I hope I can make this make sense. So I built a lower from a local company here in AL (sure it was manufactured by another and they just stamped their name on it) and tested it the other day. Everything works fine, but the gun will not hold the bolt back on an empty mag. Well after investigating I realized that the bolt stop is not far enough forward to engage the magazine follower to lift the bolt stop and catch the bolt. I noticed there seemed to be alot of sloppiness in the bolt catch and the cut it resides in. If I push the bolt catch towards the front of the lower, I can make it catch the magazine and lift. Never had this issue before so i measured my other lowers and the bolt catch cut is around 0.163", while this affected receiver is around 0.173". I haven't swapped bolt catches yet, and don't think it will matter as the bolt stops measure identical. I have looked at diagrams online to try and find what this measurement should be, but the diagrams are in CNC/CAD and I am too dumb of a veterinarian to understand it. Do I have an out of spec receiver? My uncle has the serial number after this one, and my brother has the before. Their rifles don't have this issue but I haven't been able to verify measurements on their rifles.

You should not be able to push the bolt stop fore and aft, any. So you have an issue.
Post a picture and I will tell you.

That's what I was thinking. I don't have a picture of it, but I know it's not right. Got a inquiry into the manufacturer about it, going to see what they say.

Contacted the company and they are sending me a "modified" bolt catch that fixes the problem. Can't wait to see what this entails.

Is this a AR-15 or SR-25/308LR rifle?

Are you using GI/Aluminum magazines or Tupperware magazines?

Shim the affected receivers bolt stop forward w/o binding & check operation.

AR15. It is an issue with with USGI and magpuls. I thought of shimming the back to push it forward but I am not sure even then if would engage enough for reliable operation. Going to see what this fix is before I start engineering. It's not a huge deal as this is strictly a fun gun but it would be nice for it to work as intended.

Any fore and aft movement indicates a fault with either the bolt stop or the receiver. There should be no movement in mil spec items.

It's concerting that the lower company has out of spec parts in stock to correct out of spec lowers. If the new stop doesn't solve the issue you might be able to shim it in the proper orientation. Sounds like someone may have contracted for out of spec production (seconds) to be branded with their name.

Pretty much what happened here is this guy ordered a bunch of receivers back before the election. The receivers we got were among the first he sold. My gun was affected, and my uncles gun ended up being affected. The lowers are simply out of spec. The fix was a standard bolt catch that appeared to have the nose lengthened with I assume JB weld or other epoxy. I ain't happy about it, but the guy is pretty much out of business so I happy I even got this part. Live and learn. The gun however functions flawlessly now.

quote:

Originally posted by model7LSS:
Pretty much what happened here is this guy ordered a bunch of receivers back before the election. The receivers we got were among the first he sold. My gun was affected, and my uncles gun ended up being affected. The lowers are simply out of spec. The fix was a standard bolt catch that appeared to have the nose lengthened with I assume JB weld or other epoxy. I ain't happy about it, but the guy is pretty much out of business so I happy I even got this part. Live and learn. The gun however functions flawlessly now.

I ran into a similar issue on a cheap lower I had purchased. Ended up the bore for the bolt catch spring & plunger was out of spec. allowing the plunger to bottom in the bore, not allowing the catch to come up high enough. I drilled the spring & plunger bore .015 deeper & all 4 catches I had tried before work fine now.
I just looked at 6 different brand lowers ALL have .010-.015 fore to aft slop in the bolt catch. I'll bet you have the same issue I did?
Have a good one!!

What appeared to have happened, was either the bolt catch slot was milled too far backwards, or the mag cut too far forward.

I bought a stripped upper from the guy to build a kindsa budget SPR with it. Full A2 stock, Palmetto State EPT trigger with JP springs, 18" Criterion HBAR in 223 Wylde with rifle length gas, cheapish 15" rail, and Miculek brake. It will print 5 rounds of budget 223 into 1". Gonna try to work some loads up but its a fun gun to shoot.

Seems like it would be a easy fix by using a shim of proper thickness to take up the play on the back side.

quote:

Originally posted by p dog shooter:
Seems like it would be an easy fix by using a shim of proper thickness to take up the play on the back side.

I thought about that. However, I learned the problem really wasn't the dimension of the cut, but the cut in relation to the magazine well. It's true it was sloppier than my other guns, but I am not sure a shim would have brought it far enough up. Be interesting to know who manufactured the lowers to see if any other "brand" was affected.