J&T 300 Whisper Help

[charden14]

I have a 16'' J&T 300 whisper upper on a double star lower. It will not eject consitently and when it does it fails to feed . I have installed a J&P low pro adjustable gas block in the carbine gas port position. I have cut the buffer spring to 1/4 the size it was before. I removed all the weights out of the buffer and I cut one leg off of the hammer spring. It does eject better but closes on an empty chamber. I am shooting mostly 220 smk over 9grn of H110.I even tried 10grn which was around 1200 fps and it still would not eject that was before removing the weights and cutting the spring leg. I bought some 220 Corbons and they did no better some of them wont chamber all the way and when I eject them it pulls the bullet out of the casing. I tried some varget and B-LC (2) But I loaded them at 9 gns and they would not clear the barrel. I will load some more at maybe 15grs and try it. I have a Model 1 sales reduced power spring kit on the way but do not think it will help. I am out of ideas. If anyone has any ideas before I throw this thing in the creek I would appreciete it. I think I have the gas block lined up good I ran air through it and marked center with tape so it should be close. I did not think this would work because it uses the same gas tube so I do not see how it can improve the flow. I also did some filing on the upper to make the charging handle fit better . Thanks

[Colohunter]

I would try some different powder. I didn't have very much luck with H110 and subsonics. AA 1680 has worked well for me with subsonics, I even use it with bullets as light as 150grs. It cycles and feeds the action, though does not lock back on an empty magazine.

[Spook]

what diameter gas port? AA1680 powder would be a good place to start.

[SgtCottle]

Drill the gas port to .120" to ensure that you have maximum gas pressure to cycle the action. You can tailor it down with the adjustable block if needed. With the bullets being pulled out of the brass when they won't chamber ... it would concern me that the bullets are getting jammed into the rifling. Does the fired brass look exactly like the unfired brass? Or has it been jacked up? I had two 300 Whisper barrels from Montana Rifleman that was completely jacked up and basically blew the brass up when fired. Come to find out they cut the chamber incorrectly and the barrels were sitting time bombs. Is it a pistol gas system or a carbine gas system ... that will make a huge difference.

[charden14]

I got .140" for the gas port it is in the carbine position a 1/8" drill bit fits in pretty close not tight. I measured the OAL on my reloads it is 2.065 cor bon 2.230 a big difference. I fired 12 cor bons and 4 would not chamber and two of them came apart when I tried to eject them the bullet had to be tapped out. The only noticable markings on the casings are the same three scratches they always get from the locking lugs three scratches along the case neck to the shoulder. No bulging, blown out primers or anything. The case neck diameters loaded are .340 for both reloads and corbon and the fired diameter is .345 on both. I will get some 1680 this weekend and start with about 9grn and work up. I did not mention that I use federal Small rifle magnum primers due to avalability. I am not sure what effect if any this may have. Thanks

[SgtCottle]

Any larger than .120" is excessive because the interior diameter of the gas tube is only .120".

Trying to get a carbine gas system to cycle subsonics is next to impossible, but there are rumors that they exist. After spending 50+ hours in two carbine length gas systems I sold them off. They shot beautiful supersonics but even with 265g bullets I could not get them to cycle consistently. Something is wrong with either the bullets or chamber on this rifle. Anytime the gun is "pulling bullets" there needs to be some investigation done. Stop everything else your doing (changing springs, triggers, buffers, ect...) until you get this ironed out. Personally I would send this barrel back to the manufacturer and let them know that it has issues - at the very least get a "GO" "No GO" gauge and check it out. Something is amiss there and no matter what you change - that chamber has to be looked at first.

Sarg

[thehouseproduct]

I ended up using reduced loads of 2230 or X-terminator to get mine to cycle subsonic in the carbine position. People get very hung up on the pistol powders being the only way to go slow. I am at 13.9gr of x-teminator. Roughly 80 degrees and sea level. this is with a stock springs, buffer, etc. I am unsure what the gas port is on the DTI barrels.

[Colohunter]

I ended up using reduced loads of 2230 or X-terminator to get mine to cycle subsonic in the carbine position. People get very hung up on the pistol powders being the only way to go slow. I am at 13.9gr of x-teminator. Roughly 80 degrees and sea level. this is with a stock springs, buffer, etc. I am unsure what the gas port is on the DTI barrels.

Interesting, I have only been using my X-Terminator for 223 and 6.8, what bullets are you using and what velocities are you getting with that load? I may have to try that as well.

[thehouseproduct]

Interesting, I have only been using my X-Terminator for 223 and 6.8, what bullets are you using and what velocities are you getting with that load? I may have to try that as well.
13.9 grains with a 220gr SMK

[SgtCottle]

what velocities?

[thehouseproduct]

what velocities?

1050-1100 at roughly 80 degrees, sea levelish