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Posted: 8/17/2026 9:10:54 PM EDT
[Last Edit: Namsag][Edited]
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Another project started. A bit unconventional for sure. I've been eying the .410 bore shotgun for a while now. Decided to jump in and see what I could do. I looked at pretty much everything on the market and they all have some kind of issues. FTE, FTL, jamming, polymer receivers, just to mention a few. I'm taking a different approach. Going to put one together from parts! Did I say parts? I found what I was looking for. A complete Bear Creek Arsonal .410 upper with a 20" barrel of 4150 CM and a full choke installed. I ordered it and was quite pleased at the quality of the whole upper. Very slick handguard, well machined with excellent fit and finish. It must be cleaned of it's preservative and slathered with some fresh oil before use. Same with any firearm. They all come with preservative. To take a new gun out of the box and fire away is a mistake. Clean extremely well and re lube with some good stuff. So this will be a a box fed AR 15 platform SBS. Oh boy, can I make it work and work well? Video's I found online don't bode well for this upper, or any others really. Feed and ejection issues abound. Funny thing, everyone complains that the .410 2.5" shells are not the same length. Like more than an 1/8 difference in length. One video showed the poster measuring shells from 2.210 to 2.460. That will be an issue needing resolved as the magazines are a tight fit for those rounds to begin with. Too long and it won't fit in the mag. Shorter may still drag in the mag. One poster said the shortest ones still had issues. I have three mags. Two purchassed from BCA, one came with the upper and they are a really snug fit in the magwell. Another issue. If your polymer mag is a tight fit in the magwell, the magazine will shrink on the inside exaserbating the tight issue even more. I ran into this issue with a lower that the magwell was slightly undersize wich caused feeding issues in a 5.56 AR. Tight Magpul mag fit. I've already started resolving this fit issue. I also modified the mag itself to solve yet another issue. All of this I attribute to very low produnction numbers on this caliber of semi auto firearm. BUT, it is growing in popularity. Lots of .410's out there in the trap, skeet, and sporting clays disipline as well as hunting. Usually in break open firearms. The buffer, buffer tube, buffer spring are all going to be looked at. The bolt and carrier look pretty good in this upper. The lower I'm using is an 80% lower I finished years back. Putting it to use now on this project. Will be using a drop in trigger, maybe even with FRT. That thought is in the back of the mind. So here are the main componnents. A picture is worth a thousand words. BCA complete upper, CCS olive drab buttstock, FAB Defense pistol grip, receiver extension, modified magazine, and Strike Industries trigger guard bar.  The upper with some detail shots showing the really nice handguard.  You'll notice this is a side charging upper which I've grown to like quite a bit.   The 80% lower as it is today.   Small modifications to the bottom of the magwell center groove to improve greatly the mag insertion with the help of the Strike Industries trigger guard bar. The magazine tang for the last round bolt hold open. Spring loaded. Same as on a lot of other box fed shotgun magazines. It must be depressed to insert the magazine. The modification I made removed the blunt square lip (in the magwell) that the mag tang caught on. A small chamfer so the mag doesn't catch on it.     (Left) This is the un modified mag, longer pointed tang to lift the LRBHO. (Right) This is the modified mag with a squared off and shortened tang. This is a modification that can be done on any of these spring loaded tang magazines. Check the fit and function as you go. It is really a good modification to any mag like this. The tang no longer needs to be depressed when inserting the magazine. It fits the magwell groove perfectly. No snag no drag.   The un modified mag with pointed tang and the modified mag showing the shortened and squared off tang. Both show aluminum where the mag fits snugly and the mag release bar rubbing. If this mag were metal, it may not insert at all.  The magazine has already had material removed to relieve the snug fit of the magazine, It was tight front to back and also at the top where the mag release bar engaged right at the top of the mag. You can see even after I've removed material that it still rubs the magwell with small interference. The aluminum marks on the magazine show these tight spots.   The mag release lever also drags on the magazine during insertion. Not the drop lug itself, the inch long bar drags before the lug itself is engaged.  