First go with the 300 BLK
- Thread starter Ian
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Ian
Notorious member
I got back from town in time to try the .120" gas system before dark with just one load. I went back to Reloder 7 even though L1A1 and I both figured it would never make it work, and again he was right. Since 10.5 grains was bumping supersonic with the original gas port size I backed down to 10.2 grains and the cycling was so sluggish that it barely ejected and cocked the hammer. Wouldn't strip a fresh round, much less lock back the bolt. Curious how opening the gas port slowed that load down, hard to imagine that dropping .3 grains alone would result in almost exactly a 100 fps drop in velocity. In a way I'm glad it did because it gives me some room to grow with the load, but it's going to be borderline at best. I'm thinking 1680 or 5744 are going to end up being what I need, or do some tricks to make the Reloder 7 burn faster.
On a higher note, I got to clean the bore twice today after drilling the gas port out, and both times all the bullets went into the same ragged hole, with first and second shot SD being within five fps of each other. Just a haze of Ed's Red was left in the bore and I'm still using SL-68.1 for all this. The lube just keeps impressing me. I showed L1A1 the flash hider after 30 rounds with no cleaning, it only had a little bit of soot on it, and there is no lube star.
On a higher note, I got to clean the bore twice today after drilling the gas port out, and both times all the bullets went into the same ragged hole, with first and second shot SD being within five fps of each other. Just a haze of Ed's Red was left in the bore and I'm still using SL-68.1 for all this. The lube just keeps impressing me. I showed L1A1 the flash hider after 30 rounds with no cleaning, it only had a little bit of soot on it, and there is no lube star.
fiver
Well-Known Member
something that pops up to me here and there is the 8 twist barrels.
I keep seeing others have issues with the heavier boolits too.
for some reason the number 200grs keeps popping up in my head as a better compromise or boolit length to get near with the heavier ones.
the other question I have is it port pressure or gas volume giving you the problem?
got any H-322/benchmark type powders?
I keep seeing others have issues with the heavier boolits too.
for some reason the number 200grs keeps popping up in my head as a better compromise or boolit length to get near with the heavier ones.
the other question I have is it port pressure or gas volume giving you the problem?
got any H-322/benchmark type powders?
Have you verified that the center of the gas port is aligning with the corresponding port in the gas block? The block may or may not need to be against the shoulder on the barrel. Another guy found his gas block was off slightly and had about half the diameter blocked, so no full function with even supers.
8" twist might affect stability, but not function due to lack of gas. Slower burners than Reloader 7 may not burn cleanly and I would expect higher SDs as already observed with 4198.
Too, going with lighter bullets while trying to stay subsonic may necessitate a lightweight BGC.
8" twist might affect stability, but not function due to lack of gas. Slower burners than Reloader 7 may not burn cleanly and I would expect higher SDs as already observed with 4198.
Too, going with lighter bullets while trying to stay subsonic may necessitate a lightweight BGC.
Josh
Well-Known Member
Not sure it is the 8 twist barrels, I have shot the 235's in a 1-10 with no issues, heck I also shot my 255's (same length as the 235) with good results. I would like to shoot some of those NOE's in my 300 next to my 235'vs
Ian
Notorious member
I've got some H322. I think it's pressure at this point, not volume. With RX7 making the hole bigger actually made things a little worse. The issues I see going to a slower powder are getting them to burn efficiently, and ultimate muzzle velocity. I wanna get that gas volume up without boosting the bullet too much in the last half of the barrel, though opening the port to near max seems to be dumping a lot of the pressure/volume that was making FPS. Where it's going, I have no idea, because it doesn't seem to be going to the bolt. I scribed a fresh mark on the gas block before removing it to drill the hole the first time, and the witness mark around the gas hole was perfect. Second go, same thing. I put it right back the same spot after drilling to .120", so I'm certain it's lined up with the barrel port.
Ian
Notorious member
I knew someone was going to ask that, but I didn't get the above post put up in time. Yes, it's aligned. I'm going to strip the BCG and see if the gas rings are hung up and leaking, I did notice some bad black streaks coming out of the upper vent hole on the side of the block. This is a brand-new NiB BCG but is a cheapo that one reviewer said was flaking off plating into the piston on the bolt and causing cycling issues, I've been meaning to take this one down and see after the first few rounds but haven't had it apart since I cleaned, lubed, and first installed it.
