6x45 Contender Rifle

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mtngun
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6x45 Contender Rifle

Postby mtngun » Sun Apr 19, 2015 12:55 pm

Homemade reamers. From top to bottom: neck reamer, 0.245" lubrisizer die reamer, throat reamer, chamber body reamer.

The aluminum gadget on the right is a center button that fits the 6mm bore, used to support one end of the barrel in the lathe tailstock.
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dpm6264
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Re: 6x45 Contender Rifle

Postby dpm6264 » Sun Apr 19, 2015 3:40 pm

Hi Dan,
Ahhhhhh the beginning of a new project. Cool. Now that you have reamers you should
be able to put this thing together fairly quickly I would think. Shouldn't take long to cut
the chamber, thread the barrel and cut and crown. You have a mold made yet for what
you want to shoot in that thing? You have a reamer to cut the lubrisizer looks like. Did
you make a push through sizer yet? What barrel did you get? Green mountain?
You may be shooting that thing in a couple of days.
Good luck.

Doug

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Re: 6x45 Contender Rifle

Postby mtngun » Sun Apr 19, 2015 7:02 pm

The barrel is a standard grade (not hand lapped) Shilen blank. 1-10 twist. I've never shot a 6mm before so I just guessed at the twist. Am hoping it will stabilize 80 - 85 grain jacketed for whitetail.

The stub is on the barrel today but there's still quite a bit of work to fit the stub to the action. I'll need to make an ejector from scratch since I botched the supplied ejector on an earlier project.

No mold yet, no sizing dies, no cases formed or necks turned, no pilots for my Forster trimmer/turner, no scope mount. So I've probably got 3 - 4 more Saturdays and Sundays before it'll be ready.

I think my next bench gun will be a switch barrel bolt gun, possibly mounted in a rail. It's easier to fit a barrel to a bolt gun than to a TC. Using a rail would eliminate the need for stocks and scope mounts -- only 4 bolts required to swap barrels in a rail gun. But the TC barrels have been a good learning experience for me. I'm gradually developing confidence in my gunsmithing skills so that I'm ready to move on to other projects. :)

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Re: 6x45 Contender Rifle

Postby mtngun » Sat Apr 25, 2015 6:31 pm

Update: the D reamers for the 6x45 cut well, in the sense that they cut easily and left a nice finish.
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The assembled barrel. Yes it looks funny because I'm leaving the barrel blank full diameter for benchrest purposes. Someday if I get tired of using it for benchrest experiments then I may turn it down to normal TC diameter for field carry.
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On the downside, the finished diameter seems to be hit and miss. For example, the neck reamer was 0.2675" yet the neck ended up 0.270" ! :evil:

The lubrisizer reamer was 0.2452" at its widest point, yet the first die ended up 0.248" ! :evil: I re-stoned the reamer down to 0.2429" and tried again, the 2nd and 3rd dies (one was a push-thru and the other was for a lubrisizer) ended up 0.2444" as-reamed.

The body reamer cut exactly to size or maybe even a little small.

Not sure what can be done about getting the finished diameters spot-on? :?:

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Re: 6x45 Contender Rifle

Postby mtngun » Sun Apr 26, 2015 4:49 pm

Nose punch, lubrisizer die, and push-thru die.
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Bottom of forearm, typical for 3" wide benchrest use.
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Clamps (made from scrap bullet molds :lol: ) are used to hang the forearm and the scope mount. The idea is that since the assembly simply clamps onto the barrel, no drilling or dovetail cutting is required if I decide to set the barrel back. Also, it wouldn't be that tough to swap the assembly onto another barrel.
Image

That's as far as I got this weekend. The next major step is to make a bullet mold for it.

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Re: 6x45 Contender Rifle

Postby mtngun » Tue Apr 28, 2015 6:08 pm

So I made my first ever 6mm mold. The nose didn't come out exactly as I intended but nonetheless it'll suffice for now.
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Cases have to be fireformed so I picked a moderate powder charge out of thin air.

-- 28" Shilen barrel
-- 20 gr. WC844
-- Remington 6 1/2 primers ( not a good primer for ball powder but I wanted to use these primers up)
-- 68 gr. spitzer, oven treated WW & tin, sized 0.245".
-- HVR lube
-- 2.184" COL which is 0.015" off the lands
-- 2348 fps
-- 1.46% standard deviation of velocity (poor, but not surprising for a fireforming load)
-- 2.8" ES
-- 0.88" mean radius
-- 0.91" radial standard deviation
-- about a third of the cartridges were difficult to chamber due to headspace so that did not help my shooting. :lol:
-- no fouling visible to the naked eye
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This was a trial run so I only shot a few foulers and the one group.

