16" vs 20" HB's

[survivalshop]

What if after you have the same break on both barrels, you just swap the upper, using the same lower for testing?  That would rule out some differences?  Would the 16" upper cycle well with the full rifle buffer?

Should have no problem cycling a std rifle buffer system .

The whole thing is I have to make this 16" barreled rifle shoot as well as the 20" . Might be impossible , because the barrels are different , but I believe this 16" should keep groups near as well as the 20 " @ 100 yards. I need to try to make it that way in order to compare the two at longer ranges . 

The purpose of changing the receivers is , that would make both rifles having a DPMS lowers & a STD DPMS uppers with the same older rail height ( the Tactical Machining may be of better Quality )  

 

Who knows , the rifle may shoot worse , hard to say until I try it .May not be the Receivers & just the barrel is not capable of the other 20 " , No two shoot alike . Could be something I'm doing , or not doing .

 

Hell ,if all these changes do one thing & let the rifle function with PMags & normal steel mags, I would be a happy camper.

 

I did notice one thing & it may have effected some of my shots with the 16" & that was my mag was some times hitting the table , I had to raise the rest & position of the rear bag to keep it off the table .

 

May also put some type of fixed rifle stock on , just for testing .

 

As you can see by the targets , I shot the 16" more , to give her another chance & then another . I actually think this rifle shot more consistently before I did the bedding job on the receivers.

Edited February 5, 2014 by survivalshop

[98Z5V]

 Btw, why did you go rifle length on the 16"?  Does it soften the recoil that much?  No cycling problems with such little dwell time?

 

There's so much power in the size of the .308 Win cartridge - running rifle gas on a 16" barrel on a .308 AR isn't going to affect cycling one bit, provided it's a quality barrel from a manufacturer that knows what to build.  You could probably take the barrel shorter than that, with rifle gas, and it would run.

 

EDIT - Some things are shocking...  check this out.  Read this article:

http://www.thefirearmblog.com/blog/2011/08/13/ar-15-hacksaw-pug-15/

 

When this all went down, there were SO many people giving this guy $hit, saying it wouldn't run, etc.  It ran.  Holy Sweet Jesus, it ran.  Here's the original thread:

http://www.ar15.com/forums/t_3_118/543391_Introducing_the_andamp_quot_PUGandamp_quot_.html

Edited February 5, 2014 by 98Z5V

[D.R.D.]

"The whole thing is I have to make this 16" barreled rifle shoot as well as the 20" . Might be impossible , because the barrels are different , but I believe this 16" should keep groups near as well as the 20 " @ 100 yards. "

 

I thought both barrels were Kreiger Criterian HB, by Fulton Armory, just different lengths, no?

[survivalshop]

"The whole thing is I have to make this 16" barreled rifle shoot as well as the 20" . Might be impossible , because the barrels are different , but I believe this 16" should keep groups near as well as the 20 " @ 100 yards. "

 

I thought both barrels were Kreiger Criterian HB, by Fulton Armory, just different lengths, no?

Yes ,both barrels from FA , just different lengths. If you look how the 20" is shooting , one would think the 16" would be close  Thats one reason I'm disassembling the rifle to see what if any thing is going on , just doesn't seem right to me . As said , could be just this barrel may not be up to par , as the 20" or the 20 " just came out a tac driver .

 

Could be the way the 20" is set up as a full rifle , but I believe as long as you have a good sight picture & proper trigger control , it shouldn't matter what stock you have on the rifle , being the same ammo & shooter is being used .

 

I'm almost out of Hornady match bullets & will be using SMK 's for the next testing & will take the Chrono . because the loading with IMR 4064 has not been tested yet.

 

I still think this barrel/rifle shot better before the bedding job I did . The fitment between the upper & lower were so loose , I had to try some thing , thinking it would help . Might have caused harmonic distortions when fired , who knows . 

 

This is actually fun to do this kind of testing , might learn something , also nice to have extra parts around to play with & after some measurements , the fun starts today. I can get to the range by Friday .

[D.R.D.]

I guess you'll never really know unless the builds were exact and you cut the 20" down to 16" to compare side to side.   Still looking forward to what you find.

 

Cheers,

DRD

[survivalshop]

 I noticed I did do one thing that JP VTAC hand guard instructions read & that was not to install the first adaptor for the barrel nut flush against the upper receiver . Instructions read that you may be tempted to do this for looks , but there testing reviled that accuracy suffered during long firing sessions , so I ignored it because the adaptor fit flush with the SI Defense billet upper with a little snugging . 