Ian
Notorious member
IDK. I've shot the NOE 247 out of 12-twist barrels with great accuracy using a light charge of Unique. I haven't measured the twist on my BLK barrel, but it's supposed to be 1 in 8 (for the dual-purpose of sub/supers I guess).
I have NiBo in (2) uppers. NiBo will vary in color a bit, but should NEVER peel. The gas rings should be set so that the ring gaps do not align, and there should be drag when moving the bolt in/out of the BCG.
Those black streaks should be powder residue, oil, and bullet lube.
Those black streaks should be powder residue, oil, and bullet lube.
fiver
Well-Known Member
I have wondered about the 7 and 8 twist thing, I know my AAC was built straight up for a can and quiet slow loads.
it will [since I lightened the trigger] put 100gr varmint bullets into a golf ball at 100 yds without even thinking about it [at 2400 fps]
and still will stabilize the LEE 230's without issue like it should.
it will [since I lightened the trigger] put 100gr varmint bullets into a golf ball at 100 yds without even thinking about it [at 2400 fps]
and still will stabilize the LEE 230's without issue like it should.
Ian
Notorious member
Took apart the BCG and nothing abnormal, ring gaps were spaced at 120 degrees and were floating fine in a sea slimy synthetic oil/powder residue/bullet lube. I only checked because My DI-45 leaded the gas rings up really bad once and they stuck hard. The resulting gas leakage was enough to stop the bolt from locking back but not keep it from cycling ammo. Not the case here.
I dislike removing buffer weights due to the 'deadblow' effect they provide to mitigate bolt bounce, but it's worth a try for a few shots anyway.
I dislike removing buffer weights due to the 'deadblow' effect they provide to mitigate bolt bounce, but it's worth a try for a few shots anyway.
Ian
Notorious member
Tonight I removed the buffer weights, went up to 10.7 grains of RX7, and finally got it to cycle. Get this: Velocity averaged 1059 fps for five....and had an SD of 4.6! Did I mention I like RX7? I had put two in the magazine and the bolt didn't lock, next three cycled fine but the bolt still ran home. So I pulled on the charging handle and it wouldn't lock...then the empty magazine fell out. I don't think I had it latched well enough either time.
After that I brought it back for further investigation. Last night late the realization hit me that the bolt carrier didn't look right, and that maybe the JP tuned buffer spring was a bit long and heavy. After verifying that the spring was indeed for a carbine and not a rifle, I studied the bolt carrier. Then today I went to the manufacturer's website and discovered that yes, I had purchased a carrier rated for FULL AUTO, and that it weighs a full ounce more than "normal" AR-15 carriers. I weighed it to be sure. I compared the bolt pull weight again to my other carbine with standard H2 weight and cheapo spring, it takes 7 lbs to unlock the bolt and pull back to the hammer, 10 lbs to cock the hammer, and 14.5 to lock back the bolt. With the 300, it takes 8 lbs to unlock the bolt, 14 lbs to cock the hammer, and 17 to lock the bolt. DANG. So I put back in the AR stoner spring, put the weights back in the buffer, took out the hammer and radiused and polished it so the BC only pushes it down about 3/16" on the way back past the sear engagement instead of like sixteen inches (exaggerating of course), re-greased the spring, denibbed the buffer pad, replaced the hammer spring with a standard-weight ALG and then "adjusted" a few pounds out of it, or about 30 degrees of relaxed leg angle, stuck the whole mess back together again and now it pulls at 7.5 to unlock the bolt, 10.5 to cock the hammer, and 15 to lock the bolt back. Trigger is MUCH better too, oh, and I gave the hammer notch a little polish.
Hopefully this will help the function, maybe tomorrow I'll have time to repeat the load....might even go up to 10.8 grains.
After that I brought it back for further investigation. Last night late the realization hit me that the bolt carrier didn't look right, and that maybe the JP tuned buffer spring was a bit long and heavy. After verifying that the spring was indeed for a carbine and not a rifle, I studied the bolt carrier. Then today I went to the manufacturer's website and discovered that yes, I had purchased a carrier rated for FULL AUTO, and that it weighs a full ounce more than "normal" AR-15 carriers. I weighed it to be sure. I compared the bolt pull weight again to my other carbine with standard H2 weight and cheapo spring, it takes 7 lbs to unlock the bolt and pull back to the hammer, 10 lbs to cock the hammer, and 14.5 to lock back the bolt. With the 300, it takes 8 lbs to unlock the bolt, 14 lbs to cock the hammer, and 17 to lock the bolt. DANG. So I put back in the AR stoner spring, put the weights back in the buffer, took out the hammer and radiused and polished it so the BC only pushes it down about 3/16" on the way back past the sear engagement instead of like sixteen inches (exaggerating of course), re-greased the spring, denibbed the buffer pad, replaced the hammer spring with a standard-weight ALG and then "adjusted" a few pounds out of it, or about 30 degrees of relaxed leg angle, stuck the whole mess back together again and now it pulls at 7.5 to unlock the bolt, 10.5 to cock the hammer, and 15 to lock the bolt back. Trigger is MUCH better too, oh, and I gave the hammer notch a little polish.
