First AR build - range day

[poli]

Yesterday I took my newly built Grendel to the range and shot 60 Hornady 123 gr. SST factory loads. The barrel is a Shilen 20" HBAR 1/9 twist. The first 3-shot group (0.420") was one of the best and I was very happy, but from there on it didn't go too well. These are my best 5-shot groups:

FB9A1405.jpg

All in all I would say that I shot about 1.5 MOA groups. Honestly, I was expecting to do much better, but I believe the military trigger that came with my DPMS lower kit had something to do with it. The only mod I made to the trigger was to change the spring with a softer one, but even that wasn't enough.

I had another box of 20 rounds but since I was a bit disappointed, I pulled out my other rifle that I took with me and shot several 5 round groups. And just to add insult to injury, my second 5-shot group looked like this:

FB9A1404.jpg

This was the best group out of all groups shot with this rifle which happens to have a Timney trigger, and I think would be very difficult to replicate it in the future with the same type of ammo.

What would you recommend for a target/hunting trigger for my AR?


By the way, the rifle that I shot that crazy 4+1 group is a sporterized 1930 Mosin Nagant and the ammo used was 147 gr. surplus... The fifth shot was the one that opened up the group; I should've stopped after 4 shots

[LRRPF52]

What optic mount and scope are you using?

Did you use a square receiver face, and bed the barrel extension into the upper receiver? What about the gas block?

It's harder to shoot groups with a standard trigger, unless you polish the trigger nose and hammer notch engagement.

Heavy barrels need to be bedded in the AR15 receiver, unless you use a temp-fit.

[Ridgerider]

What optic mount and scope are you using?

Did you use a square receiver face, and bed the barrel extension into the upper receiver? What about the gas block?

It's harder to shoot groups with a standard trigger, unless you polish the trigger nose and hammer notch engagement.

Heavy barrels need to be bedded in the AR15 receiver, unless you use a temp-fit.

No way should you polish the hammer notch and trigger nose (Sear) lap yes, polish no unless you want to ruin the trigger all together. Seen so many home wanabee gun smiths ruin a trigger because of what you describe. Thats why Midway and Brownells sell a jig to square and lap the trigger and hammer for correct angles and engagement.

[LRRPF52]

No way should you polish the hammer notch and trigger nose (Sear) lap yes, polish no unless you want to ruin the trigger all together. Seen so many home wanabee gun smiths ruin a trigger because of what you describe. Thats why Midway and Brownells sell a jig to square and lap the trigger and hammer for correct angles and engagement.

I'm not talking about changing the angle of the nose or even messing with it, but the flat surfaces only, to remove the tooling marks. If you polish the edge of the nose, you're looking at a potentially hazardous configuration. The hammer notch is the most difficult area to work on, which is why we stone it.

If one takes a polishing wheel to it and goes to town, thinking they are polisherin' her up real nice, and ends up with a rounded trigger nose, it's a bad thing.

Following the advice and mentoring of very respectable gunsmiths, I have performed the work on my triggers, and ended up with much improved trigger feel, with a long-lasting trigger that has never resulted in failures, doubles, etc. The first one I ever did was on one of my 3-gun carbines, and I took that gun to over 10,000 rounds of high volume fire before breaking my bolt at the cam pin hole. The trigger never malf'd on me because I did exactly what you describe, and didn't change the angle of the surfaces.

I've done it on several triggers over the years with successful results. I have also seen a few people bugger up triggers, mostly on 1911's though. Some factory 2-stage triggers are non-functional in the AR15 and AR10, and need to be looked at by a competent thinker, regardless of what is next to their name, or what training they slipped through for the cost of admission.

[poli]

I have a LaRue Tactical SPR/M4 QD LT104 mount and a Hawke Sidewinder 30 Tactical SF 6.5-20x42 scope which has a very fine reticle. Prior to installing the barrel I lapped the upper with the lapping tool but I didn't bed the barrel extension into the receiver. The upper and lower are Aero Precision and I have a Daniel Defense Low Profile Gas Block Clamp-On. I also have a Midwest Industries Gen 2 SS-Series Free Float Modular Rail Handguard.

