greater pressure than what is standard for the chambering involves risk. Some of us are willing to take that risk. All handloaders should accept that by the nature of


Actions for all shooting disciplines


the beast they sometimes are shooting loads that generate greater than standard pressure and, whether or not we follow published data, we never can be certain when this might be happening. So, a risk entails but so does a risk entail when fi ring only factory loads, as does a risk entail simply by liv- ing. I choose to take the risk associated with handloading and to therefore enjoy life more than if I did not handload. To each his own.


READING PRESSURE SIGNS


11550 N. Bruss Rd. Rathdrum, ID 83858 Phone: 208-687-0341 Fax: 208-687-1250 www.batmachine.com


Now, back to the subject at hand. How can we observe


things that suggest the level of, or at least refl ect, chamber pressure?


FEELING BOLT LIFT The fi rst so-called pressure indictor I will discuss is


applied stress (peak chamber pressure), the fewer the required number of cycles before such failure occurs. Extensive or habitual use of hotter-than-normal loads


in any gun increases risk that the number of cycles before brittle failure occurs will be less than the number of such rounds that might be fi red in that gun! This is a crapshoot. Eventually the dice will come up craps and the critical issue is that you cannot predict when that will happen. It might not happen for many millions of rounds but it might happen the next time you squeeze the trigger — as Bob Bell discovered the painful way! Generally, the larger the diameter of the case used, in


any given action, the more of a concern this is. All properly designed and produced guns are proof tested with one or more high-pressure loads, in a test that assures that any fea- sible number of shots fi red with ammunition loaded within normal pressure limits for that chambering will never result in such a failure. Naturally, when used in any given action, smaller-diam-


eter chamberings give us more assurance that high-pressure loads will not cause brittle action failure within the feasible lifetime of the action but we can never be certain because those guns are not proofed at greater pressure than otherwise similar guns chambered for larger-diameter cases. (Doing so is unnecessary and infeasible.) While we can assume (perhaps reasonably, perhaps not


reasonably) that when used in the same basic action, loads for smaller-diameter cases that generate higher than standard pressure are safer than loads for larger-diameter cases that generate (the same) higher than standard pressure, we can- not know. Ultimately, the reason we cannot know that guns chambered for smaller-diameter cartridges will tolerate more abuse is two-fold:  First, as noted, it is not feasible to proof test such a


gun at signifi cantly higher pressure; and,  Second, that gun might, therefore, include faulty steel in critical areas (which proof testing will fail to disclose). Therefore, use of any load that generates signifi cantly


Page 90 July — September 2011


ease of bolt opening after fi ring a round, along with ease of fully extracting the fi red case. Sometimes, loads that generate higher-than-standard pressure also will require extra effort to unlock the bolt. As a mirror, usually, loads that generate normal pressure will not require extra effort to unlock the bolt. However, exceptions do exist; hence, this method certainly is not foolproof. More often, if the round does not extract freely after the bolt is unlocked, probably pressure is higher than normal — probably. Variations in case design and hardness and other


variables, along with design characteristics and variations in manufacturing tolerances in the gun account for these differences. I will explore some of these variables under the heading Case Head Marking. OBSERVING PRIMER APPEARANCE


Next, consider the old canard about appearance of the


fi red primer being a good indicator of pressure. Usually this is described as fl atness and refers to how large the fl at area of the face of the fi red primer cup is, or how little of the radius around the edge of the primer remains between fl at area of primer cup and fl at area of case head. In reality, primer fl atness is such an abysmal indicator


for the novice that often I wish it had never been mentioned in print! Yes, primer face fl attening (and degree of engrave- ment of bolt-face marks on the primer face) can be helpful but this method is far from foolproof. It easily can lead the novice astray and it is apt to cause even the most seasoned handloader grief. I have examples of rifl e primers that show a fantastic


degree of fl attening, despite the fact that the loads actually generated relatively mild pressures. In these instances, fl at- tening resulted from excessive working headspace, as ex- plained below. Conversely, I have examples of primers fi red in a pressure test gun that show not one iota of fl attening or engravement into imperfections of the bolt face (because that gun had a well-polished bolt face) despite the load having generated 80,000 psi! (These examples resulted from using primers with unusually hard cups in cartridges that had minimal working headspace in the test gun.) The main culprits rendering fi red-primer appearance as


an unreliable mirror for chamber pressure are variations in headspace and primer cup hardness and thickness. The latter is easy to understand: The harder the primer cup, the less it


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164  |  Page 165  |  Page 166  |  Page 167  |  Page 168  |  Page 169  |  Page 170  |  Page 171  |  Page 172  |  Page 173  |  Page 174  |  Page 175  |  Page 176  |  Page 177  |  Page 178  |  Page 179  |  Page 180  |  Page 181  |  Page 182  |  Page 183  |  Page 184  |  Page 185  |  Page 186  |  Page 187  |  Page 188  |  Page 189  |  Page 190  |  Page 191  |  Page 192  |  Page 193  |  Page 194  |  Page 195  |  Page 196  |  Page 197  |  Page 198  |  Page 199  |  Page 200  |  Page 201  |  Page 202  |  Page 203  |  Page 204  |  Page 205  |  Page 206  |  Page 207  |  Page 208  |  Page 209  |  Page 210  |  Page 211  |  Page 212