Hopefully this will help the function, maybe tomorrow I'll have time to repeat the load....might even go up to 10.8 grains.
Ian
Notorious member
SUCCESS!
Finally. All the work I did last night paid off. Went back out with five rounds at 10.6 grains Reloder 7 and five more at 10.9 grains. I loaded either two or one in the magazine each time to test the bolt lock, every single one locked back fully with no issues. 10.6 gets 1050 fps and 10.9 gets 1101 average, with single-digit SD. I think the hotter load was bumping right at supersonic for my altitude and weather today.
So here are the other particulars relating to the function again, since this sort of data is VERY hard to find on the internet:
16" AR-15, 1-in-8" twist, unknown maker with an unusually tight chamber. Carbine-length gas system, port drilled to .120".
APF Armory NiB full-auto BCG, weighs 12 ounces.
AR-Stoner (MidwayUSA) mil-spec buffer assembly with the weight and spring it comes with.
CMMG lower parts kit, the hammer needs a serious grind job.
Tweaked "standard" weight ALG hammer spring for slightly less rate.
YHM low-profile, clamp-on fixed gas block w/DPMS carbine gas tube.
UNsuppressed for now, just running a cheap A2 flash hider. Might have to back off of 10.6 grains Reloder 7 with a can.
Brass is Federal factory new 300BLK bulk, all test loads were with virgin brass. I did a VLD inside deburr after resizing and left the rest alone. The length of the new stuff is very consistent.
Primers are TulAmmo AR small rifle.
Expanded with home-made expander/bellmouth tool to .309" ID
ACE 235 grain BLK bullet cast from air-cooled 2COWW, 1 pure, 1 SOWW that I cast five days ago, sized in a .309" push-through and lubed in a .310" H&I die, bottom two grooves only. Bullets come out about .3098". I either need to size larger or expand less, the neck tension is a bit light on these.
Seated to crimp in the groove, I'll have to measure COAL and unfired brass. They are about as long as will crimp in the forward groove and as long as will possibly work in a Gen 2 Pmag.
Crimped firmly in a Lee Precision FCD to tuck the OD of the mouth flush in the groove behind the first driving band.
Now that I have something that seems to be working (at 93 degrees, anyway) I can FINALLY do some accuracy testing. At 15 yards it's making sub-caliber groups of five, with nice, round holes. Good to go.
Finally. All the work I did last night paid off. Went back out with five rounds at 10.6 grains Reloder 7 and five more at 10.9 grains. I loaded either two or one in the magazine each time to test the bolt lock, every single one locked back fully with no issues. 10.6 gets 1050 fps and 10.9 gets 1101 average, with single-digit SD. I think the hotter load was bumping right at supersonic for my altitude and weather today.
So here are the other particulars relating to the function again, since this sort of data is VERY hard to find on the internet:
16" AR-15, 1-in-8" twist, unknown maker with an unusually tight chamber. Carbine-length gas system, port drilled to .120".
APF Armory NiB full-auto BCG, weighs 12 ounces.
AR-Stoner (MidwayUSA) mil-spec buffer assembly with the weight and spring it comes with.
CMMG lower parts kit, the hammer needs a serious grind job.
Tweaked "standard" weight ALG hammer spring for slightly less rate.
YHM low-profile, clamp-on fixed gas block w/DPMS carbine gas tube.
UNsuppressed for now, just running a cheap A2 flash hider. Might have to back off of 10.6 grains Reloder 7 with a can.
Brass is Federal factory new 300BLK bulk, all test loads were with virgin brass. I did a VLD inside deburr after resizing and left the rest alone. The length of the new stuff is very consistent.
Primers are TulAmmo AR small rifle.
