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Post by mosigdude on Sept 10, 2015 13:20:59 GMT -8
I'm a few hundred rounds into load development with my 18" AR-Platform AM30 now and finding a scattering of potential loads for hunting use. I have played with several diffferent bullets in the 125gr range and 7 different powders with varying degrees of success. The common issue I'm having is this rifle simply does not like to run with RL7 powder, which is unfortunate since I'm having some decent luck with that powder in terms of accuracy. The action cycles enough to eject but not quite enough to pick up the next round in the magazine. I have turned the gas all the way off and slowly worked my way up so I am very certain that I am not overgassed. The rifle has functioned/cycled flawlessly with other powders including CFE223, Ramshot X-Terminator, IMR4198, H4895, H322 and H335 (for the record, I am not saying these are all good powders for this caliber, some are, some aren't, these are just the ones I experimented with - I'll post a thread with these experiments a little later), some of these powder charges were at or near max and some only pushed the 125gr pill around 2000 fps and were clearly well below max but still cycled flawlessly. So I'm looking for a few answers from experience to maybe optimize this rifle for the RL7 loads...
So here is my set-up for reference: 18", mid-length, 1/11 twist, fluted semi-bull. M-16 bolt carrier, Standard 6.8SPC bolt, extractor and ejector polished, standard carbine buffer/spring, I am running a BTE adjustable gas block (wide-open right now). I used some wire-sized drill bits as a gauge when I first got the barrel and my gas port is at, or near .083".
When I first assembled this rifle, my break-in loads were copied from someone else on here (I forget who, exaclty) and were mid-upper-end loads with RL7. Then, like now, they did not function/cycle fully. At the time, I did not have the BTE gas block so when it arrived I placed a new gas tube in that block and replaced the original, still the same symptoms. I gave the carrier and bolt a once-over and, after not seeing anything obviously out of the ordinary (gas key is tight and staked, gast key ID and Gas Tube OD are in spec, gas rings in good condition), I replaced the carrier and bolt with another known-good set from another rifle and still the same result. I also measured the location of the gas port on the barrel and the gas port in the gas block and they seem aligned perfectly. Considering this rifle runs flawless with anything except RL7 powder, I'm guessing with my combination of components in the build, including the slightly heaiver M16 carrier, I just need slightly more gas for this specific powder. How large can I safely ream the gas port? Anything else in here that might be obvious to someone else that I'm missing?
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Post by GLSHOOTER on Sept 10, 2015 16:47:02 GMT -8
This is an interesting one. Everything sounds good. I'm running a non-adjustable carbine 16" and they all run. Mine eats RL7 like M&M's at a birthday party.
It will be educational as others chime in.
Greg
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Post by Deleted on Sept 10, 2015 16:55:26 GMT -8
I'm a few hundred rounds into load development with my 18" AR-Platform AM30 now and finding a scattering of potential loads for hunting use. I have played with several diffferent bullets in the 125gr range and 7 different powders with varying degrees of success. The common issue I'm having is this rifle simply does not like to run with RL7 powder, which is unfortunate since I'm having some decent luck with that powder in terms of accuracy. The action cycles enough to eject but not quite enough to pick up the next round in the magazine. I have turned the gas all the way off and slowly worked my way up so I am very certain that I am not overgassed. The rifle has functioned/cycled flawlessly with other powders including CFE223, Ramshot X-Terminator, IMR4198, H4895, H322 and H335 (for the record, I am not saying these are all good powders for this caliber, some are, some aren't, these are just the ones I experimented with - I'll post a thread with these experiments a little later), some of these powder charges were at or near max and some only pushed the 125gr pill around 2000 fps and were clearly well below max but still cycled flawlessly. So I'm looking for a few answers from experience to maybe optimize this rifle for the RL7 loads... So here is my set-up for reference: 18", mid-length, 1/11 twist, fluted semi-bull. M-16 bolt carrier, Standard 6.8SPC bolt, extractor and ejector polished, standard carbine buffer/spring, I am running a BTE adjustable gas block (wide-open right now). I used some wire-sized drill bits as a gauge when I first got the barrel and my gas port is at, or near .083". When I first assembled this rifle, my break-in loads were copied from someone else on here (I forget who, exaclty) and were mid-upper-end loads with RL7. Then, like now, they did not function/cycle fully. At the time, I did not have the BTE gas block so when it arrived I placed a new gas tube in that block and replaced the original, still the same symptoms. I gave the carrier and bolt a once-over and, after not seeing anything obviously out of the ordinary (gas key is tight and staked, gast key ID and Gas Tube OD are in spec, gas rings in good condition), I replaced the carrier and bolt with another known-good set from another rifle and still the same result. I also measured the location of the gas port on the barrel and the gas port in the gas block and they seem aligned perfectly. Considering this rifle runs flawless with anything except RL7 powder, I'm guessing with my combination of components in the build, including the slightly heaiver M16 carrier, I just need slightly more gas for this specific powder. How large can I safely ream the gas port? Anything else in here that might be obvious to someone else that I'm missing? I drill my ports out to .101 I have never had a problem after doing this. I also run an adjustable gas block after opening up the gas port.
