The Original CZ Forum
CZ LONG ARMS => CZ BREN => Topic started by: BisonWorld on December 10, 2015, 12:42:48 PM
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The start of something beautiful
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsaiuggoax.jpg)
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsfhykwibx.jpg)
And now to turn that old barrel stub into a barrel extension :)
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zps5yqo8mhz.jpg)
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpslsdq28uw.jpg)
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Place holder for more to come
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A BREN in 6.5 Grendel...be still, my beating heart.... :o 8) ;D
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Any updates/pics?
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I've gotten slightly distracted with Christmas vacation and beginning an extended rail system. I'll probably be taking a personal day off sometime soon to finish the barrel.
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Awesome. 8)
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sooooo. long overdo for an update, finally got around to taking a personal day and working on this.
so first, to open up the bolt face.
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsh4tkop3q.jpg)
that's better
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsdjgyqbs7.jpg)
the 27 inch barrel blank seemed excessive so cut it down to 18.5 inches. I will finish the barrel at 18 inches. the excess barrel will make good stock for muzzle brakes or maybe just a big paper weight
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpszzso15cx.jpg)
cutting the shank
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpse1mqxezs.jpg)
threaded shank and installed barrel extension
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpszy4cnges.jpg)
chambered using a PTG 6.5 grendel II (parallel throat) reamer.
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsrzn0b4tf.jpg)
and that is about all I got done today, spent way too much time messing with my other side project. something about too many eggs and not enough baskets or what not. ;D
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsqop7boux.jpg)
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Awesome, please keep us updated! Looking great!
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That looks great! I wouldn't mind one in 300 Black out ;)
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alright, it is long overdue for me to finish this project up, so here we go
used a center drill to cut a cone for the live center to ride in while contouring
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsbmntgu6y.jpg)
man that is a fat barrel blank, here it is after the first pass
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsrycsirwa.jpg)
I generally take off .050 a pass on this lathe while contouring making sure to constantly spray on more cutting/cooling fluid mixture through out. the barrel stays cool to the touch throughout the process. here is the barrel after 6 passes
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpso8b4vcqn.jpg)
you may have noticed that little disk left over against the chuck, I'll get to that in a second. I've also added in a relief cut next to this disk
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpscfowxso7.jpg)
the rest of the barrel has been taken down to .775 diameter at this point save for the larger area you see here, this is where the barrel sleeve/trunion will be pressed on. I will use a different cutting tool and be a little more precise cutting this area as it's diameter is a very critical dimension
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsefjlt2ev.jpg)
I take a brake from contouring the rest of the barrel now and cut the critical dimension mentioned in the last picture. after this I will decrease the amount of barrel sticking out from the chuck because, as the barrel gets thinner, it and my cutting set up become less ridged, which would causing increased tool chatter and less cutting accuracy while contouring the rest of the barrel if I left it be. decreasing the amount of barrel sticking out helps to replace the rigidity lost from the barrel thickness decreasing. unfortunately, I forgot to take a picture when finishing the contouring on the front portion of the barrel.(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsxevda94s.jpg)
here is a picture of the contouring from where the gas block will sit, this is also a very critical dimension.
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpslvbu27dv.jpg)
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the barrel is now contoured, but there is still much to do
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsr4pczw8o.jpg)
remember that little disk from earlier, well allow me to explain, on a regular bren barrel, the barrel and area with the locking lugs is all one piece, it is not threaded on, because of this, on a factory barrel no shoulder is needed for the locking lugs area (what I will call the barrel extension) to index on and thread up against. So on mine (given that I used a barrel extension that I made from an old bren barrel and this would neeed to be threaded on) I had to make a shoulder, but as the barrel sleeve/trunion butts right up against the extension and the barrel tenon diamter is larger than the diameter under the trunion, no shoulder would normally be available, so I cutt the barrel sleeve/trunion back .060 and left a shoulder built into the barrel itself.
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zps4q64vwrg.jpg)
picture of the cut barrel sleeve
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zps4s2gkmag.jpg)
the factory barrel is quite thin and so of course, so is the internal diameter of the gas block, so I opened it up. the portion of my barrel infront of the gas block is .700 and the diameter of the barrel under the gas block is .715. at this point the walls of the gas block will become very thin, I'm going to try a .725 profile barrel on my next one, but that may be iffy.
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsw5entkz4.jpg)
now that the barrel is contoured and the barrel sleeve and gas block are both ready to go on, let's first take care of the dangerous end of the barrel, I cut a 5/8 X 24 tenon for a muzzle break a friend gave me awhile back, I think it's made my ptg. All I know for sure is that it has about the shortest tenon I have ever seen on a 5/8 X 24 brake, with a max tenon length of only like .370. So I cut the tenon at .360 and hope it indexes close once threaded, luckily it did and I only needed to remove .002 extra to get it on in the correct orientation.