Expanded with home-made expander/bellmouth tool to .309" ID
ACE 235 grain BLK bullet cast from air-cooled 2COWW, 1 pure, 1 SOWW that I cast five days ago, sized in a .309" push-through and lubed in a .310" H&I die, bottom two grooves only. Bullets come out about .3098". I either need to size larger or expand less, the neck tension is a bit light on these.
Seated to crimp in the groove, I'll have to measure COAL and unfired brass. They are about as long as will crimp in the forward groove and as long as will possibly work in a Gen 2 Pmag.
Crimped firmly in a Lee Precision FCD to tuck the OD of the mouth flush in the groove behind the first driving band.
Now that I have something that seems to be working (at 93 degrees, anyway) I can FINALLY do some accuracy testing. At 15 yards it's making sub-caliber groups of five, with nice, round holes. Good to go.
Ian
Notorious member
This was tough, you'll see. There's just this tiny little window where it all will work with cast. If you're going to shoot jacketed, things are supposedly much easier, but this is the most persnickety rifle/caliber combo I've every played with...and I haven't even begun to explore lighter, supersonic bullets.
The toughest part is going to be finding a heavy bullet design for subsonic loads. If you don't care about that, just pick up a nice lightweight barrel with carbine gas system and an SKS bullet mould. Midway had two nice lightweight stainless-steel barrels left on sale this afternoon......Also there are plenty of good, squared-away complete uppers out there if you have the jingle. Noveske and AAC come to mind...
The toughest part is going to be finding a heavy bullet design for subsonic loads. If you don't care about that, just pick up a nice lightweight barrel with carbine gas system and an SKS bullet mould. Midway had two nice lightweight stainless-steel barrels left on sale this afternoon......Also there are plenty of good, squared-away complete uppers out there if you have the jingle. Noveske and AAC come to mind...
Ian
Notorious member
Hey, thanks for all the great input and links! L1A1 Rocker helped me too, in more ways than I can count. Hey L1A1, you can have your powder back now, I'm quite done with it!
One thing I forgot to add, and that is I'm very quickly falling out of love with the Magpul M3 magazines, at least the curved 20-rounders that I have. Main reason is a very bad bind/drag condition between bolt head and the follower on the last shot due to the re-designed follower which won't tilt back easily. I was having fits with that, too, and abandoned the mags for the M2 30-rounders which work like champs in all three of my ARs, even will feed .45 ACP in my Macon Armory upper if I don't load more than five at a time. Something else about the M3 20s is they have a 30-round spring in them! That makes the follower even LESS likely to tilt and really puts some drag on the BCG going back after the last shot. Neither magazine will seat in my lower with the bolt closed, finally figured that one out and it's due to how the guide rails are narrowed right at the top, presumably to help prevent "fountaining?" Not sure, but those nibs keep the cartridge column from depressing when even just two 300 BLK cartridges are put in and the mag inserted. I'm going to have to get to the bottom of that or just shoot to lock every time. Gee, I can do that now!
I would NOT use a full-auto BCG if doing this again, though the one I have appears very well made and only cost me $118, fully NiB coated and all.
One thing I forgot to add, and that is I'm very quickly falling out of love with the Magpul M3 magazines, at least the curved 20-rounders that I have. Main reason is a very bad bind/drag condition between bolt head and the follower on the last shot due to the re-designed follower which won't tilt back easily. I was having fits with that, too, and abandoned the mags for the M2 30-rounders which work like champs in all three of my ARs, even will feed .45 ACP in my Macon Armory upper if I don't load more than five at a time. Something else about the M3 20s is they have a 30-round spring in them! That makes the follower even LESS likely to tilt and really puts some drag on the BCG going back after the last shot. Neither magazine will seat in my lower with the bolt closed, finally figured that one out and it's due to how the guide rails are narrowed right at the top, presumably to help prevent "fountaining?" Not sure, but those nibs keep the cartridge column from depressing when even just two 300 BLK cartridges are put in and the mag inserted. I'm going to have to get to the bottom of that or just shoot to lock every time. Gee, I can do that now!
I would NOT use a full-auto BCG if doing this again, though the one I have appears very well made and only cost me $118, fully NiB coated and all.
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Ian, I am leaning towards Rock River. They have a decent reputation amongst HP shooters for making a quality product. I'm not inclined to build an upper, I'm no wrench jockey. At least not yet.
I'm not overly concerned with being subsonic so that makes it a bit easier, doesn't it.
I'm not overly concerned with being subsonic so that makes it a bit easier, doesn't it.