.308 Bellm Load Data

Developed by Don Shearer, Littleton, CO.

Designed especially for TC Contenders

Data developed in a TC Contender S-14  8 groove factory barrel, 1-10" twist, rechambered by Mike Bellm.                           

Maximum Chamber Dimensions

 

Cases:  Reformed R-P .444 Marlin                   

Max. Trim Length:  2.200"

Bullets:  Hornady 

Primers:  CC!-200, CCI-250, Fed. 210

About the Data, Don Shearer's testing regimen, and My Opinion of the Cartridge.:

First and foremost, it is understood that both Mike Bellm and Don Shearer disclaim any liability that may result from the use of this data.  You use it at your own risk.  Since there are variables from gun to gun that can effect the results you obtain, it is imperative that you always start low and work up.  Do not ever use any loading data like a cook book and just dump in the top load and hope for the best.  Always, if there is any hint of hard opening after firing or difficult extraction, back loads off.

 Don's testing regimen is extremely thorough, and in many respects goes above and beyond what is normally done by the perveyors of wildcat cartridges for Contenders.  Extensive study was made to determine a functional maximum pressure for the Contender using .444 Marlin brass, and I highly recommend you read his summary of the procedure we jointly worked out.  You will find it in the "Articles" section of this site.  To date, I know of no other system that is as reliable for establishing a safe maximum load in the Contender using the relatively large diameter .444 Marlin case.  Time and space does not permit detailing the extensive work Don did in preparing this data, but it can best be described as simply outstanding, and in my opinion a monumental work.

There is a contingent of shooters who look at every new barrel in eager anticipation of trying what they imagine to be the epitome of powder, bullet, and primer combination.  For those of you who fit this description, may I suggest you control your enthusiasm until you have first tried IMR 4895 and Win 760 powders.  They gave essentially the same performance.  Across the board, for accuracy and top velocity, these are statistically the top performers as very careful statistical analysis has proven.  Ie., there is absolutely nothing about the data that follows that is "seat of the pants" load development, nor is it based on what you can get away with.  We have carefully avoided entering the wildcatter's "arms race" in favor of sane performance that will not be prone to stretching and ruining Contender frames.

There were 137  5-shot groups fired at 100 yards under controlled conditions in an underground range with a very constant environment using a special rest that minimizes shooter error.  With a total of 7 different powders, 4 different bullets, and 3 different primers 29.9% of the groups were under 1," 45.3% were between 1.0" and 1.5," 16.1% were between 1.501" and 2.00" and only 4.4% were greater than 2.001."  The remaining 4.4% involved an anomaly such as shooter error which caused the group to be invalid.  And this was from a factory barrel that in its original .30/30 chambering  would shoot nothing under an inch with most groups between 2 to 3."   The design of the cartridge and the way I chamber barrels make .308 Bellm inherently very, very accurate.

While the "Triad" cartridges were developed  specifically with rechambering factory barrels in mind, the factory barrels represent a "worst case scenario."  Even more impressive performance can be had with top quality custom barrels such as those made with Shilen blanks from Virgin Valley Custom Guns, my first pick among custom TC barrel makers.  

In a custom barrel for .308 Bellm, I would suggest choosing a 1-12" or 1-14" twist rate.  The slower twist rate and the smaller amount of bullet metal displaced by normal rifling will give higher velocities than possible with the exceptionally wide rifling and 1-10" twist in the factory barrels.  Ballistic performance of the .308 Bellm in a good quality custom barrel will equal that of any of the other high performance wildcat Contender cartridges when pushed to the same pressure levels.

The .308 Bellm cartridge is my favorite cartridge of the "Triad" series.  To me it is the most useful and versatile of the 3, extremely accurate, and gives the most pronounced increase in performance over the factory chamberings.  For long range target use, it is outstanding.  And for game it carries a good trajectory for deer and antelope without holding over out to 300 yards, aka point blank range..  On larger game like elk it carries enough energy for shots to 200 yards.  Recoil, while significant, is not bad at all without a brake, and it permits optimum performance in the field while avoiding  the greater noise caused by muzzle brakes.  With a brake, it is quite pleasant to shoot.

If you hunt a wide variety of game, I feel  a .308 Bellm barrel should be your main barrel.  It will serve you extremely well.


Hornady 130 gr. Flat Base Spire Point.  # 3020 was used, but for game, #3021 Single Shot Pistol bullet is recommended also.  Refer to Hornady ballistics tables for energy and trajectory figures.

Powder:

Wt. (gr):

Muzzle Velocity (fps):

Loading Denstity (%)

IMR 4895

40.0

2126

80

 

42.0

2275

84

 

44.5

2432

89

Win 760

47.0 2173 92
  49.0 2284 96
(most accurate, this bullet)  51.0* 2402 100
 IMR 4350 48.0 2133 98
(use magnum primer) 49.0 2195 100
  50.0 2242 102
IMR 4320 41.0 2189 82
  43.0 2286 86
  44.0 2350 88

Hornady 150 gr. Flat Base Spire Point #3031

Powder: Wt. (gr): Muzzle Velocity (fps): Loading Denstity (%)
IMR 4895 39.0 2107 80
  41.0 2191 84
  43.0 2341 88
Win 760 45.0 2044 92
  47.0 2151 96
  49.0 2259 100
IMR 4350 46.0 2010 96
(use magnum primer) 47.0 2073 98
  48.0 2126 100
IMR 4320 39.0 2114 80
(most accurate, this bullet) 40.0 2122 82
  42.0 2129 86

Hornady 165 gr. Flat Base Spire Point #3040

Powder:

Wt. (gr):

Muzzle Velocity (fps):

Loading Denstity (%)

IMR 4895 37.0 2002 77
  39.0 2095 81
  40.5 2171 84
Win 760 44.0 2075 92
(most accurate, this bullet) 45.0* 2133 94
  46.0 2183 96
IMR4350 42.0 1804 89
  44.0 1933 94
  45.0 1999 96
IMR 4320 38.0 2008 79
  39.0 2073 81
  40.0 2124 83

* Note that the 45.0 gr. load above shot .330" center to center, and as I recall, Don reported it shot about .5" with the gun in "hunting configuration."

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