Jump to content
308AR.com Community
  • Visit Aero Precision
  • Visit Brownells
  • Visit EuroOptic
  • Visit Site
  • Visit Beachin Tactical
  • Visit Rainier Arms
  • Visit Ballistic Advantage
  • Visit Palmetto State Armory
  • Visit Cabelas
  • Visit Sportsmans Guide
jtallen83

Start Tweaking or Wait????

Recommended Posts

Got to run some rounds through the 300BO pistol today. Put a set of Magpul BUIS on it, zeroed in easy and did great for my old eyes at 100 yards, first some remington UMC 120gr;

IMG_0677.JPGIMG_0678.JPG

Now these Freedom Munitions 208 gr. A-Max shots were at a real slow pace, damn thing would not give the BCG enough umph to pick up a round. I maxed out the SLR gas block, 6 more clicks past what it took to run the supersonic. Also shot some S&B 200 subs and some remington UMC 220 subs with the same results. The 220's were very close to functioning, full ejection but no lock back.

I hope to do a bit of an autopsy before going back to work, check gas block alignment and such but not sure I want to change much until I have gotten the can and tried it. Those of you with cans, will it make that much difference in gas pressure?

I'm running it on a d. wilson lightweight BCG I borrowed from another rifle till he has standard BCG's in stock again. The spring and buffer are standard stuff from an Anderson kit. Faxon 10 1/2 inch barrel with pistol gas. I'm thinking if my gas block is properly aligned when I take it down I just as well put a standard Geissele GB on it and save the SLR for preparing one of my 308 AR's for a can. If I'm thinking right a standard weight BCG will take even more pressure to function than the lightweight I'm testing with, should I consider just running it with a lightweight? As soon as Tubbs gets more of his flat wire springs for the 300BO in I planned on running one of those, maybe this will help a bit?????

 

Share this post


Link to post
Share on other sites
44 minutes ago, MikedaddyH said:

In the neck !

If its not broken DONT fix it !

Guess I'm not sure if it is broke, I was hoping it would run everything being pistol gas but seems to be picky with the subs. Just pulled the BCG, damn it was a mess inside, can't imagine how much carbon/ burnt powder will pile with a can on it!

Share this post


Link to post
Share on other sites
6 hours ago, jtallen83 said:

Guess I'm not sure if it is broke, I was hoping it would run everything being pistol gas but seems to be picky with the subs. Just pulled the BCG, damn it was a mess inside, can't imagine how much carbon/ burnt powder will pile with a can on it!

Are you shooting fire balls. Unburned powder ? Change powder, adjust load first. Experiment with this before you change your gun. Just saying ' !!!

Share this post


Link to post
Share on other sites

 I use sig subs with no problems.   barrel 16" umc subs are not recommended in a can. In my 0.2.

Share this post


Link to post
Share on other sites
5 hours ago, MikedaddyH said:

Are you shooting fire balls. Unburned powder ? Change powder, adjust load first. Experiment with this before you change your gun. Just saying ' !!!

Shooting all factory ammo, just don't have the time at home to reload anymore. I didn't see any fireball but definitely saw evidence of unburned powder. LGS has some Sig subs so I'll try a box of those. Still want the pistol to shoot a good variety of ammo. Anyone see the harm in using a lightweight BCG?

Share this post


Link to post
Share on other sites

  Any time you build a specialized rifle , it will need some adjusting or you could get lucky , but with the different ammo types , some will give issues until the Action is tuned . The Can will help with the heavy Bullets . Are you sure the BCG is not over pressured . Under gased is easy to determine with the last round lock back of the BCG with the Bolt Catch . Over gas'ed can cause some real weird issues , not to mention the Pistol length gas system & its potential issues .

  I would only use a M16 type BC with any AR , my reasoning is the light weight BC can have issues with actually having enough inertia to strip the round from the Mag. & the more in the mag . the harder it is to do so . You need to accurately  determine what is really going on . You just have to go though the normal testing to figure it out .

 The Tubb's spring is a good choice , weigh the Buffer to make sure what it is .

 Any Pistol Gas system is going to be dirty , some ammo brands may be better then others or in reloading , its your Powder choice to keep the unburnt Powder to a minimum .

  I'm assuming the super sonic's are working ?

Edited by survivalshop

Share this post


Link to post
Share on other sites

Supersonics functioned, heavy subs ejected but no fresh round loaded and no lock back on empty mag. The lighter subs would stovepipe with the mouth against the extension or the front of the ejection port.

Wish I hadn't used the rocksett on the FH yet, going to soak it for the day and check the gas block alignment tonight. Think I'll wait for the BCG and Tubbs spring before doing much else. I will check the buffer, now that I think about it the buffer I am using came from my PM400, I had replaced it with an H2 in that rifle and gutted the weights out of the Anderson for the low reciprocating mass build.

Share this post


Link to post
Share on other sites

I built my 300 BLK SBR using a Noveske 10.5" barrel. For the most part, all I've shot out of her has been either Remington or Sig when it comes to subs. There was a couple hundred rounds of some offshoot brand (jameison I think). Also, I don't bother shooting too much without the can on her for the subs. After all, it was designed to be shot suppressed anyway. And yes, the can will probably add enough back pressure for the action to smooth out for you.

Supersonics, I don't usually use the can to run them. Same thing, Rem and Sigs.

