JavaScript is disabled
Our website requires JavaScript to function properly. For a better experience, please enable JavaScript in your browser settings before proceeding.
Messages
11
Reactions
5
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
 
Last Edited:
Deciphering AR platforms is not an easy task.

My order of repair is as follows.

I always check headspace 1st prior to completed assembling any home build with go no go gauges. This alone can save you a lot of headaches.

After building if rifle has issues.

I usually start with the ammo. This is my usual suspect. However if I want the gun to run on cheap stuff it may be a part that's the problem.

Then I test multiple magazines to see if they are causing the issue. Had a gun, with I'm assuming an off spec magazine catch, not like magpul pmags, kept dragging on them. Stanag mags ran fine. Eventually replaced mag catch and it ran fine with all mags.

Then I ensure the gas system is installed correctly. Aligned and not messed up, parts off spec, etc. On a 7.5" barrel I checked the gas port, it was too small and not correct per many manufacturers specs. Opened it up a few thousandths with a drill bit, ran flawlessly after.

Then I ensure the internals aren't messed up. IE buffer pin didn't drift (happened once and gun wouldn't cycle at all), bolt carrier and bolt not off spec. I've had a cheap phosphated carrier cause issues as the finish was all messed up causing the carrier to drag. Once I swapped the BCG it ran flawlessly.

My point is that the platform has tons of variables that all need to be in place to run correctly.

I'd say you best bet is to start with one variable at a time and go from there. You kind of sound like your sipping your foot into too many variables and getting lost trying to figure it out.

Hope this helps.
 
Deciphering AR platforms is not an easy task.

My order of repai is as follows.

...

You touched on two things I had in mind to add and I forgot by the time I got to the end. I had Spartan Arms confirm headspace, it checked out. I've primarily used a 10rd KAC SR25 magazine for all testing. For shooting the squirrels I was running a Magpul 25rd.

I've been putting off drilling the gas port for any idea that doesn't include removing the gas block but I think it's about time it happened.
I appreciate your reply, thank you.
 
You touched on two things I had in mind to add and I forgot by the time I got to the end. I had Spartan Arms confirm headspace, it checked out. I've primarily used a 10rd KAC SR25 magazine for all testing. For shooting the squirrels I was running a Magpul 25rd.

I've been putting off drilling the gas port for any idea that doesn't include removing the gas block but I think it's about time it happened.
I appreciate your reply, thank you.
I'd hold off before drilling your port bigger. Ensure all other variables that are not permanent are in order first.

Also, if it is lack of available gas to operate the action, perhaps different buffer weights and lighter buffer springs can fix it.
 
is it easy to manually cycle? my LR308 did not like one of my drop in triggers. the hammer sat too high for the bolt carrier to push it down into reset and sometimes the bolt would get stuck back halfway and not go back into battery. put stock factory trigger back in, no problems.
 
I'd hold off before drilling your port bigger. Ensure all other variables that are not permanent are in order first.

Also, if it is lack of available gas to operate the action, perhaps different buffer weights and lighter buffer springs can fix it.

My thoughts exactly. Though I figure opening it up a few thousandths with an adjustable gas block wouldn't create any bigger issues. Just take away the effectiveness of positions 10-15 on the gas block. I've already swapped the Sprinco Orange spring to the Tubbs and then in addition removed four coils from the tubbs and it did have a small positive effect.

is it easy to manually cycle? my LR308 did not like one of my drop in triggers. the hammer sat too high for the bolt carrier to push it down into reset and sometimes the bolt would get stuck back halfway and not go back into battery. put stock factory trigger back in, no problems.

My lower functions flawlessly. The entire rifle is very smooth to cycle manually now that I've honed the chamber. A little resistance with a round in the chamber, but nothing out of the ordinary as compared to my prebuilt 223s. Of the entire rifle I am most proud of the lower. Maybe because I milled and drilled it myself. Though it's important to note that the Geissele trigger was not added immediately, more like added after the entire rifle was complete.
 
Last Edited:
Reading threads like this is interesting and informative. Being new to AR's, i started out with a factory rifle, to try and avoid problems. This worked great with my ar15's, but not so much with my ar10. It had a few hiccups at first. All with factory ammo. One poblem was the original gas rings were worn and sloppy. I put new Mcfarland rings on the bolt and that helped. I also noticed it was temperamental if i didnt grease the bolt. I run my ar15's a lot dryer with a lighter lube, but cant do that with the AR10. After learning this, ive ran 150-200 rounds downrange, with no hiccups whatsoever. This may not be the problem with the op's rifle, but may be worth considering. I hope the op gets it worked out and lets us know what the issue was.
 
Last Edited:
Reading threads like this is interesting and informative. Being new to AR's, i started out with a factory rifle, to try and avoid problems. This worked great with my ar15's, but not so much with my ar10. It had a few hiccups at first. All with factory ammo. One poblem was the original gas rings were worn and sloppy. I put new Mcfarland rings on the bolt and that helped. I also noticed it was temperamental if i didnt grease the bolt. I run my ar15's a lot dryer with a lighter lube, but cant do that with the AR10. After learning this, ive ran 150-200 rounds downrange, with no hiccups whatsoever. This may not be the problem with the op's rifle, but may be worth considering. I hope the op gets it worked out and lets us know what the issue was.

Oh yes! One more thing I forgot to mention. I removed the one piece gas ring installed by Rhino Rifles and installed a new one purchased from JP Enterprises despite the supplier of my upper saying up and down he was sure the bolt and carrier was not the problem. Installing the new gas ring made no change. Every time I fire this rifle I clean it meticulously and reoil heavily with Lucas gun oil. Especially after firing that very very dirty malaysian 762. I store it in this heavily oiled state.
 

Upcoming Events

Tillamook Gun & Knife Show
Tillamook, OR
"The Original" Kalispell Gun Show
Kalispell, MT
Teen Rifle 1 Class
Springfield, OR
Kids Firearm Safety 2 Class
Springfield, OR

New Resource Reviews

New Classified Ads

Back Top