View Full Version : Installing Ejector Block- Tightness? Top down or bottom up?

Tom Preston
October 15, 2017, 20:04
So, getting started with the terrible, horrible, no good, very bad receiver build, my first! It came without the ejector block installed, fortunately I have one. A couple of questions-

1. How tight should the block be before it's pinned? Should it slide easily into place, need some tapping, be driven in, or require the pounding of Thor?

This one will need driving at least as is, but of course I can slim it down. If it has to be a slip fit, is it best to remove metal from the front, left, right, back, or all four sides?

2. Should the block be inserted into the top of the receiver, into the bottom, or does it matter?

Also, the block is marked on the inside of the big ear with a "2"- actually a reversed 5, if that has any meaning. If it's something special, let me know before I start filing on it!

Tom Preston
October 15, 2017, 21:30
Oh I'm not reaching for a file just yet! Merely trying to learn how the thing ought to be inserted, and how tightly. I could probably pound it in, but somehow I don't think the folks at FN designed it to be assembled that way. And if it is supposed to go in from the bottom but I insert from the top...

October 15, 2017, 22:33
A tight fit is good....

What you don't seem to understand is that the height the EB is mounted in the receiver is the critical part...pray you get that right the First time...:]

Tom Preston
October 15, 2017, 22:36
Tell me more, I've never built one of these Belgian legos before!

October 15, 2017, 22:56
99.5% of the FAL/SLR receivers produced over the years have come WITH EB's installed....for good reason. They're a bitch to get right.

Maybe search about all the fugged up DSA's stink'in up the aftermarket and you'll get the picture.

Getting an EB installed right is probably the most critical component for a properly functioning rifle....a task that doesn't lend itself well to the backyard mechanic.

I wish you luck.:beer:


I've built close to 300 FAL's/SLR's, I wouldn't ever waste time trying to fit an EB...not worth the time and effort.

October 16, 2017, 06:09
I've built close to 300 FAL's/SLR's, I wouldn't ever waste time trying to fit an EB...not worth the time and effort.


October 16, 2017, 08:49
Sometimes it is necessary - such as in replacing a defective one from a DSA or Coonan receiver.

And I have about a thousand in stock, if anyone ever needs one.

So yeah, it's supposed to be an interference fit, but I'd say tap-in, not pound-in. It can be challenging. The only published standards I've discovered in my extensive research library is from the Canadian 4th level (depot) manuals. Nothing in the REME, nothing in OREA. Probably because it was considered integral to the receiver, with only the ejector a replaceable part, and then only on later rifles.

Anyway, Canadian standards states that the fit is a .0006" / 0.015mm "push fit" and that if material needs to be removed from from e-block it should be on the right side. Which makes sense as left side would pinch mag catch.

My experience is that e-blocks should not need material removed from the sides, particularly if they came out of correct receivers. If so, assume your receiver is out of spec . On a DSA receiver, assume the out of spec location is the ridge on the left rear corner where the mag catch would be.

It is normal to have to change the corner radius, and from a functional perspective, a gap at the corners is not going to affect fittment.

You want the back of the e-block to be in contact with the back of the mag well. A gap is not permitted!

Ensure the mag catch screw enters to full depth without binding. Binding is a reject!

Insure the right arm of the e-block does not stand proud of the the rail. Protrusion is not permitted!

These are not complicated standards, but apparently neither DSA nor Coonan can consistently install an e-block of their own manufacture, into a receiver of their own manufacture, without incorporating one or more of the defects I have called out above.

Tom Preston
October 16, 2017, 09:22
And that's the answer, thank you Mark!

Except for one thing- insert from top down, or from bottom up?

Let's see what happens next, the terrible, horrible, no good, very bad receiver is definitely the culprit. There are a couple of little casting defects that I'll get rid of in there first, then it will be sand and try on the block.

I am sure the barrel will be a bad dream, and inserting the locking shoulder will be the greatest challenge, it won't even start.

October 16, 2017, 09:31
I've always done it from the bottom. although not straight up, kindof back and up - little bit of an arc. 'Cause need to clear rail, but also am fitting the corners.

October 16, 2017, 11:23
GP, would it help to have the bolt in first? for correct fit?

October 16, 2017, 11:47
This wouldn't be an ORF receiver, would it?

October 16, 2017, 14:19
GP, would it help to have the bolt in first? for correct fit?

You mean the mag catch axle? Absolutely. That's what I use to check for alignment. Of course, it assumes the hole in the receiver is straight, and on recent DSA's that not an assumption one can make.

October 16, 2017, 15:19
...I am sure the barrel will be a bad dream...

So I am assuming you received the barrel? I was wondering about that...


Tom Preston
October 16, 2017, 17:03
Just today. I panicked at first, it would not even start to thread! There was a little ding on the breech face thread, two rubs with a file and on it went.

It's lovely and hand times to Mark's "optimal" spot...

Next job, the ejector block!

Tom Preston
October 17, 2017, 08:19
So, I put a rough surface on all around with a stroke of 150 grit. The binding was side to side, so I carefully filed away on the left side- thanks Mark! It did not take much to get it to slide up, but now it was too thick front to back- the holes for the pins were all to forward.

Magazine insertion was a little tight front to back too. This receiver is supposed to be metric, but it has an inch type magazine lip recess.

So, violating the rules I started filing on the back. The well for the block has rounded corners to the rear, so I made sure to keep the block's back edges rounded too.

I had to take off like .08 inch, but cutting and trying, it fits now. This thing does not have the pin holes drilled on both sides, so there is that job to do- but the block is on, no gaps to the back or side, a slip fit without pins but rock solid with the magazine catch axle in place. Thank you all for your help!