PCC flatness

[MemphisMechanic]

I offer this up for your consideration. It was the only string on “Can You Count” where I didn’t have trigger freeze. This was the first match with a rifle for me.

 

CMMG Guard.

Sprinco red spring.

5oz .308 carbine hydraulic buffer.

Wave spring with one quarter in front of it.

Surefire comp with top port slowly dremeled open until gun shot flat.

 

Post a video up if your gun shoots as flat, or flatter:

 

 

[JAFO]

I've been thinking about opening up the small top holes on my Lantac, primarily because they keep getting clogged with lead.  I suppose doing so might also allow it to shoot flatter, but I'm skeptical it would make much difference.  Is your evaluation of how flat it shoots based solely on opening up the comp, or did you change multiple parts?

[jtrump]

9 minutes ago, JAFO said:

I've been thinking about opening up the small top holes on my Lantac, primarily because they keep getting clogged with lead.  I suppose doing so might also allow it to shoot flatter, but I'm skeptical it would make much difference.  Is your evaluation of how flat it shoots based solely on opening up the comp, or did you change multiple parts?

 

I'm waiting on my lantac to arrive,   debating opening up the holes as well.   Could you keep me posted should you try to experiment?

[jtrump]

I can defiantly see the gas porting out of the top first!   You shooting a hot load or what PF is that around @MemphisMechanic

[BigBamBoo]

I have been pretty impressed on how flat my little humble Ruger PC Carbine shoots. 

 

 

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[JAFO]

28 minutes ago, jtrump said:

 

I'm waiting on my lantac to arrive,   debating opening up the holes as well.   Could you keep me posted should you try to experiment?

 

Sure.  I've watched video of me shooting, and there's a good deal of gas being directed to the sides, so I don't know how much will end up going out the top, even if I open it up.  In retrospect, I should have gone with a comp that only had top ports.  Something like the MBX.

[MemphisMechanic]

1 hour ago, jtrump said:

I can defiantly see the gas porting out of the top first!   You shooting a hot load or what PF is that around @MemphisMechanic

 

125gr BBI on top of 3.7 Prima V. 

 

140-145 PF. I haven’t chrono’d it since shortening it from 1.115” to 1.085” to fit the short chamber of the Guard, but it was 140 before I did that.

 

Edited July 18, 2018 by MemphisMechanic

[MemphisMechanic]

1 hour ago, JAFO said:

I've been thinking about opening up the small top holes on my Lantac, primarily because they keep getting clogged with lead.  I suppose doing so might also allow it to shoot flatter, but I'm skeptical it would make much difference.  Is your evaluation of how flat it shoots based solely on opening up the comp, or did you change multiple parts?

 

I ran it with the top ports stock. Then drilled out to 5/32”. Then I cut the two holes into a single oval-shaped port.

 

I did all of that without any other changes. It got flatter and flatter each time.

 

I also think that lightening my barrel and handguard so much really helped. The port is 15” from the reciever, and doesn’t have much weight  out there resisting it’s desire to push the muzzle downward.

 

My CMMG barrel was turned down to .625” and then shortened for a pin & weld. Handgard is the absolute lightest one made. This gun is 6lbs 0.5oz and feels like all of that is behind the barrel nut.

 

Edited July 18, 2018 by MemphisMechanic

[MemphisMechanic]

1 hour ago, JAFO said:

 

Sure.  I've watched video of me shooting, and there's a good deal of gas being directed to the sides, so I don't know how much will end up going out the top, even if I open it up.  In retrospect, I should have gone with a comp that only had top ports.  Something like the MBX.

 

My comp looked like this after the topholes were drilled out, then connected with a dremel:

 

 

 

I think that if you open up the lantac you might really like it. All that matters is which hole your gas hits first. As long as that’s the 12o’clock one you should be able to open the top of the comp up more and more until it works right.

 

Just get your ammo and buffer/spring dialed in first so you know how much dot bounce you have left to kill.

 

NOTE: I did create a second upward-facing port further forward. This proved to be a waste of time; judging by the total lack of carbon and leading and what I see on video... it doesn’t do anything. Once the gas hits those big side ports, it’s gone. A PCC doesn’t have much gas to work with in the first place.

 

Edited July 18, 2018 by MemphisMechanic

[JAFO]

21 minutes ago, MemphisMechanic said:

I think that if you open up the lantac you might really like it. All that matters is which hole your gas hits first. As long as that’s the 12o’clock one you should be able to open the top of the comp up more and more until it works right.

 

Just get your ammo and buffer/spring dialed in first so you know how much dot bounce you have left to kill.

