bench rest primers

[JEB]

I'm starting to work up a load for my ar, wanting to make it as accurate as possible. i have been searching for loads that people have had the most luck with and ive come across several people listing bench rest primers as part of their load. most of my reloading has been with pistols and hunting type rifles so the maximum accuracy aspect is one i have yet to attempt. so im curious what benefits, if any, do bench rest primers offer and how are they different from standard ones?

 

[Walkalong]

If you and your rifle can shoot 1/4" to 1/2" regularly they may help cut out the occasional shot out on the edge and bring it in closer. Don't expect night and day differences. Top accuracy comes in incremental steps.

 

[JEB]

I'll probably just stick with standard primers then. no idea what the rifle is capable of at this point, but im pretty sure im no 1/4" shooter lol

 

[ants]

I never confirmed the information myself, I remember one of the other THR members asked Federal about the difference between their Gold Medal Match primers and standard primers. The answer was quality control. Benchrest primers are not hotter or colder, just made more carefully to be more consistent.

I've never confirmed that, but it sure seems to make sense.

 

[Walkalong]

That is what we were always told back in the day when I shot Benchrest and 99% of shooters used the Gold Medal match SR primers. The most experienced employees do the Match primers, so they are more consistent with the mix.

 

[Slamfire]

I have a bud, worked as an Army Gaging and Calibration Specialist at an Army Ammunition plant. He is interested in shooting so he asked questions. All Army Ammunition plants are run by the same contractors who produce your ammunition. In fact, once the military orders are met, they are allowed to use the facility to produce ammunition under their brand name to sell.

Anyway, primer mix is a mix of chemicals. The standard primer mix for military primers is the FA 956 mix, developed in the 1950's as a joint project between the Government and Industry.

PATR 2700 Encyclopedia of Explosives Vol 8 gives the composition

FA 956

Lead Styphanate 37.7 +/- 5%
Tetracene 4.0 +/- 1%
Barium Nitrate 32.0 +/- 5%
Antimony Sulfide 15.0 +/- 2%
Aluminum Powder 7.0 +/- 1%
PETN 5.0 +/- 1%
Gum Arabic 0.2%

There are plenty of primer compositions for there are many applications for primers other than small arms. This is a list of military priming mixtures, FA 70 is the old corrosive primer, I was able to identify PA101 as a fuse primer composition. All of the compositions to the right of FA90 are more sensitive than rifle primer compositions, so these are probably used on a variety of explosive or propellant devices.



It is very likely that Federal makes a different primer mix than Winchester or CCI for their military primers. The Army has moved over to performance specifications and as long as the product meets sensitivity, temperature, pressure requirements, they don't care anymore what is in the product. This is probably true for primers. What you will find is that each manufacturer provides the Government a "Mil Spec" primer, but only CCI offers their Mil Spec primers to the public.

George Frost, in his book, Making Ammunition shows a whole bunch of different variations of the FA956 mix as used by the various commercial manufacturers for the same applications.

Notice that the constituents used all have tolerances, so each batch of primer mix will be a little different based on mix percentages and purity of the constituents. And, as my friend told me, the most consistent primer mix du jour is not predictable. Employees are rewarded for making the most consistent primer mix so they have a financial incentive, and it is probable that the prize rotates around a couple of the makers. But it is not predictable who gets the prize of the day.

This is a great article on primers: Mysteries And Misconceptions Of The All-Important Primer http://www.shootingtimes.com/2011/01/04/ammunition_st_mamotaip_200909/ I recall reading that CCI Benchrest primers are made under tighter controls, they actually weigh the individual primers at the end. I do not recommend Bench Rest primers for semi auto rifles as several primer companies have told callers that the bench rest cups are thinner and the mix is more sensitive than military primer mix. This will increase the chance of a slamfire. I cannot find the post but one shooter of a real full auto Army M14 loaded new cases with bench rest primers. Shooting his M14 full auto, he had the rifle fire out of battery. Luckily the receiver heel was not knocked off or he would have been out $25,000 or more.

Now will bench rest primers make your groups smaller? Maybe for the best shooters but it will be something hard to determine with any exactness. Accuracy affects due to primers are in the noise level compared to bullets, powder charge, cases. And all of these have a smaller affect on accuracy than the skill of the shooter. Marksmanship is a skill, good equipment and good ammunition cannot compensate for poor shooting skills.

