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BCA bolt action upper for $350? (Page 18 of 21)
| What's with the typical 'bolt-action' bolt? You could order an inexpensive Bear Creek side-charging upper without a gas port. You would then have a rather nifty straight-pull bolt action. You would use a standard lower with all its parts for spring-loaded charging. It would be pretty fast because all you have to do is bring the bolt back and let it go. |
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The biggest advantage is the ability to alter it and put non buffer tube folding stock on it. It's a quieter more natural operation (if you grew up on bolt guns). Less of a chance to short stroke the operation as there's no spring tension to overcome. All the cool kid bolt guns are going to detachable mag, pistol grip, folding stock, lightweight setups. The BCA leverages the vast aftermarket support and easy to work on nature of the AR into a consumer build able bolt gun. You could build a pretty premium BCA bolt gun for the price of just a folding bolt gun chassis. ETA. I didn't think of extraction. |
I'm not here because I make sound financial decisions.
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Originally Posted By 1saxman: I think I know the answer to my own question - extraction. It could be too difficult to pull that fired case out of the chamber with a straight pull. But hey, it would be a very cheap experiment to find out. That's perfectly doable. I've built a 300 Blackout upper and a super short 5.56 upper like that on two occasions. Here's the 300:  " />But the bolt action upper just has a little better control over the feeding. |
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| Think strait pull back would only advantage larger calibers. Reason being using the force of the buffer to load flatter tipped ammo like 350 legend or 450 Bushy. I found it extremely difficult to load 350 legend (flat tipped) in the BCA bolt action upper. Switched to a 300blk barrel and never looked back. |
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Originally Posted By Tersoth: Has any seen anything about this? Supposedly a change to the bcg. https://imgur.com/a/NwuAyju Got my 308 upper today and it has the bolt in that picture. Still cutting this B down though. |
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I just found out the downside of the shorter (orig non-cut) bolt... I put a bca bolt upper on a regular lower from another AR for a quick range trip to test some loads... at some point the bolt was locked back by the bolt catch. when I went to take it apart I instinctively slapped the bolt release and the buffer spring slammed the bolt home... unfortunately the bolt was shorter than normal and the buffer went slamming by the buffer catch, bending the pin on its way. Being fully forward in the receiver, I couldn't separate the upper/lower. fortunately I had an older style buffer tube without the buffer stop pin alignment nub they're putting on these days, so I was able to unscrew the buffer tube and remove the spring/buffer that way... but it still cost me $460 to replace the bent buffer catch as I couldn't resist buying other crap I "need" to avoid the shipping charges on a $3 replacement part... |
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Originally Posted By SyberSniper: [...] but it still cost me $460 to replace the bent buffer catch as I couldn't resist buying other crap I "need" to avoid the shipping charges on a $3 replacement part [...] I could come pick up that extra $457 worth of stuff from you, so you can make this statement with integrity.  This one's on you. |
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Originally Posted By AL1EN: Looking for a handguard for my 308 build. How do I tell if this is a high or low profile receiver? Attached File Attached File Attached File Attached File |
Originally Posted By ar-jedi:
SO MUCH WIN IN ONE POST IT COULD CRASH ARFCOM !!!
SO MUCH WIN IN ONE POST IT COULD CRASH ARFCOM !!!
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Originally Posted By AL1EN: I seen where google said measure the hight of the charging handle tang, but these uppers don’t have one lol. hold it next to one with a charging handle and give it a best guess 
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Originally Posted By ar-jedi:
SO MUCH WIN IN ONE POST IT COULD CRASH ARFCOM !!!
SO MUCH WIN IN ONE POST IT COULD CRASH ARFCOM !!!
