11-03-2014, 00:02
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#1
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Asset
Join Date: Jun 2012
Location: South of the Mason Dixon, AKA: home
Posts: 47
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Piston driven SBR
I am currently in the planning stages of building a Piston SBR. My planned barrel length is going to be either a 10.5 or a 11.5 with a 9 inch BCM KMR rail. This rifle will be run primarily with a suppressor, and be used for police work (high risk warrants/ active shooter) with small buildings with tight corridors, and meth labs being common in my AO. For reference I have very little experience with piston systems as well as SBRs, I currently have a BCM EAG Carbine. It is my first and currently only AR, it has served my usage perfectly to this point and I consider it the standard to strive for when building this new rifle. Through reading I have heard repeatedly that DI rifles get less reliable the shorter the barrel and that a piston system will fix this as well as make running a suppressor much more comfortable, alleviating the "Getting spit in the face" issue.
My questions for the members here are:
What are your experiences with a piston system SBR (10.5 or 11.5 inch barrel)? Is there any noticeable differences between running one suppressed and un-suppressed?
I have only been able to find Adams Arms piston kits, places like PWS and LWRC don't appear to sale them anymore, rather they sale uppers or full rifles only. Do you know of any quality piston kits? If so do they have a low profile gas block that can fit over a BCM KMR rail?
Does anyone have an experience with Adams Arms piston kits? Good product? Bad?
The intended range for this rifle will be within 100 yards. How much accuracy loss if any have you noticed from barrels in the 10.5 to 11.5 inch range? What is considered average grouping size at 50 and 100 yards?
These are the questions I have been able to think of off the top of my head, I may come up with more later. Any advice ya'll can provide that would help me with getting this together would be much appreciated. Thanks for your time.
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therunningwolf is offline
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11-03-2014, 10:12
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#2
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Quiet Professional
Join Date: Jan 2004
Location: Free Pineland
Posts: 24,822
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Good question.
I have run SBRs at 10.5" and 11.5", with pistons and DI, with and without cans and they all ran fine, albeit much dirtier with the cans.
Have you called PWS and asked them if they can sell you an upper?
Does POF not sell uppers any more?
Best of luck.
TR
__________________
"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat." - President Theodore Roosevelt, 1910
De Oppresso Liber 01/20/2025
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The Reaper is offline
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11-03-2014, 11:03
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#3
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Guerrilla Chief
Join Date: Apr 2010
Location: Texas
Posts: 830
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Quote:
Originally Posted by The Reaper
Good question.
I have run SBRs at 10.5" and 11.5", with pistons and DI, with and without cans and they all ran fine, albeit much dirtier with the cans.
Have you called PWS and asked them if they can sell you an upper?
Does POF not sell uppers any more?
Best of luck.
TR
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I would also call PWS. I talked to them several times and they were always helpful. I have a 14.5" upper that runs flawlessly with and without a can. They do have a number of dealers so you may get your questions answered locally.
__________________
Oldrotorhead 
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Oldrotorhead is offline
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11-04-2014, 11:34
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#4
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Guerrilla
Join Date: Nov 2010
Location: CONUS
Posts: 403
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I would caution that you should do more research on what’s available if you have serious concerns about explosive environments. Most of my knowledge on the subject is open source, but a few thoughts come to mind. (Best Weapon, Cartridge and Suppressor combination for explosive environments today, would be an awesome study for someone to do. If it’s not out there now?)
I assume you are talking about 5.56? In this situation given your needs you might want to look at specific loads vs. barrel length to give you the most complete powder burn. I say this because the unburned powder can build up in the suppressor and actually cause more sparks and unexpected hot spots. This can be true for the chamber and ejection area as well with SBR’s. It would also apply to keeping your weapon and suppressor as clean as possible to help mitigate that threat.
Some of the older studies I have read for explosive environments were usage of 9mm MP5’s with AWC MK9 or Gemtech MK9K suppressors. At the time those were some of the best suppressors for those environments due to the volume, design and cartridge. Today I am sure there may be things out there that are much better. Unless there is some really interesting blast baffles that trap more now, I would think in theory a wipe and baffle design with high volume and limited shots would be the best answer as long as you had 100% powder burn.
