Hinged floorplate magazine...AR?

[WestKentucky]

i have officially settled on a load for my 6.8spc target and hunting rifle. It is 2” accurate to 300 yards and all the way out to 500 I am ringing a 12” gong easily every shot. I know whitetail range on the 6.8 is realistically we’ll inside the 500 mark, but a shot at that range to put a second round into a shot deer certainly would happen if I were to have a reasonably makable shot.

The problem I have with this load is that it is too stinking long. 130gr boattail ballistic tip is more bullet than the case is truly designed for, but it works incredibly well. Sufficient velocity to expand, extreme accuracy, affordable enough to practice with. It’s great other than being too long for an AR magazine... so to gain a little length I would like to have a hinged floorplate on that gun. Has anybody ever made such a device? Use the top of a standard magazine to get the feed lips only modified to take the 1/10” longer rounds, and a hinged plate setup shoving rounds toward the top? Roll the rifle over and just stick 5 or so in and close her up to load it... not ideal to totally divest from the detachable box, but I am not opposed to the idea if it would work.

 

[lysanderxiii]

I'm a little fuzzy on how a hinged bottom will correct a deficiency in mag-well length.

 

[Ifishsum]

I think he might be talking about not using a magazine at all and basically turning magwell into a magazine. Not sure if that would be feasible...but FWIW I have found there to be significant differences in 5.56 magazines between manufacturers. My match rounds won't even fit into a magpul and the tips drag in a couple of others but I can go almost 2.30 OAL with the black stainless AR-Stoner mags from MidwayUSA. Not sure if that also applies to 6.8 mags but might be worth a look if you haven't already

 

[WestKentucky]

6.8 mags are scarce and the ones I have are among the longest length allowed, but don’t even come close, and yes Ifishsum was correct in my desire to use the mag well as the magazine. Further thought on the project has me convinced that it is not nearly as difficult as it would seem. I’m not yet convinced enough to strip an aluminum lower and start cutting and fabricating, but I might do it to a poly lower just to prove the theory.

 

[rayatphonix]

Somewhere I found a single shot adapter for a 223 magazine. It allowed me to load 80 grain Nosler CC into my AR. I can only load one cartridge at a time. I don't know if they make such an animat for 6.8 or not. If I can lay my hands on it, I'll see if there's a name on it.

 

[rskent]

What is the length you are trying to get to?

Although I have never needed to try, I have heard of people milling out a groove in the front of an AR mag to get a little more room for the tips of their bullets. Other than that, I would think its one at a time in through the ejection port on top of the mag.

 

[rskent]

Random thinking

What if you took a steel magazine and milled both a groove in the front for the bullet tips of about three bullets. Then you milled away enough of the rear center portion of the magazine to allow the magazine to set back in the magwell. Effectively making it a magazine with sides and feed lips and no front or rear. Even if you had to put a spacer in front and had to strengthen the side walls. You could in theory, maximize the length of your round without modifying you lower at all.

 

[someguy2800]

Have you tried just seating them deeper? You can often find a length where bullets shoot just as well way off the lands.

 

[boom boom]

Look into LWRC Six 8 rifles,
"The LWRC SIX8 rifles and receivers are fully ambidextrous and equally suited to right or left-handed operators. They are based on the familiar Stoner M4/AR15/M16 architecture, but they have been optimized specifically for use with the 6.8 cartridge.

Proprietary upper and lower receiver for the 6.8mm SPC cartridge. 7075 aluminum. Type III hardcoat anodizing.
— Uses Magpul polymer high reliability 30-rd magazine with Hi-visibility follower. Unique to the SIX8 platform. Allows for
COAL (cartridge over all length) of 2.32”.

— Enlarged ejection port allows unhindered ejection of the 6.8 casings.

— Fully ambidextrous controls

— Accepts standard fire control groups, barrels and barrel nuts, buffer tubes, etc.

— Tension Screw adjusts upper / lower fit

— Inside of upper receiver coated with Teflon dry film lube per mil standard.

*Please note this is a proprietary receiver set and is not compatible with other uppers, lowers or magazines."
http://onpointfirearms.com/newsletter/2014/04/07/lwrc-six8-matched-receiver-sets-for-sale/

 

[Jim Watson]

This may not gain enough but is a start.
http://www272.pair.com/stevewag/armags/armags.html

I have read of altering magazines to single stack with the Rib down the back becoming extra length.

 

[lysanderxiii]

How about just taking a 5 round magazine and cut out the front for the length of 5 rounds and the width of the bullet noses?

That way you can keep the 'detachable' part, the feed lips but get a little more room forward.

 

[WestKentucky]

Have you tried just seating them deeper? You can often find a length where bullets shoot just as well way off the lands.

I’m seating as deep as I safely can and I’m crimping them pretty heavy. At my current setup I am about .003 away from the ogival section of the bullet so I am barely able to crimp now without loosing the bullet into the case.

 

[WestKentucky]

What is the length you are trying to get to?

Although I have never needed to try, I have heard of people milling out a groove in the front of an AR mag to get a little more room for the tips of their bullets. Other than that, I would think its one at a time in through the ejection port on top of the mag.

I am singling them in now. I want to make it a repeater so that it is sensible for hunting purposes. I know a single shot is good enough but I have made really good shots and still spent time and effort in tracking.

 

[Browning]

I have a RRA A4 NM where I have one of these Sinclair followers for longer .223 bullets.

Might work for your purposes.

https://www.sinclairintl.com/gun-pa...-single-shot-magazine-follower-prod34112.aspx

Worth a look. Maybe email Sinclair for the total OAL possible.

 

[someguy2800]

I'm honestly surprised with all the AR customizing and match shooting that nobody has come up with an AR with an extra long mag well and magazine for longer OAL's

 

[ColoradoMinuteMan]

I measured the body of my Magpul AK and AR magazines and they are nearly identical in length. It'd be interesting to know the magazine well dimensions of a 7.62x39 dedicated lower, but it might be another option to modify. It'd actually be interesting to know if a 6.8 SPC could be made to reliably feed through a 5rd. AK magazine. I measured my Magpul followers and the "useable" portion of the follower, the portion that doesn't go into a channel and is essentially the maximum cartridge overall length possible in the magazine, is .05" larger in the AK magazine. The ID of a metal AK magazine may actually be slightly longer. Anyway, just food for thought before hacking apart a lower.