RMW Extreme Build. It has begun.

[Pablo]

I keep thinking I'll have time to add detail and I just can't catch a break.

Pablo,
  Now that you have your 10mm running so well are you still looking at doing the 9x25?.
  I've got to say that the 9x25 is a great intermediate carbine round.  More versatile than the 10mm with almost as much close range stopping power and better gas pressure to run the AR. They are both a hoot to shoot!

I've been meaning to do exactly that now that I FINALLY have the 10mm running. I need to see what kind of package deal he can do. Must send email soon. See if I can have him adapt my AIM ultralight bolt and throw a GG mag in the deal. I'm going 16" barrel on this one. Underwood has 9x25 FMJ back in stock. I'm saving all that brass and will make brass do. Oh this is gonna be good.

[mrpipesmkr]

  I wanted to mention another problem I had when using the Korean, KCI .45 auto magazines in my 9x25 build.
  As most 10mm and 9x25 shooters know, these magazines can be converted from .45 auto to 10mm/9x25 by simply adjusting the feed lips down to the 10mm diameter. Usually this is enough to convert them although sometimes the spring has to be adjusted also.
  There is another problem that comes up when using these magazines to feed 9x25. Occasionally a mag That feeds 10mm perfectly will jam when feeding 9x25, with the rounds becoming stuck at the top of the mag. In some cases you can have as few as 3-5 rounds in the mag When this happens.
  The problem is with the shoulder of the 9x25 round. If you take apart the KCI mag You will see that there is a slight ridge stamped into both sides of the sheet metal of the mag Located at the top of the mag. These two ridges contact the front portion of the 10mm brass and guide the round into the feeding lips. However, the 9x25 brass is not straight like the 10mm is since it has a shoulder where the case drops down to 9mm. This 9mm part of the case happens to contact the ridges in the magazine rather than the 10mm section allowing  the rounds to angle off 1mm to each side causing a jam.
  The easiest solution is to take the magazine apart and extend the ridges on each side of the mag back toward the rear of the mag by using J.B. Weld.  It doesn't take much to extend the ridges back far enough that the 10mm portion of the case is contacting them. This forces the rounds in the upper portion of the magazine to set straight in the mag and move properly into the feed lips eliminating this kind of jam.
  Hopefully my discription here of the problem and the solution is clear but if you take your KCI mag apart and put a 9x25 round int the upper section you will see where the case is contacting the ridge. Compare that to where a 10mm case contacts the ridges and the situation becomes evident.

 

[mrpipesmkr]

Pablo,
  Had a chance to go to the range Sunday afternoon. Had a little wind and a few sprinkles but a nice cool day for the range.
  My son in law and grandson came along and we took several pistols and rifles. Don't want to even think about how many rounds of various caliber see went through but I do know we put 150 rounds each through the 10mm AR and the 9x25 AR.  We had one hang up on the carbines when the 9x25 failed to feed one round by hand cycling. Dropping the bolt release and during firing it fed perfectly.
  My main reason for going to the range was I wanted to zero both builds at measured distances. We used 100 yards as a zero for both the 10mm and the 9x25 and adjusted for drop further out, as far as 200 yards. As I've said before, I am impressed with the accuracy of both builds. We found it fairly easy, even with a little wind, to shoot 2-2 1/2 inch groups at 100 yards with the 9x25 doing a little better than the 10 in the wind. The two stage triggers I'm using on my builds really helps and having a good table to rest on makes quite a difference. At three hundred yards my groups did grow quite a bit, out to 3 1/2 - 4 inches with several fliers I prefer not to talk about!  I have to attribute this to a shaky old man with old eyeballs. My grandson did better but I haven't admitted it to him yet!
  It seems both of our builds are pretty well dialed in now. I'm starting to have confidence that when I pull the trigger on mine they are going to go bang every time!  Now I just need to find a couple of hogs to volunteer for a little ballistics test I have in mind!

[Pablo]

Wow awesome. I try to hit steel at 200 yds with my 10.5" 10mm. THAT is not a given!!

[mrpipesmkr]

  Well, my 16 inch barrels probably help accuracy a little, but your shorter barrel should turn in comparable groups.  We took the red dot off my 10mm and put a decent variable on it. I had the advantage of having some young eyes along with me to do the dialing in. My old eyes require some concentration that my grandson doesn't have to bother with.
  One thing I have noticed is that when shooting a large, general target like a steel your groups will fall off. It's psychological I think.  Because you are shooting for a hit anywhere on the steel you tend to not focus down like you will with a decent Bulls-eye target.  Just natural l think, but if you try shooting at a bulls-eye target at the same range you'll be surprised at how things tighten up for you.
 

[Pablo]

  One thing I have noticed is that when shooting a large, general target like a steel your groups will fall off. It's psychological I think.  Because you are shooting for a hit anywhere on the steel you tend to not focus down like you will with a decent Bulls-eye target.  Just natural l think, but if you try shooting at a bulls-eye target at the same range you'll be surprised at how things tighten up for you.

This SO true. I'm just thinking I can hit, don't bare down and remember all the fundamentals!

[Pablo]

Giving this a bump for the recent interest (inside and new folks) for 10mm AR feeding issues.

[10fanatic]

Can someone help me understand what is done to a BCG to allow for a 40/10mm case to be used.  Specifically the bolt face on a DI bolt.

[Pablo]

Can someone help me understand what is done to a BCG to allow for a 40/10mm case to be used.  Specifically the bolt face on a DI bolt.

Almost the same dimensions as a 6.8SPC bolt face. The ejector has a slight angle and is polished. The extractor has some material removed and is polished. The trailing edge of the lowest lug is slightly rounded and all lugs polished - the lugs do very lightly contact the next round in the mag, but you don't want the bolt to hang on the case mouth lip. (Never a worry with shouldered rifle rounds like .223 or 6. You can do a manual fit up with an empty case.....a lot of this is trial and error.

[10fanatic]

Thanks Pablo... Couple more questions...  Where in the heck do you find 10mm barrels with gas holes for DI?  All i can find are back preasure barrels. 

Also, for any reason would a 6.8spc side charging handle upper and bcg NOT work?  Just thinking about ideas and generating knowledge. 

Thanks!

[Pablo]

Thanks Pablo... Couple more questions...  Where in the heck do you find 10mm barrels with gas holes for DI?  All i can find are back preasure barrels. 

Also, for any reason would a 6.8spc side charging handle upper and bcg NOT work?  Just thinking about ideas and generating knowledge. 

Thanks!

Only RMW. No one else makes a 10mm DI AR - as you can tell by this thread, it's no cake walk.

The bolt carrier will need to be adapted to the magazine feed lip width.

[Pablo]

  Forgot to post this:

[sstewart]

Awesome Pablo


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[Pablo]

Awesome Pablo


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Thanks - I now have a decent stockpile of full power 10mm ammo!

[Pablo]

So this pup was sitting in the safe for awhile.......took in out for the waguns.org New Years day shoot and it ran like crap. Not sure what I forgot, or what I was doing wrong - misfeeds all over the place. Seemed like magazine problems. Ugg.

One thing I forgot was I had a super light recoil spring. So I changed out to an HD one (both flat wire). Thought here is the rounds need to be driven fully home.