Tubb CWS (carrier weight system) review

[JMoto]

also what buffer and spring you running?

Brass is ejecting at 2-3 o'clock, factory rifle buffer (dpms) chamber is smooth and spring is the tubb 308 spring

[imschur]

Im begining to wonder if you have an issue with your chamber.

I did a bit of googling and found a good thread at ar15.com. It's not all relevenant and it's about 5.56 BUT there's a lot of similarity to your problem. Alot to read but it's worth it.

[98Z5V]

Not relevant (really) to JMoto's situation here - I bought mine because my .308 kicked like a pissed off mule, but I still wasn't eating up brass.  I went this route to tame the recoil, and it has done that well.  I always looked at my brass after range sessions before, and it always was good enough to go right into the tumbler.  In a nutshell, it was good, so I didn't pay attention to what the CWS would do for me as far as brass goes...  <dontknow>

I really LOVE what it does for recoil.  Not just on the .308 AR, but also for the 5.56 16" recon-type gun.  Unreal, on that one, truly nuts...  :o

Now, for brass ejection, and the .308 AR - I noticed this one this weekend.  Big time.  Before, brass was launched 4 or 5 feet away, about 4 o'clock.  On the bench this weekend, on a small firing table - most of my brass was still on the table, right beside me.  I have nothing to show for this, no pics, no anything, and if the brass fell off the table, it bounced away.  I'll pay attention ot this in the future.  I'll remove the CWS and get a vid, then re-install the CWS and get another vid.  I was shocked to see brass sitting beside me, to say the least.  <thumbsup>

[survivalshop]

Although I don't have the weight system ,just the spring in my 16",308 carbine , the spring did change my ejection pattern also.

They all fall about a foot from my feet or bench, in a nice pile .

I plan on getting the spring for my 20" rifle stocked 308.

[survivalshop]

DPMS chambers are notorious for being rough & causing the same problems you are having with your brass.

Have you head spaced this rifles chamber ?

I see on the two samples of your fired brass , the one one the left seems to show early signs of cratering . Have you chrono'ed any of your hand loads ?

Also your round count is low & things may loosen up after more rounds , but I would still check head space & polish the chamber . It will hurt nothing if done correctly.

[JMoto]

DPMS chambers are notorious for being rough & causing the same problems you are having with your brass.

Have you head spaced this rifles chamber ?

I see on the two samples of your fired brass , the one one the left seems to show early signs of cratering . Have you chrono'ed any of your hand loads ?

Also your round count is low & things may loosen up after more rounds , but I would still check head space & polish the chamber . It will hurt nothing if done correctly.

The chamber on this one is very smooth, I cannot detect any roughness in it at all. No snags on a q-tip as is typical with rough machining and no irregularities visually. I actually pulled the barrel again to double check before posting.

The rifle has been headspaced (I do so on all new rifles)

I have not chrono'd the loads but If you are talking about the piece of brass on the left, it was the picture itself possibly a reflection. I check primers religiously on handloads and with every new lot of factory ammo.

I disagree on the round count though. This is not a problem that will "work itself" out.

[imschur]

Did you read the link I posted? I found the piece about measuring the case mouth interesting. I think it was the 2nd or 3rd page.

Also did you do the heavy duty extractor mod?

[JMoto]

Did you read the link I posted? I found the piece about measuring the case mouth interesting. I think it was the 2nd or 3rd page.

Also did you do the heavy duty extractor mod?

I clicked on it but it came up as a title only, meaning the article name but nothing else. I tried in firefox and safari

It has the factory extractor spring in it. The mod you are speaking of is swapping in the armalite extractor spring correct?

edited for the third time, I was thinking of a link someone else posted. I read your link the chamber is cut correctly. I am getting correct casemouth expansion according to that persons "diagnosis method"

[imschur]

No the mod Im referring to is the same as used in the AR-15 with the o-ring and the rubber thing inside the spring. know what I'm referring too?

Whats the mod your referring too?

[98Z5V]

Extractor Spring Upgrade kit, loose then installed:

[JMoto]

No the mod Im referring to is the same as used in the AR-15 with the o-ring and the rubber thing inside the spring. know what I'm referring too?

Whats the mod your referring too?

I have seen a few people running armalite springs for the extractor. Not sure of any advantage.

