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idleclamp

Too much Comp?

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I've built a 9mm AR-15 with a 10.5" barrel and a SLR Rifleworks Synergy mini comp 1/2x36.  While I've had this rifle for a while, I am just now getting  into competing with it.  But I haven't had much time to really wring it out.  I have been experimenting with different loads and finally settled on one (at least for now).  It's 4.0 grains of N320 under a 115 MG JHP.  PF is about 137.  I've noticed that the dot moves around a bit when I shoot, but I attribute that to just needing more practice with it (been shooting revolver all year).  However, I noticed something on a video at the last match I shot.  It seems like I have TOO MUCH compensation.  I posted a video of the stage I shot.  Briefly, the procedure was to pin the good guy (non-threat on a swinger) to the table and Mozambique the two targets.  This meant that I had to shoot strong hand only.  As you can see in the video, the second shot on both targets hit quite a bit lower than the first shot.  All the reading that I've been doing suggests that the comps do virtually nothing, yet many guys are running them.  The difference could be that I'm running a SBR.

 

So, I'm looking for suggestions.  My first thought is a different comp.  One that ports more out the sides.  But I figured I'd ask before I started spending money.

 

 

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With a 10.5” barrel, N320, and minor pf ammo, I seriously doubt your compensator is the reason for the second shot being low.

 

 

What’s your buffer setup?  Bolt?

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I wouldn't base any purchases or make any decisions based on shooting strong hand only.  Next time you take it to the range, BURY it in your shoulder and try again.  I suspect you'll see that pattern tighten up significantly.

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16 minutes ago, CalTeacher said:

With a 10.5” barrel, N320, and minor pf ammo, I seriously doubt your compensator is the reason for the second shot being low.

 

 

What’s your buffer setup?  Bolt?

QC10 bolt.  It's been a while, and I don't remember the buffer and spring.  I've attached pics.  I weighed the buffer and it's 5.5oz. I pulled a buffer from a stock RRA AR-15 to compare.  The length is the same, but this one is heavier.

Buffer1.jpg

Edited by idleclamp

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5 minutes ago, longbeard said:

I wouldn't base any purchases or make any decisions based on shooting strong hand only.  Next time you take it to the range, BURY it in your shoulder and try again.  I suspect you'll see that pattern tighten up significantly.

When I hold it tight, it definitely makes a difference.  But, this is a 9mm and people keep saying it doesn't need a comp, yet many people are running them.  The rifle is moving in an unexpected direction.  I'm trying to figure out why. Thanks though.

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Weight removed from the bolt?

 

 

o would run some drills with a strong hold on the gun.  Set a target at 10-12yds and run splits as fast as you can pull the trigger.  Put a piece of black tape on a target, put your dot on the tape and see how fast you pull the trigger.  See where the shots are impacting.  I suspect the second round hitting low was due to a less than optimal hold on the rifle at your match, as mentioned above.

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1 minute ago, CalTeacher said:

Weight removed from the bolt?

 

 

o would run some drills with a strong hold on the gun.  Set a target at 10-12yds and run splits as fast as you can pull the trigger.  Put a piece of black tape on a target, put your dot on the tape and see how fast you pull the trigger.  See where the shots are impacting.  I suspect the second round hitting low was due to a less than optimal hold on the rifle at your match, as mentioned above.

No, the weight is not removed.  I can certainly do that.  It was a less than optimal hold.  With an optimal hold, the second shot still goes low, albeit much less.  My point is that it seems to be moving the wrong direction for recoil, which is why I (at first) thought it was the comp.

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The problem is likely too much buffer return energy driving the nose down. If you’re shooting light loads, try a lighter buffer and spring and I’m sure you’ll have better results. If you’re shooting standard loads, try a lighter spring.


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2 minutes ago, 1911luvr said:

The problem is likely too much buffer return energy driving the nose down. If you’re shooting light loads, try a lighter buffer and spring and I’m sure you’ll have better results. If you’re shooting standard loads, try a lighter spring.


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I hope to hit the range later this week. If I make it out, I’ll try that and report back. Thanks.

