300 PRC +P

Shawn Carlock

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Joined
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Location
North Idaho
We have recently been exploring cartridges that would greatly benefit from the +P throating modifications we do. We have just built a 300 PRC for a rental rifle on our LRKM platform to use in our long range shooting classes. https://www.defensiveedge.net/index.php/classes
300 PRC photo.jpg


I choose the 300 PRC for one of several reasons:

  • soft shooting (compared to a 338 Terminator)
  • low powder consumption
  • ability to run a 215 Berger @ 3000 fps
  • 2000 yards target capability
  • ability to shoot some rounds through it in a day and not have students get beat up
  • the case has no belt
  • case design is modern and efficient
  • has been adopted by military units that we work with
  • can feed out of a detachable box mag (although the LRKM doesn't have one)
These were the key features that drew us to the 300 PRC. Is it a 300 Terminator? Of course not, it isn't ever going to shoot a 215 gr. bullet @ 3400 fps. Let's talk about what the 300 PRC is then. The 300 PRC is a 300 Winchester Mag length cartridge that has been improved with a 30 degree shoulder and less case body taper all good things to a point. There is no belt (not that these cases ever needed one) this greatly aids in feeding, especially from a detachable box magazine. It doesn't require a 4.00" mag box even with VLD/ ULD bullets. The SAMMI spec chamber will put the max OAL with a 215 Berger at roughly 3.735". The case has an H2O capacity of 99.0 gr. and that is a 7 grain advantage over the 300 Winchester Magnum (this becomes important later).

PRC 02.jpg


So with the LRKM spun up and ready to roll it was time to start load development. I started with the following base information and QuickLoad predicitions:

Shop LRKM - demo



Case
: Hornady 300 PRC

Max Case Length: 2.585"

Case Trim Length: 2.575"

Primer: CCI 250

Powder: H 1000

Bullet: 215 gr. Berger Hybrid Target

OAL Max: 3.735" raw 2.902" w / Reloading Comp

Barrel: Hart, .308", 1-9 twist, 26" finished length, Sendero Contour DE fluted

QuickLOAD Prediction: Max load 87.0 gr. H 1000, 103.4% case capacity, 3001 fps, 100% barrel burn, 4288 ft/lbs, muzzle pressure 12639 psi








Now with this info I started a pressure series to establish max pressure.



OAL: -.000" (2.902" W / Reloading Comp)

Charge Velocity Notes




82.0 gr 3080 fps Faint click a top

83.0 gr 3081 fps Faint Ejector mark

84.0 gr 3126 fps Ejector Mark

85.0 gr DNS

86.0 gr DNS

87.0 gr DNS Just starting to make OAL longer from compression .002"



As you can see this is why no matter what your source you always start 10% lower than max and work up. 87.0 grains would have blown the primer right out. Now starting with an 82.0 grain max pressure I shot a couple of groups at -.000" and -.005".



Shooting 82.0 gr @ -.000"

3058, 3044, 3065 fps .75 moa



Shooting 82.0 gr @ -.005"

3058, 3064, 3069 fps .25 moa



Now while the load at -.005" was great after inspecting the case and bolt lift (faint but detectable) I decided that I wanted to run a little less pressure.



Shooting 81.0 gr. @ -.005" 2+1 .5 moa



Shooting 81.0 gr. @ -.010" 2+1 .4 moa



After shooting these groups I decided to drop one more grain and go with -.010". After enough years of doing this you sort of get a feel for it.



Shooting 80.0 gr. @ -.010" .216" ES 9 fps Average Velocity 2996 fps



So at this point normally you whistle to yourself and think about all the great long range shots you are going to make with this kind of performance. Unfortunately my mind doesn't always work that way. My first thoughts were, "Hey, I am 7 grains of H1000 under max case compression capacity. I wonder how much velocity I would gain it I +P modified the throat?" Well there is only one way to find out.