What I've done so far will improve mag insertion and release without having increased effort to push the mag in and then pull it out with similar effort. This will also not put the squeeze on the rounds in the magazine. Ending the possible drag issue. Still more mag fitting to come. I'm not looking for drop free but might end up with that condition due to the shortened mag tang. The goal as of today is to end up with a 9" barrel length. I want to shoot mainly slugs with this gun. .410 slugs weigh in at roughly 110 grains. Slightly less that a 9mm at 115 grains. Out of a 16" barrel, the .410 slug is at roughly 1700 FPS. That excites me. Approaching double that of the 9mm out of a short pistol. I'm going to talk to Briley chokes to get some extended rifled chokes if available. One inch. Or custom made by them. I've had them make some for me in the past. The idea is to add an inch to the barrel length to get to 10". This will be a light manuverable firearm that will be fun to shoot. I won't be shortening the barrel until the 60 day period for the ATF has expired for them to contest the courts ruling on the 5th of August. I am a member of several of the organizations as plaintiffs in the recent lawsuit. I will still wait for the 5th of October before the shortening process. If the ATF doesn't respond in the 60 days, then I will shorten the barrel at that time. No registration, no tax, no fingerprints, and no picture. I plan on adding this firearm to my gun trust for some protection and ownership sharing. I will leave the gun as is and start the process to make it reliable and function properly at it's factory barrel length of 20" The gas system on this upper is a pistol length system. Thats a good place to start. Might not have to move the gas system. Find the ammo that works in the mag as well as functions the gun will be first on the things to do list. This will be a fun project. If I make it work, it will be an awesome little SBS. Now to find some 10 round mags!!! Stay tuned. |
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Originally Posted By LittleAugieMo: Anyone I've spoken with tjat has tried a AR platform has had problems with it....mostly due to ammo length... Yes, I've seen that quite a bit. It might take some higher priced ammo like Winchester AA or equivalent. I might find myself with a tape measure in some ammo store☺ Since this is a slug gun, there will be a limit as to what's available. |
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Originally Posted By backbencher: You can always reload .410 yourself and set your own ammo length. Look forward to your results. I'm pretty excited about this project. I'll get it figured out. One way or another. I will go the reload route if necessary. Right now I'm looking for a rifled choke. May have to have one made. |
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Originally Posted By J_taylor: Looking good. I like my 410 SBS. https://www.ar15.com/media/mediaFiles/548798/20260613_093955_jpg-3813209.JPG Tell me about your .410. |
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Originally Posted By Deerhurst: I have an AR with a SBR stamp and I have a 410 upper than runs well on that lower. How does that work if I want to chop the 410 upper? Will I have to 2 stamp the lower? No. The lower is already stamped as an SBR and running a SBS upper on that lower is fine. Barrel length doesn't matter. When doing a form 1, your stating what you are making as the manufacturer. One of the requirements, if you alter the original build, is that it can be returned to match the original form 1 you filed. You are the manufacturer and as long as you can return that lower to the specs on the form 1 you originally filed, It's perfectly legal. I've read this multiple times, on different blogs, seen ATF letters. All say the same thing. What are the components you used? The lower, the upper, what buffer and spring, what trigger? Tell us about your .410. |
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Originally Posted By Namsag: No. The lower is already stamped as an SBR and running a SBS upper on that lower is fine. Barrel length doesn't matter. When doing a form 1, your stating what you are making as the manufacturer. One of the requirements, if you alter the original build, is that it can be returned to match the original form 1 you filed. You are the manufacturer and as long as you can return that lower to the specs on the form 1 you originally filed, It's perfectly legal. I've read this multiple times, on different blogs, seen ATF letters. All say the same thing. What are the components you used? The lower, the upper, what buffer and spring, what trigger? Tell us about your .410. My lower is an old Spikes. I'm running a rifle tube and rifle buffer. The upper is some wacky prototype I can it nail down the origin of. It is a factory 14" and ATI says it may have been a prototype from a company they had worked with at one time but did not have do their production uppers. I got.it because the shop didn't want to sell a possible NFA violation. It runs fantastic with little bitty 2" and 2.5". That lower normally runs an 8" DI 7.62x39 upper usually. Used to have a POF 4.5LB trigger. Now has a milspec I did a trigger job on with a cross bolt safety. Well, gonna have to put an optic on that 410 now! |
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Originally Posted By Deerhurst: I have an AR with a SBR stamp and I have a 410 upper than runs well on that lower. How does that work if I want to chop the 410 upper? Will I have to 2 stamp the lower? I would think to put an SBS upper on that lower you'd need another Form 1 stamp since you're not in a free state. |
