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Load development questions


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Hello.  I have some questions.  

 

When going through load development phase and short stroke buffers, what's the general idea behind PF ?  

 

I'm running a short stroked blitz PCC buffer system and running 141 PF (10.5 inch barrel, 6 inch comp).  

 

Is my goal to lessen the PF on a short stroke or raise the PF on short stroke?  I haven't tried the JP scs-ss yet, but it's my next plan.  

 

I understand that the blitz spring is a little on the heavier side (compared to JP's short stroke) so I was curious if a heavier spring requires higher PF.  

 

I hope I've given enough information to help answer my question.  Thanks!  

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I've not done any real work with tuning yet. I will soon, since I've got a new JP on the way. But it would seem to me that the heavier the spring/buffer is, you need more force to push the bolt back far enough to reset the trigger. The trick is to find just the right amount that resets the trigger without being any more than that.

So I think you're right--"heavier spring requires higher pf"

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I'm in the middle of doing this, and so take this with a grain of salt, but... I'm chasing this from the other direction.

 

My current efforts are to find a load I like - consistent, accurate-enough, runs the gun reliably, works the comp (JP 14.5" barrel with their pinned/welded comp).  I've tried a number of factory loads, including
 

-- S&B 124gr (~150PF, pretty consistent, ran okay, but felt "snappy")

-- WWB-124gr (~160PF, worked the comp, but not very consistent, either across the chrono or on paper)

-- T-1 124gr "PCC" load (~135PF, ran fine but huge spread - over 80fps difference across a 10-round chrono run)

-- Federal "SynTech" 130gr PCC load (~138PF, best of the bunch in terms of accuracy and consistency, but felt "mushy")

 

Based on that... I'm working up my own load.  Starting with N320 under a 124gr MG as others have mentioned here.  I know I can build consistent ammo, and I'll be able to compare the "feel" with the factory loads I've tried to see what feels good.

 

Then, my thought is, once I have a load I like I'll tune the gun to suit.  I have a blitz buffer and JP spring, I have a Shooting Innovations buffer, and I also have a handful of weights for the (stock) JP-SCS I can use in various combinations.  Somewhere along the way I'm pretty sure I'll find a combination that feels right.

 

Open to ideas, if I'm thinking about this wrong.

$.02

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I’ve found that between 140-150pf is the sweet spot with 124gr jacketed bullets in my setups.  Both my rifles have 14.5” barrels with blitzkrieg buffers, 308 rifle springs and weighted spacers between the bolt and buffer.  This has proven to be the optimal setup for me in terms of reliability and dot movement.

 

i tried short stroking my buffer system with a spacer in the bottom of the tube, but with direct contact between the bolt and buffer I was destroying blitzkriegs.  Since I put the spacer between the bolt and buffer I have really tamed down the recoil of the rifle and (I hope) solved the problem of broken buffers.

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12 minutes ago, CalTeacher said:

short stroking my buffer system with a spacer in the bottom of the tube...

 

When I ordered the Blitzkrieg buffer, I called and asked about spacers (because the secret-sauce my friends had told me was buffer+spacer+wave-spring). 

 

Brian said that his new "HD" buffer works better than the old buffer+spacer+wave-spring combination, and that if I really wanted extra weight he recommended the (2.6oz) add-on weight.

 

Haven't tried it yet, but... that was the guidance.

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1 hour ago, CalTeacher said:

Both my rifles have 14.5” barrels with blitzkrieg buffers, 308 rifle springs and weighted spacers between the bolt and buffer.

Sounds like you have it tuned in nicely.

 

Which Blitzkrieg buffers are you using and is the weighted spacer the stainless steel spacer available at Blitzkrieg?

 

Thanks.

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59 minutes ago, CalTeacher said:

I’ve found that between 140-150pf is the sweet spot with 124gr jacketed bullets in my setups.  Both my rifles have 14.5” barrels with blitzkrieg buffers, 308 rifle springs and weighted spacers between the bolt and buffer.  This has proven to be the optimal setup for me in terms of reliability and dot movement.

 

i tried short stroking my buffer system with a spacer in the bottom of the tube, but with direct contact between the bolt and buffer I was destroying blitzkriegs.  Since I put the spacer between the bolt and buffer I have really tamed down the recoil of the rifle and (I hope) solved the problem of broken buffers.

 

I followed the same path...  When I bought my first 5015HD to try, I also bought one of the 2.6oz SS spacer...  The 2.6oz SS spacer was too large (in diameter) to fit in my receiver extension, so I didn't use it...  I liked the 5015HD better than the 5007, so I kept using it.

