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What is your favorite load for your PCC?


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7 hours ago, L9X25 said:

 

I am a believer in the light bullet & slow powder method.  I tuned the gun to work with the light weight projectiles and it feels great and is flat.  WSF is cleaner than HS6, but it is faster too.  Curious to see how that works out for you.  Next match you can run a few of mine through your rifle and see how they feel/compare for a point of reference.  

Sounds good.. 

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10 hours ago, Les Snyder said:

ran some Precision Delta 95s with 5.2 WSF today... about 1450fps with my PSA 16" with short throat

 

We are about the same, I run 5.1 and am just over 1400 for 133PF. 

 

My napkin math tells me that we are both about 28FPS per 10th of a grain.  

 

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On 4/16/2018 at 6:44 PM, MikieM said:

 

You mean the part about fast powders? 

In the PCC, when the gun is fired, the pressure spikes for the first couple of nanoseconds then tapers off until the bullet exits the barrel. During the time the bullet is in the barrel the slower powders (after the initial spike) exhibit higher pressures than the faster powders do. With a too light bolt/buffer this could be problematic. Or at least the potential is there.

I feel it is the opposite. A large part of what holds the bolt closed is pressure.

Pressure sealing and expanding the case to the chamber wall. When pressure drops enough for brass to loose seal, then the bolt can start moving back.

 

My opinion anyway...no scientific data to back it up. Guess I could load some fast and slow powders and see which feels best and leaves the cases the cleanest.

I do know slower loads give me dirtier cases and I always attributed that to pressure dropping to soon and loosing case seal.

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1 hour ago, Broncman said:

I feel it is the opposite. A large part of what holds the bolt closed is pressure.

Pressure sealing and expanding the case to the chamber wall. When pressure drops enough for brass to loose seal, then the bolt can start moving back.

 

My opinion anyway...no scientific data to back it up. Guess I could load some fast and slow powders and see which feels best and leaves the cases the cleanest.

I do know slower loads give me dirtier cases and I always attributed that to pressure dropping to soon and loosing case seal.

 

On the contrary. There is a wealth of information on Blowback firearms.

Wikipedia can give you a good start.

George Chinn's 1955 book "The Machine Gun" is another.

Google Orions Hammer and you'll get all the mathematical data you need.

Plus any number of articles found in the American Rifleman, The Firearms Blog,  and posts found in our own forum, just to name a few.

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http://orions-hammer.com/blowback/

 

the spreadsheet allows you to enter your data...but when I did the trials, the spreadsheet was on the side of safety... just now plugging in my 95 grain data, though, is a lot closer than what I found for the 135 data I had originally used when playing with different buffer weights a year ago... YMMV

Edited by Les Snyder
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On 9/11/2017 at 1:23 PM, Aircooled6racer said:

Hello: Interesting that there are no Sig MPX or CZ Scorpion loads listed yet? I guess they are mostly shooting factory stuff. Thanks, Eric

1. Sig MPX Gen 2

2. 124gr MG JHP

3. 6.6gr HS-6 @ 1420

4. Winchester SRP

5. 1.16 OAL

6. Works like a champ.

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26 minutes ago, BiggMike said:

1. Sig MPX Gen 2

2. 124gr MG JHP

3. 6.6gr HS-6 @ 1420

4. Winchester SRP

5. 1.16 OAL

6. Works like a champ.

Hello: Wow that is a fast load for the MPX. Is it a dirty load? I am using 3.8 grains of Tite Group with 124's. Thanks, Eric

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Just now, Aircooled6racer said:

Hello: Wow that is a fast load for the MPX. Is it a dirty load? I am using 3.8 grains of Tite Group with 124's. Thanks, Eric

Surprisingly, it is not that dirty. I think my chrono was off when i tested. i don't think it is nowhere that fast. I'm think it should be in mid to high 1300's for a PF around 140. I'm using small rifle primers so that might be adding that little extra kick. I like the load. I have a GMR-15 on order, so I hope I do not have to change this round.