I polished/lapped the trigger and hammer very gently with a buffing wheel and Mothers but while shooting I felt it was still grinding very little - I might've not done it enough.

I used a torque wrench for the barrel nut and it just happened that at 30lb torque one of the cutouts lined up perfectly with the gas tube, so I didn't tighten it up more; I don't know if this has any effect at all.

Do I bed the barrel using blue locktide?

[LRRPF52]

With that heavy of a barrel, and over 18" length, it makes sense to bed it. How did the extension slip into the upper? Was it loose, snug, tight? 30ft-lbs is on the light side for the Grendel. Try using anti-sieze on the threads, and set the tennon by backing off, then torquing repeatedly until you get to 60ft-lbs if you can.

On the handguard, use an inch-lb torque driver to make sure the clamping force of the handguard is even, and not substantial for the MI SS Gen II. There has been some discussion lately about accuracy and clamp-style handguard mounting interfaces on the barrel nut.

Yes, Blue Loc-tite is one way of bedding it into the upper receiver tunnel. Since you have a clamp-on gas block, just use equal torque on the fasteners (inch pounds).

Do the same thing for the scope rings, setting them to equal torque specs. Wheeler recommends 15-20 inch pounds.

Use a nice, solid rest, with rear bag. The AR15 requires some driving as opposed to free-recoiling like a bolt gun. Steady, firm pressure to the rear with the 3 remaining digits of your firing hand with straight pressure of the butt into your shoulder will help keep the gun tamed. If you're already well-versed in this, forgive my unsolicited remarks. If I really want to shoot groups and accuracy-test a rifle (something I have done professionally for a manufacturer day after day after day, from 0900-1700) I make sure I'm well hydrated, in a very calm mood, and I set up the position with the target in focus so that the natural point of aim of my entire bench position is directed through the center of the target.

Once I'm set up, ammo is on-hand, the gun is cradled or on bags/bipod, I get behind the gun and literally go to sleep on it, but thinking clearly in my mind what a good sight picture looks like. I then open my eyes, and settle the gun into the position by simulating recoil. Once I have a comfortable position that doesn't deviate from the NPOA, I begin my dry-fire drills until called shots are within maybe 1.5" of movement on a 100yd target, no more. I get my warm and fuzzy about the position, and then go live.

Once I do all this, I actually shoot fairly quickly, because there is no need to find the NPOA. It's already established, and the sooner I break the shot on consistent sight picture after sight picture, the better off I am.

[Buster]

Just keep shooting it.
Then shoot it some more.
The more you shoot it, the more comfortable you'll get with it, and the more likely it will "come into it's own".
After about 500 rounds, post your results.

[Ridgerider]

I'm not talking about changing the angle of the nose or even messing with it, but the flat surfaces only, to remove the tooling marks. If you polish the edge of the nose, you're looking at a potentially hazardous configuration. The hammer notch is the most difficult area to work on, which is why we stone it.

If one takes a polishing wheel to it and goes to town, thinking they are polisherin' her up real nice, and ends up with a rounded trigger nose, it's a bad thing.

Following the advice and mentoring of very respectable gunsmiths, I have performed the work on my triggers, and ended up with much improved trigger feel, with a long-lasting trigger that has never resulted in failures, doubles, etc. The first one I ever did was on one of my 3-gun carbines, and I took that gun to over 10,000 rounds of high volume fire before breaking my bolt at the cam pin hole. The trigger never malf'd on me because I did exactly what you describe, and didn't change the angle of the surfaces.

I've done it on several triggers over the years with successful results. I have also seen a few people bugger up triggers, mostly on 1911's though. Some factory 2-stage triggers are non-functional in the AR15 and AR10, and need to be looked at by a competent thinker, regardless of what is next to their name, or what training they slipped through for the cost of admission.