Notes and Things to Try Next Time:
-- adjust case sizing die to hopefully ensure 100% reliable chambering
-- the 28" barrel blank makes the TC extremely muzzle-heavy :lol: , to the point that there is no weight at all on the butt when the rifle is sitting in the rest. There's room to slide the forearm forward about 5/8" so I'll try that.
-- my nose punch was not long enough to push the bullet down into the lubrisizer die far enough, so I need to make an extra long nose punch.
-- the expander button on the Forster reloading die is so big that sometimes it telescopes the case neck down into the case. :cry: It's 0.242" diameter which seems too big to me, so I'll turn it down a few thou. I prefer expander buttons to barely touch the case.
-- with a 0.245" bullet the cartridge necks measure 0.2666" - 0.2682".
-- fired necks measure 0.2670" - 0.2683".
-- 0.2455" or 0.2460" bullets may be required to achieve a better fit in the neck, but for the time being I'll stick with 0.245" because that's what I've got. :lol:

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Re: 6x45 Contender Rifle

Postby mtngun » Wed Apr 29, 2015 12:34 pm

Original nose punch, which was already longer than standard, and the new extra long nose punch.
Image

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Re: 6x45 Contender Rifle

Postby mtngun » Fri May 01, 2015 9:29 am

More experiments with the 68 grain spitzer. First we tried seating closer to the lands:

-- 2.194" COL (about 0.005" off the lands)
-- 20 gr. WC 844
-- sized 0.245", oven treated, and lubed with HVR
-- Remington 6 1/2 primers
-- fire forming cases
-- 2344 fps
-- 1.5% standard deviation
-- no fouling to the naked eye
-- awful accuracy, 6 - 8 MOA :cry:

-- 2.216 COL (max jam fit, bore rider engraving and front band jammed hard in the leade)
-- otherwise same load as above
-- 2425 fps
-- 1.6% standard deviation
-- no fouling to the naked eye
-- awful accuracy, 6 - 8 MOA :cry:

That didn't work so let's go back to seating off the lands and try tweaking the powder charge:

-- 2.182" COL (about 0.017" off the lands)
-- 21 gr. WC844
-- otherwise same load as above
-- 2464 fps
-- 1.1% standard deviation
-- no fouling to the naked eye
-- 1.7" ES
-- 0.54" mean radius :)
-- 0.368" radial standard deviation :)
Image

-- increase powder charge to 22 gr.
-- cases already fireformed
-- otherwise same load as above
-- 2609 fps
-- 2.4% standard deviation :evil:
-- no fouling to the naked eye
-- I pushed a tight fitting patch through and there was no visible lead on it
-- 4.6 MOA with vertical stringing
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-- increase powder charge to 23 gr.
-- cases already fireformed
-- switched to CCI #41 primers because I had used up the 30 year old Remington's :lol:
-- otherwise same load as above
-- 2763 fps :)
-- 3.1% standard deviation :evil:
-- no fouling to naked eye but a tight fitting patch showed a few specs of lead. Not much, but it was there.
-- awful accuracy with mostly vertical dispersion
Image

Conclusions and Lessons Learned:
-- In 30 years of shooting Contenders, I've always gotten best results with a load that chambers easily and jumps to the rifling. Today was no exception.
-- If my only goal was to shoot little groups then I would try to fine tune the 21 grain load. But my goal is to shoot little groups at 2700 fps, not at 2460 fps. ;)
-- despite sliding the forearm forward as much as feasible, this rifle continues to be excessively muzzle heavy with its 28" full diameter barrel. There is very little weight on the butt so the butt bounces around quite a bit in recoil even though the heavy 6x45 doesn't recoil much. That's not helping the accuracy, but I don't know what to do about it? Eventually the barrel will probably be shortened but for now I want to leave it full length.
-- standard deviation was unsatisfactory with all loads. The 68 grain cast bullet does not seem compatible with WC844 powder.
-- fouling seems to rear its head above 2600 - 2700 fps.

Things to Try Next Time:
-- a different powder with the 68 grain bullet
-- a heavier bullet with the WC844 powder
-- obviously there are a million other experiments I'd like to try eventually, but the short term goal is to find a decent "standard" high velocity load that can be used as a basis for those experiments.

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Re: 6x45 Contender Rifle

Postby mtngun » Sun May 03, 2015 5:02 pm

Following up on the extra-long nose punch -- I used it today and it worked as intended, pushing the bullet down far enough to fill all the grooves. :)
Image

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Re: 6x45 Contender Rifle

Postby mtngun » Tue May 05, 2015 3:43 pm

Some new toys -- er I mean bullets -- to play with. :D

Since the rifle showed little appetite for the little 68 grain pill, I recut that cavity with a longer bore rider.
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