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How low is too low and why ?


jrdoran
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I'm not a reloader, but my shooting buddy @tomv is.   

 

We're on a quest to develop a super soft shooting 9mm load for our PCC rifles.  This was is fueled by our ultralight RFRO rifles and winter idle time on our hands.

 This is for steel challenge only so please don't turn this into a dick measuring contest about major/minor PF requirements. 

 

What started out as 100gr Berry Plated bullets with 3.8gr of N310 has now evolved into 2.25 / 2.5 of N310 with the same 100gr bullets.   My Ruger PCC seems to cycle the 2.25 fine but failed to cycle a batch of 2.0.   Tom's tricked out AR9 will cycle 2.5 reliably;     @tomv will post the chrono data, but the 2.25 was somewhere around 72 power factor.      Accuracy was good at 50' with an 8MOA dot.   maybe 2" group from a bench.  We both run 5.5"  shrouded barrels and dots.

 

Shooting the 2.0 / 2.25 / 2.5  had us giggling how soft the round felt.  Essentially like a rimfire ( mission accomplished ).

 

I'm sure there are concerns / safety and characteristics of ammo performance that we are not taking into consideration.  Don't know what we don't know yet.    

 

I would appreciate the point of view and experience of others in stepping out of the box in these ultralight soft shooting bullets.    what  started by using Atlanta Arms 100gr ammo ( about 110PF ) it now seems in a relative sense to be much more recoil and jump than the above-mentioned experiments.   

 

thoughts ? 

 

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Edited by jrdoran
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With reduced loads, inconsistent ignition becomes more likely: variation in pressure and velocity. Sounds like this hasn't happened to you.

 

One thing that gets sometimes mentioned with reduced loads is "detonation". I'm not sure if its existence has been proven or if it is actually double loads.

 

With Minor level loads, it seems that the typical blow back action is a main culprit in what is perceived as "recoil" in a PCC: a big chunk of metal moving back and forth inside the PCC. The soft loads might reduce this too. I wonder if the action takes much longer to cycle with the reduced loads. I know of a gun shop / gunsmith who has developed some sort of a gas operated AR PCC that shoots very soft and flat. Don't know if it would work at all with the kind of reduced loads that you have.

 

https://www.youtube.com/watch?v=XXVWoCetA7s

 

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Here's the chrono data from yesterday's testing using Berry's hollow base 100 gr 9mm bullets seated at 1.100" and N310 powder:

10 shot strings.

 

powder chg.    avg velocity       SD        power factor  

2.8gr                    888                  41           89

 

2.5gr                    787                  51           79    

 

2.25gr                 703                   58          70

 

2.0gr                   684                   49          68

 

As noted by perttime, SDs for these light loads are quite high. In spite of this, accuracy at 50' was acceptable for Steel Challenge with sub 2" groups and no fliers noted during accuracy testing. (The 2.8 gr load in my  AR shoots sub 1" groups  at 50').The most surprising result of this exercise was that our guns would run these loads at all.

 

 

 

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We had one 'expert'  today telling us we were downright unsafe and dangerous shooting loads like this.    Said squibs were likely.   

 

Another told us the bullet won't fragment upon steel impact.     

 

While the 2.0 didn't cycle my PCC, it really did feel super light.   Like almost cheating.

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2" group at 50 ' from a bench is horrible. There is a sign of a problem right there. You probably arnt getting enough pressure to seal bullet, may be keyholing as well . DOnt like those SD's Look at the volume per gr of your powders in that same burn rate. Dont have a chart handy, but powder like trailboss is designed to take up alot of room per gr, so does Clays. Lee online has a CC to powder gr chart you can use to compare.  You may also be able to find bulk 80 gr ish bullets that you can try.

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You are going to do what you wish. I personalty have seen 4 different rifles that the bullets " ran into each other"

inside the barrel. This is why JP has a bell-out program. A little more powder will bring down the SD. Then a little 

"tuneing"of the buffer system will be more beneficial in the long run.If you wont the recoil of a 22 then get a 22.

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If you're going to go really light on powder chrges, you'd be better off using Titegroup powder. Titegroup is very consistant when using small volumes of powder in large capacity cases. For example I use it for making 45 Colt, 44-40, 38-40, and 44 Special in 44 Mag cases. All use between 5-6 gr in a large capacity case. And all loads are very consistant at the chrono, and shoot very well.

Also, usuing a heavier bullet like 124-147 gr will give you better powder ignition as they impart more pressure when shooting.

Edited by Postal Bob
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Bullseye powder runs well below published minimums and you will likely see better SD than many powders that are loaded light.
 

Examine your fired cases and you will likely see a lot of soot on the outside of the case. This is a sign of back pressure blow by because the low powder charge didn’t produce enough internal combustion pressure to swell the case outward against the chamber walls, thus sealing the case against back pressure blow by. Most powders SD numbers come down as charge weights go up. The powder also tends to burn more cleanly at near max published loads.

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Useful feedback.     I'll let @tomv discuss the merits of N310 vs Titegroup.    

 

I've always heard that lighter bullets will have less recoil, but I do agree a heavier bullet will impart more pressure and give better combustion swell on the case. 

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Just for giggles, try a WSPM primer.     When I was loading 40 minor with N310 a few years ago I could not find  small pistol primers.

Found some magnums---they dropped my SD from 40's to around 12.    Velocity increase was around 10 fps.

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17 minutes ago, jrdoran said:

 

NO; 

 

i would probably stop stressing about it then and practice more.  ;)  I personally run about 115-120 pf  (115gr boolits) for steel in my handguns and my wife's pcc. it runs the guns just fine and is accurate, and I can also use it at local matches for calibration ammo when required.

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There is a new manufacture of pcc buffer that is local to me that makes a specific buffer for steel challenge. The website is not up and running as of yet but will be less than a week apparently. Pace Setting Design is the company. 
 

he shoots 1.8gn of ba10 with a 100gn bullet.  shooting about 65-70 pf. He runs a taccom 5” barrel. The gun shoots incredibly soft, similar to my .22’s. 
 

it shoots incredibly soft and I am having him build me one as we speak. Retail price is around $150. 

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24 minutes ago, IPSCLUVERRR said:

There is a new manufacture of pcc buffer that is local to me that makes a specific buffer for steel challenge. The website is not up and running as of yet but will be less than a week apparently. Pace Setting Design is the company. 

he shoots 1.8gn of ba10 with a 100gn bullet.  shooting about 65-70 pf. He runs a taccom 5” barrel. The gun shoots incredibly soft, similar to my .22’s. 

it shoots incredibly soft and I am having him build me one as we speak. Retail price is around $150. 

 

Interesting.   We're using 5" shrouded barrels as well.       Keep us posted on your progress. 

That is lower than our current configurations can run.  Wonder what is different in his steel challenge buffer ?    

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both my PCC's have Taccom ULW 5.25" barrels & complete uppers... i shoot 124gr plated bullets with a reduced load.. & "special"  buffer .... ... YES .. i think less recoil will enable one to shoot faster/more accurately .. simply because you don't experience much recoil.. which in turn keeps your POI on the target.. 

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