Modern Sporter - Build Discussions

[Rayf01]

I had read somewhere that anti rotation tabs caused fit issues on the upper? Is this in regards to all hand guards or just some? I don't feel like having to chop some off a Strike Industries Strike Rail, so if that's the case I will go with my second choice that doesn't have them.

[luciferco]

Start with full gas and work your way down (closing) 1 round at a time with Winchester white box ammo first.

Looking for some help for a AR type platform newbie.

I got my Modern Sporter assembled last night and took it up to the range today for its first 50 shots. I had 3 different ammo types,
AE 5.56 green tips 62gr,
Winchester 223 white box 55gr
and a few hornady match 223 73gr ELD Match.

About 20 times within those first 50 shots the BCG would not pick up another round. There were no jams, just lots of clicks with an empty chamber when i was expecting a boom. The Winchester fared the worst, i don't think i got more than 2 consecutive shots off before it would fail to strip a fresh round. Bolt is fully forward in the chamber, just didn't pick up the next round. The AE 5.56 did the best and fed about 25 rounds and only failing to chamber maybe twice.

I noticed something that stuck me as strange and i'm sure it screams out the problem to you more experienced guys. I noticed after the last round fired on any given mag the BCG would be locked back but would be forward about and inch there by blocking the first round of the next mag, requiring me to pull the charging handle back which then caused it to seat in its proper locked back position. Im guessing i have a problem in one of these 3 areas. The gas block, bolt gas rings & buffertube spring. My thought is perhaps the bolt is not getting enough gas to send it reliably to the rear of the receiver while cycling, or perhaps the buffer spring is too heavy? Here are some of my build parts and a pic of the problem.


-JP Silent capture buffer system using the black spring ( came with 4 different weight springs i think)
-JP Full mass BCG with Enhanced JP bolt 223
-Maple Ridge Armoury 18.6″ Match V1 Nitride SPR Straight fluted 223 Wylde Barrel
-SLR Adjustable Gas block
-Geissele ssa-e Trigger
- Radian raptor CH, BCM LPK

[Dennisan]

I had read somewhere that anti rotation tabs caused fit issues on the upper? Is this in regards to all hand guards or just some? I don't feel like having to chop some off a Strike Industries Strike Rail, so if that's the case I will go with my second choice that doesn't have them.

I cant speak towards all hand guards, but I had to file down the anti-rotation tabs on my strike industries gridlok for it to fit on the sporter. About 45 degrees on the inward facing side of the tabs

[hannibal.black98]

Did you possible thread in the buffer tube too far? If you are using a self contained buffer system (I am too on my Stag 10 ) you don't NEED to use the buffer retainer pin/spring...if you knew/know this and then DIDN'T use it...I can see that being one of the issues.

Another one being maybe under gassed due to a loose and/or not aligned gas port....AND/or as well as having a too heavy spring on your buffer system.

[Sniffer]

So does this kit contain all the other parts required for my friend Mikes build if he already has his own safety, grip & trigger (most other kits include these 3 things but they are not required as he already has them)?

https://truenortharms.com/ar15_defau...parts-kit.html

[jiffx2781]

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[45C]

On top of what you mention he will also need a bolt catch, mag catch and mag catch button.

Forward assist and ejection port cover as well

[Betty-Lou]

So does this kit contain all the other parts required for my friend Mikes build if he already has his own safety, grip & trigger (most other kits include these 3 things but they are not required as he already has them)?

https://truenortharms.com/ar15_defau...parts-kit.html

You'll also need a mag release and bolt catch. I think a LPK without the trigger group would be a better option.

[Uisge]

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.

Shorten the pad! That’s a darn good idea! I had similar issues, will be doing this as soon as I get home. Thanks!

[jiffx2781]

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