replying to RobG, ray allen wrote: My best friend was part of the crew that tested the M110A1E2.
Bill said that the 25-caliber gun tube was replaced with a 35-caliber gun tube, and that the hydraulics had to be redone because they were blowing hydraulic at high powder charges.
Since the gun tube in the model is 9.1" long, cutting it down to 6-3/8" would give you a 25-caliber tube.
Bill also said that when using charge 9, the crew had to dismount, he had to use an extra long lanyard, and the recoil would lift the gun completely off the ground and rock it back on the spade. The gun also had to be reset after each charge 9 shot, so the plan was to only use charge 9 for special weapons (nuclear artillery shells).
I saw some video of the initial high charge tests at night and immediately understood why the flash suppressor was added. The BRIGHT made it easy for the enemy to locate you without using counter-battery radar, which made you a tempting target.