So the +P modification is simple to work with as it doesn't require anything different in terms of dies, brass etc. Starting at the final load of the non +P round of 80.0 grains resulted in a velocity drop of almost 100 fps from the pressure reduction of the +P throat.



Charge Velocity Notes



80.0 gr. 2909 fps Max load from non +P chamber

81.0 gr. 2952 fps

82.0 gr. 2998 fps Equal to 80.0 gr load in standard chamber

83.0 gr. 3037 fps

84.0 gr. 3081 fps

85.0 gr. 3130 fps Faint bolt lift similar to 81.0 gr. in standard chamber



84.5 gr. 3106 fps no ejector mark, no bolt lift



Shot 84.5 grains @ -.005" , -.010" and -.015"



Jump Group ES



-.005" .473" 19

-.010" .258" 9

-.015" .184" 23



So clearly we will be running the -.010" load with the lower ES even though the -.015" load shot slightly tighter. The higher ES of the -.015" load make it less of a choice at distance. This is pretty standard + P improvement if case capacity allows. The thing I like the best here is the combination. The 215 Berger at 3100 fps is serious hunting medicine. The use of H1000 will ensure that it will always do the same thing day in and day out. Only using 84.5 grains of powder will allow for a decent barrel life. It uses a standard magnum bolt face. It doesn't rule any category in terms of accuracy, velocity, efficiency or match component availability but it is a great combination for certain applications.
 
Thank you for the great Work Shawn !
I dont think I could give up any of my 338's but you have my attention on this 300 Prc !!

Rum Man
 
Does the LRKM in the photo have a 26" tube ?

It does we have made them with 24' barrels and trimmed the tube back a little for the same look. Either way it makes for a bad *** short package. Actually made one in 260 Terminator with a 18" barrel and put a TBA Ti Ultra 7 on it, most of that fit under the hand guard.
 
The +P idea is the real deal and I'm shocked none of the major manufacturers have picked up on it.

I did a 7RM in similar fashion and it shoots the 160 Nosler Accubond with an average of 3160fps and single digit ES, also shoots the 175 Berger EH @ 3050 just as well.
 
okay i got to ask for us that are wondering what is the +P in the rifle mean? I know what the pistol is but what did you change on the reamer design to get the +P if you did change the reamer? Sorry just trying to understand the term.
 
We have recently been exploring cartridges that would greatly benefit from the +P throating modifications we do. We have just built a 300 PRC for a rental rifle on our LRKM platform to use in our long range shooting classes. https://www.defensiveedge.net/index.php/classes
View attachment 176776

I choose the 300 PRC for one of several reasons:

  • soft shooting (compared to a 338 Terminator)
  • low powder consumption
  • ability to run a 215 Berger @ 3000 fps
  • 2000 yards target capability
  • ability to shoot some rounds through it in a day and not have students get beat up
  • the case has no belt
  • case design is modern and efficient
  • has been adopted by military units that we work with
  • can feed out of a detachable box mag (although the LRKM doesn't have one)
These were the key features that drew us to the 300 PRC. Is it a 300 Terminator? Of course not, it isn't ever going to shoot a 215 gr. bullet @ 3400 fps. Let's talk about what the 300 PRC is then. The 300 PRC is a 300 Winchester Mag length cartridge that has been improved with a 30 degree shoulder and less case body taper all good things to a point. There is no belt (not that these cases ever needed one) this greatly aids in feeding, especially from a detachable box magazine. It doesn't require a 4.00" mag box even with VLD/ ULD bullets. The SAMMI spec chamber will put the max OAL with a 215 Berger at roughly 3.735". The case has an H2O capacity of 99.0 gr. and that is a 7 grain advantage over the 300 Winchester Magnum (this becomes important later).

