300blk mule kicking

[reverendg]

The initial recoil should have nothing to do with the recoil spring or the gas system. The initial acceleration of the projectile, and the attendant opposite reaction, takes place before the gas port is reached in the barrel, meaning the bcg is still locked in position. Nothing can be done to mitigate that recoil except to load lighter projectiles or lower powder charges.

[DwayneZ]

The initial recoil should have nothing to do with the recoil spring or the gas system. The initial acceleration of the projectile, and the attendant opposite reaction, takes place before the gas port is reached in the barrel, meaning the bcg is still locked in position. Nothing can be done to mitigate that recoil except to load lighter projectiles or lower powder charges.

Agreed, but the energy in the bcg still has to go somewhere, and it's still my shoulder the buffer spring is "attached" to. So on the buffer spring side of the semi auto we can at least manage how that piece of it handles the energy the bcg is carrying. In essence there are two recoil pulses that happen back-to-back very quickly.

And yep, only so much can be done on the cycling side of the house, but getting it to soften as much as possible while still doing a good cycle is about the end of tuning in that area.

I'm using H1 carbine buffer/spring. That seems too light for a std 300 with a large 120 gas port.

Here's why I think my issue is on buffer-spring side. As I mentioned, initially the gas block was misaligned, it was barely cycling w/ 1 in 4 fail. So I was very close to being bolt action at that point, and at that time there was very little kick, I kinda thought "ah, this is cool, it's very ez on the shoulder". But after fixing the gas block alignment is when the mule kicking started.

[DwayneZ]

That sure sounds like it is over-gassed to me. Get one of these? https://blackrivertactical.com/WP/Ad...Drive-c6464009

So the tubes are like adj gas block?
They suggest tube hole one size bigger than barrel port.
Are you suggesting just using tube that is smaller than barrel 120 ? Their largest is a 76.

The GM barrel folks don't even suggest using adj gas block for their carbine 16" that has huge 120 port. Perhaps they should. One review there mentions having issue with adj gas block and simply went back to std block.

[Clint]

For supersonic ammo only, the gas port can be reduced with an EZTUNE gas tube.

https://blackrivertactical.com/WP/BR...ine-p103167251

Just select "normal" for the tune and "300BLK super only" for the ammo, along with all the other obvious questions.

We'll select the best port size from there.


More info here:
https://www.m4carbine.net/showthread...TUNE-Gas-Tubes

[Disciple]

The initial recoil should have nothing to do with the recoil spring or the gas system. The initial acceleration of the projectile, and the attendant opposite reaction, takes place before the gas port is reached in the barrel, meaning the bcg is still locked in position. Nothing can be done to mitigate that recoil except to load lighter projectiles or lower powder charges.

The rifle barely moves before the carrier is accelerated rearward.

[DwayneZ]

The rifle barely moves before the carrier is accelerated rearward.

True.

There's a lot of energy being put into the BCG, and it has to go somewhere. Ideally the BCG should not slam into the back of the buffer tube or compress a spring into bind. If all the BCG energy goes into the spring (with a little heat) and it returns BCG back to battery, that's ideal. If the BCG has more energy than the spring can absorb then there's gonna be one of those inelastic collisions which will feel like a hard kick depending on how much extra energy the BCG is carrying beyond total spring compression.

With an over gassed system we can still fine tune the buffer weight and spring to handle that BCG energy, but it will not eliminate the extra energy from being over gassed.

My 300 is definitely over gassed (too much energy transferred to the BCG). How do we know? Because with a std carbine buffer & spring the BCG is slamming the back of the buffer tube.

To fine tune the energy there is no other way, you need to adjust how much gas energy reaches the BCG.
To changes the energy dissipation profile we can turn to buffer weight and spring K factor.
Tuning the gas is the best way.

I will try an H3 buffer weight just to see if that removes the impact force. And after that perhaps a heavier spring. After that (as needed) I will look at gas tube and gas block.

[wanderson]

I agree that it’s almost impossible to overgas a 16” .300bo.
I do think an H3 buffer is a good start, then either a stock upgrade or a good recoil pad like a Limbsaver.
On my 16” carbine sys. 300bo I mainly run an H3/std. spring for supers and switch to a std. weight 3oz buffer for subs.

A recoil reducing stock like a Fab Defense may help as well.

I’ll admit I’m a wimp, I can shoot ARs & AKs with good aftermarket stocks all day but switching over to a surplus rifle with a metal buttplate like a Mauser or an SKS will bruise me after a few rounds without a slip on pad. An unpadded M4 stock is almost as bad. Even the $10 no name M4 rubber pads are a welcome upgrade.

[DwayneZ]

I agree that it’s almost impossible to overgas a 16” .300bo.
I do think an H3 buffer is a good start, then either a stock upgrade or a good recoil pad like a Limbsaver.
On my 16” carbine sys. 300bo I mainly run an H3/std. spring for supers and switch to a std. weight 3oz buffer for subs.

A recoil reducing stock like a Fab Defense may help as well.

I’ll admit I’m a wimp, I can shoot ARs & AKs with good aftermarket stocks all day but switching over to a surplus rifle with a metal buttplate like a Mauser or an SKS will bruise me after a few rounds without a slip on pad. An unpadded M4 stock is almost as bad. Even the $10 no name M4 rubber pads are a welcome upgrade.

I think this is false. With my block misaligned it was still firing ok w/ very little recoil, but 1 in 4 would fail to pickup a new round. The misalignment was making it undergassed, but right on borderline of being ok.

At least on my M27 16", a 120 car gas port is way big for std ammo.

[bamashooter]

Just a FYI for the inexperienced shooters. Regarding "bruising, harshness, etc to the shoulder area, much of this can be eliminated or minimized by pulling the buttstock into the body with firmness. With appropriate firmness, the energy (recoil) is more of a push / shove than it is a hammering / pounding. Observing a "light" grasp of handguns and long guns is not infrequent and the results, ranging from poor marksmanship to discouragement, is all to apparent and predictable.

[Todd.K]

Supersonic is towards the higher end when subsonic needs to function. It can be reduced a bit for only supersonic, but not that much.

300 port size cannot be compared to 5.56, and piston cannot be compared to DI. The 300 has an enormous increase of bore area for the gas to expand into vs a 5.56 bore.