Modern Sporter - Build Discussions

jacotsmith said:
View attachment 345229

I just bought the kit used (from a reputable CGNer), but just realized it doesn't fit in my AR mag well either.
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Interesting! I have not seen those before... If I was to guess however, I would think they are an attempt to align the feeding path better. Some mags have a bit of wiggle in any receiver be it AR or otherwise, and in the 22lr ones it can lead to misfeeds if the angle of the ammunition changes from one round to another. I've used a dot of 5 minute epoxy on the back of magazines to correct this same thing, and just sanded until they are a snug fit.

I'd also suggest sanding/filing the tabs down, BUT I'd go at it slowly and evenly to sand them down only the minimum amount necessary as I'm virtually positive those little tabs are there to snug up your magazine.

Very cool, and let us know how it goes!
 
Can u please explain why you think a barrel torque tool puts less stress on a on a upper I have been trying to wrap my head around it. The way I think of it is, the barrel extension pin slides into the slot on the upper and the barrel nut is not putting any force on to the barrel to make it want to twist, the force is on the upper making it want to turn with the barrel nut. soo by using a barrel torque tool it’s just holding the barrel from turning, all the force that there is would be is on the pin on the barrel extension because tighting the barrel nut will make the upper want to twist with it. I totally understand for putting on a flash hider or muzzle brake i would use barrel torque tool. Sorry fairly new to building.
Thanks
Brodie
 
Brodie720 said:
Can u please explain why you think a barrel torque tool puts less stress on a on a upper I have been trying to wrap my head around it. The way I think of it is, the barrel extension pin slides into the slot on the upper and the barrel nut is not putting any force on to the barrel to make it want to twist, the force is on the upper making it want to turn with the barrel nut. soo by using a barrel torque tool it’s just holding the barrel from turning, all the force that there is would be is on the pin on the barrel extension because tighting the barrel nut will make the upper want to twist with it. I totally understand for putting on a flash hider or muzzle brake i would use barrel torque tool. Sorry fairly new to building.
Thanks
Brodie
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That was my first thought as well. But I've found out that is not the case. Firstly, if you degrease the barrel extension flange and the front face of the receiver, this allows the friction between the barrel flange and the front of the receiver to hold the barrel nut and receiver in place when the majority of torque is applied. As a result the pin shouldn't put much force into the slot, as majority of the resistence is from the friction between barrel flange and receiver front. Thats what I read, I verified that even though I've put a lot of torque(higher than recommended), the index pin doesn't cause any deformation inside the slot.
 
has anyone tried the new Cross Industries Mags in their modern sporter yet? How is the fit?

I found that my hera mags were pretty tight.
 
PinaKaleada said:
That was my first thought as well. But I've found out that is not the case. Firstly, if you degrease the barrel extension flange and the front face of the receiver, this allows the friction between the barrel flange and the front of the receiver to hold the barrel nut and receiver in place when the majority of torque is applied. As a result the pin shouldn't put much force into the slot, as majority of the resistence is from the friction between barrel flange and receiver front. Thats what I read, I verified that even though I've put a lot of torque(higher than recommended), the index pin doesn't cause any deformation inside the slot.
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Thanks for your reply. Really appreciate it.
 
Sluggo_m14 said:
the Bev block does lock in into the extension;
Will any Barrel Torque tool and vice block work with these receivers?
Will the Magpul Bev block work with these receivers?

Thanks
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Barrel torque rods work. The Bev block does work but needs to be modified since the location of the front pivot pin isn’t in the same location as an AR pivot pin.
 
Or just clamp the barrel between 2x4 in a vise with leather strip to make sure you don’t damage the finish. I was going to buy a reaction rod but 150$ for a one time tool is too much.
 
I've heard the Midwest Industries Upper Rod is the #### for dolly. Too bad they haven't been in stock for awhile now.

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jiffx2781 said:
What's happening is the bolt doesn't travel far enough past the bolt catch to allow the bolt catch enough time to come up and engage the front of the bolt. Instead it gets caught on the front of the carrier.

When I put a rifle length buffer tube on one of my second batch lowers I ran into the same "issue". They shortened the rear of the receiver so that rifle length tubes would catch the buffer retainer pin. I noticed right away that the bolt only went past the bolt catch by a little bit and figured this could be problematic. Before I even fired it I shortened the rear of the buffer pad by a good 1/8" to regain some of the lost bolt travel. The rifle works perfect.

Basically everything at the rear of the MS lower is moved forward the same distance as what the bcg sticks out the rear of the upper receiver. So yes, depending on what receiver extension you use the bcg isn't going to travel rewards as far in comparison to what it would on an AR.
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So this only happens with a rifle buffer tube? If you are using a carbine buffer tube this shouldnt happen? Is there anyway to test if you have enough bcg travel without shooting it? Thanks
 
So this only happens with a rifle buffer tube? If you are using a carbine buffer tube this shouldnt happen? Is there anyway to test if you have enough bcg travel without shooting it? Thanks

It's the same for carbine length. You can pull the charging handle back and check that the bolt face clears the catch but this is no guarantee that it will catch on the bolt face when fired. I swapped out the buffer spring on his gun and that was all that was need for the rifle to function correctly.

We did trim back a buffer, which also worked but he didn't want to have the MS using a "special" buffer.
 
With the talk regarding buffer tube length and cycling, am I going to run in to an issue using a standard mil spec tube, buffer and spring? I was trying to budget a little less and found a set from True North, but want to make sure it will work. Unless I need to go with the PWS tub which is substantially more.
 
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