View attachment 176777

So with the LRKM spun up and ready to roll it was time to start load development. I started with the following base information and QuickLoad predicitions:

Shop LRKM - demo



Case
: Hornady 300 PRC

Max Case Length: 2.585"

Case Trim Length: 2.575"

Primer: CCI 250

Powder: H 1000

Bullet: 215 gr. Berger Hybrid Target

OAL Max: 3.735" raw 2.902" w / Reloading Comp

Barrel: Hart, .308", 1-9 twist, 26" finished length, Sendero Contour DE fluted

QuickLOAD Prediction: Max load 87.0 gr. H 1000, 103.4% case capacity, 3001 fps, 100% barrel burn, 4288 ft/lbs, muzzle pressure 12639 psi








Now with this info I started a pressure series to establish max pressure.



OAL: -.000" (2.902" W / Reloading Comp)

Charge Velocity Notes




82.0 gr 3080 fps Faint click a top

83.0 gr 3081 fps Faint Ejector mark

84.0 gr 3126 fps Ejector Mark

85.0 gr DNS

86.0 gr DNS

87.0 gr DNS Just starting to make OAL longer from compression .002"



As you can see this is why no matter what your source you always start 10% lower than max and work up. 87.0 grains would have blown the primer right out. Now starting with an 82.0 grain max pressure I shot a couple of groups at -.000" and -.005".



Shooting 82.0 gr @ -.000"

3058, 3044, 3065 fps .75 moa



Shooting 82.0 gr @ -.005"

3058, 3064, 3069 fps .25 moa



Now while the load at -.005" was great after inspecting the case and bolt lift (faint but detectable) I decided that I wanted to run a little less pressure.



Shooting 81.0 gr. @ -.005" 2+1 .5 moa



Shooting 81.0 gr. @ -.010" 2+1 .4 moa



After shooting these groups I decided to drop one more grain and go with -.010". After enough years of doing this you sort of get a feel for it.



Shooting 80.0 gr. @ -.010" .216" ES 9 fps Average Velocity 2996 fps



So at this point normally you whistle to yourself and think about all the great long range shots you are going to make with this kind of performance. Unfortunately my mind doesn't always work that way. My first thoughts were, "Hey, I am 7 grains of H1000 under max case compression capacity. I wonder how much velocity I would gain it I +P modified the throat?" Well there is only one way to find out.









So the +P modification is simple to work with as it doesn't require anything different in terms of dies, brass etc. Starting at the final load of the non +P round of 80.0 grains resulted in a velocity drop of almost 100 fps from the pressure reduction of the +P throat.



Charge Velocity Notes



80.0 gr. 2909 fps Max load from non +P chamber

81.0 gr. 2952 fps

82.0 gr. 2998 fps Equal to 80.0 gr load in standard chamber

83.0 gr. 3037 fps

84.0 gr. 3081 fps

85.0 gr. 3130 fps Faint bolt lift similar to 81.0 gr. in standard chamber



84.5 gr. 3106 fps no ejector mark, no bolt lift



Shot 84.5 grains @ -.005" , -.010" and -.015"



Jump Group ES



-.005" .473" 19

-.010" .258" 9

-.015" .184" 23



So clearly we will be running the -.010" load with the lower ES even though the -.015" load shot slightly tighter. The higher ES of the -.015" load make it less of a choice at distance. This is pretty standard + P improvement if case capacity allows. The thing I like the best here is the combination. The 215 Berger at 3100 fps is serious hunting medicine. The use of H1000 will ensure that it will always do the same thing day in and day out. Only using 84.5 grains of powder will allow for a decent barrel life. It uses a standard magnum bolt face. It doesn't rule any category in terms of accuracy, velocity, efficiency or match component availability but it is a great combination for certain applications.
Not to derail the topic but I really like that stock with the action behind the trigger like that. Who makes it and what mods are done to make the trigger link up. Thanks
 
The +P mod is a throating design I patented several years ago. It is basically a step in the throat to reduce peak chamber pressure allowing more powder at the same SAMMI pressure but getting more velocity.
Shawn,
Can the +P mod be done to any existing chambering?
I am curious about a 6.5x284 norma.
 
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