 

After a while...  I noticed the cap on my 5015HD started to come off as I was cleaning it one day...  Called Brian ( very helpful guy) and he said he would replace it...  Said there was a newer version with better cap attachment and two set screws at the top that he would replace it with...  I also mentioned that the SS spacer was too tight to fit in my buffer tube...  There is a newer SS spacer that is slightly less weight with a reduced diameter...  Installed the second 5015HD with the new SS spacer in front and have been using it ever since...  No troubles so far!

 

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22 minutes ago, Flatland Shooter said:

Sounds like you have it tuned in nicely.

 

Which Blitzkrieg buffers are you using and is the weighted spacer the stainless steel spacer available at Blitzkrieg?

 

Thanks.

I have the 5007 and 5015.  I can’t tel a difference between the two on the clock.  The spacer is their weighted spacer.  I had to take .1” off the face of the spacers to get them to reliably reset my triggers.

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23 minutes ago, RaylanGivens said:

 

I followed the same path...  When I bought my first 5015HD to try, I also bought one of the 2.6oz SS spacer...  The 2.6oz SS spacer was too large (in diameter) to fit in my receiver extension, so I didn't use it...  I liked the 5015HD better than the 5007, so I kept using it.

 

After a while...  I noticed the cap on my 5015HD started to come off as I was cleaning it one day...  Called Brian ( very helpful guy) and he said he would replace it...  Said there was a newer version with better cap attachment and two set screws at the top that he would replace it with...  I also mentioned that the SS spacer was too tight to fit in my buffer tube...  There is a newer SS spacer that is slightly less weight with a reduced diameter...  Installed the second 5015HD with the new SS spacer in front and have been using it ever since...  No troubles so far!

 

Out of curiosity, are you running your bolt with or without the weight?

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1 hour ago, bgary said:

 

When I ordered the Blitzkrieg buffer, I called and asked about spacers (because the secret-sauce my friends had told me was buffer+spacer+wave-spring). 

 

Brian said that his new "HD" buffer works better than the old buffer+spacer+wave-spring combination, and that if I really wanted extra weight he recommended the (2.6oz) add-on weight.

 

Haven't tried it yet, but... that was the guidance.

I would suggest trying the weighted spacer.  Supposedly it prevents a tilted bolt from contacting the cap of the buffer, which contributes to the destruction of the buffers.

 

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The goal is to find a load that shoots flat with your setup. For me it doesn’t have to be soft or a certain pf just flat. I use Homies recipe 139pf load with a weighted bolt-blitz 5015- blitz weight- jp 308 carbine or yellow sprinco-mbx buffer-blue internal- and the longest mbx spacer in the stroke kit. My load is a 115gr jhp, 4.6gr wsf, cci 500 primer average FPS is 1210. Wsf works my comp that’s a plus, it’s a medium burn rate so I get longer lockup time (milliseconds matter) burns even, Meters within 20fps deviation. The longer the lockup the better the feel and more consistent FPS think cmmg guard or mp5 roller lock. It’s a lot of  finding what works best for your pcc.I had the gen 1 blitz weight and had to turn it to .994 to get it to run reliable in my buffer tube

Edited by Bwillis
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11 minutes ago, CalTeacher said:

The spacer is their weighted spacer.  I had to take .1” off the face of the spacers to get them to reliably reset my triggers.

 

Thanks for the tip.  I'm still sanding down the diameter to get it to move easily in the buffer tube.  Once that's fixed, I'll see if I have trigger reset problems (Hiperfire 24C).

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On 4/22/2019 at 6:10 AM, egd5 said:

I've not done any real work with tuning yet. I will soon, since I've got a new JP on the way. But it would seem to me that the heavier the spring/buffer is, you need more force to push the bolt back far enough to reset the trigger. The trick is to find just the right amount that resets the trigger without being any more than that.

So I think you're right--"heavier spring requires higher pf"

Right?  That's what I was thinking.  

But I had a 132PF load that I tested that felt so damn good, but I only had 50 of them so I don't know if it would be "hot" enough under extreme rapid fire to run reliably.  I will be testing that today.  

 

23 hours ago, bgary said:

Based on that... I'm working up my own load.  Starting with N320 under a 124gr MG as others have mentioned here.  I know I can build consistent ammo, and I'll be able to compare the "feel" with the factory loads I've tried to see what feels good.

 

Then, my thought is, once I have a load I like I'll tune the gun to suit.  I have a blitz buffer and JP spring, I have a Shooting Innovations buffer, and I also have a handful of weights for the (stock) JP-SCS I can use in various combinations.  Somewhere along the way I'm pretty sure I'll find a combination that feels right.

 

Open to ideas, if I'm thinking about this wrong.

$.02

I have played a lot with the JP Supermatch barrel.  

N320 is definitely the recommended powder for this barrel.  

