barrel length vs gas block location vs port size

[cav_scout_tj]

wet: bolt lugs, cam pin area, bolt body inside carrier, a few drops down the carrier key hole. Put a drop in the holes on the side of the carrier. The rails down the carrier bottom and around the key on top.

Basically you could dunk the while bolt carrier group in a quart of oil and that would work fine.

Dont wear a nice shirt when you shoot it. First rounds will blow off any excess.

[txjm]

Originally Posted by MIKEONE

Whats your load? Ill pop it in quickload to see approx what pressures your running.

Also whose reamer did you use for the chamber?

Mike

I would love to see what you came up with on the H335 loads. 2.262 oal. 85SGK, 23.5G and 25.5G o powder.

Thanks Chip

[txjm]

I did 3 things and shot some more this morning. All cases ejected and all but one fed properly. I tried the first load as a single in the mag and it even locked the bolt back. The rims look good, no metal missing where the extractor jumped. One thing odd that I noticed was the primers were not as flat with the same load. It was maybe 5 degrees cooler, not enough to make that much differance.
I oiled the BCG.
I polished the chamber with JB.
The barrel is a nonstandard profile and very thin. The gas block is modified to fit the barrel. I played around with limiting the gas flow through the gas block. I blocked almost half the port.
I think the main problem is the required port size must be tied to barrel diameter. In fluid flow it is not only the diameter of the oriface but also the length. I think the thin barrel really needed a much smaller port. I am going to go adjustable in some form and tweak the gas flow. I think my results this morning show that I may have limited the gas flow a little too much. Maybe the first one locked back because of the oil. Maybe I am running on the edge of functioning and the one failure to feed completely was caused by not enough gas flow. It almost fed the bolt just didn't close completely.

Thanks for all the help. I will be doing some more testing.
Chip

[leo6223]

Sounds to me like it might be trying to unlock too early when the pressure is still too high.

That can be a tough fix

[txjm]

Originally Posted by txjm

I did 3 things and shot some more this morning. All cases ejected and all but one fed properly. I tried the first load as a single in the mag and it even locked the bolt back. The rims look good, no metal missing where the extractor jumped. One thing odd that I noticed was the primers were not as flat with the same load. It was maybe 5 degrees cooler, not enough to make that much differance.
I oiled the BCG.
I polished the chamber with JB.
The barrel is a nonstandard profile and very thin. The gas block is modified to fit the barrel. I played around with limiting the gas flow through the gas block. I blocked almost half the port.

Thanks for all the help. I will be doing some more testing.
Chip

I modified my gas block to be adjustable. I started with lower end loads from above and adjusted until the rifle functioned. Everything seems to be happy now. 85G SGK don't seem to shoot as well as 80G Rem CL. H4895 seems to shoot better than 335. The 80G @ 27K + in the 18" barrel seems to be about it.

Thanks
Chip