 

 May be why it won't group & maybe not , but I just set up the TM upper with the adaptor & a drop of RED loc tite to set up over night ( per instructions , which I didn't have to look up because I have several of these hand guards )

 

 I'm using the new NIB BCG I have from Shadow OPs Weaponry & checked head space with a " GO " gage & its pretty tight as I have read about with others checking them .

 

 Inspected all components & other than how I installed the hand guard , nothing out of the ordinary , that I can find . Since the barrel is off , I'm going to give a good cleaning .Photo's to follow .

[hdbiker1]

In your post #16, what brass are you using and how much 4064?  I'll be curious how much the groups will be affected by going with 42.5gr of 4064.

[unforgiven]

G&A had a great 2 part series on loads for gas guns,if you run across it.

[survivalshop]

In your post #16, what brass are you using and how much 4064?  I'll be curious how much the groups will be affected by going with 42.5gr of 4064.

  If you look at the second target , post # 24, the SMK's are loaded to 42.5 gr. of IMR 4064. I believe I'm using WC 846 with the Hornady 168 gr. match bullets ,LC once fired brass & a COL of 2.797". The SMK are about the same COL., but I will check my reloading log to make sure of the spec's .

 

  I'll be taking my Chrono with me Friday to the range , so I can see if any adj. need to be made .

 

  I will be only taking the 16" with me ,because the rifle will have so many new parts . I have a bunch of photo's I have to down load & I have some wear on the side of the receiver extension that was not there before I bedded the receivers.

 

  Here's a note for any of you that are getting a Tactical Machining 308 upper , mine came with a set of receiver pins & after trying to push the pins from this new complete DPMS lower through the upper , they will not go in , I can get the disassembly pin to go in ,but the Pivot pin would not go . I switched the pins to the ones that came with the TM upper , they slide right in .

Edited February 6, 2014 by survivalshop

[survivalshop]

I found some things after looking at components more closely that I do not think has anything to do with how accurate the rifle will shoot ,but raises some questions , to me any way .

 

After removing the receiver extension I noticed some increased wear on the inside of the extension , which has an increase from before the bedding of the receivers.

The deeper wear mark was there ,but not as pronounced as it is now & the wear mark at the beginning of the extension , was not there ?

 

The Bolt has some wear on it more than the last I remember ( I inspected after every range session )

There are no marks or wear on barrels locking lugs 

I will be using a new NIB BCG.

 

After measuring the gas port , took an almost precision fit of a 7/64 drill bit shank (barrel port size of 0.01095 " ) I took my normal way of measuring the port distance to the barrel flange stop for the gas block  , I noticed that the gas block , through measuring the same way, is covering the gas port closest to the barrel flange stop , is 0.025" . Of course the port hole in the gas block is a bit larger in diameter , but the gas block , even fitted flush to the barrels stop flange ( which is how I had it installed ) is still being partly covered by that 0.025", so I will relieve the flange side of the port in the gas block a little to make sure there is no covering of the gas port n the barrel.

Measuring the GB port to GB face.

 

This is a great tool for removing ejectors from 5.56 or 308 Bolts 

I remove the Ejector to Head Space 

 

 

I have a idea of why the odd wear patterns , but want to do some more research on it .

 

I swapped the FCG (Geissele )to the new DPMS  complete lower & kept all other factory parts , except for the Receiver Pins ,as mentioned before with the ones that came with the TM Upper receiver.

 

 

 

 

 

 

 

 

[hdbiker1]

Can't make out the wear on the bolt.  Is it on the sides of the lugs or the locking portion (where it mates with the barrel extension).  I'd expect on both, but more uniform on the locking than the sides.  Also, on the receiver extension, is the wear on the top or bottom?  If the top, I suspect raising the rear of the upper had something to do with that.  My thinking is maybe one of those tension take down pins would work better than bedding the receivers.  But I really don't know for sure.

[survivalshop]

Had two small glitches today while assembling the rifle , 

# 1 - Red Loc tite didn't set up  for the VTAC hand guard ? Cleaned it all off this morning & used Blue  Loc tite & that stuff set up very well & have the complete upper assembled with new Tactical Machining upper .

 

NOTE ; Tactical Machining Uppers are the new DPMS low rail profile  !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

# 2 .- The Geissele G2S trigger I replaced the STD DPMS with , has the Hammer wedging the BCG & won't let the BCG cycle , I checked the buffer , retaining pin & extension  & all worked fine . I removed the Geissele Hammer & BCG cycles fine . I've been down this road before & had to remove material from the top of the Disconnector to give the Hammer some room to move , on std trigger groups  . I Emailed Geissele on what they want me to do . Damn thing worked in the CMMG lower.  Go Figure  !!!!!!!!!!!!!!!!!!!!!!!!!

