My old Bushmaster XM-177 needs a change, ideas?


Float Pilot
October 21, 2008, 11:04 PM
I am finally bored sick of my old Bushmaster shorty. 1 in 9 twist.. I have had her since the late 1980s when she was my patrol car trunk gun. While it was OK for across the room distances using hollow points, I don't do that sort of thing anymore.
Now I could use something with a touch more range and power.
And yes I already have a bunch of other rifles that fit that need.

What bothers me about my shorty...

1. Wimpy velocity due to the short barrel.

2. Limited sight radius.

3. Huge Muzzle flash.

4. Heavy barrel on a 5.56mm shorty...

So I have a few options...

A. Another barrel like a 16 inch in 5.56 mm.

B. Another barrel is another caliber, 6.8mm, 7.62x39mm (if that would work)

C, Convert the whole thing to a 20 inch A2 some caliber or another.

D. Sell the dang thing and buy another rifle.

Any random thoughts... ????

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October 21, 2008, 11:08 PM
Put a match barrel 20 inch upper and a magpul PRS stock on it with an ACOG.

Rifleman 173
October 21, 2008, 11:10 PM
I would just switch upper halves and go with a 7.62 X 39 upper. You can get one by mail from Model 1 Sales. You will need to order the upper half, bolt and charging handle. Last time I saw, you could get one for under $600. I would avoid the 6.8 SPC because ammo is about a $1.00 a round to shoot. The 6.5 Grendel, while an excellent long range rifle is hard to get ammo for and is tied up with too much propriety rights and such. The 7.62 X 39 ammo is cheaper, still readily available and you can get magazines for it from C Products, LLC that work with the rifle and ammo. If you do some research, there is a company that makes an upper half that uses the 5.45 X 39 round but finding magazines, unless you can use the regular M-4 magazines might be a little bit of a bear. All I know is that the 5.45 upper exists so I don't know what else you would need to make it work...

Dr. Tad Hussein Winslow
October 21, 2008, 11:11 PM
What are you going to do with it?

October 21, 2008, 11:11 PM
If it was a real XM-177 you could sell it and buy another airplane and pay cash. As a flat top I've killed out to 400 yards with my old XP-100 with a .223chambered and a 10.5 inch barrel. Then I use a scope. I would switch out the upper to a flat top, put a scope on it and still have a right handy rifle for the plane or the boat/truck. Nothing beats a handy rifle in my opinion.

The .223 is a great killer. Somehow, I'll bet you have more than just one rifle?

October 21, 2008, 11:20 PM
AR57 upper

Float Pilot
October 22, 2008, 01:49 AM
Somehow, I'll bet you have more than just one rifle?

Not as many as in the old days. Being semi retired from law dawging and the military does not leave you much money. Particularly with a flying business that barely pays its own way. Not to mention the ex (daughter of satan) who cleaned me out of all the cool expensive stuff...

These days I only shoot a few calibers in long guns.

22lr of course x 4
5.56mm x 1 (can you believe only one left)
6.5 x 55mm x 5 (I love Swede Mausers)
7 x 57mm x 2
7.62 nato x 3
30-06 x 3
300 Win Mag x 1
350 Rem mag x 1
358 Norma Mag x 1
375 HH x 1
38-40 (38 WCF) x 2
45-70 x 2
45-90 x 1
50-90 x 1
12 gauge x 3

All the 7.62 x 39 Aks and SKS's ended up being sold, although I still have lots of ammo. The same with 7.92x57mm mausers...
There were some lean times when I sold what I figured I could maybe buy again.

Of course that never really turns out to be true.

Float Pilot
October 23, 2008, 12:35 AM
Gee, I just had a thought... I have a bunch of regular m-16 mags. 30 and 20s.

I guess if I go to another caliber I could sell them or try to pick a caliber that can use a converted standard magazine.

I handload and am into the longer range, more thump, style of shooting these days.

October 23, 2008, 01:40 AM
I like option A.

Something more like this.

October 23, 2008, 07:56 AM
16" midlength flattop upper with a Smith Vortex flash suppressor and an optic, would be my suggestion. If you go with a fairly lightweight barrel profile, it would seem to correct all the areas you mention (muzzle blast, accuracy, weight) while still being short enough to be versatile.

I'd suggest a Rock River upper like the one below, but it's a fairly heavy barrel. You can get probably find a similar upper with a government-profile barrel from other manufacturers, though.

October 23, 2008, 08:38 AM
14.5" barrels pinned w/ muzzle brakes / flash suppressors are the worst of the worst. You get all the disadvantages of decreased muzzle velocity w/ the 14.5" barrel but none of the short barrel advantages being 16-16.5". I like the one RockyMtnTactical suggested.

