Bethany was the first to respond to the question. "Well Amanda, Sarah and I both got a buff, so it seems pretty obvious the next thing to do is give you one, too!”

Amanda mulled this over. Both of her friends had already tested the device, and there was no indication that it was painful or unsafe, for people at least. In fact, both Sarah and Beth seemed to love the changes. But what if there were hidden side effects?

In the few minutes since Bethany's transformation, the blonde bombshell had been striking all sorts of poses, giggling with glee as she watched her muscles expand to proportions that would be the envy of any bodybuilder, male or female. Sarah had been mostly quiet, her jaw frequently hanging open in disbelief as she watched the display intently. Although she was not about to admit it, she was seriously jealous about the situation. Sarah was used to being the plain girl in the group, but in the brief period between her own growth and that of her friend, she had been ecstatic. She finally stood out! But that difference was quickly lost, as the beautiful Beth easily overshadowed her in every department now. It was unfair.

Amanda remained lost inside her head, but soon had her train of thought interrupted by the suddenly pushy Sarah. "So do you want us to use this thing on you too, or what?" she said in a sharp tone, picking the gun up as she spoke. "Because if not, hurry up and say so. I want to go screw with your brother and his friends."

Robert and two buddies, Jason and Eric often came over to work out in the garage after school, and the clanking noises emanating from below indicated to Amanda that they were probably doing just that.

Amanda’s eyes lit up at the suggestion. Even though she was the big sister, Robert had grown considerably over the last few years and frequently used his size to great advantage in their petty daily conflicts. His two meathead friends were equally annoying.

Amanda finally spoke up. “Sarah… that is a brilliant idea. Let’s do it!”
Sarah grinned eagerly, and raised the gun up closer to her eyes so she could examine the dials and decide what settings to use. Bethany took this opportunity to interject.
“Wait, if we all walk in there looking like this they aren’t even going to recognize us. Maybe you should wait a bit?”

Amanda thought about this for a second. Beth had a point, but at the same time, she was really looking forward to experiencing this. Bethany could tell from Amanda’s look that she was not convinced, so she explained herself further. “Imagine the looks on their faces if you grew right in front of them!”

This quickly changed Amanda’s mind. The thought of watching her brother tremble as she became the powerful one right in front of his eyes made her feel giddy. “That’s perfect, Beth!” Amanda squealed. Sarah seemed less enthused.

“Ok fine, we’ll make you bigger later, Amanda. But I don’t think I’m big enough to really scare those guys yet. I mean, if I put a sweater on they’d probably just think I’d gained some weight.”

Amanda raised her eyebrow. “Yeah, I guess. But what do you want to do about it?”
Sarah rolled her eyes back and stroked her chin, as if to give the impression that she was thinking it over and didn’t already know what she wanted. “Well, you could use the gun on me again, to buff me up to Beth’s size, maybe? I mean, obviously we need to turn the gun to a lower setting first but I think the prank would work better with me being closer to her size.”

Amanda was skeptical but ultimately she just wanted to go downstairs and have some fun. Bethany’s response implied a similar feeling. “Alright Sarah but let’s do this quick. Hand that gun over to Amanda, I just want to go freak those guys out!” Sarah was surprised that they acquiesced to her wishes so easily, and quickly handed Amanda the device. She turned the dials way down, hoping that it would be enough to satisfy Sarah without making her into a freak. After a brief pause, she turned the height dial up a bit.

“Alright, here it comes!” Amanda raised the device and pointed it at the still topless Sarah, whose slightly shorter than shoulder length black hair was shaking as she quivered with anticipation. As she pulled the trigger, the dull yellow beam of light went straight into Sarah’s bare midriff. She cooed, closing her eyes as the strange sensation once again flowed through her body, less intense than the last time but still tingly and thoroughly enjoyable.

