77gr gas gun struggle

[jlorenzo]

Neck tension? Oal movement after cycle? How's the meplat look after chambering? Is it bumping em back into the case them upon chambering and/or using the cycle as a kinetic bullet puller. Tuning neck tension, buffer weight, spring and gas system is a juggling act. Try hand feeding right into chamber, lock the bolt in and shoot 3. If it improves you'll know.
If you let it rip one out of the mag into the chamber, then Eject it, you can measure to see if the oal changed. However this is not a good duplication of the cycle as when a live round cycles the action. Instead load 2 rounds into mag. Cycle action and fire 1 round down range. Eject the second out of chamber and measure that one. This exactly duplicates the all variables for examination. I'm sure ya know load developing gassers involves more steps than bolt guns. It can surly be a back n forth game until you waive the white flag.

Ive done this and the COAl did grow a touch. Only messed around with alight crimp once with cannelured 75gr hornadys.
I have had it shoot 5 shot groups all touching with the 77 sierras. I cannot remember what that load was though. Ive done alot of different powders with this gun so far. I think I'll get it dialed, its just much more finicky than my bolt 223 which will shoot 10 rounds of all different charge weights into a clover leaf.

 

[Pawnee Bill]

First, throw the Hornady bullets away. Put 24.0 grains of Varget underneath a 77 grain SMK at mag length. If your gun is going to shoot, it will show with this load. Ask the High Power guys. This is my go to load with the 77 gr SMK.

 

[Walt Krafft]

Pawnee Bill speaks truth.

 

[Bottom Fodder]

Bill what primers are you using

 

[Pawnee Bill]

Bill what primers are you using

CCI 450 SR Magnum

 

[Bottom Fodder]

Thanks Bill I was hoping you would say something different Lol I’m going try with a variety of primers you never know

 

[SecondsCount]

I won't say that I'm an expert AR shooter or reloader but I've been shooting them at paper for over 25 years. The most difficult part of getting good groups out of an AR is based on how well you can pull the trigger. If you are comparing what you can do with a Tikka, you are going to have a steep learning curve.

What is your foundation? Bipod and rear bag? Make sure you have consistent shoulder pressure on the stock. Be careful where you put pressure on the grip. Don't grip it like a handgun, pull it straight back into you shoulder.

LC brass should be fine. I've never tried CCI 41s but a friend swears by them. I've shot many sub MOA groups out of ARs with mixed brass. It matters but not as much as you might think.

You can get where you want to be with TAC or RL15. 8208 is a good powder as well.

Check your muzzle device and make sure it is torqued properly.

 

[BlackGrouper]

+1 for the info from SecondsCount, I can open groups up using a front rest & rear bag 3x the size just by trigger pull and also head/ shoulder pressure on the stock.
Set the front rest closer to the muzzle end and don't have anything touching during recoil such as a sling swivel.

 

[jlorenzo]

First, throw the Hornady bullets away. Put 24.0 grains of Varget underneath a 77 grain SMK at mag length. If your gun is going to shoot, it will show with this load. Ask the High Power guys. This is my go to load with the 77 gr SMK.

The velocity is just ho hum. Ive shot that load and it does shoot well but low 2600s is not what I'm after, well see I may settle although I'm saving the Varget for the bolt gun. Your right about the Hornadys, Ill use them in my Bartlien, shoots pretty much anything well.

I'm gonna have to just do a more detailed load work up. I also have a new Stoner BCG on the way.
Next time its either a CLE or WOA with a matching bolt at 20".

Also the A2 flash hider is on pretty tight in order to get it timed right. Not sure if thats a big deal or not. Like I said Ive had this gun shoot clover leafs, it just seems real finicky with seating depth and powder charge.
I agree with what has been said about fundamentals shooting a gas gun. Its definitely tricky. Always working on it. The amount of pressure on the pistol grip and the strength of the grip itself seems to make a huge difference.

I'm off a bipod and rear bag, concrete bench or prone on concrete. I shoot better prone.

 

[jlorenzo]

View attachment 1333933

THAT is the kind of group I am looking for.

 

[jlorenzo]

Switching to 8208 XBR and using the new Stoner bolt I bought seems to be doing the trick. This was in 20 mph winds also, I'm still not confident in my gas gun fundamentals either. Seems like halfway through the group I have to reset my rear bag and break my cheek weld causing different points of impact on the following shots.

