So, it's come up a couple times before - but I figured there've been some recent developments that might make things a little more feasible for making it happen - I'd love to have both the skill and money to create one, but I figured I'd throw the "challenge" out there to some of our more skilled masters and if nothing else, start a little thought experiment as to how one might go about (and if I ever have the money for it) creating a clone of the Colt MARS.  

In the last couple of years, we've seen a bunch of new and unique clones - and we've more or less gone from putting together and discussing USGI surplus parts (not that we've ever lost that aspect ) but we've seen some truly new and original creations of unique variants - we've seen custom M231 builds, R656 builds, R608s, etc. - the MARS, however, might be a new thing all together.  

For those unfamiliar with the Colt MARS - the MARS is the "Mini Assault Rifle System" and was designed to compete with many of the PDWs that now have at least something of a "cult" following like the H&K MP7A1 and FNH PS90.  It was chambered in 5.56x30 Colt MARS, and was basically a shortened version of the AR15 - not only did it have a shorty barrel - but it also had shortened receivers - in fact, the original prototypes used actual receivers that had been cut and re-welded to create the shortened length:




You can see what a magazine looks like:




I think it would be really interesting to see a "clone" of the Colt MARS built - and while it'd be practically impossible to get 5.56x30MM - 5.7x28MM, the PS90 caliber is more or less widely available to feed FN's variants - and while there's a lot of debate over the usefulness of the round - it does have a little bit of a following.  

Now, there is a "drop in" 5.7x28 upper receiver known as the AR57, but it used PS90 magazines - and in terms of building the AR as a PDW, the AR57 upper does nothing to make an AR more compact than it otherwise would be, making it little more than a novelty.  

However - I bet a Colt MARS clone in 5.7x28 would be a very interesting little PDW.  

Some photos for inspiration:






Now - how could this be done?

I think - given the skill some of our members have displayed with 80% lowers - if you took a lower without the magwell already milled out - you could probably just shorten the whole receiver without having to cut and weld it, by milling off the front of the forging and re-machining it to the appropriate length.  

The upper would still need to be welded, but could be built with a standard flattop upper receiver by cutting it and shortening it like the Colt prototypes.  

For the stock - LWRCi has released their new "Ultra Compact Stock," featuring an almost identical receiver extension and shortened buffer assembly, and an M&A fiberlite stock could probably be cut to fit it, rather than the LWRCi stock:






The biggest problems I could see are:

1. Creating a bolt to accept the 5.7x28

2. Would the 5.7x28 produce enough pressure to reliably cycle the action of a standard gas powered internal piston bolt carrier group?

3. Magazines to reliably feed 5.7x28


Now - I know the Colt MARS is a little more modern than what we usually deal with here in the Retro forum - however, I would suggest this - if a "MARS-clone" could be got to work - I'll just leave this here to mull on:




"If" I had the skill and capital to try to do this -

I think the first thing to do would be to lick the bolt issue.  However it would need to be done, you'd have to first create a bolt that would fit the 5.7x28.

If I could get a bolt - then I would get a barrel, and first try to see if it would work/how it would work in a standard AR - install the barrel and bolt, otherwise using standard parts, and see if I could get it working.  

Once and if I could get that working - the next thing would be to figure out the magazine situation - the first thing I would do is look for similarly sized/shaped magazines - maybe the M1 Carbine magazine?  And see if the 5.7x28 would fit it, and perhaps with a new follower and possibly feedlip geometry.  

At this point, you would need to give the shortened receivers a try - cutting a shortened receiver set to just the leng the magazine would need, and re-assembling the whole thing to see if the magazine could be made to feed 5.7x28.  

Finally, you could integrate the LWRCi shortened receiver extension and tune the buffer weight and gas port size.  

Anyone got any ideas on how this could/would be done - better ways - and anyone want to tackle it?  

~Augee

You can get a couple rounds of ammo on GB to experiment with.  They are pricey.

Also contact this guy from GB......TACLTC

He had a real MARS magazine for sale awhile ago.  He may have some leads.

Pics of his mag:

Added a big hurdle

I don't think it'd be that huge of an issue, but you'd be messing with BCG mass, length, and how that interacts with buffer weight and spring pressure.

I reckoned that that would all be "easy enough" if you could get over the other hurdles - buffers and springs would definitely need to fiddled with anyways for the new round.  

The biggest problem there that I forgot to mention would be cutting the receiver down with altering the cam pin geometry/function and ensuring you didn't cause any problems there.  

