First Trip to the Range

[NTXshooter]

Took the new SBR out to the range for the first time.  Tried Hornady 110 gn V-Max and 208 gn A-Max to see how it work with both super and sub-sonic ammo.  Worked great with the super sonic rounds. Sub-sonic rounds would not cycle the bolt properly. The bolt feels really tight, so maybe that is it.  Will a suppressor give it more back pressure to work the bolt?  Is this normal?

 

I also checked the muzzle velocities against what Hornady put on the box.  Hornady:  V-Max = 2,350 FPS, A-Max = 1,020 FPS.  Mine: V-Max = 2,303 FPS, A-Max 1,007 FPS.  Pretty close for a 10.5" barrel.

 

Here are the targets.  50 yards with a Tru-Glo Red Dot sight.  V-Max on the left and A-Max on the right.  Interesting how the heavier bullets punched smaller holes in the target.  The out liers on the V-Max target are from sighting in the red dot.

 

 

[Rsquared]

My 300 BLK SBR has a Noveske 10.5" barrel, and she runs fine with supers and subs. If I remember correctly, it's a pistol length gas system on it. What's yours running? Sorry, my memory sucks, and I don't remember what barrel you're using.

 

And yes....the suppressor will definitely add some additional back pressure.

[NTXshooter]

I'm running a Ranier Arms 10.5" match barrel with a pistol length gas system.

[Rsquared]

Hmm. Maybe you're onto something with the bolt feeling tight. I'd say run a couple hundred more rounds through it, then try the subs again. Or.....slap a can on it. <laughs>

[Dane Armory]

Lefty ... Hmmmm !

Stag parts ?

[NTXshooter]

Definitely going to run more rounds through it. And, if my can ever gets approved, I'll try that too

Yep, Stag upper, BCG, and lower. YHM low profile gas block.

[Magwa]

What Buffer are you using? try a H3 my 10 and 1/2 inch barrel pistol gas works great for both subs and high velocity rounds...

[survivalshop]

  Run her wet with lubricant for a while to break in the action. If not already doing it .

Edited November 13, 2014 by survivalshop

[shibiwan]

Carbine or pistol length gas system?

 

Barrel port size?

 

Buffer weight?

 

These are the most important factors if you want it to cycle reliably on supers AND subs in all shooting conditions.

Edited November 13, 2014 by shibiwan

[NTXshooter]

I'm using a standard carbine buffer. It is a pistol length gas system. Not sure of barrel port size, it is a Ranier match barrel.

[shibiwan]

Did you put it together? It's most likely port-size related. You're looking at a 0.095"-0.1" port size with a 10.5" barrel for it to run reliably with subsonics under the worst conditions.

[NTXshooter]

I did put it together. I spaced the gas block off of the shoulder. I think I'll write Rainier and ask them that question.

[Magwa]

Try a heaveier buffer it may cure all your ills.....

[shibiwan]

Try a heaveier buffer it may cure all your ills.....

 

That's the opposite of what he should do. You gotta go lighter on the buffer if it fails to cycle properly on subsonics.

[NTXshooter]

What would be a lighter buffer?

[survivalshop]

I did put it together. I spaced the gas block off of the shoulder. I think I'll write Rainier and ask them that question.

 

    Some bbl's do not require that the a gas block needs to be backed off the shoulder to compensate for a Hand Guard Cap, you can pull it off or just back it away far enough to see if the carbon pattern is completely surrounding the bbl's gas port. Meaning the the complete port is being used & not restricted .

[Magwa]

well LOL I went heavier and it works like a charm with subs and surpressed, runs like a sewing machine i tried a carbine buffer but it did not work so I went right to a H3 and presto perfect 10 and 1/2 inch barrel pistol lenght gas tube and it throws the brass at 3.30 all in a neat pile... I am not experienced enough at building these it is my first one from the ground up but it works great...

[shibiwan]

That's odd Magwa. The subs have significantly less energy (more so when firing unsuppressed) so you typically want lighter reciprocating components so it cycles.

 

Then again who am I to argue since yours works!!

[shibiwan]

What would be a lighter buffer?

 

Remove the weights from inside the buffer. Cheapest solution!

[NTXshooter]

I'm headed to the range tomorrow, I'll see if I can take some of the weight out and see what happens. Thanks to everyone for the help and suggestions.

[survivalshop]

That's odd Magwa. The subs have significantly less energy (more so when firing unsuppressed) so you typically want lighter reciprocating components so it cycles.

 

Then again who am I to argue since yours works!!

 

 

  This may boil down to , two different actions having different results . Hard to tell unless you used the exact same components & compare them . Subsonic ammo can have different results also , depending on the type of powder used & bullet configuration . If you look at the different manufacturers spec's , you will see some Manufacturers use a softer jacket or a thicker jacket & so on .

 

  I remember when I first started loading for the .44 Mag. I was using Speer & Hornady bullets , the Speer's were sized to .429" & the Hornady's were @ .430 ", now you wouldn't think that that 0.001" would make a difference with the same powder/primer loading , but it does & you could tell by the brass & the firing .    

   No two barrels/chambers are alike , so a Barrel/chamber shooting the same ammo may not act the same as another of the same configuration. On the most part they should & will , but there will be that one that will require tweaking in some way of the other to get it to perform in the same manner , as others .

 

  Yes subs have less Velocity to make them subsonic , but they normally are a heavier bullet & that , as a reloader , you know will raise chamber pressure slightly , compared to a lighter bullet at the same charge weight . In a short barrel with a short gas system & throw on a Suppressor & unless as I said , you have all the exact same components , that you know work with that combo , some actions may take some kind of tweaking some where to get them to perform .

[NTXshooter]

Ok, I found out the port size is .094. I'm headed to the range tomorrow. I've got lubed up so I will see how it does. If it still doesn't cycle, I'll take the gas block off and check the alignment. Next step after that will depend on what I find.

[98Z5V]

Remove the weights from inside the buffer. Cheapest solution!

 

Gotta build spacers to take up the length of the buffer weight you're pulling out, and insert that spacer in place of the weight.  Don't forget to account for the thickness of the pad that's between the buffer weights, on either end, when cutting the length of the spacer.

 

^^^  If you don't do that, your buffer will rip itself apart inside the receiver extension... 

 

I had to turn a rifle buffer into a carbine-weighted buffer for my 300BLK rifle, to get it to cycle properly.  NEMO 16" nitrided barrel, carbine gas system.

Edited November 16, 2014 by 98Z5V

[NTXshooter]

Update.  Second trip to the range with just the BCG wet still produced a single shot rifle.  It would either not eject and jam or not strip off the next round.  Following everyone's advice, I took one weight out of the buffer and replaced it with a piece of wood dowel rod.  Worked almost flawless with my subsonic reloads.  Still had one jam.  I think it just needs more range time.

 

Reloads were 208 gn Hornady A-Max over 11 gns of IMR 4198. Here's the ballistic data for two 10 shot groups

 

Group 1                                     Group 3

 

Max     1148 fps                        1147 fps

Min      1089 fps                        1008 fps

S-D      31                                  39

ES       93                                   139

 

I didn't measure each load, just set the powder measure and loaded the rounds.  I did check the weights a couple of times and make adjustments to make sure they were on target.

 

Here are the results, 50 yards with a red dot and 3X magnifier.  Group on the left was bore sighted, and center group is after adjustment.

 

 

 

 

 

[.308LiteHunter]

Did you try any supersonic rounds with the new buffer?

What C.O.A.L are you using for the 208 Amax?

Glad to hear it's operating better