You may not be but to say what you said some people may take a buffing wheel to their triggers and screw them up. The angles have to be maintained and any home trigger jobber needs to understand that.

[poli]

With that heavy of a barrel, and over 18" length, it makes sense to bed it. How did the extension slip into the upper? Was it loose, snug, tight? 30ft-lbs is on the light side for the Grendel. Try using anti-sieze on the threads, and set the tennon by backing off, then torquing repeatedly until you get to 60ft-lbs if you can.

The barrel was snug and I used anti-size grease on the thread. I tighten it up and loosened it few times as per instructions but I will do it again and try to get it closer to 60lb.

On the handguard, use an inch-lb torque driver to make sure the clamping force of the handguard is even, and not substantial for the MI SS Gen II. There has been some discussion lately about accuracy and clamp-style handguard mounting interfaces on the barrel nut.

Yes, Blue Loc-tite is one way of bedding it into the upper receiver tunnel. Since you have a clamp-on gas block, just use equal torque on the fasteners (inch pounds).

Do the same thing for the scope rings, setting them to equal torque specs. Wheeler recommends 15-20 inch pounds.

I didn't have a inch-lb torque driver, so I did it by hand, but I'll look into getting one.

If you're already well-versed in this, forgive my unsolicited remarks.

I always keep an open mind and appreciate when someone wants to help, especially when giving valuable advice - thank you! I've been shooting for years bolt rifles and I'm getting consistently 1/2" - 3/4" groups from my 22-250 and 308 rifles. I have a 556 Sig, but I'm not shooting it from the bench, so the advice on driving the AR will definitely help.

[poli]

Just keep shooting it.
Then shoot it some more.
The more you shoot it, the more comfortable you'll get with it, and the more likely it will "come into it's own".
After about 500 rounds, post your results.

That's exactly what I intend to do . This cartridge/rifle combo is awesome!

[Tedward]

I would recommend buying a already "Tuned Trigger" or send a run of the mill trigger to someone who knows what there doing and has some experience. It's not expensive either. http://www.triggerwork.net/index.html

It can be easier sometimes to have a trigger guy do the very important work because reading a forum is not hands on experience.

I like Busters response, go shoot it and see how you do in a week or so. Pick it up and shoot. Get up move around and shoot more. Keep doing that and you will find a reset position you go to. Meditation and shooting is not how you will be when your hunting. I think deep meditation is best for the Karate Kid. I saw it on a movie.

[Ridgerider]

I'd like shooting rifles and shooting anything else from 9-5 5 days a weeks and getting paid for it. But Tedward isnt meditation like dreaming and that the big buck you shot was really a Jackaroo.

[Buster]

That's exactly what I intend to do . This cartridge/rifle combo is awesome!

I agree....finally found my post from almost a year a go:

http://www.65grendel.com/forum/showthread.php?2629-Starting-the-Build&p=61189&viewfull=1#post61189

After 500 rounds, nickel sized group @ 200 yards

[NugginFutz]

I like Busters response, go shoot it and see how you do in a week or so. Pick it up and shoot. Get up move around and shoot more. Keep doing that and you will find a reset position you go to. Meditation and shooting is not how you will be when your hunting. I think deep meditation is best for the Karate Kid. I saw it on a movie.

Let me know how that works for you, Ted. Any pics of your long range groups would be appreciated. That was, I believe, what LRRPF52 was talking about improving, wasn't it? Not hunting.

[poli]

I think the topic was first day at the range and the ranges I've been to there really isn't time for napping and such deep thoughts. I guess I didn't know he was long range shooting on his brake in.

In fact the topic was "first AR build" as in first AR that I've ever built which I took to the range for shooting. As far as days at the range, I've had quite a few of those but I don't want to think about when I started and how many days have been because it reminds me how old I am .

My post primarily was about being a bit disappointed with the groups and asking for advice on trigger. Thanks for the recommendation - I'll look into TriggerWork.