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Just found this endlessly searching through BCA Q&A… ok it wasn't endlessly, I got pretty lucky. *What platform pattern are your AR10 Uppers? Our uppers are made based on the DPMS Gen1 Low Profile model. With the AR10, there are many different designs and models out there, and each company tends to create and design its own unique platform. For that reason, we cannot guarantee the fitment.../* |
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Originally Posted By AL1EN: Picked up a blemish Jakel lower for 70$ thoughts are it’s nice but there is a shelf between the upper and lower by the trigger pocket I’m not a fan of. https://i.imgur.com/mWdTp76.jpeg That shelf would probably annoy me until I either modified it (size reduction/shaping so it's less pronounced or more a ridge than a shelf), removed it, or, if it were ar-15 instead of 308, found a lower that matched better. I don't have proper milling equipment, so I'd probably set up a jig to hold it, clamp it in, and router most of that shelf off, leaving a little to be removed during finished by hand. Then Alumablack or your choice of coatings. |
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Yes, the Sub-X 307s have a flat(ish) tip. Sub-X 307 .338 ARC  From Hornady website I don't have issues with them feeding, for the most part. That said, right-hand feed does catch slightly if it's chambered slowly, but it's easily overcome with slightly more force -- not enough to damage or mark up the case or projectile, though. I'm using: McGowen barrel Duramag 400 Legend magazine Cryptic bolt (silver) |
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Bummer, I was hoping I could use LAW folder in the FOLDED position, but I can't. Even the LAW folder with the ARIC end cap is just a hair too short. I mean, I probably could use the folder in the folded position if I cut the bolt, but I was hoping to not have to do that. Regardless, I'm now the (proud?) owner of a 6" 300blk Bolt Action BCA upper! The "plan" is to install my 12.5" 300blk barrel on it and give it a try. |
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Originally Posted By PreacherOfGadget: Yes, the Sub-X 307s have a flat(ish) tip. Sub-X 307 .338 ARC https://static.hornady.media/presscenter/thumbs/illustrations/1411003113-1731352619-82272-338-ARC-307-gr--Sub-X.jpg From Hornady website I don't have issues with them feeding, for the most part. That said, right-hand feed does catch slightly if it's chambered slowly, but it's easily overcome with slightly more force -- not enough to damage or mark up the case or projectile, though. I'm using: McGowen barrel Duramag 400 Legend magazine Cryptic bolt (silver) Didn’t matter the speed, wouldn’t feed. Thankfully the standard rounds do. Maybe I’ll polish the ramps and see if that helps. |
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When you try to feed those big guys, what part of the cartridge is hanging up? The bullet? Or case? With fat .300 blks, I've often had to address the rear edges of the feed ramp -- sharp edges/corners liked to catch both projectile and brass on those big fat subs. And those SubX projectiles do have cuts in the projectile that could be extra susceptible to catching sharp fed ramp corners in addition to their fat tips. |
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Originally Posted By PreacherOfGadget: When you try to feed those big guys, what part of the cartridge is hanging up? The bullet? Or case? With fat .300 blks, I've often had to address the rear edges of the feed ramp -- sharp edges/corners liked to catch both projectile and brass on those big fat subs. And those SubX projectiles do have cuts in the projectile that could be extra susceptible to catching sharp fed ramp corners in addition to their fat tips. Appears to be those blunt tips, I’ll definitely be polishing the ramps. |
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So, if you're jamming on the entrance to the chamber, there's really 3 places that can be adjusted geometry wise, and one more you might want to try polishing. Place 1: Tip of bullet w/edge of chamber.... then properly radius chamber (harder to do), if not properly radiused. Polish radius to chamber so tip doesn't hang up (easier to do). Clean well after either. Place 2: Tip then side of bullet w/feed ramps ... rounding edges of feed ramps, or even widening them (especially the ridges at the top/sides of the feed ramps) overall will help wider projectiles and wider cartridges feed lower. Place 3: Case of cartridge w/magazine. ... this one can get trickier, as the feed lips control the cartridge height and the feed angle the cartridge is presented at. That requires bending feed lips. There's also the potential for rough / sharp edges that are grabbing the rounds, though you'd probably have noticed if the feed lips were that bad. This is the cheapest