300 BLK Shorty.jpg300 BLK with AAC Can.JPG

Share this post


Link to post
Share on other sites

Pulled the handguard off and slid the gas block back, the gas port was at the very back edge of the shadow left on the barrel from the gas block port. It didn't look to be blocking it but I went ahead and moved the gas block just a heavy business card thickness off the shoulder to better center it. There was signs of a little leakage but I'm thinking that will seal up with carbon after some use.

With the bolt out the carrier hangs up on the gas tube just ever so slightly, just a little extra push and it slides right in, figured I'd wait and see what it does when the dedicated BCG for the build arrives.

I may just try the lightweight buffer spring I have when I give it another test tomorrow. I would really like this build to run on anything with or without suppressor but when push comes to shove I'll settle for reliability with subs and suppressor.

Share this post


Link to post
Share on other sites
21 hours ago, jtallen83 said:

 There was signs of a little leakage but I'm thinking that will seal up with carbon after some use.

It will.

With pistol-gas, and you already have an adjustable block - I'd drill the port up a size or two, and test it again.  Even with the gas block opened all the way up, it's not feeding a fresh round.  Needs more gas.  You don't really have to worry about going too big for the supers - with the adjustable block.  :thumbup:

Share this post


Link to post
Share on other sites

Drilling is looking like the next option after testing today. Odds are it would function with the suppressor but it would seem best if it functioned regardless of ammo type or suppressor. Moving the block didn't change a thing, putting a lightweight spring had no effect. The last three clicks on the block don't change anything with the subs, ejects case but no lock back or pick up of next round, it does cock the hammer on those last three settings. This seems to tell me there is room for more gas in the block but the barrel port is not providing it. I'll be sure and measure the starting port size and where I end up so I can post up.  I've run out of time home this trip so the next round of testing will come at Christmas time, have to fill a seat in a training class at HQ first of December so I'll miss my usual Thanksgiving/first week of December R&R. Should have all the dedicated parts by then and love shooting in the cold anyway:thumbup:

Share this post


Link to post
Share on other sites

It will definitely function better with a can on it. I would pull the adjustable gas block off and use it for another build than can better utilize the adjustment feature, 300 BO is a somewhat undergassed round to start with (especially with subsonic rounds) and doesn't need an adjustable gas block. I shoot both subs and supersonic with the can on or off with no problems and my gas block is just a generic steel micro gas block  I agree with Tom on the gas port, start drilling it out a step at a time until you get reliable functioning with the subs and no can. It should then function just fine with everything.

Share this post


Link to post
Share on other sites

  I find it strange that in almost forty years of building AR's in both semi & select fire configurations, that you have another barrel that needs to have the Barrels Gas Port opened & I have had only one , in all those years . It was a XM177 Build , 10.5" BBL. & would not function reliably in full auto , the opening of the port fixed it .

  Its true we have a lot more Barrel makers for AR's now a days & one would think they would all have this Gas Port thingy down pat , but you have some bad luck with barrels .:laffs: 

Share this post


Link to post
Share on other sites

Wish I'd have measured it when I moved the block a bit, have to wait till Christmas leave to do that now. The X-caliber escapade made sense after hearing their comments but Faxon has put out a ton of 300BO barrels so I wouldn't have thought it would be an issue. Be sure I'm going to look the build over well before drilling but so far didn't see anything else that might be the issue. I might try a standard gas block before drilling, can't hurt to check the GB of the possibility list. I'm thinking that QPQ finish will make drilling a bitch..............

Share this post


Link to post
Share on other sites

Before you even think too hard about drilling, find out the size of the hole !!!!!  

If the hole is in a specific size range ( and not too small) your problem may be blockage (constriction in the gas tube) or the gas block might be covering some of the gas port hole. There might be an issue with the gas tube to bolt carrier mating surface causing a leak that you cannot see with the naked eye. 

I would suggest doing a canned air test before you do a teardown of the rifle. Also mark the position of the gas block before it is taken off, then look for carbon build up on it and on the barrel by the gas port hole. This may show a misalignments of parts.

Añyway just throwing that out there , because once its drilled bigger there's no going back ... Only band aids to fix your new problem.

Share this post


Link to post
Share on other sites
4 hours ago, MikedaddyH said:

Before you even think too hard about drilling, find out the size of the hole !!!!!

Such a good activity for so many activities!

Sounds like a good 308ARdotCOM t-shirt!

Share this post


Link to post
Share on other sites

   Not sure of Pistol gas system size's , but at least Faxon publishes them for reference .

  • Barrel Material: 4150 
  • Barrel Type: Button Rifled 
  • Barrel Caliber: 300BLK AAC
  • Barrel Twist: 1:8RH
  • Barrel Length: 10.5
  • Barrel Profile: Medium
  • Barrel Gas System: Pistol
  • Inside Finish: QPQ Nitride
  • Outside Finish: QPQ Nitride
  • Muzzle Thread: 5/8"-24 
  • Gas Block Diameter: .750"
  • Gas Hole Diameter: .075"
  • Gas Block Journal Length: 1.9"
  • Barrel Extension: M4
  • Weight: 1.15 lbs
  • Magnetic Particle Inspected!
  • 11-degree Target Crown

Share this post


Link to post
Share on other sites
On 11/16/2016 at 1:32 PM, survivalshop said:

   Not sure of Pistol gas system size's , but at least Faxon publishes them for reference .

  • Gas Hole Diameter: .075"

I seem to remember reading over at 300blktalk.com that the 300 blackout gas ports were in the .090+ range. JT,, I'm sure if you go there and post a question about it you'll get some good info on that. There are some very knowledgeable guys over there when it comes to the 300 blackout and they are a good bunch too, nothing like arfcom!

Edited by 392heminut

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...