98, I am familiar with that setup, I just was not sure if I could run it because the lr308 uses a dual spring. I never though of swapping to a single spring and a d-fender with the plastic booster.

[survivalshop]

The chamber on this one is very smooth, I cannot detect any roughness in it at all. No snags on a q-tip as is typical with rough machining and no irregularities visually. I actually pulled the barrel again to double check before posting.

The rifle has been headspaced (I do so on all new rifles)

I have not chrono'd the loads but If you are talking about the piece of brass on the left, it was the picture itself possibly a reflection. I check primers religiously on handloads and with every new lot of factory ammo.

I disagree on the round count though. This is not a problem that will "work itself" out.

Using a Q-tip is not going to tell you accurately if the chamber is rough on a molecular level or how clean it is as far as the reaming process.

You can look at your other rifles & see if it has the same polish or mirror like finish to it.

Brass actually flow into every pore in the chamber when the cartridge fires off & with the proper timing (semi auto ) the brass has cooled enough to contract from the side walls of the chamber , than & only then will the case free up & be able to be extracted, but you probably already know this.

The way I see it , you have one of two (or both) problems . The chamber is too rough to release the case properly or you are over gased & the timing is off  or both . 

If you want to check your gas, you need to restrict the gas to the BCG, if you can't get a gas regulated gas block or gas tube , you can move your gas block forward , a couple of thousands ,at a time to pinch off the gas hole a little ,it won't take much.

That will depend on how your gas block is attached .

As far as round count , if your bolt is not seated yet ,it can also cause problems with timing of the gas system .

[imschur]

some guys polish dpms chambers with these things or bore mops with polishing compound

[JMoto]

survivalshop, imschur, First of all let me thank you both for taking so much time to assist in the matter. It is rare to find people who are not only knowledgeable, but willing to share/work with others.

With all of the reports of rough chambers I assumed it was almost gouged from the way people have been talking about it, like it was from a damaged reamer or something. I looked at it and it is not exactly mirrored but it is rather shiny and I cannot see any tool marks. In comparing it with a couple of other barrels I have laying around I see some that are less shiny and some that are moreso. Is there a more exact way to tell?

I understand how timing works and brass flow, but others may not, so there was no harm in posting that info. It is something rarely spoken of on the internet.

I am very certain that the rig is overgassed. I have a 223 in the same configuration and with match loads I run with 90% of the gas turned off and it is more than enough to cycle.  I too though of bumping the gas block to limit the gas but because the barrel is dimpled for the gas block set screws which makes this not possible.  I may try and run a PRI adjustable gas block with a new hanguard if I can find a HG that will fit over it.

You spoke of how the bolt is seating, I am getting more than 70% engagement of the lugs according to the wear on the back of them.

[imschur]

I just wish we could solve the problem.

I had another thought. I wonder if its also possible they didnt package the correct recoil spring.

[JMoto]

I just wish we could solve the problem.

I had another thought. I wonder if its also possible they didnt package the correct recoil spring.

DPMS or TUBB? I have had the same problem with both springs. I will say that it was pretty darned tough to get the tubb spring in there/compressed to put the buffer in. If it were not for my ninja heritage I would not have been able to stop it from mortoring through the window!

[imschur]

ahh ok you got that covered  <thumbsup>

Ninja  ;D

[survivalshop]

I thought I was wrestling an alligator to get my Tubbs spring in my Carbine, so I know what you mean .

As far as the bolt lugs , that's what I was thinking & sounds like they are OK .

If you look at your once fired brass closely , with a magnifier , you may well see if there are imperfections with the chamber .

Most use Flitz metal polish with a bore mope ,cleaning rod & batt. operated drill to polish the chambers up . Its quick & easy , if needed.

You say your bbl. is dimpled ,meaning there cuts in the bbl for a set screw to detent into a recess in the bbl. or cross pins ?

How different is the gas tube compared to the STD. ones ? There are reg. gas tubes out there ,not sure what configuration or sizes.

We as fellow shooters & builders want to help as much as we can to figure your problem out .

