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View Full Version : Top loading an OLL through the upper.


DedEye
01-17-2007, 2:03 AM
Bear with me for a moment while I explain my question and confusion.

From what I'd heard of the Fab 10 and the Bushmaster Ca-legal Carbon 15, they were designed so that you could load them from the top without pivoting open the lower. I saw tonight from looking at said guns that this is not to case. My question then becomes this:

Is it possible/has anyone built an OLL with a fixed ten round magazine that can be loaded through a hole or opening in the upper, without shotgunning the upper and lower open? Obviously the upper would have to be the custom designed portion, though I'm not sure if any lower would work with said design. Thoughts?

Lateralus
01-17-2007, 2:14 AM
the last time i tried to load rounds through the breach, i learned how fast a bolt carrier comes forward when the bolt catch is bumped....

DedEye
01-17-2007, 2:18 AM
Right. I'm wondering if it would be possible to design some kind of custom upper/lower combo with a cover on the top that when slid back to reveal the magazine would also lock the bolt to the rear.

hoffmang
01-17-2007, 2:32 AM
DedEye,

There isn't a good solution for toploading short of pulling the rear takedown pin.

The other options are bullet tip magazine locks when they become available and featureless build based on the U-15 or the Monsterman Grip.

-Gene

fun2none
01-17-2007, 5:26 AM
http://www.geocities.com/offroadaviator/m4xray.jpg

The upper and lower x-ray picture will help shed some light on such a project. The new upper would have to over come the following design challenges:

- gas tube is in the way (this is the deal breaker)
- charging handle is in the way
- the bolt cam-key recess and guide channel in upper must be retained
- removing material from upper for a loading port would compromise its strength
- no stripper clip guide

Having said that, it could be done if 1) appropriate gas piston upper is used to solve the gas tube interference problem 2) a custom made steel upper receiver with flip-up loading cover is used.

In the end, it's cheaper to buy a MonsterMan or U15.

wildcard
01-17-2007, 8:32 AM
If i've learned nothing else, I now know what aluminum looks like through a X-Ray machine. Love the pic..

DedEye
01-18-2007, 11:16 AM
Awesome picture, that answers my question quite well. Thanks for the info.

It's too bad, that seems like it would be a more convenient way to use an OLL with features.

avidone
01-18-2007, 5:10 PM
http://www.geocities.com/offroadaviator/m4xray.jpg

The upper and lower x-ray picture will help shed some light on such a project. The new upper would have to over come the following design challenges:

- gas tube is in the way (this is the deal breaker)
- charging handle is in the way
- the bolt cam-key recess and guide channel in upper must be retained
- removing material from upper for a loading port would compromise its strength
- no stripper clip guide

Having said that, it could be done if 1) appropriate gas piston upper is used to solve the gas tube interference problem 2) a custom made steel upper receiver with flip-up loading cover is used.

In the end, it's cheaper to buy a MonsterMan or U15.

That picture looks somehow familliar.......

best45auto
01-18-2007, 5:38 PM
the last time i tried to load rounds through the breach, i learned how fast a bolt carrier comes forward when the bolt catch is bumped....


tell me about it:D

stator
01-19-2007, 7:46 AM
Bear with me for a moment while I explain my question and confusion.

From what I'd heard of the Fab 10 and the Bushmaster Ca-legal Carbon 15, they were designed so that you could load them from the top without pivoting open the lower. I saw tonight from looking at said guns that this is not to case. My question then becomes this:

Is it possible/has anyone built an OLL with a fixed ten round magazine that can be loaded through a hole or opening in the upper, without shotgunning the upper and lower open? Obviously the upper would have to be the custom designed portion, though I'm not sure if any lower would work with said design. Thoughts?

I looked at milling the top of the upper out to allow stripper clip loading. However, the problem is the gas tube is in the way and due to the design of the BC and the timing necessary, it cannot be shortened.