 

I have two top holes prior to the first of three side ports, and then two smaller top holes positioned over the last side port.  From what you've tried, enlarging the second set of holes would be a waste, so I guess I'll try the two at the rear.

 

As for the buffer/spring combo, I have been using a hydraulic buffer with a .308 rifle spring for my load, but I was thinking of backing off to a .308 carbine spring.  It's currently got a pretty smooth recoil, but others have told me it's got more dot movement than they have with a standard buffer.  I haven't tried messing with a wave spring at all.

[jtrump]

1 hour ago, JAFO said:

 

Sure.  I've watched video of me shooting, and there's a good deal of gas being directed to the sides, so I don't know how much will end up going out the top, even if I open it up.  In retrospect, I should have gone with a comp that only had top ports.  Something like the MBX.

 

My friend has the MBX and it is doing his gun no favors in terms of flatness, our guns are setup basically identical except I'm running a JP comp and he runs an MBX.   I would say ours handle/felt recoil/muzzle rise and dot movement are SUPER close.

[MemphisMechanic]

27 minutes ago, JAFO said:

 It's currently got a pretty smooth recoil, but others have told me it's got more dot movement than they have with a standard buffer.

 

Smoothness and softness don’t matter. Only dot movement (flat shooting) matters.  

 

I would highly recommend trying a wave spring with a single quarter dopped on top of it at the back of the buffer tube.

 

A guard and a full blowback are different animals, but my gun REALLY smoothed out. I don’t know how much of it was from de-stroking it a full inch, and how much was from the wave spring’s movement itself.

[MemphisMechanic]

1 hour ago, JAFO said:

 

I have two top holes prior to the first of three side ports, and then two smaller top holes positioned over the last side port.  From what you've tried, enlarging the second set of holes would be a waste, so I guess I'll try the two at the rear.

 

Definitely open up the rear ones. How much? Good question. Depends on the gun. Just go slow and test it every time until it flattens out.

 

Obviously you have to already be pretty close to flat; it isn’t an Open gun and the comp has very little pressure to work with.

 

I believe the only reason to open up the front holes  would be to make them easier to clean.

 

Edited July 18, 2018 by MemphisMechanic

[Patrick Scott]

The video angle/shooting position is not nearly as good as the OP, but here is my gun. Blowback, 140PF ,124gr JHPs, .308 recoil spring, hydraulic buffer, wave spring, full length stroke, CK Arms comp. Gun weight is 7lbs, and I only weigh 135lbs soaking wet. 

 

Edited July 18, 2018 by Patrick Scott

[rowdyb]

the camera on my head jiggles more than the gun or the sight.

 

 

[MemphisMechanic]

@Patrick Scott I don’t know. It looks plenty flat if you pinch-zoom in.  

[Flatland Shooter]

3 hours ago, MemphisMechanic said:

I ran it with the top ports stock. Then drilled out to 5/32”. Then I cut the two holes into a single oval-shaped port.

 

I did all of that without any other changes. It got flatter and flatter each time.

 

 

Do you think you might have the same results if you had increased the size of the hole instead of cutting them into one oval shaped port?

[MemphisMechanic]

Eventually, I’m sure. Eventually, they’d have touched anyway.  

 

My thinking was drilling it out would send more gas outward as well as upward... and I wanted upward.

[JAFO]

Had to go back to an early thread to find the Amazon link for the wave springs.  Guess I'll try one of those first, along with the 308 carbine spring to see where things are before I start drilling out.

[Fo0]

MBX claims ' softest shooting blow back gun available' 

[HoMiE]

Second string had like one hole in target after reload. 

 

 

Edited July 19, 2018 by HoMiE
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[MemphisMechanic]

@HoMiE that looks flat...

 

I’ve never seen someone do the outsides then the insides on strings like that.

 

Always the left pair first, then the right pair on string 2. Or vice versa.

 

What was your thinking behind running Can You Count that way?

Edited July 19, 2018 by MemphisMechanic

[HoMiE]

53 minutes ago, MemphisMechanic said:

@HoMiE that looks flat...

 

I’ve never seen someone do the outsides then the insides on strings like that.

 

Always the left pair first, then the right pair on string 2. Or vice versa.

 

What was your thinking behind running Can You Count that way?

The outside targets are closer and lower so I don’t need to get the gun up as far, then just bring rifle up on reload. 

[rowdyb]

that's how i shoot it with a pistol, outsides then in. i am jealous of all you guy's pcc reload skills.

[HoMiE]

8 minutes ago, rowdyb said:

that's how i shoot it with a pistol, outsides then in. i am jealous of all you guy's pcc reload skills.

I also shoot production so get a lot of practice, but pcc is definitely harder reloading.