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Originally Posted By backbencher: I would think to put an SBS upper on that lower you'd need another Form 1 stamp since you're not in a free state. About as free as Florida. Can own anything NFA, no FRT stuff. One would think something but you never can tell what the AFT will actually say. |
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Originally Posted By Deerhurst: My lower is an old Spikes. I'm running a rifle tube and rifle buffer. The upper is some wacky prototype I can it nail down the origin of. It is a factory 14" and ATI says it may have been a prototype from a company they had worked with at one time but did not have do their production uppers. I got.it because the shop didn't want to sell a possible NFA violation. It runs fantastic with little bitty 2" and 2.5". That lower normally runs an 8" DI 7.62x39 upper usually. Well, gonna have to put an optic on that 410 now! Amen on the optic. Your upper looks like it could be the ATI but not sure. |
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Originally Posted By Namsag: Tell me about your .410. |
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Originally Posted By Deerhurst: About as free as Florida. Can own anything NFA, no FRT stuff. One would think something but you never can tell what the AFT will actually say. Originally Posted By Deerhurst: Originally Posted By backbencher: I would think to put an SBS upper on that lower you'd need another Form 1 stamp since you're not in a free state. About as free as Florida. Can own anything NFA, no FRT stuff. One would think something but you never can tell what the AFT will actually say. So 27 states don't need a Form 1 for SBR/SBS as of last week. Pretty sure Oregon does. And you're not nearly as free as Florida, non-resident permits only to neighboring states, otherwise we can only OC, and in Portland we can OC but only UNLOADED. 
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Originally Posted By backbencher: So 27 states don't need a Form 1 for SBR/SBS as of last week. Pretty sure Oregon does. And you're not nearly as free as Florida, non-resident permits only to neighboring states, otherwise we can only OC, and in Portland we can OC but only UNLOADED. Portland is a city, not a state. I've been known to OC my battle belt and setup after matches. Nobody at the burger join so much as batts an eye to 5 guys with battle belts, pistols, mags, etc. I can have SBR/SBS in OR. You can have them in FL. I have a MG. FL can have MGs. I stated ownership, not the paperwork. I'll state again, I can have anything 2A in OR that you can have in FL, which everyone seems to use as a metric for freedom yet is more 2A restricted than states such as Idaho. The 4473 thing hasn't been hashed out in OR yet. The state law contradicts itself when it comes to NFA. Definitely have a few local to me shops that are chomping at the bit to send things out the door on 4473s. |
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The project is moving forward. Marking this off the list of things to do. I have found ammo that fits nicely in the magazines. Slugs and 7.5 shot loads. It's Federal Top Gun. Just under 1/32 of an inch clearance and that's good. The slugs are rated at 1775 FPS, 109 grains. Slightly less than a 9mm at 115 grains. The shot is rated at 1330 FPS, 1/2 oz of hard pellets. Magazines have now been worked over to fit nicely in the magwell. Most of the material removed is from the front and back of the mag. The sides just at the top of the mag had some material removed. Slightly bowed out. Shortening the LRBHO tang made a huge difference in insertion. Mag slips in like the tang isn't present. Once inserted, there is no play whatsoever. Not drop free but very easy to be removed.    
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Originally Posted By Deerhurst: I am assuming the mag was originally closed in the front? What is the purpose of opening the front up like that? I did not open the front of the mag. Thats the way it comes. No ID on the mag so I don't know who makes it. That opening in the front is different. I've not seen anything previous like it. I'd like to get some 10 or 15 round mags to add to the (3) 5 rounders I have. Maybe someone on here recognizes the mag and can ID them for me. Probably should make a call to BCA and ask the question! |
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Update: Cleaned the upper to remove the protectant and then lubed the necessary parts. A fair amount of really fine metal chips from manufacturing. I set up the upper with a Holosun 503B mounted at the back of the receiver for a larger sight picture. The .410 laser bore sight arrived today so I put it to imediate use. Fit the chamber really good. All sighted in. Installed a Rise Armament Rave 140 trigger with a 3.5 lb pull. Excellent trigger with lifetime warrantee. Changed the stock from the HERA CCS to a HERA CCS Gen 2. Better feel, looks better. Using an Armaspec Stealth recoil spring for an AR15 carbine. See if that works!!! Got three chokes coming from Carlson. Cylinder, Imp Cylinder, and Full. Upper came with an in house full choke I didn't like. I'm going to an indoor range to start so slugs will be used, no shot allowed. Starting choke Imp Cylinder.    
