Bolt hold open issue???

[Calplinker]

Just assembled a Seekins upper and lower and the bolt doesn't want to stay back. If pressed very firmly while pulling the charging handle back it barely stays. Even the slightest touch such as pushing the loose charging handle forward causes it to slam forward.

Usually, it doesn't want to hold back at all.

Been awhile since I built this or an AR, so any ideas?

[SkyHawk]

Maybe the wrong spring installed behind the bolt catch plunger? That would be the first thing I checked. It sounds like your bolt catch has too much pressure behind it and also may not be getting the full travel to the 'hold open' position. The spring is designed to keep the bolt catch in the 'no catch' position, so the wrong (too strong) spring would seem to be a possibility. Plus if too long a spring were used, then you would barely get the bolt catch into the 'hold open' position.

[hermosabeach]

Have you tried this with multiple magazines to see if a weak mag spring or worn magazine?

If you manually activate the BHO, is the problem the same?

[Niviticus]

What kind of mags are you using?

[SkyHawk]

What kind of mags are you using?

From my reading, he hasn't even gotten to the empty mag part of the test. It seems he indicates his bolt catch isn't working when manually operated - but it is hard to say, not much clarity in the OP

[arnie19]

I have had to slightly modify most of my 80% lowers so the bolt catch would work .I drilled the hole deeper where the plunger goes in so it would go in flush with the metal around it .This allows the stop to rise up farther to catch the bolt head .Also had to grind one bolt stop a little in the back as it was hitting and not allowing it to move enough .

[Niviticus]

I would try an empty mag in it just to see.

[AR-15 Rep]

Could be a couple different things. Check the travel of the bolt catch. It should move about 7/32 max travel. If you don't get that, then dissasemble the bolt catch. Diameter of the hole should be 5/32 and depth approx 1/2". These are not exact tech specs just a quick way to judge where a problem may exist. Check the spring length should be just a little over 3/8 of an inch long. check those things and see what you come up with.