I do have F Class friends who experiment with primers, many of them are using CCI Bench rest primers, so they must be good. I have shot many cleans on the two MOA targets with standard primers, if the shot is not in the ten ring it was not due to primers!

 

[JEB]

lots of helpful information guys! i greatly appreciate it! great information Slamfire, thank you very much!

this is exactly why i love this forum. lots of knowledge to be shared and absorbed. think i will work on the load and get it as good as i can with standard primers and plan on picking up some bench rest primers later on and see if it makes any difference.

 

[Walkalong]

but only CCI offers their Mil Spec primers to the public.

Federal now markets an "AR" primer. I wonder if it is their version of the mil-spec primer.

Now will bench rest primers make your groups smaller? Maybe for the best shooters but it will be something hard to determine with any exactness.

During the first primer shortage that I was a part of many Benchrest shooters switched to standard Winchester SR primers. Many reported no difference that they could tell.

Accuracy affects due to primers are in the noise level compared to bullets, powder charge, cases. And all of these have a smaller affect on accuracy than the skill of the shooter. Marksmanship is a skill, good equipment and good ammunition cannot compensate for poor shooting skills.

All true.

 

[pert near]

In my quest for ultimate accuracy I've tried just about every SRP available, including Match/Benchrest primers. I have some very accurate rifles but none are bona fide bench guns. I've not been able to tell any difference in primer brands except that a particular rifle may "like" one or two better than the others. The benchrest primers cost more so in general I don't believe them to be worth the extra money for my applications. But I don't discourage anyone from trying them as sometimes being perfect equals confidence! I was always a big CCI fan but during the primer famine I tried some Wolf brand primers mainly because they were cheaper & available. To my surprise they are excellent & I have a rifle or two that prefers them. Go figure...

JIMHO

 

[Blue68f100]

Once I have a load worked up, I always try different primers to see if it improves. In some cases it does, in some it does not. For the 223R I mainly use the CCI #41 but I do have some loads that shoot better with the Rem 7 1/2. The only way to know is by tring them out.

 

[Jack B.]

I believe ants and Walkalong are correct . More consistent control of assembly and only their best employees make the bench rest primers.

 

[spitballer]

several primer companies have told callers that the bench rest cups are thinner...

...IMHO this gets to the crux of the matter, cup thickness. I found out the hard way that cup thickness matters!

A couple of years ago in Hodgdon's Annual Reloading Manual there was a good article discussing primer selection and the compatibility of different primers with different types of propellant, and one of the things I took away from that article is that regular primers tend to be more consistent when used with stick powder, while mag primers generally do better with ball powders. I understand this, and I also believe our resident experts when they say that stick powder is still used by the majority of match shooters where accuracy matters.

However:

...it does seem to me that there would be instances when the primer with the thicker cup would be selected for use with a full/compressed case of stick powder simply for pressure reasons, even though the ignition may not be as consistent, such as in lengthy barrels that tend to produce sustained Cup pressure?

My only experience is with the widely available CCI primers - perhaps there are regular primers available with thicker cups from other manufacturers? thx - btw great post

 

[Berger.Fan222]

Combined with hand weighing every charge of a stick powder, bench rest primers can reduce velocity variations. This starts to be more important at longer ranges (500-1000 yards), but it is less important for work at 100-200 yards.

 

[Slamfire]

...it does seem to me that there would be instances when the primer with the thicker cup would be selected for use with a full/compressed case of stick powder simply for pressure reasons, even though the ignition may not be as consistent, such as in lengthy barrels that tend to produce sustained Cup pressure?

Issues such as you raised are beyond my ability to measure. I ran my own test of primers, but I don't have, nor am I going to pay for Bench Rest primers. I ran a test to compare velocities of a series of primers, including Tula 7.62, with my standard 30-06 match load of 168 SMK 47.0 grs IMR 4895.

I have lots of 174 FMJBT's, five gallon buckets of LC match brass, so I used those and all the primers I have rolling around the reloading room. Any load I have developed with 174’s is perfectly safe with 168 match bullets.

I do not recommend the use of bench rest primers or Federal primers in Garands, Federals are the most slamfiring primers around, so I am not publishing any federal primer data in my Garand, because someone may think it might be an endorsement of use.

