Tweet
Hey Everyone,
I'm new here and I'm struggling with a 450 Bushmaster build I'm currently into. Hoping to get it done before Ohio's rifle season coming up in 1.5 weeks. Just a warning, this post is going to be long as I will try to detail everything I can.
Main Issue: Bolt Cycling/Feeding issues
I have a 16" barrel, 0.936" gas junction, mid-length gas system on this build. Std low profile gas block. Initially, I thought that the bolt wasn't ejecting a spent case with a loaded magazine in the gun. I tried taking video with my phone and saw the bolt cycle, just not well because the frame rate was too low. It almost seemed to me that the casing was still pressurized to the chamber as the bolt tried to extract it. I did one shot tests with no mag, and it was jamming. Extracting the case, but no ejection. I started with standard carbine buffer weight and a flatwire spring, carbine length. I swapped the spring for an unused std carbine spring, then for a used carbine spring, all with the same issues in the single shot test. I ordered an adjustable weight buffer system and also pulled an H3 buffer from a 6.5 creedmoor build my father did. I started the adjustable weight buffer at an H1 weight, roughly 3.7oz. I got ejection at 1-2 o'clock. I swapped in my father's H3 buffer, I got a nice 4 o'clock ejection. I got bolt cycling with 3 rounds out of the magazine, but no bolt lock back. I did some other tests, mainly adjusting to an H2 weight buffer to see if that would work as well, but got a 2-3 o'clock ejection, so I adjusted the adjustable weight buffer up to an H3. I swapped back in the flatwire spring, and now I can't pick up another round out of the magazine. This issue has been very frustrating, as everything I researched on 450 Bushmaster going into the build suggested standard parts would work. I don't think the gun is undergassed for these reasons:
1.) I pulled the gas block off, and carbon buildup suggests the block is centered directly over the gas port
2.) Standard gas ports on AR barrels are 0.089" - 0.096" based on my research, and a 3/32" drill bit fits the hole perfectly and measures to 0.0938", so within spec, albeit towards the top end (i.e. more gas)
3.) When increasing the buffer weights, I immediately saw better results since I got ejection, even if it was in the 1-2 o'clock position. Furthermore, heavier buffers bettered the ejection pattern results.
My adjustable weight buffer in H3 configuration (3 tungsten weights, 3 spacers, tip and roll pin w/ buffer body) weigh 5.584oz. My father's standard H3 buffer weighs 5.619oz. From what I've researched, I should be using an H1 or an H2, but my results say otherwise.
My next steps are to confirm proper cycling minus bolt lock-back with the used std carbine spring and H3 buffer, and minimum get it ready for deer season. I have an adjustable gas block that I will also play around with next, but I'm running out of time (and ammo!)
My questions:
1.) Did I diagnose the gun issues correctly? Is it overgassed? If so, what else can I do to try and fix my cycling issues?
2.) I'm running an AR Stoner mag. I've seen some posts suggesting this may be an issue. If it is, how can I check that without another magazine? If I need another mag, what should I look for? I need it yesterday lol
3.) What is everyone's experience with rifle break-in periods? My .223 Rem (my 1st build) took a long time before it ran smooth, but it runs like butter now. Unfortunately, I don't have the ammo (nor funds and time) to shoot hundreds of rounds through this gun. It's at roughly 70 right now.
Extra info I may have missed:
I'm shooting Hornady Custom 250gr FTX and Hornady Black 250gr FTX because that's what I could get around me. Barrel is 1:16 twist for heavier rounds.
Any help is appreciated. Thanks
I'm new here and I'm struggling with a 450 Bushmaster build I'm currently into. Hoping to get it done before Ohio's rifle season coming up in 1.5 weeks. Just a warning, this post is going to be long as I will try to detail everything I can.
Main Issue: Bolt Cycling/Feeding issues
I have a 16" barrel, 0.936" gas junction, mid-length gas system on this build. Std low profile gas block. Initially, I thought that the bolt wasn't ejecting a spent case with a loaded magazine in the gun. I tried taking video with my phone and saw the bolt cycle, just not well because the frame rate was too low. It almost seemed to me that the casing was still pressurized to the chamber as the bolt tried to extract it. I did one shot tests with no mag, and it was jamming. Extracting the case, but no ejection. I started with standard carbine buffer weight and a flatwire spring, carbine length. I swapped the spring for an unused std carbine spring, then for a used carbine spring, all with the same issues in the single shot test. I ordered an adjustable weight buffer system and also pulled an H3 buffer from a 6.5 creedmoor build my father did. I started the adjustable weight buffer at an H1 weight, roughly 3.7oz. I got ejection at 1-2 o'clock. I swapped in my father's H3 buffer, I got a nice 4 o'clock ejection. I got bolt cycling with 3 rounds out of the magazine, but no bolt lock back. I did some other tests, mainly adjusting to an H2 weight buffer to see if that would work as well, but got a 2-3 o'clock ejection, so I adjusted the adjustable weight buffer up to an H3. I swapped back in the flatwire spring, and now I can't pick up another round out of the magazine. This issue has been very frustrating, as everything I researched on 450 Bushmaster going into the build suggested standard parts would work. I don't think the gun is undergassed for these reasons:
1.) I pulled the gas block off, and carbon buildup suggests the block is centered directly over the gas port
2.) Standard gas ports on AR barrels are 0.089" - 0.096" based on my research, and a 3/32" drill bit fits the hole perfectly and measures to 0.0938", so within spec, albeit towards the top end (i.e. more gas)
3.) When increasing the buffer weights, I immediately saw better results since I got ejection, even if it was in the 1-2 o'clock position. Furthermore, heavier buffers bettered the ejection pattern results.
My adjustable weight buffer in H3 configuration (3 tungsten weights, 3 spacers, tip and roll pin w/ buffer body) weigh 5.584oz. My father's standard H3 buffer weighs 5.619oz. From what I've researched, I should be using an H1 or an H2, but my results say otherwise.
My next steps are to confirm proper cycling minus bolt lock-back with the used std carbine spring and H3 buffer, and minimum get it ready for deer season. I have an adjustable gas block that I will also play around with next, but I'm running out of time (and ammo!)
My questions:
1.) Did I diagnose the gun issues correctly? Is it overgassed? If so, what else can I do to try and fix my cycling issues?
2.) I'm running an AR Stoner mag. I've seen some posts suggesting this may be an issue. If it is, how can I check that without another magazine? If I need another mag, what should I look for? I need it yesterday lol
3.) What is everyone's experience with rifle break-in periods? My .223 Rem (my 1st build) took a long time before it ran smooth, but it runs like butter now. Unfortunately, I don't have the ammo (nor funds and time) to shoot hundreds of rounds through this gun. It's at roughly 70 right now.
Extra info I may have missed:
I'm shooting Hornady Custom 250gr FTX and Hornady Black 250gr FTX because that's what I could get around me. Barrel is 1:16 twist for heavier rounds.
Any help is appreciated. Thanks
Comment