~Augee

Might not be as big of an issue!  I looked at the AR57 site and it turns out it's blow back operated!  So it's at least possible to have a blow back 5.7 AR, but to fit a new receiver you'd be looking at designing a bolt and heat treating it.

http://www.57center.com/22.html

Looking at their barrel it seems to just thread directly in to the receiver.  Dunno what the chamber / feed ramps look like but it would seem to me a steel bushing that threads on to the barrel and slips in to a standard AR receiver would work to allow for a barrel nut to thread on like normal... that would solve the finding a barrel problem.  If you were to make a new bolt you could flip it over and put a notch in to catch a standard charging handle, much like a M261 .22 adapter which does not have a gas key.

So tagged!    A MARS clone in 5.7 would be a sweet little (tiny) SBR.

I'd be more interested in a gas-operated MARS than a blow-back operated version, FWIW.

I'd rather build it in the MARS caliber and make my own ammunition.

I say start production on the real ting and make the original ammo too.


Having the gun would be cool.
Having to explain what it is and why it is not this would really get one my nerves about the 1000th time someone asked me "what caliber is that M16" gets old quick.

My m231 buffer would work with this project.. But lets try to mimic the original.

I have an AR57 upper so if anybody wants some specific pictures of one to get things rolling along just let me know.

One thing to keep in mind with the AR57 bolt, it is set up for bottom ejection

google fu

says india is making 5.56x30

Should I arrange an overseas trip to set up a contract?
the retro forum could fund it.
We can make this happen.

If I'm doing the math (quickly) right it looks like a straight up blow back bolt for the 5.7 round would need to weigh about 1.5lb.  M16 spec carriers (without the bolt) weigh about 9.5oz.  This beast would need to weigh 24oz.

Banshee:  I sent you an email with some pic requests.  If you have a scale could you weigh your AR57 bolt and carrier?

more google fu

Got it and bear with me on the photos and I do have a scale and can weigh the bolt and buffer

Edit: the battery is dead on my scale and will get it up and running here in a bit but it is much lighter than my 9mm bolt that was sitting next to it in the safe and I would say close to a standard .223 bolt weight

In to see if someone picks up a clone of this thing, she's gorgeous!

I converted the bullet weight on the Indian PDW to grains.  It's only 40 grains at 2130 FPS.  

That's no good.

I was at a gunshow in NW Mississippi about 3 years ago and saw a box of 5.56x30 at a collectable ammo table.  It was about $100 IIRC.  It was in plain pasteboard box with some stamping on it, I think.

People have been bushing bolt faces for smaller diameter cartridge case heads for a hundred years, or thereabouts, so that shouldn't be an issue.  Likewise with altering extractor hooks.  I should think most any competent - and interested - precision gunsmith with experience in wildcat cartridges should be able to handle those jobs.

Now if a guy was gonna use M1 Carbine mags as a basis, there's the 30-cal Carbine based 5.7 Johnson cartridge, information for which is probably more available than the Colt cartridge (and an American creation):

5.7 Johnson

And you know, wasn't there somebody on another forum of ARFCOM doing conversions to 7.62x25, and have the magazines, bolt face and extractor parts figured out already?

The gentleman making various uppers in a lot of different calibers like 7.62 x 25 Tok and a stretched 357 sig is Ronald Williams out of Florida. He is also using mags from various established weapons. I think the 7.62 Tok  uses a pps43 smg mag. He also seems to be very responsive to questions in the other forum.

I think John Thomas may have to amaze us all!!!!

Member RDTCU built a PDR from scratch, designed and machined the whole thing, if anyone could help design the system it's him.

I was giving this some non-serious thought lately when I ran across Sierra 300 BLK data for 30 carbine type bullets loaded to 1.970 OAL.  I still think .221 Fireball is probably the simplest COA

Actually I built a more common AR version a few years ago of a 5.7X28 as pictured below

This was just a test case and I used the FN pistol 20 round magazine but nobody cared since it didn't use the big-ass 50 round FN magazine. I tried the expensive HK 4.6X30 magazine, which was more straight up and down, but it was a little difficult to get it lined up with the barrel extension feed ramps. believe it or not the 5.7X28 rounds in the FN pistol magazine lined right up to the barrel extension feed ramps and it all worked like a champ. The rifle uses a modified AR bolt and carrier. The bolt face must be reduced in size, the extractor modified and the ejector hole reworked and some re-profiling of the lower part of the carrier and lugs on the bolt so they will pass through the magazine. The gas system is pistol length but for the life of me I can't remember the gas port size but for commercial ammo it's probably to small -- I only use reloads in the rifle. The HK 4.6X30 magazine is steel and could probably be made to work just fine but I settled for the FN mags probably because I'm lazy and the other mag worked. The cut down FSB was put there to hold the handguard cap in place.