As far as pistons go, I would be hesitant on bolt on/clamp on kits like Adams arms because ( I would fear) they could hammer themselves off if not properly mounted. I question how much a beating they can take. I think they make sense if you can pin them to the barrel like a regular site block. There is another company that has an add on that was even simpler (osprey?), although I cannot attest to its quality. I do know, that it uses the factory M4 pinned site block.
Other considerations would be what brands have been known to run well suppressed. The change in impulse sometimes requires a different setting on piston guns. If it’s a non-adjustable kit that may cause problems for you in basic reliability and tailoring it to custom powder loads.
Otherwise I would look at well known brands like LWRC. Often, LWRC uppers are available on Gunbroker and sites like that on a regular basis. Don’t hesitate to call any company you are wondering about first though. Often times LE/MIL sales are not always advertised. If you want to spend big money, you can always get an HK416 upper. ($2 -3-4k? for LE/MIL) Also, agree about the above posted brands.
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35NCO is offline
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11-04-2014, 12:47
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#5
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Guerrilla
Join Date: Apr 2008
Location: Fayetteville, NC
Posts: 280
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Quote:
Originally Posted by 35NCO
I would caution that you should do more research on what’s available if you have serious concerns about explosive environments. Most of my knowledge on the subject is open source, but a few thoughts come to mind. (Best Weapon, Cartridge and Suppressor combination for explosive environments today, would be an awesome study for someone to do. If it’s not out there now?)
I assume you are talking about 5.56? In this situation given your needs you might want to look at specific loads vs. barrel length to give you the most complete powder burn. I say this because the unburned powder can build up in the suppressor and actually cause more sparks and unexpected hot spots. This can be true for the chamber and ejection area as well with SBR’s. It would also apply to keeping your weapon and suppressor as clean as possible to help mitigate that threat.
Some of the older studies I have read for explosive environments were usage of 9mm MP5’s with AWC MK9 or Gemtech MK9K suppressors. At the time those were some of the best suppressors for those environments due to the volume, design and cartridge. Today I am sure there may be things out there that are much better. Unless there is some really interesting blast baffles that trap more now, I would think in theory a wipe and baffle design with high volume and limited shots would be the best answer as long as you had 100% powder burn.
As far as pistons go, I would be hesitant on bolt on/clamp on kits like Adams arms because ( I would fear) they could hammer themselves off if not properly mounted. I question how much a beating they can take. I think they make sense if you can pin them to the barrel like a regular site block. There is another company that has an add on that was even simpler (osprey?), although I cannot attest to its quality. I do know, that it uses the factory M4 pinned site block.
Other considerations would be what brands have been known to run well suppressed. The change in impulse sometimes requires a different setting on piston guns. If it’s a non-adjustable kit that may cause problems for you in basic reliability and tailoring it to custom powder loads.
Otherwise I would look at well known brands like LWRC. Often, LWRC uppers are available on Gunbroker and sites like that on a regular basis. Don’t hesitate to call any company you are wondering about first though. Often times LE/MIL sales are not always advertised. If you want to spend big money, you can always get an HK416 upper. ($2 -3-4k? for LE/MIL) Also, agree about the above posted brands.
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My best friend is the armorer at Osprey. I just got off the phone with him, he told me that Osprey has not offered a piston driven AR15 based rifle. When we spoke he was in the room with Grange, who also confirmed that Osprey has never built a piston operated rifle.
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69harley is offline
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11-04-2014, 13:24
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#6
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Asset
Join Date: Jun 2012
Location: South of the Mason Dixon, AKA: home
Posts: 47
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After doing some reading and from the info I have been getting from members here, I am starting to lean more toward a DI SBR with an adjustable gas block. I think this will solve most of the issues I want it to. My next few questions relate to ammunition choices in different environments and in relation to barrel lengths.