I'm sure you have your baseline data, but if not, 3.6 grain will be a great starting point on your load.  

Please report back when you can regarding which setup feels the best.  

 

Just curious, why aren't you short stroking?  JP just released a newly refined SCS-SS system that is supposed to be the best in the market.  

 

16 hours ago, CalTeacher said:

I’ve found that between 140-150pf is the sweet spot with 124gr jacketed bullets in my setups.  Both my rifles have 14.5” barrels with blitzkrieg buffers, 308 rifle springs and weighted spacers between the bolt and buffer.  This has proven to be the optimal setup for me in terms of reliability and dot movement.

  

 i tried short stroking my buffer system with a spacer in the bottom of the tube, but with direct contact between the bolt and buffer I was destroying blitzkriegs.  Since I put the spacer between the bolt and buffer I have really tamed down the recoil of the rifle and (I hope) solved the problem of broken buffers.

Not being a dick or anything here, but why 124 over 115?  

That was my dilemma for the months leading up to my delivery of the PCC.  

 

I decided with 115gr RN and so far so good, but I also have a couple 124gr loads that I will be trying today.  (4.7gr gm3, 124gr jhp, 1.135 OAL) 

 

Blitz released a new spacer that goes in front of the buffer (direct contact with the bolt).  I've been using it and it's been alright so far.  I am waiting for JP to ship me their new SCS-SS so I have a comparison.  Though, I feel like I really need to load much hotter due to the heavy ass spring on this blitz setup vs the JP setup.  I'm also not sure if I wanna commit to hydraulic vs non hydraulic yet.  

 

16 hours ago, bgary said:

 

When I ordered the Blitzkrieg buffer, I called and asked about spacers (because the secret-sauce my friends had told me was buffer+spacer+wave-spring). 

 

 Brian said that his new "HD" buffer works better than the old buffer+spacer+wave-spring combination, and that if I really wanted extra weight he recommended the (2.6oz) add-on weight.

  

 Haven't tried it yet, but... that was the guidance.

You called them and they answered?!  wtf?  I've been calling them and leaving them VMs for days.  No replies back.  Maybe they hate me already?  

The new HD buffer is not short stroke.  I have the new HD buffer and there were no options for a short stroked HD buffer.  

 

 

15 hours ago, RaylanGivens said:

 

I followed the same path...  When I bought my first 5015HD to try, I also bought one of the 2.6oz SS spacer...  The 2.6oz SS spacer was too large (in diameter) to fit in my receiver extension, so I didn't use it...  I liked the 5015HD better than the 5007, so I kept using it.

 

 After a while...  I noticed the cap on my 5015HD started to come off as I was cleaning it one day...  Called Brian ( very helpful guy) and he said he would replace it...  Said there was a newer version with better cap attachment and two set screws at the top that he would replace it with...  I also mentioned that the SS spacer was too tight to fit in my buffer tube...  There is a newer SS spacer that is slightly less weight with a reduced diameter...  Installed the second 5015HD with the new SS spacer in front and have been using it ever since...  No troubles so far!

  

How can you tell the difference between 5015 / 5007 springs?  I've been trying to reach out to them to see which spring I have with my kit but I haven't gotten a reply back in over a week.  

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2 minutes ago, slippp said:

Just curious, why aren't you short stroking?  JP just released a newly refined SCS-SS system that is supposed to be the best in the market.  

 

I probably will be.  Or, at the very least, will try it.  Among the hodge-podge of parts I've amassed, I've got a handful of JP weights and a "short-stroke conversion kit".  At the moment I'm running the GMR-13 with the stock buffer (3 steel weights, 1 tungsten, IIRC), and figure I'll try a variety of combinations when I start tuning for feel and dot-bounce.

 

2 minutes ago, slippp said:

The new HD buffer is not short stroke.  I have the new HD buffer and there were no options for a short stroked HD buffer.  

 

From my notes:  Brian said that adding the weight to the HD buffer would short-stroke it.  It adds 2.6oz of weight and 3/4" of length to the buffer, "slows the bolt and short-strokes the system".    He did say, though, that in his opinion short-stroking reduces the feel of the bolt slamming forward but "doesn't affect speed".

 

He also said that in his testing, loads running around 140PF seemed to produce the best feel.

 

ymmv....

Bruce

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2 minutes ago, bgary said:

From my notes:  Brian said that adding the weight to the HD buffer would short-stroke it.  It adds 2.6oz of weight and 3/4" of length to the buffer, "slows the bolt and short-strokes the system".    He did say, though, that in his opinion short-stroking reduces the feel of the bolt slamming forward but "doesn't affect speed".

 

 He also said that in his testing, loads running around 140PF seemed to produce the best feel.

  

 ymmv....

