Nice! Thanks for the update. Also, this is the difference in magazines that I was referring to:

In response to your mag question, we made a magwell assembly (it's multiple pieces due to the bullpup design) with the magazine moved back .03" compared to my GAP guns.

And I'm not pleased with performance. The back of the case wants to hang up under the bolt unless it's pulled absolutely to the rear. It's very easy to get the brass out of sorts this way and I think we will move the mag forward to a more normal position...can't say we didn't give it a shot. Can post pics for you.

quote:

Originally posted by Tyler Kemp:
And I'm not pleased with performance. The back of the case wants to hang up under the bolt unless it's pulled absolutely to the rear.

Did you modify the bolt stop and open up the rear of the feed port on the bottom of the receiver?

jpl,

We did not, doing that would certainly make it feed more reliable, but then we'd be offering something that was no longer a drop-in chassis. I supposed we could always make the mag well 30 thousandths back if someone wanted to mod their action though.

Have you posted about this on the gunsmithing board? See if you can get some good advice there. This is too good a project to get a hang up.

quote:

Originally posted by Tyler Kemp:


I'm quite happy with the newest version. We will be running a small batch in early 2017 and letting customers run them for a few months. If there is some consensus on small changes to make, that will be implemented and then it's time for a big batch of bullpup chassis!

Looking good Tyler! Looking REAL Good!

quote:

Originally posted by Tyler Kemp:
We did not, doing that would certainly make it feed more reliable, but then we'd be offering something that was no longer a drop-in chassis.

I guess I'm not explaining myself well enough, so let me try again. Look at the two magazines in this picture:



The "standard" aics magazine on the bottom has a spacer at the front, and the alpha magazine on top does not have a spacer. This is desirable because without the spacer there is more internal length in the magazine, which allows the use of longer, pointier, higher BC bullets. And high BC bullets are desirable when shooting long range, which is what we're talking about in this forum...

So, if the no-spacer magazine is desirable, how can we use it? The outside dimensions of the magazine are the same, so it will plug into most rifles already set up for aics-type magazines. But there's a problem. Without the spacer, the loaded round can be longer, and the tip of the bullet further forward relative to the receiver. This means that the tip can catch under the receiver before it gets to the feed ramp. What is the solution? Many people just cut out a chunk of the receiver to give clearance. If you look at this picture, you can see the top of the no-spacer magazine, the long pointy bullet, and the notch that lets the round come up through the bottom of the receiver:



However, in my opinion it is not a good idea to cut out that part of a receiver. That is a piece of high grade steel responsible, in part, for containing several tons of white hot fire a few inches from my face. I'd much prefer to cut the rear part of the receiver to get clearance for a longer round. The rear part of the receiver is holding much less force with much lower consequences if it fails.

Sure, plenty of people have notched out their receivers without any problems, but that area IS under load and cutting it out erodes the safety factor built into them. You could probably take 2 lug nuts off of each wheel on your car and have no problems. But I don't think this makes it a good idea, especially when there is NO reason to do it. Why not just cut the rear of the receiver? This could be a feature and selling point for a new product (that moves the magazine back to take advantage of longer COL).

Here are a few pictures of a FEA showing stresses in the area we're talking about. This is a side cutaway of the model with colors showing stress:



Looking at the feed ramp with the top half of the receiver removed for visibility:



Now look what happens when you start cutting out the feed ramp:



Most disasters are a chain of factors that happen to combine in just the wrong way. Personally, I'd like to have as many links in there as are easy and reasonable. Like safety glasses. I've never needed them, but I still wear them because it's an easy link to add to the chain. Muzzle control? Another reasonable link to add to the chain. Not taking shortcuts to get a longer round...

Now this picture shows what is, in my opinion, the proper way to use alpha magazines, particularly with magnum rounds. Basically, the magazine is moved back relative to the receiver with a few modifications: the bottom metal (that holds the magazine) is moved back by opening up the bolt holes off-center and filling with a steel washer/bushing, the REAR of the receiver is cut to give the clearance needed, the bolt stop is shortened, and the inletting adjusted. The front of the receiver was NOT cut (green oval). This particular bottom metal (not naming names) was so far forward that even AICS magazines with spacers would hang rounds up under the receiver (you can see part of the original inletting).



And once again, the easier but wrong way (in my opinion):



So this is what I've been getting at. A bottom metal can be modified pretty easily, but a bullpup chassis not so much. A few different dimensions would need to change, but I believe it is a significantly better solution to move the magazine. Also fyi, magazines with spacers still work fine with this modification. Some of the receiver manufacturers build receivers that basically already have these mods (they are a touch longer at the bottom feed port). I would like to have a bottom metal/chassis *option* to go along with the receiver and magazine options as well. Since you are in the design/prototype phase, it would be much easier to think about this now rather than try to re-work things later on. Are you following my reasoning with all of this?

It's possible to put wood screws in with a hammer, but there's a better way. Yes a cordless drill is a bit more complicated than a hammer, but the extra effort is worth it when you want to use a screw instead of a nail.

Basically, I'm interested in your chassis and I think being able to properly use non-spacer aplha magazines would be a nice feature.

$0.02

jpl,

I believe I'm totally following what you're saying. I'll try and make it as short and succinct as possible and tell me if I'm making sense:

1) No-spacer mags allow longer OAL, more powder, and better external ballistics

2) These mags can have feeding issues, and either need the front of the receiver notched OR the safer option, the magazine moved back.

3) Moving the magazine back can cause another feeding issue, alleviated by modifying the rear of the receiver

My response to this, is that we did move the mag well back to see if it would work well, but the feeding issues appear to be a reliability problem with an unmodified receiver. We are using "Accurate Mags", have tried with 6.5 SAUM, although haven't tried Magpul mags with 308.

It appears if we kept the magwell moved back, you do in fact have extra room, but that one would need a modified receiver to feed properly and not hang up the casehead on the bolt nose?

Love this project!! Love doesn't fund continued development, though. Hope you get something to sell down the road (soon!). Really appreciate the details and your development process.

We are starting the first (small) production batch in a number of weeks. Will only be some minor tweaks to the pictures you see, and of course anodization.



Here's a stock 20" 700 in 308.