Model 1 Sales 300 whisper upper function problems

[mtb8r3]

Sorry for the delay...
Yes, I was using .223 LC brass cut down. 10 gr with 210 Berger’s showed no pressure signs, but 10.2g was just beginning to flatten the primer (Winchester). You may be correct about case volume. If you get the chance, send me an average case measure of grains of water and I will post a comparison. The 10.2 gr load will eject, but not chamber another round. I am thinking that a slightly slower powder may be in order.

Now that I have had some time (and weather) to do some more testing, my 185 Lapua moly load with 10.2 g H110 is shooting 1" 10 shot groups at 100.

[Zed Stewart]

Just in case everybody doesn't know, H110 and 296 are the same powder. The minor differences in published loading data is from different lots of powder being compared, not actually different powder.

[jripper]

I always figured they were, but could never get a positive answer.

Thanks

[sharpshooter33]

hello gang. I've been outta the loop for awhile working on other projects. Now that I've got some time I went to the range with a wrench for my adjustable gas tube on my M1S 300/221 barrel.

I am using a 16" M1S 300/221 barrel, standard stock and buffer situp and AR15 bolt carrier.

On last report I tried the 220 Corbon and found as you did it didn't cycle the bolt. I opened my adj gas tube all the way up today and it ejected the spent casing, but would not pickup a new round. I'm going to take the barrel off tonight and measure the gas port. If it comes out under .120 that will be my next step. I'll open it and send it off to have it threaded. I'm working on this for a suppressor project. Does anyone know how a suppressor will effect the function if any?

I'm assuming that there would be noticable function changes if it's functioning with 220gr before it should function after.

I'll let you all know what I have to do to get mine to cycle like a champ, but I agree with Jripper that for the $$$ these are a good buy. We also could help them out by letting them know about the hole diameter fix so future 300/221 don't suffer our problems and shoot the company down.

Thanks for everyones input here it has really helped me.

[sharpshooter33]

BTW I believe the threading is 5/8 x 24tpi?
If so it matches Bushmasters threading for there 308 rifles and they have a nice AK style brake to fit it.

I'm having my AR10T and 300/221 threaded 5/8 x 24tpi for muzzle brakes of that size and also a suppressor.

[sharpshooter33]

Hey I pulled my M1S 300/221 barrel off last night. The hole is around .118 I believe. I'm gonna open it and the hole in the block and tube up to .120+

Hey did anyone check the I.D. of the gas tubes. They are around .120 I think. If the port is opened up the gas won't flow any faster than the smallest point. Opening up the port wouldn't make any difference after about .130. I'm going to make sure mine is opened up to .120 to .130 then I'm gonna work on loads. The Corbon's shot 6" lower from 150gr to 220gr at 50yards. I don't have a Chrono either, but I'm thinking I can get mine working with subsonic 220gr if I use my own loads. I think Corbon 220 subsonics must be anorexic. Has anyone Chrono'd there load out of a AR15?

going shopping this week for some AA1680. Already have the 220gr and brass waiting for me.

Question the 11gr AA1680 for the 220gr tha Jripper is using, what type of cases are you using. I've got Federal, LC and 221.

Thanks
David

[jripper]

Thought I'd chime in again. I have been told that most tube are .120 inside. I think when I drilled mine out, that was the closet bit size that I had, as going over the inside tube diameter will not help. Also, if you look at ballistics of a 220 sierra at 1000, and a 150 grain at 2000, it is not suprising that there was that much of a change in point of impact. Also, make sure your bolt works freely. Mine was very stiff, and I think that makes a difference in how light a load it will cycle. I have not chronographed the corbon subs myself, but in another post on this sight, someone chrono them, and they only came in at 850 fps. My subsonic loads were loaded into Federal 223 brass, that I re-formed into 300 whisper.
I have also heard that putting a supressor on your gun will create more back pressure, and improve cycling, but I can not verify this, as I live the in Republic of Illinois, and can't own one.

Lastly, another post on this sight stated that the threads on the model 1 barrels were at 1/2 x36, but there again, I can not verify this myself.

Joel

[sharpshooter33]

AGT(adjustable gas tube) Has everyone been using one of these? I noticed when I disassembled mine to send the barrel off for threading that the gas tube is leaking at the adjustment block.

My 300/221 was close to cycling with the subsonic from Corbon. I'm wondering now if the gas tube could have been enough to make it not cycle fully.

Has anyone use a standard gas tube? I'm wondering if there is any problems with a standard tube. Does it create that much difference from subsonic to supersonic? I'm thinking of trying the standard gas tube. At this point the only advantage of the adjustable would be the ability to turn it completely off. I don't think the recoil/return gas on the supersonic rounds it that drastic that I really need the AGT.

Any opinions on this? :?:

[mac66]

Hello all-- I too have had ongoing problems with my .300 whisper. It is an AR-15 w/ a 16" barrel with the gas port in the carbine position. I first purchased a JP adjustable gas block and a "Pigtail" gas tube. It will now eject the empty (supersonic) and, about 50% of the time, chamber a new round. Subsonic rounds smokestack and/or fail to feed. After reading the above posts, I have been looking at the gas port diameter and will open it up to .125 this week. I also polished the chamber with my Dremel and Flitz to reduce any friction that may be contributing to the problem. I'll try to test fire this week. Thanks for the ideas.

[sharpshooter33]

mac66,
I would trade out the pigtail tube for standard. The pigtail will be doing the opposite of what you want. It is slowing the ejection. I could be wrong about that, but from what I understand the pigtail delays the gas operation. It was good for 7.5" AR15 barrels, but I'm not sure it a good idea for the 300 Whisper. Can anyone else provide info on the pigtail.

My understanding of the pigtail was that the bolt on 7.5" was either tearing away cases because there wasn't enough time before the case was being ripped from the chamber or it was sending it back too violently and ripping the cases.

Someone with an understanding or experience with this chime in.
Who's 300 do you have? Is it also a Model 1?

Originally Posted by mac66

Hello all-- I too have had ongoing problems with my .300 whisper. It is an AR-15 w/ a 16" barrel with the gas port in the carbine position. I first purchased a JP adjustable gas block and a "Pigtail" gas tube. It will now eject the empty (supersonic) and, about 50% of the time, chamber a new round. Subsonic rounds smokestack and/or fail to feed. After reading the above posts, I have been looking at the gas port diameter and will open it up to .125 this week. I also polished the chamber with my Dremel and Flitz to reduce any friction that may be contributing to the problem. I'll try to test fire this week. Thanks for the ideas.