part, so if you follow the "modify the cheapest part first", keep that in mind. Polish Point: Bolt face ... if the bolt face is rough, there's more resistance to the rear of the cartridge moving upward when it pops free of the magazine. This can exacerbate alignment issues that are pre-existing. .375 SOCOM and .458 SOCOM are GREAT examples of the above points. Tromix, an original producer of and the go-to for reliable .375/.458 SOCOM parts, makes modifications in line with points 1, 2, and the polish point in all their barrels/bolts (in addition to a ejector geometry modification) -- and as a result, they don't have the feeding issues that many others have. M4 feed ramps were designed to properly position a 5.56 cartridge for chambering, and weren't designed with larger cartridges in mind. They work well and are cost effective, but for larger rounds they don't work perfectly. There's a point starting around .350 cal (depending on case geometry) where widened feed ramps or a single large central feed ramp become necessary for reliable operation across nearly if not all loadings. .300 BLK, 338 ARC, .350 Legend are all cartridges I feel can benefit from feed ramp geometry designed or modified for them to increase feed reliability across loadings, but it's just not cost effective for most barrel manufacturers to do that because it's possible to get away with not doing it. If altering feed ramp geometry, try not to reduce the face of the lugs on the barrel extension that make contact with the rear lugs of the bolt. It's a matter of removing small amounts. I've widened and polished multiple .300 blk barrel feed ramps and got them to go from finicky feeders to eating everything put on their plates. Anyway, I think I've rambled enough for now. Got to get back to .... ah .... things I should be doing. |
| Come to find out jakl-10 lowers don’t use standard ar10 parts for example the pivot and take down pins. So I just had to order the jakl build kit that comes with a F5 stock. Hoping that adapter on the stock will fit with this bca upper. This F-ing lower is becoming a pain in the a** |
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Originally Posted By PreacherOfGadget: So, if you're jamming on the entrance to the chamber, there's really 3 places that can be adjusted geometry wise, and one more you might want to try polishing. Place 1: Tip of bullet w/edge of chamber.... then properly radius chamber (harder to do), if not properly radiused. Polish radius to chamber so tip doesn't hang up (easier to do). Clean well after either. Place 2: Tip then side of bullet w/feed ramps ... rounding edges of feed ramps, or even widening them (especially the ridges at the top/sides of the feed ramps) overall will help wider projectiles and wider cartridges feed lower. Place 3: Case of cartridge w/magazine. ... this one can get trickier, as the feed lips control the cartridge height and the feed angle the cartridge is presented at. That requires bending feed lips. There's also the potential for rough / sharp edges that are grabbing the rounds, though you'd probably have noticed if the feed lips were that bad. This is the cheapest part, so if you follow the "modify the cheapest part first", keep that in mind. Polish Point: Bolt face ... if the bolt face is rough, there's more resistance to the rear of the cartridge moving upward when it pops free of the magazine. This can exacerbate alignment issues that are pre-existing. .375 SOCOM and .458 SOCOM are GREAT examples of the above points. Tromix, an original producer of and the go-to for reliable .375/.458 SOCOM parts, makes modifications in line with points 1, 2, and the polish point in all their barrels/bolts (in addition to a ejector geometry modification) -- and as a result, they don't have the feeding issues that many others have. M4 feed ramps were designed to properly position a 5.56 cartridge for chambering, and weren't designed with larger cartridges in mind. They work well and are cost effective, but for larger rounds they don't work perfectly. There's a point starting around .350 cal (depending on case geometry) where widened feed ramps or a single large central feed ramp become necessary for reliable operation across nearly if not all loadings. .300 BLK, 338 ARC, .350 Legend are all cartridges I feel can benefit from feed ramp geometry designed or modified for them to increase feed reliability across loadings, but it's just not cost effective for most barrel manufacturers to do that because it's possible to get away with not doing it. If altering feed ramp geometry, try not to reduce the face of the lugs on the barrel extension that make contact with the rear lugs of the bolt. It's a matter of removing small amounts. I've widened and polished multiple .300 blk barrel feed ramps and got them to go from finicky feeders to eating everything put on their plates. Anyway, I think I've rambled enough for now. Got to get back to .... ah .... things I should be doing. What do you use to do yours? |
