So I took various buffers and springs, and a notebook to the range..

AR/M4 AR Technical Discussion
1

…expecting to tune two new ARs. I was really expecting to find a perfect fit for each, which in my mind was a:
~3:00-4.00 ejection with 5.56 and maybe 4:00-4:30 with 223/wolf but function with it.

So I took a 10.5" with .093" (Colt sized) and a 16.5" Middy (Its a Nordic barrel, and they are actually 16.5" to bolt face insead of the 16" advertised) with a .085" gas port. Had standard (on the long side, 11 1/8") and extra power buffer springs (Springco RED), H, Spikes ST-2, H2, and H3 buffers. Both have Denny’s BCG build on Young Chrome M16 carriers, which I think have extra power extra springs but blue inserts, no o-ring. Wolf 223, PMC 223, and M193 (Armscor/Philippines). Now I’m complete freaking lost, my results do not make since. I didn’t test every configuration, I was frustrated and limited in time. I was expecting both configurations to be overgassed but the Middy more so than the 10.5" carbine.

10.5" 5.56 chamber .093" gas port:
Standard Spring, H Buffer
Wolf 223: 2:30 13ft
PMC: 1:00 5ft
M193: 1:00-1:30 2-5ft

Standard Spring, H3 Buffer
Wolf 223: 3:00 9ft
PMC: 1:30 8ft
M193: 1:30 3-8ft

Heavy Spring, H Buffer
Wolf 223: 2:30 11ft
PMC: 2:00 4-8ft
M193: 2:00 4-8ft

Heavy Spring, H3 Buffer
Wolf 223: 1:30-3:00 5-10ft
PMC: 1:30-2:00 8ft
M193: 1:30-2:00 7ft

Functioned in every setup. The ejection results for the Heavy spring + H3 buffer do not appear to make since. At the time I ordered I follwed the advise to size stuff to colt size so everything would run in it, before I learned this is to much gas. I’m thinking of crushing the gas tube some or buying a adjustable gas block. I’m at a loss, I though a heavy spring and a H3 buffer would tame a colt sized gas port 10.5".

I was running out of time but took out my next rifle:
16" Midlength gas, .085" gas port (per manufactor), 223 wylde chamber:
Standard Spring, Spikes ST-2 (similar to H2)
Wolf: would not feed next rd, appeared to be short stroking
PMC 223: 50/50 results, same
5.56: 4:00 8ft and smooth

Shouldn’t .085" gas port with a 16.5" Middy gas system be overgassed? I guess this is perfect if I onlyh shoot 5.56, will try a H next time out. It did function in fa on my selectfire that had a H2 with 5.56. I know another person took a .071" middy and cut it to 12.5" and opened to .080" and theirs ran with 5.56 and wolf 223.

2

I really don’t know where to begin with your post. One thing I can tell you is that you are too absorbed into the whole ejection pattern thing.

Put a buffer in there that will allow you weapon to function with the ammo you have or plan to use.

One thing i can tell you is this- DO NOT CRUSH YOUR GAS TUBE OR USE AN ADJUSTABLE GAS BLOCK.

With a mid length you shouldn’t really need more than an H buffer. With your 10.5’ unsuppressed you should be able to run it with an H2. Forget that silly Spike’s ST-2 nonsense.

3

I’m going to be shooting 5.56 almost all the time. I shows signs of being overgassed even shooting underpowered wolf 223 with a Xtra power spring and a H3… and you think I should switch it to a standard spring and a H2 :confused:.

I think I’m going to take pull gas block and measure gas port.

4

Iraqgunz, why no adjustable gas port? I am looking at a Noveske CQB with a Switchblock for suppressed use. Not always, but thre are times when I will want the can. I don’t build them, just shoot them, so give me your thoughts on it…Thanks.
I hope this isn’t a hijack, but it sounds pertinant.

5

If it was overgassed you’d have ripped case heads, possibly blown primers, extractor marks, ejector shearing. Because the bolt is unlocking too soon.

6

A Noveske Switchblock is designed to do something particular and I would have no problems using one.