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On 5/3/2018 at 10:45 PM, Les Snyder said:

http://orions-hammer.com/blowback/

 

the spreadsheet allows you to enter your data...but when I did the trials, the spreadsheet was on the side of safety... just now plugging in my 95 grain data, though, is a lot closer than what I found for the 135 data I had originally used when playing with different buffer weights a year ago... YMMV

 

"The same chamber pressure that pushes the bullet down the bore, pushes the bolt backwards.  If the bolt weighed the same amount as the bullet, then it would fly back with bullet velocity, shooting the shooter!  So our basic tool to keep the bolt velocity down is mass. "

 

Interesting read, Les...  Thanks!

 

PCC is probably the first time a lot of us have tried to understand how blowback guns really operate... 

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On ‎12‎/‎26‎/‎2017 at 8:02 PM, longbeard said:

I run a Taccom ulw currently. I use Titegroup 3.6 with a 125gr bullet to get around 130pf. 

 

Im building a second PCC with a 16" barrel. What's the increase in fps you guys are seeing between these barrel sizes using the same loads and what's considered reasonable fps from a 16" barrel?  

 

I seem to remember having trouble getting down to minor at the beginning of the season when shooting a psa I was using.  My 900 fps loads were like 1050 out of a full sized barrel.  I kept downloading and it began to seem like too low a charge.  Curious what you all are doing. 

Here are two results.  The top set is from a 16" AR, The bottom is from a Taccom ULW Barrel.

Bullet Brand Everglades
Bullet Type Round Nose
Bullet Weight 147gr
Powder Name Titegroup
Powder Weight 3.0gr
Primer Federal
COL 1.130-1.135
Average Chronograph Speed 973.9
Standard Deviation 52.48
Chronograph Speed Low/High 890 1033
Power Factor 143
         
         
Bullet Brand Rocky Mountain
Bullet Type Round Nose
Bullet Weight 147gr
Powder Name Titegroup
Powder Weight 3.0gr
Primer CCI
COL 1.130-1.135
Average Chronograph Speed 890
Standard Deviation 8.86
Chronograph Speed Low/High 877 903
Power Factor 130
 
   
   
   
   
   
   
   
   
     
   
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1 hour ago, stick said:

Here are two results.  The top set is from a 16" AR, The bottom is from a Taccom ULW Barrel.

Bullet Brand Everglades
Bullet Type Round Nose
Bullet Weight 147gr
Powder Name Titegroup
Powder Weight 3.0gr
Primer Federal
COL 1.130-1.135
Average Chronograph Speed 973.9
Standard Deviation 52.48
Chronograph Speed Low/High 890 1033
Power Factor 143
         
         
Bullet Brand Rocky Mountain
Bullet Type Round Nose
Bullet Weight 147gr
Powder Name Titegroup
Powder Weight 3.0gr
Primer CCI
COL 1.130-1.135
Average Chronograph Speed 890
Standard Deviation 8.86
Chronograph Speed Low/High 877 903
Power Factor 130
 
   
   
   
   
   
   
   
   
     
   

 

I use both a JP GMR-13 with a 16" barrel and another AR-15 with a TACCOM upper (5.25" barrel), and both Vihtavuori N320 and N350 powder.  My results mirror yours using the slow powder.  It works for a short barrel, but not for a longer one.  Switching to the N350 for the JP rifle, I get much better results, with a vastly lower SD using a slow burning powder rather than the fast burning one.

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3 hours ago, stick said:

Here are two results.  The top set is from a 16" AR, The bottom is from a Taccom ULW Barrel.

Bullet Brand Everglades
Bullet Type Round Nose
Bullet Weight 147gr
Powder Name Titegroup
Powder Weight 3.0gr
Primer Federal
COL 1.130-1.135
Average Chronograph Speed 973.9
Standard Deviation 52.48
Chronograph Speed Low/High 890 1033
Power Factor 143
         
         
Bullet Brand Rocky Mountain
Bullet Type Round Nose
Bullet Weight 147gr
Powder Name Titegroup
Powder Weight 3.0gr
Primer CCI
COL 1.130-1.135
Average Chronograph Speed 890
Standard Deviation 8.86
Chronograph Speed Low/High 877 903
Power Factor 130
 
   
   
   
   
   
   
   
   
     
   

This seems inline with what I have now.  I'm roughly 100fps difference between ULW and 16".  Not too far off your results.