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Whew. Different tools for different parts. Easiest part first: Bolt face -- ideal way is using high grit stone, and gentle circular motion (not rotating the bolt). Second best, which I do, is high grit sandpaper laid on a flat surface. Same motion. Hardest next: Chamber entrance -- I've never addressed reshaping this in rifle caliber barrels, and I'm not sure I would because of the chance of messing things up and the challenge of working with the extension lugs in the way. I'd polish it without a second thought, and have, but I'd be wary of recontouring in here. I have reshaped the feed cone and radius on multiple 9mm AR barrel chambers. I stuffed a patch of rag into the front of the chamber before slowly grinding the edges until they had a round shape. To do this, I made a custom grinding bit by modifying an orange Dremel barrel grinding bit. I recontoured it to give it a shape like a spinning top. It takes a little bit to get the hand motion right, but if you keep such a grinding bit parallel to the bore, and moving in a circular motion, you avoid contact with anything but the edge of the chamber that is being radiused. Hand slips here can mess up your chamber. I run the Dremel fairly slow to try and avoid mistakes. Then, to polish around the chamber entrance I use the Dremel polishing bit that has an ogive shape similar to some bullets, working up to red polish. I use this same Dremel polishing bit for the feed ramps. The one that's usually most effective for making a robust system: Feed ramps -- stuff the chamber with a rag patch or such to protect it and keep metal grindings out. It seems tempting to use a barrel grinding bit to open up the feed ramps all the way, but I take a less aggressive approach than that. I usually address these edges first, before opening up lower down in. Standard Feed ramps  Craddock Precision has this barrel extension, which is a better geometry than standard M4 for larger rounds:  So, that's about the ideal shape, though I never have had to recontour that much. Notice how the center triangle has disappeared in the widening of the feed ramps. (That central ridge be smooth, not sharp.) Lowering the outside left and right edges will move the bullet tip lower and to the outside. Lowering the inside edges will move the bullet tip lower and toward the center. You have to take a balanced amount off the center and the outside, or you could alter the feed angle to another position outside the chamber. Remove as little of the inner face of the lugs as possible so that lug engagement with the bolt stays as high as possible. You can loose some and survive, but not too much. And the cheapest part to modify: Magazine feed lips -- There are a couple decent tools out there for bending feed lips. (I know Brownell's makes one) It's been a while since I had to do this, and if I did again, I'd get a mag lip bending tool, or make one with by making a precise cut in a hard metal bar with a dremel wheel to replicate a feed lip tool's geometry. It's possible to do with the right pair of pliers, but there's not a lot of space to work and it's easy to create sharp edges when bending with pliers. I'll get a picture of the custom grinding bit I made for radiusing later and add it. Anyone considering this, you can mess up a barrel if you do this wrong. It is easier to remove than it is to add, so go slow! |
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Originally Posted By PreacherOfGadget: Whew. Different tools for different parts. Easiest part first: Bolt face -- ideal way is using high grit stone, and gentle circular motion (not rotating the bolt). Second best, which I do, is high grit sandpaper laid on a flat surface. Same motion. Hardest next: Chamber entrance -- I've never addressed reshaping this in rifle caliber barrels, and I'm not sure I would because of the chance of messing things up and the challenge of working with the extension lugs in the way. I'd polish it without a second thought, and have, but I'd be wary of recontouring in here. I have reshaped the feed cone and radius on multiple 9mm AR barrel chambers. I stuffed a patch of rag into the front of the chamber before slowly grinding the edges until they had a round shape. To do this, I made a custom grinding bit by modifying an orange Dremel barrel grinding bit. I recontoured it to give it a shape like a spinning top. It takes a little bit to get the hand motion right, but if you keep such a grinding bit parallel to the bore, and moving in a circular motion, you avoid contact with anything but the edge of the chamber that is being radiused. Hand slips here can mess up your chamber. I run the Dremel fairly slow to try and avoid mistakes. Then, to polish around the chamber entrance I use the Dremel polishing bit that has an