Sarah, despite her musculature, was still only 5'7 and so was not an especially imposing figure prior to this second spurt. Over the next minute, that changed considerably as she grew even bigger. The thick mounds of muscle in her arms and legs looked almost as if they were being inflated by an invisible bicycle pump, growing thicker and denser with each rhythmic pulse; the veins and striations becoming more pronounced as it went on. Her already strained shorts could no longer endure the stress as the sound of fabric tearing became audible to everyone. The rips gradually made their way up the legs of her shorts as the heads of her quadriceps continued growing thicker and wider. Sarah winced from discomfort, and with a swift pull from her hand tore the weakened garment clean off, leaving her standing there in only her striped white and green panties. They looked more like a thong at the moment, though.

Sarah’s trunk widened as her expanding pectorals pushed her swelling breasts forward, while her lats widened out from her torso. Her merely-impressive 6 pack developed into a truly incredible 8 pack bounded by obliques that looked embossed onto her skin. Her trapezius muscles grew as well, surging larger and higher with each pulse. The locks of her black hair, which minutes earlier had dangled above her shoulders, were now clinging to the damp sweat on her expanding traps, which were starting to look like a cobra hood around the base of her neck.

Both Amanda and Bethany sat on the bed, transfixed at the transformation occurring in front of them, remaining motionless until the last waves of growth weakened and finally ceased. Her mouth hung open; she was seemingly winded from the spurt and her eight pack slowly heaved in unison with each breath. She was glistening with sweat from the ordeal. Sarah’s eyes had remained closed for the experience, and she opened them to gaze upon her newer new body for the first time. Elation overcame her.

“Holy shit!” Sarah exclaimed. She hopped over to Amanda’s wall mirror, and much as Bethany had earlier, began striking poses, flexing whatever muscle groups caught her interest. Bethany and Amanda stood up and followed her to get a closer look, but Sarah did not even notice until she saw them in the mirror beside her – well, parts of them anyway. She was so big that she took up most of the view, and all she could really see were some hands feeling her abs and arms. She could tell from the reflection that she was clearly buffer than Beth, and a shit-eating grin crept across her face as she realized that she had to be taller than her friend as well. She was at least 6 feet tall, if not more.

To say the least, Sarah was pleased with her new look, and even more pleased with the attention it was drawing from her friends as they moved their hands over her shoulders and arms to feel just how big she really was. She struck a double bicep pose, causing her friends' eyes to widen. Beth’s biceps were huge, but the blonde realized that she was now quite overshadowed by Sarah. They had to be close to 30 inches around. The veins crisscrossing her biceps grew more prominent as she flexed them a few times.

The raven-haired amazon turned around to face her friends, who had taken a step back to admire her while she flexed. She confidently put her hands on her hips and broke the silence. “Well girls? How do I look now?”
Neither responded at first, but Beth soon answered. “I think you said everything that needed to be said…‘Holy shit’ is right Sarah, you look like you could beat up a superhero!”
Sarah giggled, still enthralled with the attention. “No doubt!” She flexed her arms a few more times and looked at her friend. “Hey Beth, let’s have a little contest.”
Bethany rose an eyebrow.
“Just a quick little arm wrestling match.”
Bethany shrugged. “Sure I guess… but I think we already know who is going to win.”
Sarah looked around for a surface to use. Amanda suggested her desk.

It had a thick metal base and weighed at least a few hundred pounds. Sarah swept the papers and books strewn on top of the desk onto the floor, gripped it on both sides and carried it to the middle of the room as if it were a laundry basket. She sat at one side of the desk and thumped her elbow down onto the surface. Beth was a little nervous but she soon took her position on the opposite side and clasped her hand with Sarah’s.
“Don’t worry I’ll go easy on you.” Sarah said with a cheesy grin. “Ok Amanda, on the count of three."

Amanda stood off to the side, eager to watch. “Alright, ready? 1... 2… 3!”

The two girls instantly began struggling, though there was little movement in either direction at first. Bethany grimaced as she struggled to gain any ground against Sarah, who seemed nonchalant. As Beth’s face began to turn bright red, she managed to force her friend’s arm back only a few inches before Sarah put all of her strength into her effort. She slammed Bethany’s hand against the desk and jumped up triumphantly, striking another double bicep pose. She kissed each of them smugly, while Beth rolled her eyes.

“Ok, that’s enough goofing off."