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Hello everyone!
I'm happy to have found a local community forum that's all about firearms.
What prompted me to join was a rifle I built just about a year ago. I started with an 80% DPMS style 308 lower and built up from there. I built this rifle to be an accurate supressor ready bunker-proof truck rifle inside 300 yards. After a lot of work this rifle now cycles Hornady 168gr and 178gr reliably, however I am much more interested in getting 145gr+ to function. I'll catch you up on the important parts of the build:
Lower-
80% Arms Lower
Geissele SD3G Trigger
Strike Industries M4 length receiver extension
Tubb Precision AR-10 Stainless Steel Buffer Spring - Changed down from Sprinco Orange
LR308 Carbine Heavy Buffer
Upper-
Rhino Rifles 308 Upper Receiver - No link/Company ceased operations
Rhino Rifles Nickel Boron bcg - No link/Company ceased operations
Sprinco Dual .308 Bolt Carrier Extractor Spring Set
BA Hanson 14" Barrel/Carbine length gas
SLR Sentry 7 Clamp On ADJ GB
Griffin Armament 30SD Flash Comp
I believe everything else is extraneous but if you need more information I will add it later.
I took my upper, bcg, barrel and gasblock to Spartan Arms in Bellingham to be assembled since I didn't own the wrench to torque my barrel and the muzzle needed to be pinned and welded. I had it all done at the same time which thinking back wasn't the greatest idea before getting the rifle dialed in. (no way to fully remove the gas block if it ended up faulty, luckily not the case) Upon receiving the upper I found that the feed ramps of the receiver and the barrel were not perfectly aligned, normal for parts not made for each other I believe, and not to an extent that is worrying. But did make me think twice about returning to spartan arms since they failed to mention anything about it. (I will end up grinding the dual feed ramps into one large ramp sooner or later, making sure they are mated perfectly) Anyways.. with great anticipation I began the rifles' trials.
First problem right off the bat. No matter how far open the gasblock I just wasn't getting enough gas to reset the bolt. The brass was in between stovepipes and two oclock ejection. Extracted brass had deep grooves cut in line with the extractor and of course dents from stovepiping against the extra heavy orange buffer spring. I probably went through over 100 rounds attempting to diagnose the issue going between my supplier of the receiver/bolt assembly to arfcom. My upper receiver supplier told me that BA barrels are often out of spec and if my bolt was even locking forward my problem was most likely due to a tight chamber. I measured and it was slightly out of spec. I honed the chamber exactly as told (I trust him). Extraction difficulty decreased, I could now semi comfortably hand cycle the rifle. After someone on arfcom told me that the charge handle shouldn't feel like I'm pulling the weight of an elephant up a hill. I concurred and I tossed the extra heavy sprinco for a tubbs and my problems changed from a constant cycle issue to an intermittent failure to feed. Minor success.
I was now able to fire between 1-3 shots of decent Hornady American Shooter 308WIN 149gr ammunition. 168gr was now running, apparently, flawlessly. (I don't buy a ton of that stuff but I'm up to something like 80 rounds, no failures) People told me during wear in of new parts, the rifle will become more and more reliable. I took that as a recommendation to wear in my rifle. I went to SGAmmo and purchased a case of 300 malaysian surplus 762x51 146gr L2A2 ammunition. (NON-NATO)
After a week of living in the woods and blowing away ground squirrels in eastern washington it was clear to me that my rifles problems were not getting any better. I shot around 250 rounds having to hand cycle the bolt every single time. That ammo was absolute crap, I knew that. But my mission here is to get my rifle cycling 145gr and up. Lower is fine, but not the goal.
Before firing the last fifty or so malaysian 146grs I decided to take old Tubb's advice and began clipping coils off of the buffer spring. I took a slow motion video of the bolt attempting to cycle and it definitely wasn't an overgassing problem. The bolt was failing to move far enough back to engage the bolt lock/release. So I clipped one coil, no change, two coils, it cycled two rounds of the malaysian before repeated failure, three coils, same result no progression, four coils and a complete wipedown and oiling of internals, it cycled over five rounds before a repeated failure to feed. I ran out of the malaysian surplus and had 50 more rounds of hornady american shooter, almost the same exact results.
This last trial was performed prone on a bipod to minimize any slack wristing. I took the rifle hunting with 168gr hornady and it functioned flawlessly between five non-consecutive shots.
I've tested the gas key for leaks. Dwell time is in spec for a 308 carbine at 7.5" from gas port to first muzzle port. Ahh I'll add things as I think of them. Any help would be very much appreciated.
Over and out
Edit: Things I forgot to mention:
-During assembly I requested that Spartan Arms check the headspacing-tested good.
-Testing has been done with Magpul 25rd and Knights Armament 10rd magazines.
-One additional step I took from recommendation off arfcom was replacing the gas ring- I installed a new JP Enterprises one piece in place of the one piece already installed.- no change observed.