October 23, 2008, 12:54 PM
The real XM-177/car-15 were a delight to carry as they had a thin profile light weight barrel. Pure joy to carry, I never suffered with them (I had three different ones in two tours of good old Vietnam).

If I had lots of money to blow on another AR-15, I would do a custom barrel in a length that figured to 16" with a Vais brake, it would be a chrome moly barrel from a top maker and would be a one in eight and a half twist in 6.5mm, and chambered for the 6.5 Grendel on a flat top receiver.

I really see that your problem with your present AR is more a matter of weight and the lack of a flat top receiver for a good scope mounting. I think Bushmaster has lighter weight barrels now a days and I know they have flat top uppers. What is the cheapest way to go and get what you want? I don't know how you will get a lighter weight unless you buy a separate barrel, the upper is and easy deal, you already have all the parts you need for the new upper, so that saves you a bunch of money. The price of a new barrel and the stripped upper would be at the outside 250.00. I'll bet Bushmaster would do you a special with gas tube, no front sight, gas block, put together fairly cheap.

Float Pilot
October 23, 2008, 11:37 PM
I have been pricing uppers...

The down side is that back when I bought this carbine it only cost me $425.

These days an upper assembly cost more. Buying a plain-jane 16 inch carbine barrel is starting to look like an affordable option.

Big question... Can standard 5.56mm AR magazines be converted to wrok reliably with any other caliber? (6.5mm Grendel or 6.8mmSPC)

October 24, 2008, 03:23 AM
M-16A1 (near) clone complete with triangular handguards

October 24, 2008, 11:20 AM
No sir, they need separate magazines for both the 6.5 and a different mag for the 6.8.

Personally I would not give closet space for the 6.8. The .277 in the AR is just a looser in my opinion. You might want to do some reading up on the subject before you jump in.

I think the two links above will help you make up your mind, and provide you with and idea of costs. The 6.5 Grendel is a real winner out to 600 yards and handles the wind better than the 7.62 NATO. The bottom link will link you in for brass costs and magazines. Just remember there is more than one source for mags than Alexander Arms.

Float Pilot
October 24, 2008, 03:28 PM
No sir, they need separate magazines for both the 6.5 and a different mag for the 6.8.

Dang,,,, that stinks... I have a fair number of standard 20s (old colts) and 30s.. I was hoping a diffeerent follower would work on something else.

Since I already shoot a BUNCH of 6.5 x 55mm I am already a big fan of the 6.5 for accuracy and down range performance.

I have been checking out the Alexander Arms site... Wow....

Things are right spendy these days... And my business did not do well at all this year. If Comrade O gets in, he will spread what little I have left to his other comrades...

October 24, 2008, 04:41 PM
Your shorty is frickin' cool. I wouldn't change a thing, personally.

October 24, 2008, 04:50 PM
Senior Member

Join Date: 01-19-06
Posts: 1,791

Your shorty is frickin' cool. I wouldn't change a thing, personally.>>

I agree. :D

Nothing wrong with what you have there. It's plenty cool enough. The muzzle flash I can see as being a problem,but then again, you could fix that and the sight radius problem with a 14.5" bbl or 16" bbl with a decent FH, if you really HAD TO.

Float Pilot
October 25, 2008, 02:42 AM
Well it looks like the 50 Beowulf can use stock magazines. According to the guys on that site if the stock mags don't work you can modify the feed lips until they do. Of course there is not much magazine capacity with those big rounds.

October 25, 2008, 03:14 AM
I handload and am into the longer range, more thump, style of shooting these days.
How about a .243 WSSM conversion upper from Olympic? I believe these single stack into standard AR Mags just like the .50 Beowulf. I'd put a new stock on it, or at least drop in a H3 buffer if you keep CAR stock on it though.

October 25, 2008, 02:49 PM
I see a problem that is fundamental to all of the AR platforms out there. Short ctgs only, not much room to move the bullet forward.. Any more length to the case is a handicap.

The 6.5 Grendel is about the limit in case length and the ability to get longer bullets to work. That .50 Beowulf is quite the ctg. I would not be afraid to swat any bear with it.

The Beowulf uses a short squat bullet allows for a long ctg.

You might want to keep and eye open on the used list of the forum, you have to watch a couple of times a day and be ready to pounce.

October 26, 2008, 11:49 AM
Float Pilot, when youre ready to sell that xm177 upper, let me know... Ive been looking for one. :)

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