ogive shape similar to some bullets, working up to red polish. I use this same Dremel polishing bit for the feed ramps. The one that's usually most effective for making a robust system: Feed ramps -- stuff the chamber with a rag patch or such to protect it and keep metal grindings out. It seems tempting to use a barrel grinding bit to open up the feed ramps all the way, but I take a less aggressive approach than that. I usually address these edges first, before opening up lower down in. Standard Feed ramps https://i.imgur.com/bzRfDXj.jpeg Craddock Precision has this barrel extension, which is a better geometry than standard M4 for larger rounds: https://i.imgur.com/HEA6eBO.jpeg So, that's about the ideal shape, though I never have had to recontour that much. Notice how the center triangle has disappeared in the widening of the feed ramps. (That central ridge be smooth, not sharp.) Lowering the outside left and right edges will move the bullet tip lower and to the outside. Lowering the inside edges will move the bullet tip lower and toward the center. You have to take a balanced amount off the center and the outside, or you could alter the feed angle to another position outside the chamber. Remove as little of the inner face of the lugs as possible so that lug engagement with the bolt stays as high as possible. You can loose some and survive, but not too much. And the cheapest part to modify: Magazine feed lips -- There are a couple decent tools out there for bending feed lips. (I know Brownell's makes one) It's been a while since I had to do this, and if I did again, I'd get a mag lip bending tool, or make one with by making a precise cut in a hard metal bar with a dremel wheel to replicate a feed lip tool's geometry. It's possible to do with the right pair of pliers, but there's not a lot of space to work and it's easy to create sharp edges when bending with pliers. I'll get a picture of the custom grinding bit I made for radiusing later and add it. Anyone considering this, you can mess up a barrel if you do this wrong. It is easier to remove than it is to add, so go slow! Appreciate the detailed response sir! Do you touch the feed ramps in the upper itself? |
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Hmmm... I don't think I have had any on which I felt it was necessary. If I did it might have been with my Faxon barreled .458 SOCOM pistol. These are the bits I've used, including the one I customized the contour on.  I want to stress again, I've only used that tool for radiusing 9mm chambers. If I were to use it with a rifle caliber, I'd remake the tool smaller so there'd be less chance of hitting the barrel extension lugs. I'd really make radiusing the chamber the very last thing I'd try. Nothing wrong with polishing the radius, though. Hard to mess anything up doing that. |
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I need to add a caveat to using one of these with an uncut bolt and a LAW folder in the folded position. It "can" be done, but it will require you to use two hands and most likely hold the straight up by placing the muzzle on the ground. You will need to use your right hand to operate the bolt as normal, but you will need your left hand to hold down the "release" button on the LAW folder. When the folder is open, it is that vertical piece that I think is made to keep the BCG from sliding out of the back of the gun is the problem.  That vertical piece is attached to the spring loaded locking/release mechanism and it slides to the left when the release button is pushed and/or when the folder is closed.  What might also work is a some type of metal O ring that just sits in that spot and keeps the locking mechanism open. Just tighten the tension on the hinge so is this not swing. I've probably worked the action 600 times so far. It isn't too bad. First thing I did when I got it was put a bunch of thick lube on it and went to town. Whatever grit and dust was in there was going to be my grinding powder. Probably cycled it 300 times before I took it apart, cleaned it, re-lubed it, function checked it, and then cycled it a bunch more. I cycles really easily unloaded. It is a hair tougher loaded. I only have two 300blk snap caps, so using those are annoying to reload, but I don't want a bunch of light primer taps on my ammo. |
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Update! Or.....spend 90 seconds reading the LAW folder manual, and 60 seconds removing the one hex screw so you can remove the spring and latch, then another 30 seconds to loosen, then tighten the hinge tension. I can now cycle while folded with an uncut BCG. I just stuck the spring and latch in a plastic baggie with the BCG extender plug it comes with anyway. |
