On the shotgun power factor topic ,it seems that no one(to my knowledge)uses buckshot which typically starts at  size SSG. Buckshot is invariably heavier loads loads of  lead shot. 

I have noticed that at present most competitors are using  lighter birdshot .In vary rare instances heavier 35g AAA being the largest shot size used.It seems that most competitors are using 28 g(1 ounce)(432gr) loads(or lighter).

Having fired both buck and bird shot  of all sizes it seems that the choice is the weight of the shot and the velocity of the shot that make a difference on the felt recoil.This is personal choice so whatever your load of choice  , the reality is that whatevever load drops a pepper popper (and makes POWER FACTOR) is the real consideration.On this point I would like to point out that I have Chronographed(among others) a 28 gram no 6  hand load that drops a pepperpoppper at 30m but only factors 365. 

The power factor requirement FOR SHOTGUN = 520 . A typical 28g load should at least reach a velocity of 1205 fps to factor at 520.If you factor 519.9 you will continue to shoot the match WITHOUT score.

In factory form the following typical  loads exist in 2 3/4 "(70mm)cartridges.

DRAM EQUIVILANT     SHOT WEIGHT   VELOCITY           POWER FACTOR 

-                                 24g(370gr)            1325fps              490   *

-                                 24g                      1435fps              530   *

2 3/4                           28g (432gr)          1180fps              509  *

3 1/4                           28g                     1290fps              557  #

2 3/4                           32g(494gr)           1145fps              565  #

3                                32g                      1200fps              592  #

3 1/4                          32g                      1255fps              620  $

3 1/4                          36g(556gr)            1220fps              678  $

3 1/2                          36g                      1300fps              722  $

3 3/4                          36g                      1330fps              740  $

The specs for Cartridges of 2 1/2 "  and shorter in length are probably even lower in velocity and charge weight or both HOWEVER I have never tested or used these.

The following can be deduced from abovementioned :

24g loads in factory form probably won't factor ,although  depending on the manufacturer it might (barely)

28g loads in factory form are better with a slightly better chance of factoring

(for 24 and 28g loads it seems that it is wise to choose the highest velocity amunition if power factor is to attained)

32g loads in factory form are in all likelyhood always going to factor

36 g loads (and heavier) in factory form always make factor and granted they seem (subjectively) to bump harder .

The only factory loads that I have  CHRONOGRAPHED is 35g NO 3=620POWER FACTOR (Swartklip) and   35gAAA =617POWER FACTOR  (Swartklip)

The position in above mentioned regard will change for the handloader who reloads his own ammo , however very few competitors reload(yet).A session over the chronograph may produce some alarming results ,particularly at a match.

I would be pleased to hear from others regarding their findings since it is a matter of time before shotguns will be chronographed at matches(maybe the 3 gun nationals ?)

So what now ? I suggest chronographing your favourite load and ensure that it makes the cut-off.

"don't get caught with your power factor down" 

 

Regards

 

Carl Talbot