloader or have a friend that is, possibly you could simply seat the bulets a little deeper in the case.
As far as your modifications go, I doubt you will see any wide ranging differences in POI. I'd check fire a few to be sure though. Good shooting..
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Old November 30, 2008, 09:19 AM   #9
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Quote:
The articles also cautioned about Military rounds with the lead at the rear exposed and the tip removed, that sometimes when fired the bullet would launch ok but the lead would shoot out of the jacket and leave it stuck in the barrel.
Yep, that could happen. The next shot, with a jacket stuck in the barel might be kinda exciting!

I'd advise against seating your bullets deeper to get the COL down. That'll raise pressure and you can't tell how much it'll go up.

Load them single-shot and don't buy any more.
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Old November 30, 2008, 09:50 AM   #10
Jim Watson
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I am not clear.
Are these 175 gr FMJs?
If so, the cut-nose Dum-Dum did not really work very well, so Captain Bertie Clay and the rest of the British army moved on to other expansive bullets to deal with savage tribesmen on the subcontinent and in Africa.
The NRA once tried the drilled FMJ and found that because the jacket was the thickest at the nose of the bullet, there was no expansion until the hole was to large as to risk blowing through the core and even then was erratic.

However, if they were 175 gr softpoints, filing back the exposed lead even to the mouth of the jacket will have little effect on trajectory or expansion. (That used to be known as the "protected point" before plastic bullet noses were invented.)

Seating them 11 thou deeper is not going to cause the pressure to skyrocket. It might bring it down a smidgen as it introduced some freebore into the bullet launch.
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Old November 30, 2008, 01:35 PM   #11
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Mr. Watson knows what he's talking about.
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Old November 30, 2008, 02:51 PM   #12
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Change in weight and profile can and probably will change POI, may not be much and may change how effective it is if a hunting round.
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Old November 30, 2008, 04:39 PM   #13
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Quote:
I recently bought some 175 gr RN factory loads for my 7 X 57 Mauser, and discovered that they wouldn't cycle through my bolt action rifle.
How could anyone read this, think he was talking about military FMJ? The highlighted word means of recent manufacture. I'm not aware of any factory making FMJ ROUNDNOSE ammo for 7mm mauser.

As for expansion, who knows. I'd guess there might be a change, BUT that 175 7mm bullet is meant for heavy game, a little texas whitetail isn't going to make for much expansion anyway.
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Old November 30, 2008, 10:08 PM   #14
Major Dave (retired)
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Clarification : not FMJ military ammo.

These are 175 gr (before my modification) round nose soft point, currently factory loaded by Federal.

They had a considerable amount of exposed lead at the tip, before I shortened the COL by 11 thousandths, and the remaining lead tip still extends beyond the end of the copper jacket.

Thanks for the input, guys.
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Last edited by Major Dave (retired); November 30, 2008 at 10:13 PM. Reason: Clarification
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Old November 30, 2008, 11:04 PM   #15
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Quote:
How could anyone read this, think he was talking about military FMJ? The highlighted word means of recent manufacture.
I (along with several others, apparently) understood "recently" to be referring to the date of purchase. He could quite easily have recently purchased ammo manufactured years or even decades ago.
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Old December 1, 2008, 02:25 PM   #16
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Major Dave (retired), for .011 thousands I would have seated the bullets deeper with the correct seater plug, Federal is not in the habit of loading 7 and 8MMX57MM Mauser to max and moving the bullet back .011 would not be noticeable.

The term Dum Dum had to do with a location and the practice of manufacturing bullets with expose lead, your bullets by definition were Dum Dum before you started, the term has been changed to soft nose/exposed lead.

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Old December 1, 2008, 02:30 PM   #17
F. Guffey
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Major Dave (retired), for .011 thousands I would have seated the bullets deeper with the correct seater plug, Federal is not in the habit of loading 7 and 8MMX57MM Mauser to max and moving the bullet back .011 would not be noticeable.

The term Dum Dum had to do with a location and the practice of manufacturing bullets with expose lead, your bullets by definition were Dum Dum before you started, the term has been changed to soft nose/exposed lead.