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Originally Posted By Deerhurst: I'd be curious if the ATI mags work. I think that's what mine are and they are 10 round. Just got back into town late last night. I'll have to get some photos for you. I opened up a mag and this is what I found. There is no block or spacer in the mag. The follower is a no tilt design and has some long legs for this. Pretty much a standard spring design. The spring is not captured in any way by the follower, the spring just presses up against the follower. Different on the bottom retainer. The loop of the spring is captured or guided on the plate. It centers the spring in the mag, at least at the bottom. I will note that the follower does NOT tilt at all. It stays in the same plane, loaded or empty. You can't make it tilt. It also has a little drag on the fit (front to back) as I had to lightly push it out of the mag for these pictures. Don't think you could shake it out of the mag. The plunger (LRBHO) doesn't look to be removable. There is a visable tab in the follower that possibly would release it. Not messing with it as it works perfectly now. No tilt with a little drag, in itself is really good. No drag woiuld be perfect. I hate a mag that allows the follower to tilt at any time. I think its a poor design if it does. The spring has a little twist in it from top to bottom. Rubs the side of the mag but not enough to disrupt it's function. I don't think another round could be added without substantual shortening of the followers no tilt legs, that affecting the no tilt design. The modifications I made to these three mags is really good. The LRBHO tang is absolutely a no issue now. Mag inserts with ease. I'd consider this mag to be of really good design and manufactured pretty well. My mods just made it better. Show me what you got on the 10 rounders you use. How they fit in the magwell. How the follower works, etc. Open it up for pics. I really appreciate your input. Some information just can't be found on the net. Did some searching and found that this mag looks to be a Charles Daly 5 rounder. Found on MagShack. https://themagshack.com/shop/shotgun-magazines/410-gauge-magazines/charles-daly-ar-410-gauge-5-round-magazine/ They make a 10 and 15 rounder as well. Both out of stock at MagShack. I went to the Charles Daly website and ordered several 10 and 15 rounders.    |
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Can do! Been busy lately, maybe moving states, installing a trailer brake controller in my old pickup, fun like that. Completely forgot about this until I saw your reply. My mags fit in a standard magwell just like a normal AR mag. I've never pulled them apart. I did measure the barrel, it's 14". Cheese grater quad rail makes me wonder if I can stuff a normal handguard on there. The muzzle device is a special thread, appears to be M16x1.00. I don't have a metric thread checker since I can't turn metric threads on my lathe I never bothered to get one. |
 Your mag looks similar to mine internally. Probably an upgrade. My mags have zero markings. Not even a caliber. It runs the 50mm stuff fine and the larger stuff. Also ran great with a binary trigger last I ran it years ago. It's got a bar for an ejector so I don't think a super safety will work. The only markings on the entire thing is "TS 870 NBD 36/65" on the barrel. I'm tempted to chop it down a bit more, thread it 5/8-24. |
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Originally Posted By Namsag: I hate a mag that allows the follower to tilt at any time. I think its a poor design if it does. The Unimag, designed by an ARFCOMer, is an AR mag that feeds half a dozen different cartridges and intentionally has a follower that tilts at different angles to feed different loads. Non-tilt followers are a relatively new innovation in the AR world, and benefit the AR feed cycle - I don't that applies to every cartridge and every gun. Mausers are renowned for their controlled round feed and have a tilting follower, for example. |
