Need some thoughts on my new project.
I am reconfiguring my of my SBR's and I am looking to get some opinions on installing a Magpul UBR on it. Currently I am running a B5 SOPMOD which weighs in around 7.5 ounces. With some of the front end accessories especially the suppressor it is throwing the balance way off.
Any thoughts on using a UBR to balance it out?
The UBR definitely adds some weight to the rear, and it will help balance the SBR.
A few years ago I put a UBR on an 18" barrel rifle which had an A2 stock. Balance with the new UBR stock was fine. Unfortunately I struggled off and on with the vertical aspect of my 100-yard zero. A few months ago I replaced the shot-out 18" with a new barrel -- one of higher quality. I still had consistency issues with vertical point of impact, and it cost me some precision positions in competition.
A buddy stated my vertical issues may be due to the stock. After a bunch of testing, I realized he was right. For whatever reason with my face/cheek/eye position mechanics, I don't get a consistent cheek weld & eye position with the UBR. I don't know if I'm the Lone Ranger on this challenge with the UBR.
Anyway, I replaced my UBR with a Magpul PRS G3, and I'll never look back.
FWIW I have a Magpul STR stock on the lower I use for 16", 14", and 11" uppers. The STR works for me, and I don't have issues with weight or balance among the various uppers.
I have to say that you that you always respond on my rifle posts, which is awesome to have a constant voice. So I want to say thank you for that.
Cheek placement is the biggest concern I have about the UBR, the way it opens in the back. Obviously on a 10.5" 5.56 I don't have intentions of going "long" distances but I want to be able to use it to its full potential. With the suppressor, M600 Scout and DBAL it just gets really heavy in the front.
The STR might not be a bad choice it weighs 12.5oz, over the B5's it might be the better choice.
With the storage tubes in the STR, you have the capability of tuning the weight. Try 2 or 4 AA batteries in it, if you need more weight. If you need even more, you could cast lead slugs to fit the compartments.
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You may have other cheekweld or head position issues, but the gap in the comb between the end of the receiver extension and the butt should be a complete non-issue unless your shooting position is, let's say, very unconventional.
They came up with the design in part because a lot of people have the opposite problem - their face sticking off the FRONT of collapsible stocks.
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Yep, the cheekpiece can be unscrewed and semi-permanently fixed further away from the receiver by several increments. By default, it’s the only collapsing stock that I’ve shouldered that does not, could not grab my beard hairs. I can’t see people really needing to move the cheekpiece back unless they’ve got some sort of magnifier setup or a piece of glass nearly as long as the rifle with some special eye relief issues or something. The stock is solid as all get-out, so you don’t have to worry about that.
My cheek weld tends to be more rearward on the stock. With the UBR stock fully extended, my cheek wasn't fully on the cheek piece. So I shot the UBR with the stock one or clicks less than fully extended. This required that I move the scope on that AR a little further forward than on my ARs with the PRS and STR stocks.
I feel the major issue for me was that the top of the UBR stock didn't seem to mate well with my cheek shape. I can't explain why, because there's nothing really unusual with the UBR's stock shape.
The shape on the top of the STR stock is a little different than many collapsible stocks. Think of it as a longer wedge area for the cheek weld. At first I wasn't certain if I would like it, but it works for me. If there's any way for you to see and fondle a new stock before buying it, definitely do so.
Cheek weld is quite personal. Based on successes and failures with my precision rifles, I find that a lightly-pressured cheek weld works best for me. With normal-height scope rings (2.5" scope center over bore) I had to use a pretty firm cheek weld on the UBR to get my eye in the center of the optic. With high scope rings (2.9" scope center over bore) I no longer had the too-firm cheek weld with the UBR, but now I had a somewhat nebulous "cheek touch" on the stock.
I suspect a lot of my challenges with the UBR are my cheek build and my preferred shooting position. YMMV
I really thought the UBR would be the ticket, then I shot one in a two gun match. The STR is also my choice after discovering the prone stages really challenged my cheek position.
That must be why I like the UBR, I don’t remember the last time I shot prone ... these days, it’s just too far down, and it’s no fun getting back up ... come to think of it, it’s been a long while since I’ve even shot in the kneeling position ... off-hand and bench is about all I do anymore
If you really want something you'll find a way ...
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I've shot my 18" AR with the UBR in a whole boat load of positions. In addition to practice days and training courses, this AR with the UBR was my primary rifle in the following matches over a number of years:
- Competition Dynamics -- Team Challenge
- Nightforce Precision/Tactical 2-rifle match
- Johnson 3-gun -- 2-rifle match
- NRA Whittington Center -- AR match
It's fair to say that prone off bipod was one of the least common shooting positions in these matches. Positions included:
- standing off hand -- often while wearing a pack, and sometimes with a bolt action slung over the weak-side shoulder
- kneeling without support
- kneeling with sling support
- tripod for support -- standing & kneeling positions
- rifle supported by rocks, trees, barricades, fence posts
- prone without sling, bipod, or bag support
Of these, I likely shot the most consistently from prone with bipod and rear bag support.
This rifle isn't babied. Its first barrel was definitely shot out when I pulled it. The original rail definitely showed some wear, and I suspect the currently Mlok will end up the same way. The NF 3.5-15x has its share of scratches.
In all honesty, I tried to like the UBR. But it really wasn't for me, from any position.
Update.... installed the STR yesterday and you guys were right it was perfect. I am installing my flashlight on Monday so if I need to I will add some batteries to balance it out.
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