It ran flawlessly so I had to mess with it...short stroke setup

[BigBamBoo]

Well...when things are going good...working great...etc., I just can't leave well enough alone.

 

So today I set up my PCC rig....Taccom ULW upper, Taccom bolt, QC10 Glock lower, Hyperfire Eclipse, Blitzkrieg hydro buffer, etc....with a shortened bolt stroke.

 

I used a standard IPSC target at 25 yards to determine what worked best based on double taps as quickly as I could work the trigger.

 

The cut down mil-spec buffer allows for the bolt to just reset the trigger, but no more travel. This shortens the bolt stroke by 1.325" in my rig.

 

I started with a JP .308 carbine spring and the weight in the bolt. It would not reset the trigger reliably.

So out came the bolt weight. With the .308 carbine spring, it felt kinda "harsh" but ran fine.

 

Next I tried a AR-15 (.223) extra power carbine spring. I got a bit of dot wobble.

 

Settled on a JP AR-15 rifle spring. This gives me very nice double taps at 25 yards and a smooth, flat feeling recoil impulse. Dot just stays on target if I do my part. I ran 150+ rounds through it with zero problems.

 

Just thought I would share as folks have asked about the bolt weight, etc. Oh...I am running WWB 115gr ammo.

 

Just an added note, I can not use the bolt catch with this setup, but that is not a big deal for me.

 

 

 

 

Edited November 14, 2017 by BigBamBoo

[Screaminyz]

Just to clarify, JP AR15 rifle spring with or without weight installed in the end?


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[11287]

What did you use to cut down the mil spec buffer?

[BigBamBoo]

15 minutes ago, Screaminyz said:

Just to clarify, JP AR15 rifle spring with or without weight installed in the end?


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JP AR-15 (.223) rifle length spring with the weight in the bolt removed.

 

As I mentioned above, this is with the Taccom ULW upper. If you are running a longer barrel, you might need more weight to keep the bolt closed longer. I inspect the brass to make sure I am not getting bulged, split, etc., cases. That is a good indication of too light of a bolt, and/or buffer and spring combo.

 

 

[BigBamBoo]

2 minutes ago, 11287 said:

What did you use to cut down the mil spec buffer?

 

Just a cheap tubing cutter. You can get them at pretty much any hardware store for under $10.00.

[BigBamBoo]

I forgot to mention that when playing around with a spacer solution, I started with washers to dial in the perfect bolt stroke. And while this worked well for a spacer...it also pre-loaded the recoil spring and made the rig dip due to the very strong return to battery of the bolt.

 

 The cut down buffer does not load the spring and does not add much weight either.

 

 

[MikieM]

I would assume Big, that a reduction in rearward movement of the bolt would, or should, reduce the time the gun cycles per trigger pull. Am I correct?

And further more, a faster cycle time could, or should, mean better split times. Also correct?

[BigBamBoo]

13 minutes ago, MikieM said:

I would assume Big, that a reduction in rearward movement of the bolt would, or should, reduce the time the gun cycles per trigger pull. Am I correct?

And further more, a faster cycle time could, or should, mean better split times. Also correct?

 

 That is the idea. I was able to remove 1 1/4"+ from the bolt travel.

 

It feels a bit more "snappy", but the dot really stays on target when running the trigger as fast as I can...which aint all that fast.

 

I like to tinker, and this project was something I wanted to play with so I did it. I really like the results so I will keep the rig this way and see how it does over the long haul. I am hoping to make a match this weekend and put it through it's paces.

Edited November 15, 2017 by BigBamBoo

[bladewurk]

Interesting...

[Patrick Scott]

I have run similar setups to this. Can you still manually lock the bolt back with the bolt catch? I couldn't on mine when tuned to just reset the trigger. That was a deal breaker for me. Being able to lock the the bolt back manually is too important to me for malfunction clearance and inserting mags that are too tight to insert on a closed bolt.

[BigBamBoo]

No, I can not lock back the bolt. With the Glock mag lower I do not have any problems seating fully loaded mags. Now if this was on my Colt rig, might be a different story. I am going to run it for a bit and see what I think after I have a chance to shoot it in a match or two. So far, I like the recoil impulse better then the standard bolt stroke.

[Patrick Scott]

I agree that impulse was better, but it was minor and not(to me) worth giving up the ability to lock the bolt back.  Nice job!