I have settled on a 11.5 inch barrel, my questions with it:
What have the members here found to be a good grain bullet while using a 11.5 inch barrel? Both suppressed and un-suppressed?
Are there currently any production ammo that will ensure 100% powder burn or are these reloads? This rifle will be chambered in 5.56.
If I am looking at reloads for effective use of a 11.5 inch suppressed 5.56 in an explosive environment does anyone have any loads that they have used to good effect they can recommend? Meaning any info I would need to produce them myself not the actual rounds.
Is there any members that has experience they wouldn't mind sharing (via pm if necessary) on working in explosive environments? (Meth labs, etc.)
So far the build I have in mind is as follows:
BCM 11.5 inch barrel
BCM upper and parts
BCM or Fail Zero BCG
BCM Ambi Charging handle
Syrac Ordnance adjustable gas block
Griffin Armament M4SD II comp.
Troy Irons with a CSAT aperture and Tritium Front sight post
Aimpoint T-1
DBAL I2
SureFire Fury
BCM KMR, still up in the air about if I want the 9 inch or 10 inch.
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therunningwolf is offline
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11-04-2014, 14:03
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#7
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Quiet Professional
Join Date: Jan 2004
Location: Free Pineland
Posts: 24,822
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You are going to be at indoor distances only for fragmentation effect from the 11.5" barrel with virtually any load.
There will be a large fireball without the can with almost all factory loads. You may be able to mitigate this effect somewhat by handloading, but I do not know of any commercially available 5.56 powder that will burn 100% in a 11.5." Very few canister powders have flash retardant applied. Surprisingly, several military loads do not have flash retardant either.
There are costs to going short.
Most makers do not guarantee function if you are building a Frankenrifle. I would look for a vendor that sells a complete rifle or upper.
I would not use this in an explosive environment without a can, and would do some testing before I tried it live.
Best of luck.
TR
__________________
"It is not the critic who counts; not the man who points out how the strong man stumbles, or where the doer of deeds could have done them better. The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood; who strives valiantly; who errs, who comes short again and again, because there is no effort without error and shortcoming; but who does actually strive to do the deeds; who knows great enthusiasms, the great devotions; who spends himself in a worthy cause; who at the best knows in the end the triumph of high achievement, and who at the worst, if he fails, at least fails while daring greatly, so that his place shall never be with those cold and timid souls who neither know victory nor defeat." - President Theodore Roosevelt, 1910
De Oppresso Liber 01/20/2025
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The Reaper is offline
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11-04-2014, 16:42
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#8
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Quiet Professional
Join Date: Mar 2012
Location: Occupied Northlandia
Posts: 1,697
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How about ditch the rifle and serve the warrants while they are out of the house. Then have EOD clear for booby traps and WHAMO! Problem solved, problem staying solved.
We are getting back to the Branch Davidian thought process again. Solve every problem with a 10" SBR and a can!
How about solving the problems with our brains?
To stay on topic though, I never had problems in "tight places" with my M4. 
__________________
"The rifle itself has no moral stature, since it has no will of its own. Naturally, it may be used by evil men for evil purposes, but there are more good men than evil, and while the latter cannot be persuaded to the path of righteousness by propaganda, they can certainly be corrected by good men with rifles." — Jeff Cooper
Last edited by miclo18d; 11-04-2014 at 16:47.
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miclo18d is offline
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11-04-2014, 16:56
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#9
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Guerrilla
Join Date: Nov 2010
Location: CONUS
Posts: 403
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Quote:
Originally Posted by 69harley
My best friend is the armorer at Osprey.....
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I think we are talking about different companies. I meant these guys below. Sorry I was going from memory, I should have been more specific. Its now "Osprey Defense".
http://www.ospreydefense.com/index-2.html
http://www.brownells.com/rifle-parts...prod31987.aspx
Like I said, I cannot attest to whatever quality the product is. I have handled it and it seemed to make sense to me on how it works. I just have never shot one.
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35NCO is offline
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11-04-2014, 18:14
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#10
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Area Commander
Join Date: Jan 2004
Location: Buckingham, Pa.
