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Page Armory » 50 Cal
Posted: 5/6/2005 6:41:25 PM EDT
[Last Edit: 5/17/2005 4:45:51 PM EDT by V8Astro]
So we all agree that the 12 lb pull on the UL50 is a little tough. With unmodified trigger parts I think the best I shot was a 3 MOA group. Yuck.

I realized that the overtravel on the trigger could use some work. The hammer spring is wound so tight that once it breaks the overtravel in the trigger was causing me to shoot left every time.

Here's what I did.
1) I cut one leg off the hammer spring. I've done this to alot of stock AR-15's with great results. Then, using a Chevy small block exhaust valve, I slipped the loop of spring with the long leg around the end of the valve and wound the spring a little tighter. This effectivly reduces some of the pressure on the hammer when the spring is wound up.

2) I drilled a #21 hole thru my selector switch and tapped it with a 10-32 tap. When the selector is in the fire position, the hole goes straight down to the trigger underneath. I then threaded a 10-32 machine screw into the selector body which goes all the way thru and acts as an overtravel stop. I kept inching the screw in until I got all the overtravel out, but not so tight that it would jam the trigger against the bottom of the hammer. I then stacked the appropriate amount of washers under the screw to get the proper clearance and used some green threadlock to keep it there.

3) I borrowed some honing stones from my neighbor (who just got back from gunsmithing school). I made just enuf passes on the trigger and the hammer to clean things up. I learned my lesson with my Browning Hi-Power that a bunch of very light passes is better than a few heavy passes with the stone (buuuuuurrrrrp...oh sh!t).

I'll get some pics, and a trigger pull scale. This prolly seems a little vague but I thought it might inspire some others.

Also, does anyone here shoot Talon reman ammo? How does it shoot for you?
Link Posted: 5/7/2005 4:41:07 AM EDT
I am glad someone else said that they were getting ~3moa out of their UL50! Because I am too, I thought that it was just mine (or me), but maybe not!

The mod you did to the selector swith sounds like the trigger that Bushmaster sells. I like it! By cutting one side of the spring have you had any FTF? What is the approx. trigger weight now?

I shoot Tallon ammo from sportsmans guide (only shot about 35 rnds so far). I can not even begin to talk about accuracy till I get the trigger fixed, it just sucks right now.

I have thought about getting a drop in kit and just shaping the hammer to look like the one that Marcus sent with the gun. Just not sure if the spring is strong enough to fire a 50bmg primer. I really like (want) the Jard 1.5lb trigger!!!
Link Posted: 5/7/2005 8:40:31 AM EDT
I had cut one leg off the trigger spring before I did the mods listed above. It still fired all 12 rounds I put thru it at the range. I'll have to see how it does now that I've wound the spring up.

The Bushy 2-stage is my favorite trigger I've used in an AR. It came with my varminter, then when I sold that gun I took it out and put it in another gun. Darn if I didn't sell that one with the trigger in it. Oh well...I got a very nice M1 Garand out of that deal.

From what I've seen, I think you should be able to use the UL50 hammer with the Bushy 2-stage setup. I just don't know if it'll set the primer off because the hammer spring is very light. I'd like to try it tho. I'm gonna see if my gun shootin buddy wants a Bushy 2-stage for his AR, that way we can try it in my UL50 first! Haha, then we can take the Jard out of his AR. No amount of red threadlock will ever keep it in adjustment, and the sear surface wore down considerably.
Link Posted: 5/8/2005 1:10:16 PM EDT
Look like my mods worked great. I fired 5 rounds today and they all went off with no light strikes.

I'm gonna take a depth mike to the primer and see how far the firing pin punched in and compare it to the first rounds I fired.
Link Posted: 5/9/2005 4:44:26 AM EDT
Know anything about the depth on the primers yet? I did something similar to what you did, but I did not do anything to the selector, just the spring mod and polish the contact surfaces. The pull is MUCH better now but it still has a ton of creep in it. Looking forward to your pics!!
Link Posted: 5/9/2005 7:26:11 PM EDT
[Last Edit: 5/9/2005 7:31:45 PM EDT by V8Astro]
I measured the depth of the primer crater and found that there's no noticeable difference among them. You can see visually that the first few rounds fired with the bone stock trigger are indeed a harder strike because of the small lip at the outer edge of the crater. Other than that they are all within .001" of each other.

Here's the pics of the my trigger assy


You can see the overtravel screw. You can also tell that I polished all the parkerized finish off the engagement surface on the hammer.


Here you can see the washers I used to shim the overtravel screw with. You don't want the screw to take ALL the overtravel out otherwise the trigger drags on the bottom of the hammer. Note the one leg on the hammer spring.

Stay tuned. My next project will be making a 60" gun case out of fiberglass. Then I'll take it to a truck shop and have them spray it Rhino Liner. Total cost before painting should be ~$45.
Link Posted: 5/10/2005 6:57:07 AM EDT
NICE! Keep up the good work!!

Now figure out a way to get the creep out if it

Link Posted: 5/10/2005 8:51:59 AM EDT

Originally Posted By caver101:

Now figure out a way to get the creep out if it

That's not creep! It's just the first stage!

One work-around that's effective on my BFG is to first apply the safety, pull the trigger, flip the safety off, then shoot for effect.
Link Posted: 5/12/2005 2:08:56 PM EDT
I've done some more testing with my trigger. I had and extra trigger laying around so I got out the Mothers Mag polish and the buffing wheel. Keeping the trigger as square as possible I polished the top and front of the trigger sear surface. Then I took a round honing stone and making very light passes went over the edge of the sear (as gunsmiths scream and run). The hamme holds even when I try push it off with a screwdriver.

I took the Burris 6-20x scope off my .223 and put it on the UL50. The extra inch of eye relief makes it much more pleasurable to shoot. On 20x it did get me once tho, but not enuf to ring my head (like the shitty Bushnell did).
Link Posted: 5/17/2005 4:53:18 PM EDT
[Last Edit: 5/17/2005 4:55:24 PM EDT by V8Astro]
I took a 1/4-28 tap and finish tapping the threaded hole that the grip screw goes into. I then took a set screw to set the sear engagement. This way I can control how much creep is in the trigger. By screwing the set screw further up it pushes on the bottom of the trigger, disengaging it from the hammer. I had to grind some metal off the end of the rear of the trigger so the safety would engage all the way.



I had originally cut one leg off the hammer spring. I found that I get a crisper release with a stock spring that has both legs. I did wind the spring up more like I posted before. This reduces some of the pressure, but not too much.

Link Posted: 5/17/2005 5:40:12 PM EDT
[Last Edit: 5/17/2005 5:42:31 PM EDT by klm66]
V8Astro that is how I did my first mod. It is just like the JARD AR trigger system.

Then I went to the JP Enterprises trigger to make sear engagement easyier.
Link Posted: 5/19/2005 3:53:13 PM EDT
I found this site on my HD favorites. I have done this to 3 to 4 AR15s and works very good for me and should work good for the 50BMG AR15 lower mods.

15-Minute Practical Trigger Job for the AR-15


I thought I would pass this on to all.
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