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Originally Posted By Deerhurst: Can do! Been busy lately, maybe moving states, installing a trailer brake controller in my old pickup, fun like that. Completely forgot about this until I saw your reply. My mags fit in a standard magwell just like a normal AR mag. I've never pulled them apart. I did measure the barrel, it's 14". Cheese grater quad rail makes me wonder if I can stuff a normal handguard on there. The muzzle device is a special thread, appears to be M16x1.00. I don't have a metric thread checker since I can't turn metric threads on my lathe I never bothered to get one. Yeah, life just keeps moving on. Wish I could stop the clock from time to time. You say you have ATI mags or think thats what they are. Ammo choice and fit is an issue talked about the most in these .410 bore AR's. I found the Federal Top Gun ammo fits nicely. A hair shorter than the mag interior. Since your mags seem to fit looser, like an AR15 mag, what ammo are you using? I ask because my mags fit in the magwell with no slop. Zero front to rear movement, no side to side either. If my mag was looser fitting, I would be concerned if those Federal rounds would fit in them. (smaller inside) Fill me in on what you shoot, your ammo used. I'm after any info I can get. I just ordered some chokes from information provided by Bear Creek Arsonal. The manufacturer of this upper. I think they gave me bad information. Doing research, what they said, their choke doesn't match up with that manufacturers choke dimensions. I probably ordered 3 chokes that are not going to work. Pisses me off that information needs to be extracted like pulling Wisdom teeth. I spoke with Briley Chokes today. They are the worlds largest choke manufacturer for all makes and models. I inquired about custom made rifled chokes for the 410. The gal on the other end didn't have a clue. Couldn't talk to a machinist, against the rules. I asked about 410 chokes they make, for any manufacturer and that was a waste if time. It was a 15 minute call that netted exactly no usable information. Frustating! |
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See if you can cross reference the thread. Might be the same as a Saiga 410 and might be able to use chokes for that. Mine has fed and eaten every round I've physically been able to fit in the mag. It doesn't do the real long stuff since it doesn't fit in the mag. I have not shot it much due to the "can I put it on a SBR lower" debate. |
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Originally Posted By Deerhurst: See if you can cross reference the thread. Might be the same as a Saiga 410 and might be able to use chokes for that. Mine has fed and eaten every round I've physically been able to fit in the mag. It doesn't do the real long stuff since it doesn't fit in the mag. I have not shot it much due to the "can I put it on a SBR lower" debate. The Saiga .410 choke is an external choke. Threads are 15mm x .75 pitch external. I want to keep it internal. I have finally identified the choke system for this upper. It is a Browning standard Invector choke. I've seen it labled as Winchoke/Invector/Mosberg style. Also as Winchester/Browning/Invector choke. Even Invector Long! It's 1.880 long, .490 diameter, with 32 standard threads per inch. I think it could use a couple more names as it's not confusing enough yet! I had ordered three chokes for it. I ordered the wrong style. Almost $200 for the three. That price may drop with the correct style. I see it's a bit lower cost. |
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Originally Posted By Namsag: The Saiga .410 choke is an external choke. Threads are 15mm x .75 pitch external. I want to keep it internal. I have finally identified the choke system for this upper. It is a Browning standard Invector choke. I've seen it labled as Winchoke/Invector/Mosberg style. Also as Winchester/Browning/Invector choke. Even Invector Long! It's 1.880 long, .490 diameter, with 32 standard threads per inch. I think it could use a couple more names as it's not confusing enough yet! I had ordered three chokes for it. I ordered the wrong style. Almost $200 for the three. That price may drop with the correct style. I see it's a bit lower cost. I love my Saiga 410. My upper is externally threaded. Assumed yours was as well. |
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Originally Posted By Deerhurst: The only markings on the entire thing is "TS 870 NBD 36/65" on the barrel. I'm tempted to chop it down a bit more, thread it 5/8-24. Is the barrel thick enough to thread 11/16-24? That's what we did with my .410 SBS and suppressor. |
Browning had the 410 Invector tubes for some time then someone (Carlson?) named a slightly different tube used in the Stevens 301 as “Short Invector” which has caused all sorts of confusion. That “short” tube is not only shorter than the true Invector tube it also has a different thread specification and is no way interchangeable.