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Was researching the BCA issues and cures and fell into this thread. Some good advice and tricks but I still put on the thinking cap. Have two BCA bolts. AR15 7.62x39 and AR10 308. Both are basically MOA out of the box with no modifications. The AR15 was rough cycling so I went to work smoothing the action with minimal work. Tried the tape wrap and it did improve the cycling but I wanted a more permanent fix so it was FreeCAD and the 3D printers turn. I created a shim to slide over the rear wings of the bolt that aligns the carrier so it does not bind but you have to JB weld it in place or use contact cement. Also the buffer catch interfered with the shim so I lopped off the bottom side to clear the buffer catch. Simple fix for a jammed up bolt. Now the action moves like it should with no effort. Moving forward I wanted the bolt to not ride on the housing so I created the spacer to move the bolt outward a bit and the spacer rides on the housing also creating enough friction when it is locked in battery without doing any permanent modifications. You will need 10-32x3/4 cap screws to mount this with the lock washers. The spacer fits snugly into the recessed seat on the bolt carrier and matches the bolt handle profile. With minimal work you can have a reliable working bolt action. Remembering that BCA is a mass producer, you are going to have to do some tinkering to get their products to do exactly what you want them to do. Next stop will most likely be a Harrell tuner to tighten those groups because it is easier than tweaking the barrel torque. Will have the 3D files uploaded to Thingiverse for those who want an easy fix |
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Maybe I missed it, but is there a running list of solid rails with anti-rotation tabs that work with these uppers? I know my Midwest Combat rails and Aero Atlas rails do not fit because of the anti-rotation wings. However, I have and old PSA rail that has the anti-rotation tabs up on the pic rail section that does work. What else is available? Troy? Would BCM work? |
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Hmmm... in all honesty, it would be nice to have a post documenting anti-rotation tabs, height and placement so compatibility can be determined. BCM's anti-rotation tabs are high enough to work fine with BCA's receivers. They use the same tabs for all of their free float rails, so that applies to KMR, MCMR, QRF, and Raider Rail.  My most recently purchased BCA bolt-action receiver (late spring 2025) measures 0.31" from the bottom of the picatinny rail down to the point where the receiver begins widening. So any anti-rotation device that sits above the main body of the receiver, in the ~0.3" below the rail should work. Most handguards that just extend the body of the handguard backward to form anti-rotation tabs will not work. There are some handguards with large enough barrel nuts, like those designed for suppressors, that have an extension of the handguard rearward which is high enough to clear the body of the receiver; for example, based on my measurements, I suspect the MI Suppressor Series One Piece (ID 1.67", 1.95" between m-lok slots) would fit or need only minor modification of the tabs to fit. Troy MRF rails probably will not work because the tabs are too low, and others similar to it might have issues, too. Their rails w/o anti-rotation tabs work fine. I have a BCA bolt action upper in 338 ARC with a Gen2 SOCC Low Profile M-LOK BattleRail. No tabs on that line or their Bravo Rails. I don't think there's one on my Alpha Rail either. ETA: Looks like UTG Pro Arwen and Forerunner handguards should work.  Image from OpticsPlanet Dark Storm Industries, too  Image from OpticsPlanet SLR Solo Intrepid Lite  Image from OpticsPlanet SLR Solo's is a little different, as it uses the gas tube for anti-rotation. ZRO Delta Mission Ready LVOA Rail Some of Samson's rails might, or might work with minor modification Stern Defense MOD4 and MOD5 M-Lok Handguards Next Level Armament NLA AR-15 M-LOK Handguards Sharps Bros. Full Top Rail M-LOK Handguard Outerwild AR15 Premium Line Handguard XTS AR-15 M-LOK Rail I want to make clear the ETA list is a list of handguards that should work based on apparent geometry. Do not take this as any sort of endorsement of their quality. |
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Thanks! I've been meaning to try a BCM rail, so that might work. I don't like the cheap PSA rail I dug out of the parts bin, but it was the only one I had that would fit and was longer than 6 inches.  12.5" Chrome-lined Green Mountain barrel in 300blk. SIG Tango 1-4 & Magpul sling It can be operated while folded, but the folder does not latch shut. I contacted LAW tactical earlier today to see if I could get some spare parts to work on before I go about cutting down my bolt...I really don't want to do that. I want to keep the back of the action sealed when the bolt is closed. |
BCA bolt action upper for $350? (Page 18 of 21)
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