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Post by mosigdude on Sept 10, 2015 19:34:44 GMT -8
Then I will do the same!! It is close to functioning as is, it just needs a little extra push, I'm almost certain this willl take care of it!
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Post by GLSHOOTER on Sept 11, 2015 6:28:15 GMT -8
Then I will do the same!! It is close to functioning as is, it just needs a little extra push, I'm almost certain this will take care of it! Thinking back to last year I seem to recall that Ritch mentioned he had made sure my port was OK. I suspect there was a drill bit involved.. LOL Greg
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Post by mosigdude on Sept 11, 2015 9:40:41 GMT -8
It Lives!! After the replies, I planned to drill the port to .100ish regardless since I can always tune it back down with the adjustable gas block if necessary but just to keep it experimental and informative for anyone else trekking along, I turned this into a mini evaluation.
I loaded up a handful of 2400fps RL7 - 125gr ProHunter loads. 2400fps is considerably slower than my accuracy loads but I figured this would give me some buffer for cold weather, it isn't smoking hot here today at 81 degrees but I also don't know how much RL7 varies when I get into the teen-temps during the colder parts of hunting season. Anyhow, I thought this would be a decent proof load for function.
My original port size was around .083" and my adjustable gas block was wide open, all loads except RL7 were functioning great with this. RL7 loads were ejecting but not quite pushing the bolt back far enough to pick up the next round or to lock open on an empty mag, as stated before, I had verified that I wasn't overgassed and getting bolt override.
I first drilled the port out to .092", gas block still wide open. 3 of the 5 loads cycled and locked back on an empty magazine. I suspect any faster RL7 load would have worked at this diameter.
I next drilled the port to an even .100", gas block still fully open, the remaining 15 rounds all locked back on an empty magazine. Cured!
Hopefully if anyone else has any issues along the way this will help.
Back to load development...
Cheers, Tim
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Post by GLSHOOTER on Sept 11, 2015 11:30:06 GMT -8
I'm glad it worked for you. It is amazing how many guys will not drill a port. They will drop $100.00 on new buffers and springs rather than just fix the source issue. When they fix it for one it screws it up for another. With that GB you have all your bases covered. I don't care if my A-30 is mildly over-gassed as it is a mot point. If it runs 100% that's all I care about as long as the brass does not get trashed.
Greg
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Post by mosigdude on Sept 11, 2015 12:59:21 GMT -8
Agree 100%, the only reason I even mentioned not being overgassed was I wanted to eliminate the thought that I could be getting bolt bounce that was outrunning the magazine spring. I've never had that happen but some supposedly have. Either way it's running now!
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Post by madcat on Sept 11, 2015 20:42:56 GMT -8
I drilled my gas port up when I got my barrel too. It cycles everything
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Post by mosigdude on Sept 11, 2015 21:36:50 GMT -8
This is my first of 7 different BHW barrels that has required enlargement of the port but I'm certainly not opposed to doing so and have done so on other barrels in the past. I guess I can't even say 'required' since it functioned flawlessly with all but the RL7 loads. Either way, when I'm playing with anything new I expect to have to do minor tweaks to fit it to my specific application, this is no different and it was a silly-easy fix. Not a complaint at all!
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Post by madcat on Sept 12, 2015 6:55:47 GMT -8
Its a wildcat. Gas port size is part of the customazation. Its good for it to be small as you can alway go bigger.
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Post by cpct on Sept 20, 2015 8:34:10 GMT -8
After reading all this, I too opened up my gas port. I'm going out soon to test. I've done all the bolt mods and now, opened up the port. I'm hoping for more consistent brass throw. Last time I shot my A30, some brass was never leaving the port, causing crushed brass and nasty double feeds. That was before these mods, though. I'll report after I shoot again. SO busy at school these days!!
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Post by geepee3 on Sept 20, 2015 9:33:41 GMT -8
I feel like the odd man out. I never checked my gas port diameter. My 18" mid-length cycles just fine with super-sonic loads. In fact I have a BTE adjustable gas block with it adjusted to a restrictive flow. I did try a few some sub-sonic loads with the gas block restricted that would not cycle correctly. So I do need to open the gas block to full open port and try again.
Glenn
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Post by cpct on Oct 23, 2015 5:05:29 GMT -8
So, ran a function test with a magazine full of 130 grain Barnes over 28 grains of RL7 after opening up the gas port and doing the bolt work. I'm getting consistent ejection....reliable ejection, but still "weak". It's throwing at the 2 o'clock position and only about 2 feet.
My thoughts, after reading Glenn's result, is headspace. maybe the shoulder needs to be bumped up a bit more than it is now so the ejector can fully grab the case rim. My barrel is an 18" mid, as well, threaded, but NO muzzle device, just thread protector. My gas block is a Yankee Hill Low Pro, btw.
This sounds strange to me because I know, by simple seating force, the case rim SHOULD fully seat when chambered.
Thoughts?
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Post by madcat on Oct 23, 2015 6:52:13 GMT -8
What did you open your port to? Also isnt 2:00 a bit foward indicating over gas?
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