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Steve Rose - RAS
"Let your gun therefore be the constant companion of your walks"
Thomas Jefferson - 1785
"Let your gun therefore be the constant companion of your walks"
Thomas Jefferson - 1785
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Originally Posted By VaFish: Is the barrel thick enough to thread 11/16-24? That's what we did with my .410 SBS and suppressor. The barrel on this BCA upper is .625 at the muzzle. (20 inches) Thats 5/8 and 1/16 less in diameter than 11/16. I have not removed the handguard yet. The barrel is larger closer to the chamber. Guess I'll have to see what I got. What adapter and suppressor are you using? |
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Originally Posted By GunCat: Browning had the 410 Invector tubes for some time then someone (Carlson?) named a slightly different tube used in the Stevens 301 as “Short Invector” which has caused all sorts of confusion. That “short” tube is not only shorter than the true Invector tube it also has a different thread specification and is no way interchangeable. https://www.ar15.com/media/mediaFiles/31644/410-3818297.jpg Yeah, I was one of the confused. I ordered three Carlson tubes off Amazon. All three were the so called Short Invector. They should name it the Stevens 301 as that is the only gun I'm aware of them fitting! Ordered from the same vendor but three different companies sent tubes. Carlson, Midwest, and another. Will get sent back. Hope I can do it on one return!!! Now to order three more of the correct style. Not sure Amazon had them. Ther's always Briley and Carlsons I guess. |
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Originally Posted By Namsag: The barrel on this BCA upper is .625 at the muzzle. (20 inches) Thats 5/8 and 1/16 less in diameter than 11/16. I have not removed the handguard yet. The barrel is larger closer to the chamber. Guess I'll have to see what I got. What adapter and suppressor are you using? 5/8-24 would work. My upper has ~5/8 diameter threads. |
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Originally Posted By Namsag: The barrel on this BCA upper is .625 at the muzzle. (20 inches) Thats 5/8 and 1/16 less in diameter than 11/16. I have not removed the handguard yet. The barrel is larger closer to the chamber. Guess I'll have to see what I got. What adapter and suppressor are you using? I had Rex Silentium custom make a .410 suppressor. The suppressor itself has HUB threads on it, so it can use any normal HUB adapter, had the barrel externally threaded 11/16-24. Outside of my threads measure 0.69" so you need at least that thick and then probably some for a shoulder (my barrel is 0.86" where I cut it). You might be able to use a metric thread like M15-1. But it looks like HUB to 5/8-24 adapters are pretty common. The Rex suppressor is from their custom MGx line, it's a 12 baffle can. I can tell you how to order it if you are interested. Some master dealers like Hansohn Brothers offer a 30% discount and Rex will honor that on custom orders. Cool thing about it, it's based on their .358 rifle suppressor in reverse and has HUB threads on each end, so I can unscrew the end cap, turn it around and use it on .358 rifles as well. Works very well and on a 12" barrel single shot most of the ammo listed under 1,200 fps is sub sonic and really quiet. Remington has some #9 Low Decibel .410 ammo. Sounds like you are throwing a handful of rocks into some bushes. |
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Originally Posted By VaFish: I had Rex Silentium custom make a .410 suppressor. The suppressor itself has HUB threads on it, so it can use any normal HUB adapter, had the barrel externally threaded 11/16-24. Outside of my threads measure 0.69" so you need at least that thick and then probably some for a shoulder (my barrel is 0.86" where I cut it). You might be able to use a metric thread like M15-1. But it looks like HUB to 5/8-24 adapters are pretty common. The Rex suppressor is from their custom MGx line, it's a 12 baffle can. I can tell you how to order it if you are interested. Some master dealers like Hansohn Brothers offer a 30% discount and Rex will honor that on custom orders. Cool thing about it, it's based on their .358 rifle suppressor in reverse and has HUB threads on each end, so I can unscrew the end cap, turn it around and use it on .358 rifles as well. Works very well and on a 12" barrel single shot most of the ammo listed under 1,200 fps is sub sonic and really quiet. Remington has some #9 Low Decibel .410 ammo. Sounds like you are throwing a handful of rocks into some bushes. That would be great! My original plan was not to suppress. You might have changed that thought process! I removed the handguard and measured the barrel diameter's. .750 at the gas block. .700 out to the 11" mark. Will be easy to thread the barrel for a hub adapter. 5/8 hub adapter will work just fine. Original plan was for a 10" barrel. Think I'm going to stick to that. I want to keep it short. How long is that Rex Silentium suppressor? |