 

I also changed out the VLTOR Flash Suppressor to a Smith's Enterprise , Good Iron ,Muzzle Brake .

[survivalshop]

Can't make out the wear on the bolt.  Is it on the sides of the lugs or the locking portion (where it mates with the barrel extension).  I'd expect on both, but more uniform on the locking than the sides.  Also, on the receiver extension, is the wear on the top or bottom?  If the top, I suspect raising the rear of the upper had something to do with that.  My thinking is maybe one of those tension take down pins would work better than bedding the receivers.  But I really don't know for sure.

Wear is on the side , left side . If you were looking into the extension from the open end , the wear is from the 3 o'clock to 5 ;30 position .

 

I know you get break in marks on the bolt lugs ,but these are a little deep , like its too soft of metallurgy . This rifle has not had many rounds through it , in the hundreds ,but way under 1K. Its a DPMS BCG.

[hdbiker1]

Sounds like you might have more than one issue.  I just don't know if it's related to the upper or lower.  Trial and error comes to mind.  Swap out uppers and lowers and see what happens.  Good luck.  I'm currently working on two uppers for a MaTen, one in 308 and the other in 260.  Accuracy is not consistent.  I'm hoping it's just a load thing.

[survivalshop]

I had a complete DPMS lower assembly & new  Tactical machining upper & new NIB BCG. I was going to use for another 308 build ,but built a new rifle around the 16" HB . Once I get the Geissele hammer to not inter fear with the Bolt Carriers travel , its a done deal , all together & just waiting to get to the range tomorrow . Have to break in a new rifle ,except for the barrel.

[survivalshop]

Changed FCG to the Spike's Enhanced one that came out of this rifle , now back in another brand lower & it functions just fine , so maybe some range time today if the rain holds off . I have to use the Chronograph today to test hand loads with 168 SMK's & 4064 .

 

If I didn't have to remove my hand guard to make room for my vice blocks to remove the muzzle device , it would be this dirty . I had to clean it to check my muzzle crown.My Smith's Enterprises brake will not need hand guard removal to remove it .

 

If I would have checked ( my bag , I know better ), I would not have bought the Tactical Machining 308 upper because of the rail height , but after putting the scope on , the sight picture is pretty good , I think better than the higher original rail height of the SI Defense upper.

I could order the 1/4 " rail from JP , but I'm not going pay that kind of $$$ for looks .

Edited February 7, 2014 by survivalshop

[survivalshop]

Have not had a reply from Geissele yet & do not want to compare this rife to what was shot before because the Trigger (FCG ) makes a big difference & even trying to get a comparison with the STD AR trigger, is not a good one . The Spike's NIB coated Enhanced trigger is an improvement over the std AR trigger ,but not to the Geissele.

 

It rained all night , big time & the Range is a swamp , normal for Florida,I should be used to it .

Edited February 9, 2014 by survivalshop

[survivalshop]

Reply from Geissele.

 

 

 

 

ames Clark (Geissele Automatics)

Feb 07 02:28 PM

Good Afternoon Michael,

Thank you for your interest in our products. I am sorry you are having problems with your G2S trigger.

We have found with the DPMS .308 rifle that there may be a need to modify our hammer in order to make it compatible. I have attached a file to show what modifications must be made to make it compatible. We recommend to have a qualified gunsmith make the required modifications. I hope this helps.

Please let us know if we can be of further assistance.

Attachment(s)

 

 

I will take care of it tonight . They want material removed from the back of the Hammer , About 0.015 " at an 20 deg. angle. To make it compatible with a DPMS

No Problem , I will hit the range on Sunday.

The drawing they sent me, made a big deal about copy rights . 

Edited February 7, 2014 by survivalshop

[survivalshop]

The Geissele FCG is working great now , but I had to remove more than 0.015" that was on the drawing I was supplied . Took a bunch fitments to get it . I first started with stones & after taking my other 308 out to measure the max. movement of the hammer on that rifle . I came up with a figure , I measured the max travel of the hammer with the depth feature of my digital caliper , since this SSA trigger is in another DPMS lower .

 

 I pushed the Hammer (SSA )as far down as it would go & took the measurement , it was 0.265 " above the top shelf of the lower receiver , then measured the other Hammer (G2S ) & came up with 0.380",( this was after a couple of hand stoning sessions ) Thats a big difference & I can see why it impedes the travel of the BCG . I tried to stone & that was too slow on this hard material , so the side of the fine grinding wheel was put to good use .I could get a nice flush platform to remove a little material at a time .