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I think you would be better served with a brake similar to this.   I have them on two PCC's, albeit with longer barrels, and they allow me to double tap groups tighter than that at 25 yards as quickly as I can pull the trigger. 

mbr95-AR9mm-Custom-TPI-Competition-Muzzle-Brake-1-2-x-36-Pitch-Thread-1-800x800-800x800.jpg

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I wouldn't spend any money on a new comp.  From the looks of the video, the gun was jumping around way too much.  I would get a buffer recoil system.  I think you would benefit from the bounce being limited.  From the distance your were shooting, your double taps should have been pretty tight.

 

I run the Taccom 3 stage buffer with the short stroke kit in all of my PCC's

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2 hours ago, stick said:

I wouldn't spend any money on a new comp.  From the looks of the video, the gun was jumping around way too much.  I would get a buffer recoil system.  I think you would benefit from the bounce being limited.  From the distance your were shooting, your double taps should have been pretty tight.

 

I run the Taccom 3 stage buffer with the short stroke kit in all of my PCC's

This. Remove the weight. I run a similar load/PF as you. Longer barrel 14.5 pinned JP barrel with their tactical comp. Gun is scary soft very fast, dot does not move & I shoot 1-handed and off shoulder due to being blind in my right eye on hard right hand leans all the time.

 

gerritm

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I concur, I would play with the buffer weight/buffer spring and BCG weight before anything. The reciprocating mass seems to effect PCCs more than anything.  Also try holding the rifle differently and take a few shots at 15-20 yards to see the difference. I know with my configuration holding the gun as tight as possible isn't optimal for close splits. 

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I made it to the range a couple days ago.  First off, i figured out that the buffer is heavier (5.5 oz) and the spring that was in it was a JP .308 spring.

 

The first thing I did was add a plug at the opposite of the recoil spring to shorten the stroke.  I forgot that I had taken it out trying to work out another problem.  That made an immediate difference.  Then I started trying different combinations of 3 recoil springs and the other buffer I have which is a Spikes 9mm 7.5 oz buffer.  Nothing seemed to make a noticeably more difference than restricting the stroke.  One thing I did not try was removing the weight from the BCG because I forgot to bring the tools to do so. I also switched to the 16” upper for a little bit and there was even less jump (obviously).  But it doesn’t swing as fast as the 10.5”.

 

At the next range session, I will bring the tools to remove the BCG weight and see what that does.  Thanks for all the help!

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1 hour ago, andrewt556 said:

Comp's also make chronoing more difficult. 

How so?

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2 hours ago, Sarge said:

How so?

Sometimes you dont get a good reading. Went to uspsa major match yesterday and pretty much every comped pcc had trouble at chrono. 

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1 hour ago, andrewt556 said:

Sometimes you dont get a good reading. Went to uspsa major match yesterday and pretty much every comped pcc had trouble at chrono. 

That sounds like a chrono issue to me. I have seen dozens of chronos run PCC with no issues.

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42 minutes ago, Sarge said:

That sounds like a chrono issue to me. I have seen dozens of chronos run PCC with no issues.

Not sure it just seemed the only pcc's that had trouble had comps. I have a taccom ulw which is a 4" barrel with a 16" shroud and I expected trouble but it turned out fine. 

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As mentioned you muzzle likely dipping because of your heavy buffer/spring combo and the amount of forward and reward travel the buffer has. Remove the bolt weight, get the Taccom Short Stroke 3 -Stage kit.  If you want to see less dot movement try running a spacer at the bottom of the buffer tube to further shorten the stroke. I only installed a comp after my first match and the timer did not pick up my last shots on a classifier. 

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6 minutes ago, 3gunnuts said:

As mentioned you muzzle likely dipping because of your heavy buffer/spring combo and the amount of forward and reward travel the buffer has. Remove the bolt weight, get the Taccom Short Stroke 3 -Stage kit.  If you want to see less dot movement try running a spacer at the bottom of the buffer tube to further shorten the stroke. I only installed a comp after my first match and the timer did not pick up my last shots on a classifier. 

The spacer made an immediate difference. Next time to the range I’m going to try it with the BCG weight removed. If I can’t get it to feel the way I want, that will probably be my next step. Thanks.

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