Posts: 1,746
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LMT makes a 12" SBR upper.
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rubberneck is offline
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11-04-2014, 19:40
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#11
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Quiet Professional
Join Date: Jun 2004
Location: Occupied Pineland
Posts: 4,701
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300BLK. It does just fine in SBR barrels with pistol length (DI) gas systems.
__________________
A nation can survive its fools, and even the ambitious. But it cannot survive treason from within. An enemy at the gates is less formidable, for he is known and carries his banner openly. But the traitor moves amongst those within the gate freely, his sly whispers rustling through all the alleys, heard in the very halls of government itself. For the traitor appears not a traitor; he speaks in accents familiar to his victims, and he wears their face and their arguments, he appeals to the baseness that lies deep in the hearts of all men. He rots the soul of a nation, he works secretly and unknown in the night to undermine the pillars of the city, he infects the body politic so that it can no longer resist. A murderer is less to fear.
~ Marcus Tullius Cicero (42B.C)
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Peregrino is offline
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11-05-2014, 07:38
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#12
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Quiet Professional
Join Date: Jun 2004
Location: Occupied Pineland
Posts: 4,701
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Quote:
Originally Posted by Brush Okie
How about 50 Beowulf and the other large caliber AR options? Just curious, my favorite CQB weapon is a 12 gauge pump, but that is just me.
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Novelties. Find someone who has one and will let you play with it. You will figure it out for yourself very quickly - especially if they make you purchase your own ammo.
__________________
A nation can survive its fools, and even the ambitious. But it cannot survive treason from within. An enemy at the gates is less formidable, for he is known and carries his banner openly. But the traitor moves amongst those within the gate freely, his sly whispers rustling through all the alleys, heard in the very halls of government itself. For the traitor appears not a traitor; he speaks in accents familiar to his victims, and he wears their face and their arguments, he appeals to the baseness that lies deep in the hearts of all men. He rots the soul of a nation, he works secretly and unknown in the night to undermine the pillars of the city, he infects the body politic so that it can no longer resist. A murderer is less to fear.
~ Marcus Tullius Cicero (42B.C)
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Peregrino is offline
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11-05-2014, 08:48
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#13
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Guerrilla
Join Date: Apr 2008
Location: Fayetteville, NC
Posts: 280
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Quote:
Originally Posted by 35NCO
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http://ospreyarmament.com
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69harley is offline
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11-06-2014, 07:11
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#14
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Guerrilla Chief
Join Date: Mar 2006
Location: Philadelphia
Posts: 704
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Quote:
Originally Posted by miclo18d
How about ditch the rifle and serve the warrants while they are out of the house.
We are getting back to the Branch Davidian thought process again. Solve every problem with a 10" SBR and a can!
How about solving the problems with our brains?
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Five-O is offline
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11-08-2014, 10:05
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#15
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Quiet Professional
Join Date: Oct 2007
Location: San Antonio, TX
Posts: 377
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Quote:
Originally Posted by miclo18d
How about ditch the rifle and serve the warrants while they are out of the house. Then have EOD clear for booby traps and WHAMO! Problem solved, problem staying solved.
We are getting back to the Branch Davidian thought process again. Solve every problem with a 10" SBR and a can!
How about solving the problems with our brains?
To stay on topic though, I never had problems in "tight places" with my M4. |
This is why we need a "LIKE" button for this forum...
Sorry, OP, but you have to realize that many of us feel that law enforcement is WAAAAAYYYYYY too quick to don the black jumpsuit, body armor and rifles.... I'm a law-and-order guy myself, but the militarization of police has gone way too far.
You are preparing for close-range firefights when you should be practicing conflict resolution...
Police departments with Hummvees? MRAPS? Automatic weapons?
And now, I am going to sit back and wait for multiple comments about how out of touch I am about the dangers modern law enforcement faces....
Maybe so, but the perception _I_ have is widely shared... so ask yourself - how did this become an "us-against-them" situation?
__________________
Ars Longa, vita brevis
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RichL025 is offline
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