I see some promise here though and velocity/pressure looks good. Liking 8208 so far.

 

[lawman29]

When I am doing load development I always shoot off of a front rest and rear bag on the bench. Once you find a load, use the bi-pod and work on your technique.

 

[jlorenzo]

When I am doing load development I always shoot off of a front rest and rear bag on the bench. Once you find a load, use the bi-pod and work on your technique.

I was thinking I need to do the same. Don't even have a good front rest. Gonna look around.

 

[10XSHOOTER]

What did you torque the barrel nut to? 50 ft lbs? Also have you changed buffers? heavier/Lighter.
Don't use Green loctite, if you ever want to change barrels. Blue will hold it! Lock bolt to the barrel extention while the loctite sets. every thing is then lined up.

 

[jlorenzo]

What did you torque the barrel nut to? 50 ft lbs? Also have you changed buffers? heavier/Lighter.
Don't use Green loctite, if you ever want to change barrels. Blue will hold it! Lock bolt to the barrel extention while the loctite sets. every thing is then lined up.

I believe 57 ft lbs as per the BAT machine guy talking about putting together uppers on youtube, videos seem to be gone. Said to start there. I used a tiny bit of copper anti seize on the receiver threads.

 

[10XSHOOTER]

Unless you have extra upper receivers like the Army. 57 lbs will stretch the receiver threads. Max of 50 lbs.

 

[skeeljc]

My PSA (upper/lower, bolt/carrier) with a 20" White Oak 1 in 8 twist Three Gun barrel will shoot 75 grain Hornady BT with RL-15 into 5 shot .75" group consistently at 100 yards. I did ream the takedown pin bores and install oversize pins. I seat the Hornady 75's to 2.25" with no crimp. I use a Redding bushing die and bump the shoulder back .004". I shoot for .0015" to .002" neck tension. I run a Geissele SSA two stage trigger.

 

[darkangel_r2]

Wylde or 556?

How was the fit on the barrel extension? If it was loose tighten in up with some shims and heat fitting.

how are you processing your brass? Die type, trimming, chamfering, ect?

How are you measuring your charges?

How are you seating your bullets?

You may want to try a stainless steel mag with thin front and back walls. You can load out to 2.3ish with those. That can help in many cases especially with the 75s.

If there is any part of the gun that has wiggle room and it doesn't need to move try to tighten it up to eliminate unnecessary movement.

What is your optic?

How are you shooting for groups? Position, rests, conditions, ect.

Make sure there is no contact on the barrel and if you have the tool lap the receiver face.

 

[6ShotsOr5?]

My White Oak 18” 1:7 SPR barrel is chambered in 223 Wylde. My receiver is pretty cheap mil-spec with one of the foam wedges to keep things tight. I have a Geissele SSA-E trigger, and an adjustable gas block. I have never tried hand loads in that rifle, but after trying many different factory loads, I found the Black Hills 77 grain 5.56x45 ammo shot the best, around 1 MOA down to 0.8 MOA depending on conditions. I think my bolt was an upgrade from JP Enterprises — it’s been a long time since I built the rifle — but I expect that has more impact on reliability and function than accuracy.

 

[mac86951]

Do you use a concentricity gauge on your ammo. Last time I had an accuracy issue with 75+ i found that the bullets didn't fit my seating die well and concentricity was all over the place. If i sorted my ammo after; i found sub 1" groups at 209y, indicating this was a key loading component.


Barrel nut torque? Mil spec is 30-80ftlbs; most accurate assemblers that i know torque to 30 and increase until barrel nut clears the gas port with no gas tube contact. Or use a WOA like barrel nut that doesn't contact gas tube no matter what.

Facing off the receiver can help too; and I'll add that I've never found a barrel to shoot all heavies equally, Nosler, Sierra, Hornady, Berger try them all, the barrel will choose.

24.0gr Varget is 2650-2700fps from a 20" barrel. That is about as expected. If you want more velocity; you're asking for trouble when the weather changes. By all means, do what you gotta, just saying; consistency is key, my suggestion ignore velocity it's a gross measurement at best. The target tells all.

-Mac