Is it my gun or ammo?

**hubcap52** · 10-23-19, 19:17

I've got a 450 Bushmaster AR. Went out last weekend to test some ammo--Hornady factory (2 different lots) and some handloads. All handloads fired and functioned fine.

Of 9 rounds of factory tried, only 6 fired, some of them only after multiple attempts.

Help me understand what's going on.

**Clint** · 10-23-19, 20:11

I'd look at firing pin protrusion and headspace to start.

**Liam** · 10-24-19, 00:14

Can you send photos for a more accurate answer?

**M Sadler** · 10-24-19, 07:03

Originally Posted by Clint

I'd look at firing pin protrusion and headspace to start.

... or brass, or maybe all three. OP, is your upper receiver group Bushmaster or aftermarket?

**hubcap52** · 10-24-19, 21:04

Originally Posted by Liam

Can you send photos for a more accurate answer?

Pix of what?

**hubcap52** · 10-24-19, 21:05

Originally Posted by M Sadler

... or brass, or maybe all three. OP, is your upper receiver group Bushmaster or aftermarket?

Upper is BM OEM. Lower is a build. I've used it with other uppers without trouble. I checked case length and it was OK.

**26 Inf** · 10-25-19, 01:56

Originally Posted by hubcap52

Lower is a build.

What ammo with the other uppers?

Any chance your hammer springs aren't routed like this:

https://i.imgur.com/RhlhD6z.jpg

https://www.google.com/url?sa=i&rct=...72072307427864

What I'm wondering is whether or not you are getting light primer strikes.

What primers are you using in your loads?

In terms of excessive headspace causing light strikes - you say upper is OEM mfgr BCM, did that include the bolt?

**Bonehead** · 10-25-19, 14:48

Originally Posted by 26 Inf

What ammo with the other uppers?

Any chance your hammer springs aren't routed like this:

https://i.imgur.com/RhlhD6z.jpg

https://www.google.com/url?sa=i&rct=...72072307427864

What I'm wondering is whether or not you are getting light primer strikes.

What primers are you using in your loads?

In terms of excessive headspace causing light strikes - you say upper is OEM mfgr BCM, did that include the bolt?

Light strikes sounds likely. Did the primers show marks on the initial attempt to fire, a dimple? Either a headspace or light hammer strike sounds like it could be it. Unusual that the OP's handloads all worked, maybe a "softer" primer or longer length?