Gene Beggs
Active member
This evening in the tunnel, I tested the latest prototype of the barrel indexing system. The rifle is one of my 'Ultralite' stocked sporters chambered in 6 Beggs with a .269 neck. The barrel tenon on this rifle is the smallest diameter I have tested at .800 before threading.
I, as well as others, have had some concern for the strength of the tenon after it is turned down to accept the indexing bushing which fits in between the tenon and action threads. My tests today removed all doubt in my mind about the strength and integrity of the differentially threaded bushing installation.
For the tests today, I used the barrel and cases last fired at the Nationals in Phoenix. The barrel tenon was turned down from 1.055 to .800 and threaded 24 tpi. The barrel was reinstalled and headspace checked; it was unchanged. Powder was H4198 with Winchester WSR primers. Bart's 68 gr., bullets.
I started with 22 grains of H4198 working up in half grain increments to 27.5 grains; a compressed load. Primers were flattened, bolt lift was a little stiff and of course, there was a 'click at the top' but 27.5 grains (49 clicks on my Jones measure) is well beyond my normal hot load of 47 clicks which produces around 3350 fps with fine accuracy.
For those of you who may be wondering; I did use safety shields and sand bags over and around the action for the tests. I'm no fool and have great respect for the enormous pressures generated by these downsized, high intensity cartridges. Safety must always be priority number one.
After firing forty rounds at extremely elevated pressures, the barrel torque was checked and found to be unchanged. I now have complete confidence in the strength and integrity of the barrel indexing system.
The original prototype used a .900 diameter tenon, the second .875 and the last .800. .8750 was chosen for the first production batch of bushings which should be available next week.
BTW, the last group fired this evening was estimated conservatively at around .125. Tommorow, I will rotate the barrel a quarter turn, use the same load and see if this has any affect on POI and group size.
Later,
Gene Beggs
I, as well as others, have had some concern for the strength of the tenon after it is turned down to accept the indexing bushing which fits in between the tenon and action threads. My tests today removed all doubt in my mind about the strength and integrity of the differentially threaded bushing installation.
For the tests today, I used the barrel and cases last fired at the Nationals in Phoenix. The barrel tenon was turned down from 1.055 to .800 and threaded 24 tpi. The barrel was reinstalled and headspace checked; it was unchanged. Powder was H4198 with Winchester WSR primers. Bart's 68 gr., bullets.
I started with 22 grains of H4198 working up in half grain increments to 27.5 grains; a compressed load. Primers were flattened, bolt lift was a little stiff and of course, there was a 'click at the top' but 27.5 grains (49 clicks on my Jones measure) is well beyond my normal hot load of 47 clicks which produces around 3350 fps with fine accuracy.
For those of you who may be wondering; I did use safety shields and sand bags over and around the action for the tests. I'm no fool and have great respect for the enormous pressures generated by these downsized, high intensity cartridges. Safety must always be priority number one.
After firing forty rounds at extremely elevated pressures, the barrel torque was checked and found to be unchanged. I now have complete confidence in the strength and integrity of the barrel indexing system.
The original prototype used a .900 diameter tenon, the second .875 and the last .800. .8750 was chosen for the first production batch of bushings which should be available next week.
BTW, the last group fired this evening was estimated conservatively at around .125. Tommorow, I will rotate the barrel a quarter turn, use the same load and see if this has any affect on POI and group size.
Later,
Gene Beggs