I used the great old WLR nickel plated primers. These were made prior to 1999. Winchester changed their primers in 1999 to make them "more" sensitive and changed the primer color to brass. These brass Winchester primers have thinner cups than the older version I do not recommend their use in Garands/M1a's. I also do not recommend the use of brass WSR as primer piercing in my AR's ate up a handfull of firing pins at loads that never bothered the great old nickel plated WSR.

Tula 7.62 primers were advertised by Graf as equivalent to CCI #34 primers. CCI #34 primers are advertised as being “mil spec” primers by CCI. Mil Spec primers are the only appropriate primers to use in Garands and M1a’s as they are less sensitive than commercial primers and greatly reduce the risk of an out of battery slamfire.

Tula 7.62 and Wolf primers shot very well and I have been using Tula 7.62 in matches, I have a high confidence in their accuracy ability.

I will agree with anyone that ten shot groups and data points don't definitively prove anything. But, I will say all the primers I tested gave good extreme spreads and standard deviations, the Russian primers seemed a bit more consistent. All are welcome to conduct their own tests.

30-06 Primer Test

Colombian Mauser Match

 174 FMJBT White Box 1968 NM M72, Headstamp LC67 match, box velocity 2640 fps
14 Nov 2011 T =  68 °F    

Ave Vel = 2698     
Std Dev = 51     
ES = 117      
High = 2771     
Low = 2654      
N = 5     
      

174 FMJBT 47.0 IMR 4895  Lot L7889 thrown LC62NM CCI #34 OAL 3.30  
14 Nov 2011 T =  74 °F    
     

Ave Vel = 2645     
Std Dev = 12     
ES = 42      
High = 2671     
Low = 2629      
N = 10     

Very good group      
   

174 FMJBT 47.0 IMR 4895  Lot L7889 thrown LC62NM Tula 7.62 lot 1-10 primers OAL 3.30
14 Nov 2011 T =  74 °F    

Ave Vel = 2665     
Std Dev = 9     
ES = 28      
High = 2677     
Low = 2649      
N = 10     

Excellent Group    

      

174 FMJBT 47.0 IMR 4895  Lot L7889 thrown LC62NM Wolf NCLR lot 18-09 OAL 3.30
  14 Nov 2011 T =  74 °F    
     

Ave Vel = 2656     
Std Dev = 15     
ES = 36      
High = 2677     
Low = 2641      
N = 9     

 

174 FMJBT 47.0 IMR 4895  Lot L7889 thrown LC62NM Fed 210S OAL 3.30  
 14 Nov 2011 T =  74 °F    

Ave Vel = 2656     
Std Dev = 13     
ES = 34      
High = 2674     
Low = 2640      
N = 10     

174 FMJBT 47.0 IMR 4895  Lot L7889 thrown LC62NM WLR (Nickle) OAL 3.30
14 Nov 2011 T =  74 °F    

Ave Vel = 2665     
Std Dev = 18     
ES = 60      
High = 2696     
Low = 2636      
N = 10  
   
Excellent group      

      

174 FMJBT 47.0 IMR 4895  Lot L7889 thrown LC62NM CCI200 OAL 3.30  
14 Nov 2011 T =  74 °F    
      
Ave Vel = 2680     
Std Dev = 14     
ES = 56      
High = 2712     
Low = 2656      
N = 10     

V. Good group



[IMG]http://img.photobucket.com/albums/v479/SlamFire/Rifles%20various/DSCF2878ColumbianMauser.jpg[/IMG]

M1 Garand BMR Receiver Douglas Barrel 1:10 twist

  150 gr FMJBT 1966 Ball      
14 Nov 2011 T= 74 ° F     
  
Ave Vel = 2545       
Std Dev = 20      
ES = 68      
Low = 2513      
High = 2581       
N=  8      


174 FMJBT White Box 1968 NM M72, Headstamp LC67 match, box velocity 2640 fps 
14 Nov 2011 T =  74 °F     
  

Ave Vel = 2592      
Std Dev = 28      
ES = 103       
High = 2647      
Low = 2544       
N = 10      

174 FMJBT 47.0 IMR 4895  Lot L7889 thrown LC62NM CCI #34 OAL 3.30   
 14 Nov 2011 T =  74 °F     

Ave Vel = 2632      
Std Dev = 20      
ES = 60       
High = 2671      
Low = 2611       
N = 10      


