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I Think I "Want" a Bigger Hammer!


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On 2/10/2016 at 0:16 PM, wildcat junkie said:

 

A 200gr bullet in .323 (8mm) is akin to a 165gr .308 bullet. It is a medium weight for caliber bullet. I already use the same bullet in the 8X57 & it a very efficient killer that is suitable for any North American game.

 

The 8mm-06 A.I. is a 30-06 case necked up to .323, then fire-formed in a chamber that the shoulder of the 30-06 case (now 8mm-06) will headspace in. The shoulder is blown out to 40* & almost all of the case taper is eliminated. The fire-forming procedure is very critical to form good cases that don't have the brass stretched near the cartridge head thus weakening the brass. The chamber must be cut to properly headspace a standard 30-06 case to accomplish this W/O complicated case forming steps on the loading bench.

 

This increases the case capacity and allows higher pressure to be employed due to the straighter case walls & 40* shoulder. This same type of case geometry is employed in the modern "short magnum" cartridges.

 

So are you firing the 30-06 cartridge in the gun to fire form the new case?

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9 hours ago, chas0218 said:

So are you firing the 30-06 cartridge in the gun to fire form the new case?

Yes, after necking it up to .323. If the "Ackley Improved" chamber is cut properly, (mine is) the "parent case" shoulder will still head-space. Many 30-06 A.I chambers are cut W/O setting the barrel back resulting in a long chamber that requires a lot of farting around to keep from stretching the case at the web when it is fireformed. On the other hand, I must not screw my 8mm-06 A.I. down all the way when necking up or it will bump the shoulder back with similar results.

 

The A.I chamber has the same "datum line" as the parent cartridge. In everyday terms, there is a certain location on the shoulder that is the same as far as head-space for both cartridges.

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For the last few days I have been farting around with some details & doing some preliminary load development.

 

Unlike my 8X57IS Oberndorf Classic Mauser that has a very short throat in the chamber, this rifle ended up with a very long throat. While the short COAL (3.32") required for the 8X57 works most efficiently with 200gr bullets, the relatively longer COAL (4.20") required to even get anywhere near the land of the rifling with the bullet ogive, lends itself to the longer pointed boattail 180gr .323 Nosler Ballistic Tip bullets.

I can't get enough Norma MRP into the case to get to 60K chamber pressure W/the 200gr .323 Speer Hotcore bullets. Mv plateaued at around 2900 fps. The 180gr .323 Nosler Ballistic Tip bullets allow the use of Alliant RL17 to fill the case to a lightly compressed load and chamber pressures are in the 64K+ range.

The sharp shoulder angles & minimal taper of the case (not unlike today's WSM cartridges) will withstand high pressures better than the parent cartridge geometry. I was able to easily top 3100 fps W/the 180gr BTs W/O flattening the primers, but I think I will shoot for just under 3100 fps which is plenty enough snot churning out over 3800 ft# of muzzle energy with a maxium + - 3" point blank range of 300 yds.

 

Back to the build:

 

I promised to show how easy the Silly Putty is to work with. My old method of using modeling clay to control the bedding compound left a mess in the stock that was hard to clean out. The Silly Putty does not stick tenaciously to anything except itself making removal easier.

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A few minutes of picking out the bits of glass and the Silly Putty is ready for another project.

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Once the action was bedded I went to work on the barrel channel. After filling in the black nose cap section with some black Accraglas, I scraped the military profile barrel channel to allow at least .040" clearance of the new barrel profile from just in front of the chamber to the fore-end tip which was filled to .030" clearance previously. An application of the release agent was made to the action bedding and the fore-end tip filling to prevent unwanted squeeze-out from bonding to these areas.

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I then wrapped .030" thick pattern maker's wax on the barrel from a point 3" in front of the receiver ring. The wax was then covered with packing tape to prevent the heat of the epoxy cure from making a bond to the wax.

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This was followed with the release agent application and after it dried the barrel channel had bedding compound applied sparingly and the barrelelled action was placed into the stock and the action screws firmly tightened.. The "squeeze-out" was (again) just about perfect.

DSC05093_zpsfrrvthqz.jpg

 

When the compound had set to a firm, but not hard consistency, I trimmed the excess & separated the barreled action from the stock.  After the compound set up over night, I sanded the top of the stock flush with the wood. Now the fore-end is completely sealed from the elements and has a fiberglass "spine" to help prevent warping.

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Look closely & you can see the .030" "free-float" gap between the stock and the barrel starting 3" in front of the receiver ring.

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Here is what the progress looks like to this point. The rifle can be fired and could even be hunted with as long as I didn't get caught in the rain. As you see it, the rifle weighs 8# 6oz. Not bad for a 26" barreled rifle with a full sized 3-9 scope that will achieve ballistics equal to or greater than a .300 Win Mag.

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Thats' enough for this post. I will follow up with some PIX of Dennis Olsen's excellent gunsmithing talents.

 

Edited by wildcat junkie
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Some pictures of Dennis Olsen's Handywork.

 

Here are 2 M98K actions. Both have M98/29 barrels. The top has been cut & crowned to 26" but it is still the military profile after the rear sight sleeve has been removed.

 

The bottom action has the same barrel contoured to my specifications.

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Here is a before & after comparison of the bottom metal. Except for some shaping I did on the trigger bow & a "straddle" floorplate, the one on the left as as issued W/the locking screw arrangement. The one on the right has had the lock screw holes filled and finished as well as some nice contour work on the trigger guard bow.

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Same treatment to the front action screw.

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Some more pictures of the bottom metal.

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I had Dennis stamp the camber W/the cartridge. (notice the eagle and swastika on the front portion of the receiver ring at the top right corner of the picture)

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Finally, a closeup shot of the muzzle crown.

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5 hours ago, Pygmy said:

Gonna be PUUUURTY, Wildcat.....<<sigh>>.....

My son wasn't going to hunt this year until I showed him the "Big Hammer"! Now he bought his license & even applied for a doe tag in 6C.

 

Iv'e got about a dozen watermelons that din't quite ripen before leaf spot got to the vines. Ought to make for a fun day on the 200yd range. "SLEDGE-O-MATIC"

Edited by wildcat junkie
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  • 3 weeks later...

IT"S GETTING THERE!

I'm still rubbing in coats of boiled linseed oil & buffing it with a cloth. The bad news is, it takes forever! The good news is, I can go ahead & hunt with the gun  and keep rubbing/ buffing. Once the metal is done rust bluing I can assemble the weapon and hunt with it. Every day when I come in from the woods, I'll give it a coat of boiled linseed oil. That will help preserve the metal finish too. It is starting to take on the sheen I'm looking for, but there are still a few pores that haven't completely filled yet..

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 I got a rust blue cycle competed last night. The way it took color, I think 4-5 cycles will get it dark enough to suit me. The last one I did took 9 cycles.!

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I'm hiving some fun with it on this thread. 

My Dakota Arms 3-position shroud/safety left Rochester last night. I'm hoping it gets here today so I can fit it & start rust bluing it. I'm running low on solution so I want to have all the parts ready so as to not waste solution by throwing the pads soaked in it away.

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I wasn't going to do the safety right now, but I scraped up the $$$ to buy the safety. I found it for less than $150 shipped from Brownells.

 

I'm hoping to have it done by Saturday morning so we can have a watermelon smashing session on the 200yd rang at the local club. We'll be taking the 30/40 Krag, (with a new taller front sight & new loads) Curtis' 7mm-08 AXIS II, the 8x57 Oberndorph Classic, and the 8mm-06 Ackley. Maybe I'll get some videos?

 

 

Edited by wildcat junkie
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