[Jgun]

Jmoto,

You mentioned trying a PRI adjustable if it fits. I don't know of any other adjustable gas block out there that is any smaller.  If you can't fit the PRI because of the boss on the side where the adjustment screw is located, I think that your going to have to replace the hand guard if you want to run one. The other thing you may have to keep in mind is that even if it fits under whatever hand guard you use, Your most likely still going to have to makes a hole in the side of the handguard in order to have access to the adjustment screw without removing the hand guard. That is of course assuming that you go with a handguard that covers the GB vs one that ends right behind. I saw one of these adjustable steel GBs on a gun and thought they looked interesting, but they don't appear to be as small as the PRI although they are steel.

  http://secure.adpay.com/clicknbuy.aspx?  p=2079&itemid=2541516&networkview=False&catid=5500&pcatid=500MS&procid=aa3588af-7a29-45de-bb9d-66e4dd5714d1         

[imschur]

At this point I might take it shooting with the HG removed to do some testing. IIRC this is an SASS barrel and GB right? This eliminates the abilty to use an adjustable block without making one yourself. Maybe try either an adjustable or pigtail  gas tube. If this is not an SASS you might be able to machine the hard corner off the boss ans eliminate the high spot.

If you try the adjustable tube or gb go to the range with the HG off.

In the end if reducing the flow solves the problem you can probably mofify your gas block with a smaller hole permanently.

Also JMoto there is absolutely nothing to lose polishing the chamber. Even if it is ok it will be "more better" :) for your effort. 

[JMoto]

Jgun, your link came up bad but I am thinking that is the link for the paladin block. The problem with that is that it is full on, partial, and full off. If I buy that there is no guarantee that it will eliminate enough gas

imschur, another member recently put a JP adjustable block on his SASS 308 barrel and it cleared so there is some hope for a factory adjustable block. The pri unit is designed for a straight tube so it should clear no problem and according to their dimensions compared with the over barrel height of the JP tube the combination of the two should work. We will know when I get some funds together to get the parts. The PRI runs with a straight tube so I will have to use a tube alignment tool to straighten out my mid length tube since they only make a carbine and rifle length straight tube. Or I could run the JP as the other member did. I have to get a hold of JP and see if I can squeeze the dimensions out of them as he used a railed gas block and I want to use the non railed version. If their gas tube hole has the same relationship to the barrel as it does on the railed version I am all set.

As for more chamber polishing, you can polish a chamber too much. If you have a mirror finish in the chamber it will actually increase case flow to the front of the chamber causing a higher chance for case head separation and possible damage to my pretty face. If the adjustable gas block adventure becomes impossible to complete I may just chuck this sucker up and spin a finish reamer through it.

EDIT: the adjustable gas tubes are only in carbine and rifle length as far as I have seen. If I am mistaken please let me know. It would be nice to buy a tube and try it before I waste money on a block and handguard

Once again, I truly do appreciate all the time everyone has spent on here and please do not feel like I am brushing off anyones idea(s). I err on the side of caution when dealing with such things.

[survivalshop]

We all know how funds can get in the way of things .

I haven't seen a mid length adj. gas tube , but I have never looked for one. Some one will know here.

As far a polishing the chamber , you don't have to over do it ,in the polishing . Polish a little & try it out , if it operates better do a little more ,until you are satisfied.

If the chamber is properly head spaced ,the case will not flow any farther then is allowed by the chamber dimensions, that's what they are there for .

Every match chamber I know ,that's a real match chamber , is final polished along with the barrel .

[imschur]

I had a lengthy email conversation with the folks at JP today. To say it was enlightening is an understatement. For the purposes of this thread two important items. They convinced that every civilian 308 AR will benefit from an adjustable gas block ( I think John Boyette mentioned this a while back too) In general most of these rifles are over gassed which is why the carrier weights and heavy buffers work. These are remedies. A better solution is the adjustable gas block and find the sweet spot for perfect bolt timing. This is how JP is able to use the low mass carrier.

Ammunition - These rifles have gas systems designed for very specific military appications with known set of internal ballistics thst operate in a narrow range. This allows a fixed gas system to function acceptably.

Civilian ammo is all over the place. Keep trying ammo until you find what works best in you rifle.

as a side note Hornady is now suggesting gas guns have adjustable gas blocks if they are going to utilize the superformance ammunition.

I will start other topics on all of this but I thought it would help this thread  as well.

[MajorJim]

Dumb questions

Are the Tubb CWS and the BCM extractor upgrade kit the same for .223 and .308? 

[JMoto]

Dumb questions

Are the Tubb CWS and the BCM extractor upgrade kit the same for .223 and .308?

Yes