 

 Took two fitments after that & my final measurement of the max Hammer height was 0.268 " & its a beautiful thing , I feel no more resistance pulling the charging handle back than the other rifle .Far better than stopping about 3/4 of the way .

 

 Its raining again out there , so no Range today , I planed on tomorrow any way . 

 

What fun !

[blue109]

Good to know about the issue. Hadn't heard that before and I've been looking at those triggers.

[survivalshop]

  Range time today & after trying three different bullets & two different powders , the new 16" ran with out a malfunction & shot a lot better than the old 16" and get this , are you ready , all testing was done using PMAG's , yes no malfunctions at all . 

 This is a first for this 16" barrel . It took swapping out the Upper & lower receivers , BCG , Buffer /spring ,receiver extension . Same hand guard ( I installed it to JP's directions ) Barrel & Stock . I will replace the A2 pistol grip with the Tango Down one that was on the other rifle , I guess I have a new rifle , the ser.# changed  <dontknow>

 

  I will post photo's after I get around to down load them. The muzzle brake worked real well & the DPMS std. 308  Carbine Buffer / spring worked great also .The brass dropped in a pile next to the bench @ about  3 o'clock /3:30, so its a beautiful thing.

 

  I shot some Barnes Bullets & SMK's , the 150 TTSX barnes bullets shot pretty good, I had 44 gr. of WC 846 loaded in those , but not the Tac/Le 168's , they opened up a bit , the SMK"s, well they do what they do & mostly shot real good , just some fliers on my part . The barrel was cleaned with Copper bore solvent so may take some more shooting to season it & I forgot my Chronograph , so I have to load some more SMK's with 4064 to get some readings. 

 

  The IMR 4064 @ 42.5 hrs. shot pretty good , I have my load for WC 846 down pat , so will have to play around with the IMR , all brass looked OK. I seated the 168 Barnes Tac/LE bullets to Barnes Manual COL & I don't have many left , so I probably will not play with them , I'm getting much better results with SMK & Hornady's.

 

  The rifle even feels lighter , wish I would have weighted it before I rebuilt her. The Billet CMMG & SI Defense upper with that rail on the side , are pretty hefty .

[D.R.D.]

Awesome - congrats on the improvements!

So, can you now list the specs for what the rifle in currently made of?

[survivalshop]

Sure. 

 

-DPMS Complete Carbine Lower assembly( its not stamped as a receiver only )

-Tactical Machining Forged upper receiver( I believe it is forged ) Had to use there receiver pins , that came with the upper ,DPMS pins would not fit .

-Fulton Armory , Krieger Criterion , 16" HB w/ rifle length gas system 

-Shadow Ops Weaponry ,308, NIB BCG

-JP VTAC 12" FF hand guard 

- Geissele, G2S fire control group

-Magpul CTR Carbine stock

-Tango Down , pistol grip ( I will put it on tonight) Its sporting & was tested with a std A2

-Smith Enterprises ,Good iron 308  muzzle brake 

-Nikon , Buckmaster , 6x18x40 scope w/Burris extreem tactical rings

- std 308 charging handle ( I have to order a Tac-1 or Rob will tongue lash me ) & its a bitch to get at it  now.

-some one's low profile , clamp on gas block ?

 

I think that's it .

 

 

[D.R.D.]

Nice.  Any idea if one would run into a similar problem with the G2S trigger using a SI-Defense or DPMS upper?

[survivalshop]

Nice.  Any idea if one would run into a similar problem with the G2S trigger using a SI-Defense or DPMS upper?

Geissele said it pertained to DPMS lower's , but I can see there could be an Tolerance Stacking issue when you use two different manufacturers Receivers (upper /lower's) That is probably what has been going on with this rifle the whole time . The early CMMG was designed when a PMag for it was not around , so probably only DPMS mags were used for development & I don't blame CMMG ,because the rifle functioned fine with any steel mag.

If you have a fitment problem , its an easy fix & you could always send it to Geissele to have them fit it correctly & just for the price to ship it to them .

 

I personally will never mix uppers & lowers again , I've talked about this before . I had more than one issue with this combo & I got tired of playing with it , I want a functioning system & the CMMG/SI Defense combo just didn't work out & I don't blame ether of them , I blame me ! I wanted a Billet upper for this 308 billet CMMG lower & at the time there were few to none available . This was before the great wind bag King was around.