I am referring to those gimmicky adjustable blocks.

7

Ryan,

Who makes the 10.5"? Having looked a little closer I think both of those are way to big (gas ports). My BCM 11.5" is nowhere near that saize and a middy shouldn’t be that big either (AFAIK).

So I guess I would talk to whoever makes or sold them and ask WTF.

If you are going to keep them then you may want to look at the Vltor A5 system.

To be honest I could care less about ejection patterns. I want an AR that will work with the ammo I have and so far after 4000 rounds mine does.

8

You can fine tune your ejection pattern with extractor tension and ejector spring length is you’re really intent on painting a pretty picture. As long as the upper is reliable, it really doesn’t matter where the brass is going.

9

Cutting extractor springs?

10

Actually it’s the ejector spring that gets cut. You can play with the extractor tension by using different springs or ‘O’ rings. Rifles usually need more extractor tension then less, but too much tension effects ejection. You can tune the ejection to drop the brass right next to you, or let the rifle throw it as far away as possible. As long as my upper is reliable, I don’t try to tune anything.

11

Cutting extractor springs?

There was a document that Remington put out with steps on how to do this.

IMO, the ejection pattern thing is way over played.

To the OP, what symptoms are telling you its overgassed in particular?

12

The buffer and spring system in your gun is there to ensure the reliable functioning of your gun and longevity of its parts.

It is not there to tailor the recoil to your pleasure or to fine tune the ejection pattern.

13

So lightest combination and heaviest combination all function 100%, its not like buffers and springs are expensive, I just like to pick the combo that functions smoothly and ejects cleanly. I’m going to run each on a selectfire slower sometimes, so setting it up so its smooth and has slower rate of fire is fairly important.

I was surprised that a 10.5" with standard colt sized gas port (.093") could not be tamed, even with the lowest power 223 load I could find, even with heavy spring and H3 buffer. And the 16.5" with a .085" gas port that I would think would be overgassed, is behaving like has a much smaller gas port. Just looking for answers.

14

Did you actually measure your gas port? where did you get those numbers?

15

Scotty,

The OP continues to mention a 10.5" barrel with a Colt standard size gas port of .093. Does that sound right to you? I was under the impression that it was smaller than that.

I think I read somewhere it was around .070-073. Doesn’t .093 seem a tad bit large?

16

I don’t know what the gas port is on a real MK18 barrel as nobody has removed the front sight base from one because they are too expensive and collectable.

17

Does it stand to reason that the stated gas port size sounds way too large?

18

that would be huge. way too big. that’s at the upper end of sizing for a 20" gun. but colt’s done plenty of experimenting over the ages- maybe it’s an old CQBR barrel? i cant verify it personally, but i was under the impression the mk18 barrels are at .070

OP- was the barrel chopped down from a longer barrel?

19

Ryan - which Nordic do you have? Just to give you something to compare to, I have the Lilja one - when I was running an M4 style stock, I was using a Sprinco standard (Blue) spring and a carbine buffer. No problems with a bunch of different ammo with the exception of Tula which occasionally failed to pick up the next round and lock back on firing the last round (it really is weak). PMC did work fine. I now have a rifle stock/buffer/spring in there - same results with that - everything fine except the occasional hiccup with that Tula shit…but thankfully I have now shot it all and won’t be buying it again - if I want cheap ammo for close up practice, I’ll stick with my usual Brown/Silver Bears. The rifle is a very nice soft and accurate shooter; ejection pattern is 3:30-4 Oclock. Did not measure my gas port, but given Liljas quality I doubt it is anything other than what it is supposed to be.

20

The adjustable gas blocks I looked at use a set screw that needs an allen key to adjust. Carbon build up will freeze up the set screw. Combine that with the fact allen heads are not very durable, the adjustable gas block will, in time, become a non-adjustable gas block. Also, the hole for the set screw is another potential path for gas leakage.

Switch blocks are not really “adjustable”. They simply have three settings- Normal, for shooting without a suppressor; Suppressed and Off