Beauty shots and observations posted to arfcom available HERE
I'm happy to have found a local community forum that's all about firearms.
What prompted me to join was a rifle I built just about a year ago. I started with an 80% DPMS style 308 lower and built up from there. I built this rifle to be an accurate supressor ready bunker-proof truck rifle inside 300 yards. After a lot of work this rifle now cycles Hornady 168gr and 178gr reliably, however I am much more interested in getting 145gr+ to function. I'll catch you up on the important parts of the build:
Lower-
80% Arms Lower
Geissele SD3G Trigger
Strike Industries M4 length receiver extension
Tubb Precision AR-10 Stainless Steel Buffer Spring - Changed down from Sprinco Orange
LR308 Carbine Heavy Buffer
Upper-
Rhino Rifles 308 Upper Receiver - No link/Company ceased operations
Rhino Rifles Nickel Boron bcg - No link/Company ceased operations
Sprinco Dual .308 Bolt Carrier Extractor Spring Set
BA Hanson 14" Barrel/Carbine length gas
SLR Sentry 7 Clamp On ADJ GB
Griffin Armament 30SD Flash Comp
I believe everything else is extraneous but if you need more information I will add it later.
I took my upper, bcg, barrel and gasblock to Spartan Arms in Bellingham to be assembled since I didn't own the wrench to torque my barrel and the muzzle needed to be pinned and welded. I had it all done at the same time which thinking back wasn't the greatest idea before getting the rifle dialed in. (no way to fully remove the gas block if it ended up faulty, luckily not the case) Upon receiving the upper I found that the feed ramps of the receiver and the barrel were not perfectly aligned, normal for parts not made for each other I believe, and not to an extent that is worrying. But did make me think twice about returning to spartan arms since they failed to mention anything about it. (I will end up grinding the dual feed ramps into one large ramp sooner or later, making sure they are mated perfectly) Anyways.. with great anticipation I began the rifles' trials.
First problem right off the bat. No matter how far open the gasblock I just wasn't getting enough gas to reset the bolt. The brass was in between stovepipes and two oclock ejection. Extracted brass had deep grooves cut in line with the extractor and of course dents from stovepiping against the extra heavy orange buffer spring. I probably went through over 100 rounds attempting to diagnose the issue going between my supplier of the receiver/bolt assembly to arfcom. My upper receiver supplier told me that BA barrels are often out of spec and if my bolt was even locking forward my problem was most likely due to a tight chamber. I measured and it was slightly out of spec. I honed the chamber exactly as told (I trust him). Extraction difficulty decreased, I could now semi comfortably hand cycle the rifle. After someone on arfcom told me that the charge handle shouldn't feel like I'm pulling the weight of an elephant up a hill. I concurred and I tossed the extra heavy sprinco for a tubbs and my problems changed from a constant cycle issue to an intermittent failure to feed. Minor success.
I was now able to fire between 1-3 shots of decent Hornady American Shooter 308WIN 149gr ammunition. 168gr was now running, apparently, flawlessly. (I don't buy a ton of that stuff but I'm up to something like 80 rounds, no failures) People told me during wear in of new parts, the rifle will become more and more reliable. I took that as a recommendation to wear in my rifle. I went to SGAmmo and purchased a case of 300 malaysian surplus 762x51 146gr L2A2 ammunition. (NON-NATO)
After a week of living in the woods and blowing away ground squirrels in eastern washington it was clear to me that my rifles problems were not getting any better. I shot around 250 rounds having to hand cycle the bolt every single time. That ammo was absolute crap, I knew that. But my mission here is to get my rifle cycling 145gr and up. Lower is fine, but not the goal.
Before firing the last fifty or so malaysian 146grs I decided to take old Tubb's advice and began clipping coils off of the buffer spring. I took a slow motion video of the bolt attempting to cycle and it definitely wasn't an overgassing problem. The bolt was failing to move far enough back to engage the bolt lock/release. So I clipped one coil, no change, two coils, it cycled two rounds of the malaysian before repeated failure, three coils, same result no progression, four coils and a complete wipedown and oiling of internals, it cycled over five rounds before a repeated failure to feed. I ran out of the malaysian surplus and had 50 more rounds of hornady american shooter, almost the same exact results.
This last trial was performed prone on a bipod to minimize any slack wristing. I took the rifle hunting with 168gr hornady and it functioned flawlessly between five non-consecutive shots.
I've tested the gas key for leaks. Dwell time is in spec for a 308 carbine at 7.5" from gas port to first muzzle port. Ahh I'll add things as I think of them. Any help would be very much appreciated.
Over and out
Edit: Things I forgot to mention:
-During assembly I requested that Spartan Arms check the headspacing-tested good.
-Testing has been done with Magpul 25rd and Knights Armament 10rd magazines.
-One additional step I took from recommendation off arfcom was replacing the gas ring- I installed a new JP Enterprises one piece in place of the one piece already installed.- no change observed.
Beauty shots and observations posted to arfcom available HERE
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