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Old December 1, 2008, 07:20 PM   #18
Major Dave (retired)
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Reseat factory loads?

Can you reseat the bullets on factory loads, to shorten the COL?

What is the procedure for that?
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Old December 1, 2008, 07:21 PM   #19
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Official 7x57 COL is 3.071". I'm surprised Federal exceeded that and expect it was a mistake. I am also surprised such a small excess (3.9 thousandths) would affect feeding. Please double-check that your chambering is what you believe it to be!

As to the effect of your filing, a 0.284" diameter lead spherical cap of 0.011" height will remove 0.151 grains of lead. That is likely to be less than the bullet-to-bullet weight variation when the bullets are intact. It is of no consequence, nor will you see it on the target nor downrange. The size of that meplat is within a range the BRL determined to be optimal for minimizing pointed bullet drag coefficient, so it just won't really do anything measurable, either. What little it does do will be within the noise of any group size you can practically expect to shoot with that cartridge.

Edit: You were composing and posting while I was. To answer your question, you need a reloading press and a shell holder and a seating die for 7x57. The shell holder would be put on the press ram and a loaded cartridge inserted and the press handle pushed all the way down (ram up). The seating die's stem would be backed way out or removed from the die and the die body screwed into the press just far enough that it just stops on the loaded round. It is then backed out half a turn and fixed into position with its lock ring. The seating stem is then reinstalled and turned in until it just touches down on the bullet nose. The press ram is still all the way up. Then the press ram would then be withdrawn and the seating stem would be tweaked down, say an eighth of a turn, and the ram run up and down all the way again and the cartridge COL re-measured. Repeat until the cartridge comes out the right COL. Once so adjusted, the other rounds are then run through the press to correct them.
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Last edited by Unclenick; December 2, 2008 at 02:07 PM. Reason: Corrected number
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Old December 1, 2008, 10:19 PM   #20
F. Guffey
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Major Dave (retired), we will start going the other way, bullets are pulled for different reasons, when pulling it is easier to seat the bullet first to brake the bullet loose? then pull, there are many different seating die designs, most of my dies will only allow the plug to be removed and installed from the bottom.
I would install the cartridge in the shell holder and raise the ram to the top, then raise the seater plug and install the die into the press, adjust it down until the crimp portion of the die contacted the mouth of the case, then adjust the die up 1/2 turn then secure the lock nut, I would then adjust the seater plug down until it contacted the pullet, I would then lower the ram and adjust the seater plug down one turn, secure the nut, raise the ram to seat the bullet, lower the ram remove the cartridge and measure.

The seater plug can me adjusted in thousands with a dial caliper or depth micrometer, or by dividing the numbers of threads on the stem into 1.000.

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Old December 2, 2008, 01:01 PM   #21
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Before attempting to seat any crimped bullet deeper... Make sure it isn't crimped into a cannellure. If it is; you'll need to pull the bullet (at least past the cannellure), then reseat the bullet to the desired depth. Failure to do so usually results in a bulged neck, or collapsed shoulder.
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Old December 2, 2008, 02:30 PM   #22
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Good point. I tried looking the round up on the federalpremium.com web site, but while the bullet they show in the photo has a cannelure, it is not a round nose bullet by any description I would use. It appears to have a semi-pointed radial ogive leading to what might be a shpherical exposed tip? I can't tell if they've shown the right bullet or not? Since most modern round nose bullets have cannelures, though, I think your caution probably applies.


Major Dave,

You might want to have a gunsmith look at your gun (you didn't say what it is) and check how those rounds feed? It could be it just needs a little feed ramp or magazine lip (or receiver cut) cleanup?

Nick
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Old December 14, 2008, 02:44 PM   #23
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Go get a copy of Dr Franklin Mann's book "the bullets flight from powder to target". Yes it is from the turn of the previous century but he tests, retests and documents about every possible way you could mess with a bullet and its impact on the accuracy of the load.

Fascinating to read and yes he addresses "mutilated bullets".
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