174 FMJBT 47.0 IMR 4895  Lot L7889 thrown LC62NM Tula 7.62 lot 1-10 primers OAL 3.30
 14 Nov 2011 T =  74 °F     

Ave Vel = 2582      
Std Dev = 15      
ES = 49       
High = 2602      
Low = 2553       
N = 10      

 excellent group     

174 FMJBT 47.0 IMR 4895  Lot L7889 thrown LC62NM Wolf NCLR lot 18-09 OAL 3.30  
14 Nov 2011 T =  74 °F     
  

Ave Vel = 2607      
Std Dev = 17      
ES = 57       
High = 2642      
Low = 2585       
N = 10      

174 FMJBT 47.0 IMR 4895  Lot L7889 thrown LC62NM WLR (Nickle) OAL 3.30  
14 Nov 2011 T =  74 °F     
 
Ave Vel = 2650      
Std Dev = 19      
ES = 68       
High = 2688      
Low = 2620       
N = 10      

Very good group      
  

174 FMJBT 47.0 IMR 4895  Lot L7889 thrown LC62NM CCI200 OAL 3.30   
14 Nov 2011 T =  74 °F     
 
Ave Vel = 2599      
Std Dev = 22      
ES = 75       
High = 2637      
Low = 2562       
N = 10      

Very good group

 

[Captcurt]

I was always a big CCI fan but during the primer famine I tried some Wolf brand primers mainly because they were cheaper & available. To my surprise they are excellent & I have a rifle or two that prefers them. Go figure...

JIMHO

Same here with PMC. I found a 1000 during the famine and my old 270 loves them. As for the Benchrest primers, I have some CCI BR-4's that worked so well in my 223 Vanguard that it was boring to shoot it. Put the crosshairs on the target, squeeze and it was a done deal.

 

[jhansman]

I never confirmed the information myself, I remember one of the other THR members asked Federal about the difference between their Gold Medal Match primers and standard primers. The answer was quality control. Benchrest primers are not hotter or colder, just made more carefully to be more consistent.

I've never confirmed that, but it sure seems to make sense.

Which is why you cannot find them for sale. I use them in my Howa 1500, and it pains me that they are rarer than hen's teeth right now. I've never tested them against "regular" SR primers, but I can say that my recipe has resulted in dime-sized groups at 100 yds. Whether the primer really made a difference, I cannot say with certainty. I do like to think so.

 

[ants]

Which is why you cannot find them for sale. I use them in my Howa 1500, and it pains me that they are rarer than hen's teeth right now. I've never tested them against "regular" SR primers, but I can say that my recipe has resulted in dime-sized groups at 100 yds. Whether the primer really made a difference, I cannot say with certainty. I do like to think so.

Amen, brother. Each of us can only do his/her best as we see it. Amen.

 

[Hondo 60]

I seriously doubt you'd notice a difference with bench rest primers.
Atleast I wouldn't.
The AR platform IMHO just isn't set up to notice such a tiny difference.

Benchrest primers are for long-distance EXTREMELY accurate shooting
Just my 2¢ worth YMMV

 

[Walkalong]

Leave out the "long-distance and" you have it. 100 or 1000 yards, doesn't matter.

 

[HOWARD J]

I asked a guy what is the difference between bench rest & standard primers.
" we use only our best people on a weekend & if we drop any on the floor we don't pick them up"
WHATEVER................

 

[Sofie007]

I'll probably just stick with standard primers then. no idea what the rifle is capable of at this point, but im pretty sure im no 1/4" shooter lol

Firmly believe that BR/Match primers are well worth the incremental price (often 1 to 3 cents). Did design of experiment (i.e. DOE) with 308 Win that showed significant precision improvement. (Remember, ve!ocity variation doesn't exactly equate to Point of Impact variation. Often times my best groups had large MV variation.). Well worth it. Want most of variation in only the shooter: not in ammo or gun.

 

[spitballer]

I don't have, nor am I going to pay for Bench Rest primers...

...I'll buy this. I mean, bench rest primers would hardly be appropriate in a carbine with hard bullets that need pressure and need it fast. My dilemma has to do with effective pressure, or at least I think it does. It's the only way I can explain pierced primers when I'm using a combination that is identical in every way to the combination used to formulate load data - except for barrel length. Perhaps this is more of a bench rest issue and inappropriate for current discussion, sorry. I'll check with 6mm.

 

[Nature Boy]

From my own testing I've come to the conclusion that Federal 210M match primers make a positive difference in my loads. They are also hard as hell to find.

Last week I was lucky enough to get my hands on a case. I should have enough to burn a barrel out now.