 

 

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2 hours ago, longbeard said:

This seems inline with what I have now.  I'm roughly 100fps difference between ULW and 16".  Not too far off your results.

 

 

 

It depends on what kind of powder you use.  The above results is typical for a fast burning powder, which is appropriate for a shorter barrel.  Switch to a slower burning powder for a longer barrel.

 

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I've been testing some loads and thought I'd put it out there.

Lead Star rifle with a 16" Faxon barrel..

 

95gr MG / 1.09 / 6.7 HS 6 / 1500 fps / SNAPPY... any less HS 6 gets messy so I stopped there.  

 

124 Xtreme / 1.09 / 3.1 N320 / 1000 fps / Soft but only for Steel Challenge 

 

165 Xtreme / 1.13 / 3.1 Clays / 850 fps / Super Soft at 140pf!! (softer than the 124's) will play with this one for a while.  

             *** I've loaded 165's for my carry optics but never with Clays, always with n320.***

 

 

 

 

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For Steel Challenge in my Ruger PC --- 105 grain 9mm Bayou, 3.3 grains N310. One inch 3 shot groups from a 25 yard bench rest and it kicks like my 10/22. N310 also burns very clean... very little carbon build up. Dirty powders in blow back actions are a malf waiting to happen. Ejection is positive and 5-6 feet.

I can't complain... their 95 grain RN works with the same powder charge, same recoil, and 1.75 inch groups.

 

One thing about the PC.... the chamber seems to be a bit shorter than my M&P pistols. Don't leave any more than a hint of driving band above the case mouth. It will engage the rifling and prevent going into battery... ask me how I know (LOL). I didn't measure the OAL, I just shortened it to where it worked.

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Jones arms kronos- 16" ballistic advantage barrel, faxon bolt (weight removed), hiperfire 243g trigger, blitzkrieg buffer with jp 308 rifle length spring, delrin spacer and 25# wave spring

124 grain round nose xtreme, 3.2 grains titegroup, winchester primers, at 1.125 OAL. Makes 130 pf

7k rounds on the gun so far and have had zero ftf, fte or malfs of any kind. The gun cycles very quickly as my buffer set up moves just far enough to reset reset the trigger and feed the next bullet. Dot bounce is straight 12 o,clock about an inch and then immediately back to zero. Tests were done on scaled targets at 15 yards.



Sent from my Pixel XL using Tapatalk

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I've tried a lot of different bullet and powder combos in my 16" AR9, but I've found my new favorite load.    I loaded 4.4gr of N350 under a 115gr Berry's RN plated at 1.130" with a S&B small rifle primer.    I have a Kaw Valley 308 carbine spring and a PSA 9mm AR buffer, and the dot comes right back to where it was.  Double taps at 20 yards were within inches of each other, pulling the trigger as fast as I could.  I had an average power factor just a bit over 130.

 

The huge up side to this is that I have over 16,000 of these bullets on hand that were purchased at a steep discount.   The down side is I have no more N350 left. 

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Now to another topic that this gun is all parts.

1  Spikes lower, Taccom ULW  5.25 Barrel and extreme Bolt ELF Trigger  Blitz KYNSHOT buffer 308 JP spring 

2 145 gr. Acme RN

3  3.1 win 231

4. win ssp

5. 1.115 OAL

6. 135 to 139 PF

7. Erratic 

8. Splits .88

9. Very snappy and accurate problem cases eject like dribbling. Slow bolt in comparison bolt uses a 2 oz. slug.

    Comparison is the Freedom ordinance bolt is on 1oz. lighter bolt. Would consider removing the Taccom bolt slug        open to rcommmendations.  

10. Dot Movement minimal. 

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