.308 BELLM Load Data

Developed by Don Shearer, Littleton, CO. 

Designed especially for TC Contenders to correct factory .30/30 chamber misalignment, cut out the factory throat, and permit cutting a new minimum diameter throat properly aligned with the bore for top accuracy.  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:  CCI-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 to correct factory chamber misalignment 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 by Match Grade Machine, 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.

Typical Accuracy From Barrels Rechambered to .308 Bellm

Target courtesy of Brad Barnett

And a nice British Columbia buck

photo courtesy of Cam Cooke

.308 Bellm Loading Data

Thoroughly tested for accuracy and acceptable pressure levels, the result of very extensive work by Don Shearer.

Notes regarding primers to use with the following data:

308 Bellm Load Data  130 Grain Hornady bullet  All loads using IMR 4895 and IMR 4320 should use standard large rifle primer (Federal-210)  All loads using Win 760 and IMR 4350 should use magnum large rifle primers (CCI-250) 

150 Grain Hornady bullets  All loads using IMR 4895 and 4320 should use standard large rifle primers (Federal-210)  All loads using Win 760 and IMR 4350 should use magnum large rifle primers (CCI-250) 

165 Grain Hornady bullets  All loads using IMR 4895, IMR 4320 and IMR 4350 should use standard large rifle primers (Federal -210)  All loads using Win 760 should use magnum large rifle primers (CCI-250) 

Note that I have used the magnum primers for IMR 4350 loads for the 130 and 150 grain bullet, but standard primer for the 165 grain bullet. I tested with both primers and selected the combinations that did the best, and the best was defined as the load that yielded the highest velocity along with the smallest 5-shot group.

NOTE: There is roughly a 100 feet per second margin of safety built into the data. .308 Bellm can be loaded hotter than the loads posted at your own risk. High summer temperatures increase pressure, which is one reason for the data being conservative instead of inviting potential problems with stretched Contender frames. 

G2 frames will handle more stress than the Contender frames, but the next component to fail is the lower lip of the barrel lug bending down if over loaded.

For comparison purposes, factory .300 Savage 150 gr. ammo with a SAAMI maximum pressure of 46,000 psi, (c.u.p. method) in a standard .300 Savage chamber averages 2350 to 2400 fps from a 14" barrel. Due to the thinness of .300 Savage brass, extraction with factory ammo was always a chronic problem and just a bit too much for Contenders. The thicker/stronger .444 Marlin brass takes much of the strain off of the frame and gives flawless extraction with the loads listed below. 

Other purveyors of wildcat .30 cal. cartridges push the limits with their data harder than I deem prudent.

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.

Hornady 150 gr. Flat Base Spire Point #3031

Hornady 165 gr. Flat Base Spire Point #3040

* 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."