Back to 6.8

[7br]

Ok, I lied. Got the AR15 back out. Both groups were shot at 50 yards. The powder was 14.5grains of SR4759. Neither load would even come close to unlocking the bolt. The first picture is the 280412. The top two holes are the first round from the magazine. The second is the 280468S. The first shot is not in the picture. It was 6inches high and about 2 inches left of the group.

[Moonie]

Ok, really interested in this as I now have a 280412 mold. What are you sizing this boolit to? I'm planning on having Buckshot make a push through sizer for mine very soon.

Have you tried H4895 with this boolit and if so what results have you had?

[7br]

Ok, really interested in this as I now have a 280412 mold. What are you sizing this boolit to? I'm planning on having Buckshot make a push through sizer for mine very soon.

Have you tried H4895 with this boolit and if so what results have you had?

Sized to .278 with a buckshot manufactered sizer. He did an excellent job on mine. I have tried 4895. Bolt cycles reliably at about 25 grains, but the accuracy is not there.

My rifle has a 20in DPMS upper. A carbine length barrel might work better with a shorter gas system. The 14.5gr load was taken from another site and was supposed to cycle the firearm on 12.5" barrels. I think the explanation is that the shorter length from chamber to gas port means that there is more gas available to work the action.

Next step will to increase the loads until bolt cycles and go from there.

[Calamity Jake]

You want to try the Saeco 270? I can send samples.

You can also put a lighter buffer spring in it so it will cycle with your 14.5 load.

[7br]

You want to try the Saeco 270? I can send samples.

You can also put a lighter buffer spring in it so it will cycle with your 14.5 load.

Thanks, but the saeco is too long.

A lighter buffer spring is worth pondering? How do I tell if it is lighter than the one I have?
I suppose brownells would have them. Anyone else?

[Moonie]

I got one for my 5.56 upper in case I needed it with my light loads. Currently I haven't needed it with my 18gr H4895 Bator load, the standard carbine setup works it fine. Might experiment some more however.

[82nd airborne]

Thanks, but the saeco is too long.

A lighter buffer spring is worth pondering? How do I tell if it is lighter than the one I have?
I suppose brownells would have them. Anyone else?

If it doesnt even unlock the bolt, it will take more than just a lighter buffer spring.
There are different weights of buffers as well, which is something you could play with.
Your best option would be to drill the gas port out, which is easy, then put a PRI adjustable gas block on so you can adjust it to fit any of your loads. Then you would only have $70ish in making it cycle with a huge variety of loads.

To open the gas port up. Take a drill bit (.125") and wrap in tape, leaving only as much bit exposed needed to go through one wall of the barrel. use several layers, the best method is to get it started, then pull the trigger on the drill, which will let get very thick, very fast.
Then slowly drill the port. with a properly sharpened drill bit, it will center its self on the existing hole. The tape will keep you from going to far and hitting the other side of the barrel when you break through. Dont run the drill full speed, run it slow, with lube so you done work harden the area you are trying to drill.
Be sure to swab the barrel before firing. You don't want to scratch it up. Then run a couple rounds through to remove any burrs from opening the port.

[7br]

Your best option would be to drill the gas port out, which is easy, then put a PRI adjustable gas block on so you can adjust it to fit any of your loads.

Okay, How would I remove the current gasblock. It looks like a standard configuration of barrel. There is a chance that I may shoot an ar15 open sight match. Is there any advantage going with stainless steel over the aluminum gasblock with a picatinny rail?

[Combat Diver]

The sight tower is removed by drifting out the two pins (one above the bayonet lug, second above the sling swivel)

CD

[82nd airborne]

The sight tower is removed by drifting out the two pins (one above the bayonet lug, second above the sling swivel)

CD

Correct. They only come out one way though, as they are tapered.
About the only adjustable you will find that is aluminum is the JP, and it likes to adjust itself when you are not looking. I prefer the PRI steel adjustable for that reason, however, it has no rail. This leaves you with a sight that mounts on the front of the barrel, on a freefloat rail or some such method of attachment.
There is another way. You can put the lo profile adjustable on, then replace the sandwich type handgaurds for a free float that covers the block, but still allows you to adjust due to vents. Then take your front sight and put it back on without the gas tube. This would now be a faux fsb, but it works. Several different options there.

[7br]

You can put the lo profile adjustable on, then replace the sandwich type handgaurds for a free float that covers the block, but still allows you to adjust due to vents. Then take your front sight and put it back on without the gas tube. This would now be a faux fsb, but it works. Several different options there.
And I would still have the front swivel attach point. Iff'n I were to open the port on the barrel and later go back with the original gas block, would there be any issues?

Read a couple of the reviews of the JP blocks and they mentioned the auto adust feature.

Ok, so I am going to put off buying that encore barrel now.

[82nd airborne]

Actually, now that I think of it, I believe someone makes a GI looking front sight block that has an adjustable gas port. I will look for that and see what I can find.

[Moonie]

And I would still have the front swivel attach point. Iff'n I were to open the port on the barrel and later go back with the original gas block, would there be any issues?

Read a couple of the reviews of the JP blocks and they mentioned the auto adust feature.

Ok, so I am going to put off buying that encore barrel now.

Once you open up the port you MUST use the adjustable gas block, using the original gas block will have you WAY over gassed.

[82nd airborne]

Correct, but I doubt youd go back to the original once you had the adjustable. My dad got a 6.8 from M1S when they first came out and it is badly overgassed. It will run a 110g cast boolit all the way down to 1500fps and still cycle!