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsnjqzjb1x.jpg)
alright, after finishing that and crowning the barrel, it was time to assemble. putting on the gas block and barrel sleeve requires a 20 ton press and a good eye. I think it came out well and the alignment is just about perfect, (there is about a degree or two flexibility on line up for it to still function fine, this one was bleep close to right on the money)
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zps5jcdzb6d.jpg)
and we are assembled and ready to go, getting gas port sizes worked up for the load I will be shooting will take a little while as I do load development and settle on what I want, but other than that it is good to go.(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpstyluwv9l.jpg)
So of course I through it in my gun and test fired just to double check my work, and good news, nothing blew up this time :D
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/593e1946-a169-4b1d-a94e-7638c1981715_zps2biegnob.jpg)
and that is all that I have for you guys today, hope you have enjoyed so far, as more projects develop or modifications are made I will continue to post them in this thread. Still a few more barrel and configurations I want to try with this gun and it has been quite a bit of fun. If I can remember I will also post my single stage trigger modification which takes the factory bren trigger down to around 2-2.5 lbs without changing any spring weights.
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsbpoufnvq.jpg)
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BisonWorld -- you are talented. About the extent of my knowledge is "field-stripping" !!!!!
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Jealous doesn't BEGIN to cover it! 8) 8) 8) That is VERY cool work, sir - gonna get the barrel coated the same color as the rifle?
Some shooting video with a regular BREN for contrast would be awesome!
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I'll finishing up the polish work on they front section of the barrel (I had just begun which is why it looks a bit smudged in the photo) then will hopefully be sending it off to be dimpled, after that, I don't know, been thinking making this one a little colorful, we'll just have to wait and find out.
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Waitaminnit...
nothing blew up this time...
Whaddya mean, THIS time... :o 8)
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Waitaminnit...nothing blew up this time...
Whaddya mean, THIS time... :o 8)
well once upon a time, when I was just starting out, let's just say I learned a valuable life lesson
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsueuzlw32.jpg)
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsoaaw914t.jpg)
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Now there's a story...:)
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Waitaminnit...nothing blew up this time...
Whaddya mean, THIS time... :o 8)
well once upon a time, when I was just starting out, let's just say I learned a valuable life lesson
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsueuzlw32.jpg)
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpsoaaw914t.jpg)
I'm familiar with that rifle and that room, any lasting damage to your hand?
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On another forum people are grousing about 6.5mm Grendel...and after a few pages of grousing, it's actually more about the AR platform with the Grendel rather than the round itself. :) Makes me wanna grab that rifle and show it off. :D
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well if you ever make it out to Kansas City, you are more than welcome to shoot it. started on gas system tuning today, so far so good, I have a few different brands of factory ammunition on order to do some reliability testing. will hopefully be taking it out for accuracy testing and do some load development sometime in the next couple weeks.
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Wish I could take you up on that one! :) Gonna get some video soon?
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The question has been asked elsewhere - any thing special you have to do with magazines to make the BREN 6.5 run right as a self loader?
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na, feeds just fine from any 6.5 grendel AR-15 mag I've tried so far. E-landers and ASC mags are what I've tried and they work great, I haven't tried any C-products mags, but I'm sure they would be fine as well. the magazine is held at about the same height on a bren as an AR, but the feed ramp is less steep and as both the bolt lugs and the barrel lugs are longer (as in total outside diameter and front to back) the jump into the chamber levels out more during the feeding process.
I'm not much of a film-o-grapher or whatever, but I may take a phone video when I take it out. not sure when that will be, but hopefully soon.
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This is the first of the new generation of pistol/carbines, and the first real carbine CZ-USA has ever imported for civilian use, not including the brief flirtation with the SA vz-58 via CzechpointUSA. It's pretty groundbreaking in that they bucked the system by getting something very non-PC approved during the depth of the current Administration for importation. It alos can lead to speculation as in, is CZ-UB going to move more into the semi-auto rifle field, and where could this go? I'm imaging a BREN 805 in 6.5 Grendel right now....so yeah, it's a little bigger than just another Skorpion. Like the video says - the only similarity is the name. Now if they'd just bring it in, in a REAL caliber, like 10mm..... :o 8)
just saw this old post,
seems like you have been waiting for a 6.5 grendel before I had even considered doing one.
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Ya think? ;) Don't have a single round of ammo, rifle r magazine, but yeah, I've been thinking this round is really the bees knees from what I know of it, and the BREN 805 really impresses the dog snot out of me. I handled the two LE carbines at SHOT 2015 and they fit like gloves.
Problem is, money and talent in gun smithing - I have neither. :'( I have a gun smith buddy in Mesa who is a wizard with bolt action rifles, but doesn't like semi-autos. Oh well. So, I live vicariously through your triumphs, and I don't mean the motorcycles. 8) ;D
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ready for accuracy testing tomorrow 8)
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/06cc31bc-8893-4515-9009-887c2e5b1de9_zpshbsohhr5.jpg)
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Sweet! 8)
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ready for accuracy testing tomorrow 8)
(http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/06cc31bc-8893-4515-9009-887c2e5b1de9_zpshbsohhr5.jpg)
Very cool. Needs a factory stock but, very cool.