Edit to add: Marty of Teppo Jutsu (before he went overseas) sent me a barrel to try. It's chambered for a rimless 256 Winchester Magnum. I had to pin and weld on an extension because I didn't want to pay for the SBR stamp. The barrel is a little long at 11.5" and is nitrited. I can get between 2500 and 2600 FPS with a Sierra 70gr bullet. I use a modified magpul magazine -- it has a little spacer up front with a ramp. I really don't know if anybody cares about this stuff, I just like to play with them.

below is pictured the .223 brass on the left and the rimless 256WM on the right. I guess it would be a 6.4X33

 

Could 5.56x30 be made with shortened and resized 5.56?

Augee, I sent you an email with some thoughts.

Yes.

That would make 5.56x30 a more viable round than 5.7 IMO.

I shortened and reformed 5.56 brass for 300 BLK (110 grain 308 at 2325 fps from a 16" barrel).  I REALLY like the 300 BLK platform, and carried it as a patrol carbine when I had the high country dam patrol contract.  Problem is ammo is out of this world price-wise, and reloading components for it (300 BLK specific projectiles) are STUPID expensive.  The 300 BLK uses a special long nosed projectile to insure feeding short 125s jam, as they are .20-.25 inch short.  I personally think the 7.62x40 Wilson using standard 308 projectiles made more sense, as you can use cheap 110s and 125s......

Anyway, since I am not needing a patrol carbine now, I sold the 300 BLK, and plan on cloning the MK262 Mod1 loads for my 1/7.

After all the work I did on the 5.7X28 I would have to agree with you.

One of those would have been cool with a quad stack mag

Me too, but I was kinda thinking 5.7 Johnson or 7.62x25 because magazines already exist.

However, the Fireball is a very efficient and useful cartridge:  OAL of the case is 1.4" or 35.6mm, pretty close to the proprietary Colt round.





Not sure I believe everything in that velocity chart at first glance, but it's a pretty decent little cartridge with a lot of very well known history as far as loading data what works.

From a 24" barrel it is believable.

I believe you are on to something. Knights had the 221 fireball necked out to 6mm (6X35) and designed a PDW around it. I believe Hornady makes the ammo but I don't know if it's available to anybody but Knight's Armament. Below is an add for the knights PDW.

I bought a bag of remmy 110gr FMJ RN and I suspect you will be correct but it's just a cheap experiment.   Right now 300 BLK is a hand loading option as you said but I already had a large selection of 308 bullets and plenty of W296.  I did find a good deal on unfired Armscor brass that seems to be pretty good quality.

 

That mag looks like it was designed for something else and adapted to the MARS rifle. It's got two slots on each side; rather than the large hole on the left like an AR mag. It's also got that notch in the back for a lever type mag catch. The follower also looks like it was chopped down to fit and not made specifically for the mag.

Glad this thread has generated some interest - now we just need someone to volunteer to build it!  

TCBA_Joe suggested that the magazine could be done by taking a USGI magazine and cutting down the back ribs and folding them back over and re-riveting.  

I "chose" 5.7x28 mostly because I'm not a reloader, and I don't know anything about wildcat rounds, so I didn't know anything about the feasibility of making a 5.56x30 from a 5.56x45.  

22_boomer - nice build!  

I'm wondering as well, if it would work (in whatever caliber) with a pistol length gas system - there's the 8" upper that one of our members made a while back using DOE/M231 handguards that could be an interesting adaptation to this as well.  

Like I said, I'd love to build one myself, but I have neither the technological/engineering know how or reloading or wildcatting knowledge to effectively tackle it - however, listening to everyone's input is helping me learn, too... if it could be produced, I would buy one.

~Augee

If someone were to be able to hand load 5.56x30mm I don't see why a 20 round mag with a block in the back couldn't be used for testing before someone goes whole hog cutting down a mag.  This would negate the need for redesigning a bolt and bolt carrier...  I'm guessing it would be a custom job / order for a barrel that would fit a 5.56x30mm with a barrel extension installed.

MARS Patent:

http://www.google.com/patents/US5827992?dq=5,827,992#v=onepage&q=&f=false

I don't have time to go through it all right now but skimming it this seems relevant:  

If I can help with a part. let me know.
Pretty much if I give my guy a good drawing of it, he can make it.
This process is much cheaper when we are making 100 at time though.

If one were to make a MARS clone, aside from choosing the caliber, what fabrication task is the highest hurdle? Seems to me an %80 lower can be pretty easily trimmed back in the mag well area (not that I could do it). Is it in fact the building a shorter upper and matching bolt/carrier?

I don't mind making my own shortened .223 cases.

