Quoted: flat primers

One of the signs of over pressure ammo, and no adjustment in the world to the gas system is going to compensate for the amount that the over pressured ammo/case has bound the bolt to the receiver extension, and case to the chamber walls when the ammo went over the top.

Simple put, your ammo pressure is over the top, and the binding caused by this is causing the system to loose too much momentum (unlock stroke) as it goes to unlock and extract the case from the chamber.  You can play with the adjustable gas tube until your blue in the face, but until you back your loads down to normal working pressures in the rig at hand, your not going to solve the short stroking problem.

1. You're loading for a gas gun (auto loader), and not a bolt-action rifle. The two are worlds apart, and the reason that you need to work up your loads from the reduced starting points listed in the manuals.

2. If one of the carrier is not passing a free drop test, then you will need to polish the sides of the key to allow the problematic key to glide down the upper barrel track.  The key and cam are the only bearing areas that can really cause any carrier binding during the free drop test. If you mean that the carrier will slide down, but just the bolt will not cam over/lock home, this is normal on new bolts until they mate-in with the barrel extension.

Note: if the binding is the last few inches before lock up that the carrier binds, the gas tube is out of alignment with that carrier’s key, and the tube will need to re-indexed.

Give me the specs on the barrel,
including chamber ream (cal, including headspace spec) throat lenght to engaugment from end of chamber cut, barrel length, gas port size, and do confirm that the chamber  has been finaled reamed correctly and polished (read no grooving from the reamer).

Also, with the reduced loads, are you still getting signs of over-pressure from the primers.

Note: If this is a DPMS barrel, they are ream all their chambers to 5.56 nato, but do have a batch of barrels from time to time that are short reamed.  It's not a problem on their completed rigs, just the barrels that are sold loose. Was the barrel/bolt combo checked for headspace?

Quoted: I do not understand "the throat length to engagement from end of chamber cut" dimension, but I'm sure it's on the drawing.

Just checking to confirm that you are not embedding the bullet into the lands on loading (read a short throated), nor forgot to trim your brass to the needed length.
You are able to drop a live round into the chamber, lightly tap the back of the case with a pencil eraser, then tilt the barrel and the round will fall out?

Forest headspace gauges lengths:
Forster .223 Go Gauge 1.4636
Forster .223 No-Go Gauge 1.4666
Forster .223 Field Gauge 1.4696  

DPMS bolt is on the short headspace side, and the Young bolt sounds about right.
Guessing that the Chamber was cut for the young bolt?



24" barrel, .825" dia. Port size .089"
Your barrel gas port size is about right; so don’t worry about the port size.

Using the Young Bolt, check for correct stroking again (lock back on empty mag) with standard loads. If there is still no joy, then its time to strip the gas system down and re-check it for gas block alignment to barrel port (and confirm it was tight), gas block port to gas tube port alignment, Key port to carrier ports and correct seal of the two to each other.

From there, check to confirm that the B/C does pass a 45* free drop test in the upper receiver, and that the recoil spring and buffer have been de-bur’d.

My guess is that you are running a speed hammer, so there shouldn't be problems with hammer bind/wedge causing short stroking.

If everything check out, then it’s just time to CLP lube all the upper bearing surfaces including the buffer and let the rifle just break in (read self polish out).  As for polishing out the chamber by hand, DON’T.  Let live fire do this for you (even if this means that you have to re-lube the rifle sporadically for the first hundred rounds).  Also, might be in your best interest to just install a standard gas tube until the rifle breaks in.  This will weed out any leaks in the adjustable gas tube that may be causing a problem.

P.S. Just how much of a Space gun is the rig? Is it full blown, or just a few parts littered through the rifle?

Quick test on the buffer and spring length is to just pull back on the charging handle and see if you can lock the bolt back on the bolt catch.  If the buffer or spring is too long for the carbine stock (receiver extension), then they will just bind up/limit the distance of the assemblies and the bolt will stop short of the catch.

Granted that the spring does seem a tad long, it may not just have taken a set yet.



Just to cover this one more time, you are sure that the gas tube hole and the gas block holes are aligned, and that the carrier key is not leaking?

Also, you stated that the carrier didn't go all the way home during the 45* test. Did you mean that the bolt just won't rotate/lock home, or that you had key sides/cam sides/bolt lug to barrel extension lug binding?

With total no joy of the factory ammo even attempting to unlock the bolt, you have to have either major binding or a major gas leak in the system.

Quoted: It does require some effort to lock it back. Guessing here. maybe 15? pounds.

When pulling back on the charging handle, you should feel the bolt unlock, and the hammer start to cock.  About half way back on the carrier, the pull tension should be consistent/smooth/lighter than the initial pull to Buffer bottom out/end of stroke when you can lock the bolt back on the catch.

If you are getting about half way back and the tension gets stronger, then the hammer tail could be wedging against the disconnector and causing carrier/hammer binding.  If the very last inch or so of the charge is just way harder than the rest of the pull, then the spring is the standard model (read too long for carbine receiver extension), and not only are you getting spring binding at end of compression/stroke, you have too pre-load on the spring from the beginning (read could explain the reason the bolt doesn't even move at ignition unlock).

leftyshooter,
Give me a couple of days to get my head screwed on straight and I will come up with a solution to the problem.  

As of now, I got food poisoning yesterday morning, and still doing the multi trips to the bathroom on a hourly bases as things are exiting my body from all openings at once.

Glad to hear you got it running!!!