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Originally Posted By Namsag: That would be great! My original plan was not to suppress. You might have changed that thought process! I removed the handguard and measured the barrel diameter's. .750 at the gas block. .700 out to the 11" mark. Will be easy to thread the barrel for a hub adapter. 5/8 hub adapter will work just fine. Original plan was for a 10" barrel. Think I'm going to stick to that. I want to keep it short. How long is that Rex Silentium suppressor? Originally Posted By Namsag: Originally Posted By VaFish: I had Rex Silentium custom make a .410 suppressor. The suppressor itself has HUB threads on it, so it can use any normal HUB adapter, had the barrel externally threaded 11/16-24. Outside of my threads measure 0.69" so you need at least that thick and then probably some for a shoulder (my barrel is 0.86" where I cut it). You might be able to use a metric thread like M15-1. But it looks like HUB to 5/8-24 adapters are pretty common. The Rex suppressor is from their custom MGx line, it's a 12 baffle can. I can tell you how to order it if you are interested. Some master dealers like Hansohn Brothers offer a 30% discount and Rex will honor that on custom orders. Cool thing about it, it's based on their .358 rifle suppressor in reverse and has HUB threads on each end, so I can unscrew the end cap, turn it around and use it on .358 rifles as well. Works very well and on a 12" barrel single shot most of the ammo listed under 1,200 fps is sub sonic and really quiet. Remington has some #9 Low Decibel .410 ammo. Sounds like you are throwing a handful of rocks into some bushes. That would be great! My original plan was not to suppress. You might have changed that thought process! I removed the handguard and measured the barrel diameter's. .750 at the gas block. .700 out to the 11" mark. Will be easy to thread the barrel for a hub adapter. 5/8 hub adapter will work just fine. Original plan was for a 10" barrel. Think I'm going to stick to that. I want to keep it short. How long is that Rex Silentium suppressor? It's 9 7/8" long by my tape measure. But the MGx Custom suppressor can be any size from 3 to 12 baffles. Each baffle adds 0.625" 10 baffles would take you down to 8.625" length. I went with the full 12 baffles for maximum quiet. It balances really well on a 12" barrel H&R Topper. |
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Finally got around to pulling the very nice handguard to get at the gas block. Pulled the standard AR style gas block, .750 diameter, and found a somewhat unusual gas port arrangment. Four ports sitting in a ball milled grove. 4.5 inches from the bolt face. Good distance for going forward with the shortening of this barrel. The diameter of the four holes is .042. that works for the 20" barrel I'm starting with. Leaves good room for opening at least two of them to a larger diameter if more gas is needed for a 10" barrel. The .410 hits the pretty much standard pressure peak of about 12,500 psi but has substantially less volume. Almost guarentees opening the ports to capture more gas. There were several very small pieces of metal shavings in the port area. Not enough to cause a problem but a reminder to clean your gun before the first firing. This is not an area you would consider opening to clean but glad I did. I also purchassed three choke tubes for this upper. Suppossed to be Browning/Winchester Standard Invector. They screwed in about 2.5 turns and started to get tight. I could force it further so I believe it's just slightly undersize. The tubes all checked to meet the Standard Invector choke tube dimensions. More grief to deal with I guess. Will send it off to Rose Action Sports to get the threads chassed with the barrel at the full length. I want to get it to run reliably. Also to accept the new chokes purchassed that don't fit. I need to use the Imp Cylinder tube to run slugs. The upper came with a full choke which can't be used except with shot. Some of the issues may be created because I'm piece mealing this together. Not a proven package deal. I'm going towards running a drop-in trigger with FRT so I purchassed a F3 5.1oz buffer from Tromix. High satisfaction rating for FRT systems.  
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Originally Posted By backbencher: Ah. The holes are so small to prevent shot from getting stuck. If you widen em, there will be a bottom limit on the smallest size shot you can use. The size of the holes and location determine the amount of gas needed to function the action of a semi auto rifle or shotgun. In a shotgun, the shot remains in the wad/cup until it exits the barrel. No shot ever touches the gas ports. Thats true for all types of shotgun shells including slugs. I have short barreled shotguns with .120 gas ports. I'll figure the total volume of those 4 ports and increase it (by a percentage) to increase gas flow as necessary to run the short barreled action. In a rifle the projectile will pass over the gas port. (Usually a single port) |
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