Anyone using the BPM adjustable gas tube on the AR-10 platform?

[Fire4EffectCA]

I have been using the MGI adjustable gas tube on my very early Knight’s SR-25 (1993 1st 100 made) and I would like to upgrade to an adjustable model sold by BPM. Does anyone have experience with these? Any issues? The MGI adjustable gas tube installed on my SR-25 just clears the barrel and handguard and I suspect the hole I drilled in the handguard for the MGI adjustable gas tube will not work with the BPM adjustable gas tube. Most likely I will have to create a slotted opening.

A Little History

I installed the MGI adjustable gas tube about 20 years ago and I do enjoy the reduced recoil, but I had a problem this past Friday when I switched from custom factory loaded 308 WIN ammo to Federal 168 gr Matchking BTHP. After firing the first shot the bolt would not strip the next round in the magazine. I did not have the proper Allen wrench with me so I could not adjust the system until I got home. When I got home I was surprised to see the amount of carbon around the adjustment block. I checked the adjustment screw and it was loose. Normally the screw would be tight due to carbon locking the threads. This rifle is shot very little, but I have not had this issue before. The last three times I shot it were 2006, 2017 and this past Friday. It shoots under 1 MOA easily.

 

[bfoosh006]

Pics not working for me ?

 

[Fire4EffectCA]

Pics not working for me ?

I don't know why you can't see them.

 

[Fire4EffectCA]

I had a very informative conversation with the owner of Barnes Precision Machine and I am going to give his adjustable gas tube a try. It appears to be a significant upgrade from the original product from MGI.

 

[Fire4EffectCA]

I received my Barnes Precision Machine adjustable gas tube this past Friday and installed it yesterday. Construction and machining appear to be excellent. The adjustable gas block sits further back than the MGI adjustable gas tube it replaces so I had to create a new opening for adjusting the gas tube. I did my best to locate the new opening, but landmarks to make measurements from did not allow for precise measurements. I was off a little to the rear and to the left and a 0.25" hole would allow an Allen wrench to actuate the adjustment screw, but I did not like the hole being off center. I decided to change the opening to a square, which permitted me to center the adjustment block in the hand guard opening. Now I need to find time to get to the range.

This SR-25 is one of the first 100 built back in 1993 and I purchased it directly from Knights 27 years ago. I don’t believe a lot of the first 100 SR-25’s were released to the public. Fortunately I was able to pick up a new handguard 20 years ago so I will always be able to put it in its original configuration.

 

[Fire4EffectCA]

The rifle performed well, but it looks like I am running full open to lock the bolt back on the last shot. I could not locate any significant leaks so my rifle may not be over gassed.

I fired the three different loads listed below.

Custom Load: DS Mfg 308 Win 168 gr Hornady BTHP (1993 mfg)
Factory Load: Federal 308 Win 168gr Sierra Matchking BTHP
Factory Load: Federal 308 Win 175gr Sierra Matchking BTHP

The custom loaded DS Mfg 308 Win was purchased back in 1993. They used new Winchester brass and I believe 168 gr Hornady BTHP bullets. I don’t know what powder and primers they used. This load was outstanding. All three loads shot under 1 MOA and I typically shoot between .6 to .8 MOA, but I was able to shoot 4 shots into 0.2” and all 5 into 0.64” at 100 yards. That 4 shot group is insane. See attached photo.

The loads above are listed in order of accuracy. The DS Mfg was the most accurate. The Federal 308 Win 175gr was the least accurate. All shot under 1 MOA.