New 300BA build, need first hand experience

[Pacheco]

Hello y'all , new member here looking for opinions and first hand experience.
So long story short looking to build a 300BA dedicated rifle(probably).

So looking at the carbine gas system since all the 300 ive shot had a pistol length gas system and they recoiled pretty hard. My problem is not recoil but follow up shots.
Ibknow a brake would reduce recoil but I have a spare vg6 gamma(CA compliant).
Not going to shoot subs or slow heavy cartridges so i see no need for the dirtier and more violent PLGS.
Any input folks?

[Flatliner]

Many here are far smarter and more experienced than me but to solve that specific problem, my approach would be an inexpensive adjustable gas block I set and forget.

[dellet]

There are two different things going on. Recoil does not change with gas port location or size.

Gas port location or port size can/will effect followup shots.

Recoil in simplest form is a combination of energy created by bullet weight and velocity absorbed by rifle weight and stock design. Where you place the cycling gas port, or if it even has one will not change this.

What port size and placement change is cycling speed of the carrier and buffer combined with their weight. This second movement of parts and pounding can delay accurate follow up shots.

While it is true you can slow this speed and drop the reciprocating mass of the carrier and buffer with an adjustable gas block. It seems to work better and give a wider range of adjustment by starting out with less gas and pressure to begin with. Carbine gas length allows this. The problem with anything but a custom barrel is that the port will be too large and the sysyem will be over gassed.

I use carbine length for barrels as short at 10" and find them easier to shoot than any of my tuned pistol length barrels.

[TRshootem]

I'm looking at a 10"-11" barrel for a pistol upper. I have two 'pick your brain' questions in regard to a carbine gas port for this barrel.

First: 1/8 twist or other option?

Port size, carbine location... recommended diameter?

This is a 410 SS blank, can be chambered, profiled, ported, threaded and cut to my specification. This nice 'left over' chunk is waiting to be used

[dellet]

If it came from a decent blank, it might be worth holding onto. Unless they all disappeared in the latest panic you can probably buy one for $75 or less. That way if you don’t like it, you still have the blank.

If you want to shoot both sub and super, 1/8 is fine. One of the things I have found with the faster twists like 5 & 6 it can limit some supers. I only had trouble with a couple in the 1/6 and that was in a 24” barrel. Things start coming apart at 2300 fps in the 1/5. The 1/8 for subs will stabilize just about everything out there. You may not have maximum BC so drop some out at 3-400 yards might suffer.

If you use a suppressor all the time, I might be tempted to have a port drilled around .090” just to see what happens. My 16” is .097” and works fine with subs un-suppressed, just limited to 5 or 6 powders. I had an 18” for awhile with a .089” port and the same loads from the 16” worked fine. The longer the dwell time, the smaller the port you can get away with.

The barrel I have started as a 10.5”. The guy that had it drilled the port to .125” and welded a can to keep from getting a stamp. I had the shoulder cut and muzzle crowned so it’s probably about 10.25”. Without a suppressor, I have only found working loads with 3 powders for subs. Supers H110/296 works as well as the factory loads I have tried.

Suppressed, I still use an adjustable block and dial it back. The fastest powder used for suppressed subs is 296, favorite load is probably a 178 Amax with 296.

To put things in perspective, I put an 8” upper together last weekend of slightly unknown origin. Factory subs cycled but would not lock back reliably. Thoughts went to tight BCG being new, lack of lube whatever. Finally pulled the gas block to check alignment and leakage. Block was not quite as centered as I would like, but looked pretty small compared to the carbon ring. Measured the port at .076”. This was an experimental 16” pistol gas barrel that got cut down. Drilled the port to .084” to get factory subs to cycle and lock back reliably suppressed.

If you want to tinker and learn, I would start with a small port. If you want to put it together and hit the range, I would probably start around .105”. Even at .125” it won’t be obnoxious over gassed with suppressed supers.

Long winded but hopefully useful.

[TRshootem]

Dellet, thanks for your thoughts and details. My 10.5" pistol has a .95 port, works fine for subs, adjustable block tames just enough for supers and usually suppressed. By the time I pay my friends cost for his time a new BA barrel will be cheaper. He will no doubt do this in his spare time, I would want to honor his skill and friendship with an investment in his time. Gonna think some more on what I will do. It was our thought this .30 cal chunk of metal would be a real shooter, like the 16" .308 build the rest of it went to.

I have been casting some 200 gr Lee to coat for the BLK, sure has been awhile since my last run of these. They are nicely accurate with N120 or 1680, but man, what a bunch of time spent.

Thanks again, later.

TR
'

[dellet]

Dellet, thanks for your thoughts and details. My 10.5" pistol has a .95 port, works fine for subs, adjustable block tames just enough for supers and usually suppressed. By the time I pay my friends cost for his time a new BA barrel will be cheaper. He will no doubt do this in his spare time, I would want to honor his skill and friendship with an investment in his time. Gonna think some more on what I will do. It was our thought this .30 cal chunk of metal would be a real shooter, like the 16" .308 build the rest of it went to.

I have been casting some 200 gr Lee to coat for the BLK, sure has been awhile since my last run of these. They are nicely accurate with N120 or 1680, but man, what a bunch of time spent.

Thanks again, later.

TR
'

I guess if we could get a weekend out of lockup and without snow around here we could try to meet up somewhere and you could shoot mine. Might be a good excuse no matter what.