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@BisonWorld - Are you able to weigh that bad boy for us?
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sure, with which stock? the factory bren stock or the XLR and KNS adapter? optic or not optic.
accuracy test got post-pone due to some bleepty cold weather, If it's nice this weekend I'll try to get out.
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You are too nice! I did not want to be an inconvenience if you had already zero'd the scope... If you have not zero'd yet and were willing it would be great to know the weight of the rifle w/o optic, mount, or magazine, and with the XLR+KNS stock setup.
Really neat muzzle brake by the way... Is that make or buy?
And... really impressive work on the barrel/trunion/gas block. Very well done sir.
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no problem,
muzzle brake is made by PTG I believe, I'll get you the weights without the optic sometime this week.
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It was low 70s today...just sayin'... 8) ;)
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and I shot a bunch of clays, 8) haha, the 805 isn't my only project going on, just probably my most enjoyable one. I'm going to try to make it out sometime over the long weekend.
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Outstanding, sir, outstanding. :)
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well things were pretty disappointing at the range, best 5 shot group was just a little under an inch at 100 yards, but everything else just got worse from there, some pretty significant diagonal stringing from high left to low right. so back to the drawing board to find out what went wrong and fix from there.
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Darn. :(
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eh !@## happens, here is the best group of the day, right under an inch (http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/c3abe7ab-2b32-4cd9-939c-2aa2576a298d_zpshhcgczj2.jpg)
and the worst, a little less than 3 inches :( (http://i1062.photobucket.com/albums/t494/BisonWorld/Mobile%20Uploads/image_zpssf4dmj1w.jpg)
i don't know why this picture only shows up upside down.
while this barrel was done on a cheap green mountain blank, I would expecta bit better than this, so I'll go and recheck everything (already eliminated the optic by trying a couple while I was out at the range.) shoot it with the muzzle brake off, borescope the barrel and make sure the crown wasn't damaged somehow, look at the throat to make sure it was cut square, etc.
it simply could be it doesn't like the factory hornady load or maybe just the bullet weight I'm shooting (though the diagonal stringing is a bit of a head scratcher). on my precision .223 barrel it absolutely hates my 75 gr hpbt load that shoots well in just about every gas gun I've ever done, but loves 53 gr v-max bullets. So I'll try some other bullets as well.
one thing I did notice was some pretty significant denting of the brass on loading, so I'll look into getting that fixed at a minimum.
not giving up on it just yet :)
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Both pictures show up here right side up. I'd be happy with 1-2 MOA with a military style semi auto rifle, but I'll bet you're gonna tinker this thing into being able to shoot National Match. :)
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The stringing, is it happening in ascending/descending order? If so, might suggest barrel heating up...
If not, it might have to do w/ barrel oscillations which often seems to be in a figure 8 pattern, albeit not exactly repeated from shot to shot... So furthest movement from center are fastest and nearest to center are slowest... Part of tuning barrel and cartridge together.
BW -- are you using the standard gas block or is yours diy? In 5.56 standard, the bren is advertised to have a "pencil" barrel. When you up caliber and if keeping same barrel diameter, that would suggest increased flex...
However, you blank looks thicker, so this may not be the issue, but thought I'd throw this out there.
Look forward to your continued updates on this build.
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barrel diameter is quite a bit thicker on mine as I open up the gas block. shot placement begins high left and drifts to low right while firing. firing was done about one round every 3-5 seconds, with 3 5-shot groups shot before letting the barrel cool. the barrel heating up is likely causing part of the issue as the largest group was also shot while the barrel was the hottest. there are a few things I'll be modifying
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Very interested in how this goes. 8)
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with the XLR stock without the optics and rings, the rifle weighs 9.4lbs. with the factory bren adjustable stock it is 8.6. probably a little less with the non-adjustable factory stock
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I doubt you're planning on humping this through the Outback, so weight probably isn't going to be a huge deal, but I do have to ask which stock you think you're going to "stick" with? Personally, I liked the factory folder I handled at SHOT 2015.
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with the XLR stock without the optics and rings, the rifle weighs 9.4lbs. with the factory bren adjustable stock it is 8.6. probably a little less with the non-adjustable factory stock
Right on! Thank you sir!
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I doubt you're planning on humping this through the Outback, so weight probably isn't going to be a huge deal, but I do have to ask which stock you think you're going to "stick" with? Personally, I liked the factory folder I handled at SHOT 2015.
not sure yet, haven't had enough time behind the xlr to tell if i like the additional rearward weight, It's a very high quality stock with a metric ton of adjustment though. ya, it is a little on the heavy side, but the barrel is also a pretty heavy profile, nearly a pound heavier than the factory barrel.
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Fluting the barrel next for more cooling area and rigidity?