With the amount of powder it uses, as a reloader this excites me.

The parts are exclusive.. Its going to be costly. Good things cost money.

You would have to machine from billet.

The hardest part would be the bolt carrier and the location of the fire control group pins.

The patent shows they cut the firing pin and put a pocket in the hammer.  The receiver should only be a 1/2 inch shorter.  I'm guessing they left the pins in place.  Otherwise the PG and trigger area would look different. They moved the trigger back slightly in conjunction with milling a pocket in the hammer and shortening the firing pin.

The 5.7 Johnson (designed by Melvin Johnson of Johnson rifle and LMG fame) was a neat little cartridge.  IMI was the last one to produce an M1 Carbine in this caliber.  It had a bad rep for feeding issues, but I think that is because most people who converted their Carbines cobbled them together.  It is a much more substantial round than the FN 5.7 that everyone loves so much!  Modern loads only loose about 300-350 FPS under a 20" shooting M193.  You could have two uppers: One in 5.7 Johnson and one in .30 Carbine.  I shoot my Winchester M1 Carbine 3 times as much as my ARs, as it it cheap to reload.  I use Berry 110 plated at 1900+FPS and Bear Creek 115 Moly Coated cast at 1750.  It's a hoot!

.221 Fireball with the right propellant will match current production 5.56 pressures and velocities.

It's something I've been interested in for a while now, due to soldier's load possibilities and logistics.  The KAC PDW 6x35 mags are very small, and you can carry 1.3 times as many of them as you can STANAG 5.56 NATO mags in the same space.






Propellant technology combined with weapon evolution is making the compact carbine with assault rifle performance a reality.

I really wish KAC would look into making the PDW in 300BLK.

I'd like to see shorter lowers and uppers for pistol calibers too. This MARS idea could expand to more builds.

Count me in--FWIW, I recall an article from Small Arms Review or American Rifleman mag that described Colt had to cut 30 round AR mags & weld them to make mags for the prototype MARS. Unfortunately, I'm not skilled in this area....

As already noted, I think .221 Fireball would be closer to the MARS 5.56 x 30 rather than the 5.7 x 28. I reload the 5.7 & it's more a pistol round than rifle, even through a rifle barrel 10.5" PDW or 16" carbine PS90. And before someone chimes in about Elite Ammo--I know & am not interested.

Back to topic, sort of:

For those "retro types" like me with flight of ideas.....

http://world.guns.ru/smg/usa/imp-221-guu-4--p-e.html

ETA: sorry, I can't find my copy of the Colt MARS article--I found the one I have about the Colt SCAMP (small caliber automatic machine pistol) which isn't very helpful. Will keep looking--I know I've got it.

I think a chopped M231 upper would be appropriate myself.

You guys are diseased!

I can't wait to see what one (or more) or you wizards come up with!

I remember something like the Imp sold by Bushmaster (the original one) from my 1985 G&A Annual



 

Oh, how my Wife hates my holding onto old gun magazines--paper ones, in addition to aluminum, steel & (dare I say it--polymer).

For those who care to get one: Small Arms Review, Jan 2009, Vol. 12, No.4 pp. 69-73. The article is by Christopher R. Bartocci, who was a technical specialist to Colt Defense, LLC at the time of printing.

Highlights:

The MARS buffer looks like a cropped carbine buffer--the photo caption says it was the same weight as an M4 H buffer, essentially-same weights, just bobbed shorter.

The magazine portion of the receiver was cut & welded; the upper was cut just ahead of the fired case deflector & the dust cover cropped.

Ammo was made by Mr. Michael Harris, by trimming a 5.56 NATO to appropriate dimensions (as a reloader-- this would be fun!) and, as already noted--a 55gr FMJ was 2,620fps out of a 10" barrel, 1/7 twist.

There were 3 prototypes made--all of M4 parts cut & welded.

The bolt carrier was shortened & only had one carrier key screw. The firing pin was shortened, the the bolt itself was a standard bolt.

The mags & followers were cut down--they don't say what they did to the followers, but the 30rnd M4 mags were welded.

The trigger, hammer & auto sear were moved slightly rearward to accommodate the new BCG.

One of the rifles had a 1.5x optic.

And I had my head up my ass--I apologize if I mislead anyone--the SCAMP was really retro--this was patented in 1998.

So--those are the highlights.

I wish I knew how to weld aluminum--this would be a fun project!

ETA: with M193 ammo, the projectile isn't going to fragment as much as from a longer barrel due to the velocity being under 2,700fps. They did load some SS109/M855. I suspect that won't matter to us plinkers--but the terminal ballistics would require a more effective projectile, FWIW.