 Bruce

 

Yeah.  I have the weight.  It reduces lockup time significantly and it definitely short strokes haha.  

 

I guess I gotta chrono and actually find the real and non theory crafted FPS.  

 

The only real FPS data I have was 3.4-3.6gr GM3, which had a high of 131 PF and a low of 127PF.  I bumped up the powder to 4.4 and I was around 137 PF.  I'm currently on a 4.6-4.8gr load but I have no actual FPS data.  

 

I'm wondering if I should switch to 124gr if I'm bumping it up this hot.  

 

 

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17 hours ago, CalTeacher said:

I’ve found that between 140-150pf is the sweet spot with 124gr jacketed bullets in my setups.  Both my rifles have 14.5” barrels with blitzkrieg buffers, 308 rifle springs and weighted spacers between the bolt and buffer.  This has proven to be the optimal setup for me in terms of reliability and dot movement.

 

i tried short stroking my buffer system with a spacer in the bottom of the tube, but with direct contact between the bolt and buffer I was destroying blitzkriegs.  Since I put the spacer between the bolt and buffer I have really tamed down the recoil of the rifle and (I hope) solved the problem of broken buffers.

This^^^^^^

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18 hours ago, CalTeacher said:

Out of curiosity, are you running your bolt with or without the weight?

 

I'm running a Taccom Extreme bolt with the weight and the Blitz SS weight in front of the 5015HD buffer.

 

I took two identical bolts to the range...  One without the weight (my standard setup at the time) and a new one with the weight...  I shot them both and decided to continue with the weight in the bolt...  It was a highly subjective decision...  The brass coming out of the heavier bolt was cleaner, though.

 

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3 hours ago, slippp said:

You called them and they answered?!  wtf?  I've been calling them and leaving them VMs for days.  No replies back.  Maybe they hate me already?  

The new HD buffer is not short stroke.  I have the new HD buffer and there were no options for a short stroked HD buffer.  

 

How can you tell the difference between 5015 / 5007 springs?  I've been trying to reach out to them to see which spring I have with my kit but I haven't gotten a reply back in over a week.  

 

Blitzkrieg's phone number is Brian's cell phone...  I don't usually have much trouble getting through.

 

You short stroke the 5015HD buffer with external spacers of some sort...  make them out of delron...  use the Blitz SS spacer...  use quarters...  whatever you want.

 

Not sure what you mean about the springs...  I've never taken one apart...  The 5007 and 5015HD have the part number stamped on the outside of the case...  The 5015HD has a heavier spring...  Perhaps you bought some kind of kit...  I bought my parts separately, so no idea...  Look on their web site and see what it came with.

 

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Can you please PM me the number?  I tried calling three times today and nothing. 

 

And to make it worse, both of my blitzkrieg buffers broke today.  The piston heads both came off.....   

 

I took a look at it and it seems like there is still red loctite on the set screw, so I didn't bother messing with it.  But the fact that this happened makes me hard pass on replacing this buffer and instead going with the JP SCS-SS 

 

https://www.blitzkriegcomponents.com/ProductDetails.asp?ProductCode=AR15-KYNJP-9C

 

This is what I ordered.  

4 hours ago, RaylanGivens said:

 

Blitzkrieg's phone number is Brian's cell phone...  I don't usually have much trouble getting through.

 

You short stroke the 5015HD buffer with external spacers of some sort...  make them out of delron...  use the Blitz SS spacer...  use quarters...  whatever you want.

 

 Not sure what you mean about the springs...  I've never taken one apart...  The 5007 and 5015HD have the part number stamped on the outside of the case...  The 5015HD has a heavier spring...  Perhaps you bought some kind of kit...  I bought my parts separately, so no idea...  Look on their web site and see what it came with.

  

 

buffer 2.jpg

Edited by slippp
added pic
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12 hours ago, slippp said:

 

 

Not being a dick or anything here, but why 124 over 115?  

That was my dilemma for the months leading up to my delivery of the PCC.  

 

I decided with 115gr RN and so far so good, but I also have a couple 124gr loads that I will be trying today.  (4.7gr gm3, 124gr jhp, 1.135 OAL) 

 

Blitz released a new spacer that goes in front of the buffer (direct contact with the bolt).  I've been using it and it's been alright so far.  I am waiting for JP to ship me their new SCS-SS so I have a comparison.  Though, I feel like I really need to load much hotter due to the heavy ass spring on this blitz setup vs the JP setup.  I'm also not sure if I wanna commit to hydraulic vs non hydraulic yet.  

 

I haven’t tried 115s yet.  My load is just the sweet spot I’ve found with 124s.  I’m tempted to pick up some 115jhp to test out, but I can’t see me gaining much from the additional effort in developing a new load.  One of these days I’ll get to it.

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