M4A1 BOYS Hopup

[Five-sEvEn]

http://pageproducer.arczip.com/daedalus03/vhop.html

The M4a1B uses a solid hop up arm with two

points of contact with the bucking and BB. The hop bucking on

the Boys M4a1 has a cut in the middle to facilitate V-hop up.

 

 

Notch?

 

I decided to take this idea a little further. With the invention of the h-hop, you can put 2 points on contact on the bucking, and while attemping to copy my kurage (firefly) hopup by x-acto-ing a stock rubber (that had quite a bit of wear if I may add), I decided to stop at just x-acto-ing out a notch in the middle.

 

Modified on left, Kurage on right.

 

Modified hopup with big-out packing (thick). I'd stick the white one in to test but I don't want to take it out of my other gun at the moment. When I test it in 2 weeks, I'll test out both.

 

Kurage hopup with big-out packing (thick). Works better with the white (skinny) packing, with my K KM barrel, but I'm too cheap ATM to buy another set

 

 

I'm wondering if my modified version looks anything like the inside of a BOYS hopup. Pics would be nice. I wont be anywhere near a place big enough to test distance and accuracy until 2 weeks from now, so now I'll just have to figure out how to do this with pics and 75 feet of test space.

 

 

 

Thoughts anyone?

[TerranCmdr]

So, I'm confused. What affect does this have on the hop-up and BB? Does it make it more accurate?

[Md0ggyd0g]

Well 2 points of contact is better than one.

[Five-sEvEn]

So, I'm confused.  What affect does this have on the hop-up and BB?  Does it make it more accurate?

<{POST_SNAPBACK}>

 

No idea... I'm hoping for increased range and accuracy over the stock hopup much like how the BOYS and Kurage hopup gives increased range and accuracy over traditional hopup designs.

 

I just haven't had the chance to test my design yet.

[tonytheknife]

Its a simple concept. More surface area of the hopup on the BB causes more friction, and thus more back spin. The problem is that it could send your BB's veering too far up, and when it eventually wears down on one side or another of the slit, your BB's will veer left and right. But, like Five-seven said, testing is needed. I could be completely wrong.

[Five-sEvEn]

Actually, I believe the actual goal is more stable trajectory and longer range. I don't see how more hopup can lead to increased range, but I can see how specific points of contact can lead to increased consistancy and trajectory.

This saturday I get to test it out. yay!

[Five-sEvEn]

Update:

 

Test setup:

Shooting from kneeling position on ground about 70' away. Scope wasn't sighted in, but hopup corrected for level trajectory to target.

Used TM .25 "Tactical Grade" in all 3 tests.

 

 

Data:

NO ACTUAL MEASUREMENTS HAVE BEEN TAKEN YET

My AK's performance before the modified rubber:

Groupings about equivilant to a stock G-Spec using TM .25s "Tactical Grade"

G-Spec's groupings were about 3"x3.5" without flyers(2). AK's was around 3.5"x5" without flyers (1).

 

My AK's performance after the modified rubber:

Without measurments they look MUCH tighter. Vertical deviation shrunk from an average of about 4in to about an inch, flyers not counted (1).

Grouping is about 1"x4".

 

Trajectory before the modification through the scope:

Trajectory seemed out aobut 150' straight, then shooting up about a foot, and then dropping sharply at around 175'.

 

Trajectory after the modification through the scope:

It was getting late so I couldn't tell the path of the BB, but it seemed to be shooting straighter (no sudden increase at 150'), but still dropping at about the same distance or maybe a little less.

 

If anyone is interested I'll scan my target sheets and post them when I wake up.

[tonytheknife]

WoW! those are some results. I must apologize for my doubts. Thats cool as hell.

Cheers

Tony