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Before and After Feed Ramp Mod, groups from STAG

5K views 38 replies 22 participants last post by  Frankyoz 
#1 ·
I got to shoot the Stag again before the snow closed in. This is a Stag A5 , 16 inch barrel, 1 in 10 twist, SPEC II chamber. A2 Butt stock, Tubbs Flat spring and a Leupold 6x 42mm Scope.

When fired before feed ramp mod to an M4 style, it would fail to feed and deform enough rounds thaat it would throw a few out of the group.


After the Feed Ramp modification it does not hang up while feeding and the groups are much better since the bullets are not being deformed.


You can see from a standard non-M4 style feed ramp area how the larger 6.8 SPC cartridge could hang up or deform.


Compared to the new modified ramps:


Now the Stag loads them smooth as butter.



 
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#2 ·
Nice. I have to do this mod soon. You were aiming for that square right? :wink:
 
#3 ·
Actually the scope is zeroed for 110 grain Nosler Accubonds and I was aiming for the diamond which is out of the photo. This rifle changes impact point quite a bit with different bullets. It even changes impact point by a few inches just by changing the primers.....
 
#5 ·
Nice work!
Its almost hard to believe that such a seemingly small thing can make such a huge difference.
 
#6 ·
Nicely done Float! Fantastic improvement.


Not to hijack, but I noticed you are in Alaska. One of my students (and friend) has a house in Alaska on Lake Clark. He owns a Super Cub and has been trying to get me out there for about six years. I really need to take him up on the invitation. Anyway, nice solution on the Stag.
 
#7 ·
if the squares on your target are one inch squares
Yes they are one inch squares. My various careers have given me various skills that are/were only good for certain things. Unfortunately nothing that I can make money with now that I am a geezer...
30 years ago I could really shoot tight groups...
 
#13 ·
Mike W said:
I don't know, it's a small town in the middle of nowhere.
Mike, I put a post on ARFCOM for a Dallas area AR gunsmith for you. Let's see if we get any responses. Several million people in the DFW area, I'm hoping we can find a 'smith for you.

http://www.ar15.com/forums/topic.html?b ... 975&page=1

FloatPilot... congrats on the group improvements, and great job on the 6.8 Alaska Feed Ramps. :)
 
#14 ·
Definitly need to email those pics to stag... that is certifiable proof that the M4 feed ramps make a huge difference to the accuracy and reliability of their rigs....
 
#15 ·
marinesg1012 said:
Definitly need to email those pics to stag... that is certifiable proof that the M4 feed ramps make a huge difference to the accuracy and reliability of their rigs....
Super idea... this could also be posted in Stag's Industry forum on AR15.com, and in the Variants section. :twisted:
 
#17 ·
ArtFWTx said:
Mike W said:
I don't know, it's a small town in the middle of nowhere.
Mike, I put a post on ARFCOM for a Dallas area AR gunsmith for you. Let's see if we get any responses. Several million people in the DFW area, I'm hoping we can find a 'smith for you.

http://www.ar15.com/forums/topic.html?b ... 975&page=1

FloatPilot... congrats on the group improvements, and great job on the 6.8 Alaska Feed Ramps. :)
thanks, I hope someone pops up who is good.
 
#19 ·
Great job Float! That is exactly what my Stag needs. It shoots fine with most loads except 90 Sierras but I want it to be reliable with all loads. I will send mine to Adco soon. CMT makes parts with the M4 ramps I believe and why they don't use them is beyond me. :? I just replaced the stock spring with an SSS flatwire but have yet to shoot it. Thanks for the report.
 
#20 ·
Float Pilot said:
Actually the scope is zeroed for 110 grain Nosler Accubonds and I was aiming for the diamond which is out of the photo. This rifle changes impact point quite a bit with different bullets. It even changes impact point by a few inches just by changing the primers.....
What Dremel "bit" did you use to make the ramps? They look nice. 8)
 
#21 ·
Vast improvement... nice blending... great shooting...

I am glad I had TIM cut ramps in the upper receiver...great damage control
 
#22 ·
You want to use the cone stone bit. The one that the broader section will fill the extension ramp. Set it up so it fills the extension ramp and slowly work the angle down. Pay particular attention to the sides you do not want a over hang of the extension into the ramp on the receiver. Once you get it exactly the way you want get some mild polish like Flitz and use the felt wheel bot and buff it to a mirror shine. Go very slow taking only a little at a time. You can always take more but can never put any back. :wink:

Float Pilot glad to see you finally took the plunge. Aren't you much happier now and wondering why you didn't do it sooner? :lol: :lol:

As everyone can clearly see this is why M4 ramps are mandatory not only a nice option.
 
#23 ·
My rotary tool is not exactly a dremil. It is a cable drive rotary tool wth the motor mounted under one of my work benches. The controller is a foot pedal. So my various bits would not corrispond to a dremil set.
I also have a series of Swiss files in my gunsmithing tools, plus a series of honing stones that are in various shapes.
I have done feed ramps on various other firearms, but this 6.8 was down the list of things that neded to be done around here...

The big trick with this Stag was to load up several crimped dummy rounds in various bullet weight. Then load a few rounds into a mag, so you can see how the rounds from each side are feeding (or not)...
I put some chalk on the ramp area and then looked for the rub marks where the bullet tips were dragging.
Do a little, polish it up and then try loading some more times... repeat as needed....

One of the big hang-ups in this Stag was the sharp edges and burrs on the locking lugs. The bullets where actually being scratched pretty good AFTER they came off the feed ramp and were passing through the lug area. This is just plain poor quality control.... There were little bits of copper jacketing being shaved off by these burrs.

So I grabbed a big hand full of chop sticks from the Chinese place in town.... Then I glued crocus cloth and various grades of emery cloth onto the chop sticks. These were perfect for getting into the lugs and taking off the offending burrs.
 
#24 ·
HA Ha that is a neat idea. You can also use lapping compound and lap the bolt into the extension with hand cycling. With the 90 degree attachment head on the dremel you can get into the extension and knock them off as well. This is also what causes the 2 long and sometimes deep scratched down the cases many see on new uppers.
 
#25 ·
I have notriced that the new feed ramps have changed which loads were the most accurate.
In the past, (pre-ramps) I needed to load the cartridges long (2.260 to 2.280) for accuarcy.
Now it seems to work better with them shortened up to 2.250. In the past the shorter roudns would not load at all.

As Elmer Fudd would say Vweerrry Interwesting.....
 
#26 ·
Thanks for putting that post together.

All this time, I thought the M4 ramps were only for feeding reliability.... my Stag 5H upper has been 100% reliable and darn accurate so I didn't sweat it. Now, maybe it can become goshdarn accurate! :)

My Stag upper was doing almost the same thing yours was. It was throwing the first (or was it last?) round out of the magazine out of the group by a half an inch or more, ruining what would have been what I'd call excellent groups for a cheap 16" 6.8 upper.



Good shooting,
desmobob
 
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