AR Varmint Guns and Buffer spring acting like kinetic hammer

[BobbyJ]

No arbor, no force gage. All brass was washed(inside necks clean no carbon) spray lubed 1 shot. Mandrel I.d. necks 0.002 under bullet diameter. My take, 1. bullets under 50 gr tend to "stay put" 2. While I did get my ramps cleaned up during assembly(with my intended hunting bullets). Longer bullets and longer coal showed some sharp/rough feed ramps. 3. Magazine ammo feed position plays apart(at least with this magazine/upper). This was just a quick mess around check on ammo stability with a rifle whose primarily use is winter hunting. So my brass is clearanced 0.003-0.004 and I use the 10rd magpul magazine, I don't want to have to forward assist rds (or have a unfired rd/bullet stuck in chamber) in below zero weather. Rifle is consistently sub moa in current setup/load off a bipod. Really all I need, considering the barrel was 50.00 new, whole rifle under 350.00.

Where did you find a 50.00 AR barrel? And entire AR for 350.00 that shoots that well. Crazy.

 

[dellet]

I don't plan on fast shooting a varmint gun. What you said makes sense. You want to go with the lightest BCG that will reliably shut the action. Which then means you might have to adjust the gas port.

For now I just have a standard BCG just added a new bolt so it wears into the new barrels chamber vs swapping bolts from my ARs which would work.

What adjustable low profile block works best for this. I just haev a standard Aero Low profile block on it.

I use an SLR.

You lose more energy by reducing speed than mass.
Mass has some other qualities worth keeping.

It takes more energy to start more mass moving. As far as the carrier in an AR15, this means the bolt will stay closed longer, allowing pressure to drop more and the brass to relax from its expanded state against the chamber walls. Makes for easier extraction and less expansion of the base of the brass. Brass lasts longer, no need for a small base die.

@Coyotefurharvester probably had the best answer for your bullet movement problem. Squeaky clean inside necks, the nemesis of precision loaders. This probably reduces bullet movement as much as anything else.

Shooting 300 Blackout magnifies this problem, rifle components and carrier speed is the same. Bullets that weigh 3-4 times the weight in the same case. Slowing the carrier speed, keeping necks clean, using a .306” expander, pretty well eliminated all bullet movement for me.

 

[Coyotefurharvester]

I assembled it from clearance items I picked up(about 1 year of collecting) about 5 years ago. I would go with a Superlative Arms gas block. Mine is a standard LP .750, but my brass is 3-4 o'clock with or without a suppressor so I'm just running with it. What a rabbit hole this hobby is,lol.

 

[akajun]

When discussing loaded round runout with a well known shooter/ manufacturer he stated that in a AR it really doesn’t matter , single load , mag feed, as soon as the bullet hits the barrel extension or anything in its way as it slams home you’ve turned your .001 runout round into a banana
He also stated that using uncrimped rounds can cause the bullet to push back and maybe cause popped out primers if your loads are on the borderline
I later confirmed all this myself at home with my case indicator
I started using the Lee factory crimp die for all my short line loads and I did see an improvement in accuracy
My slow fire rounds are all single loaded, and crimping made no difference
I’ll say that single loading did not push the bullet back but did still increase runout when chambered

 

[jelenko]

When discussing loaded round runout with a well known shooter/ manufacturer he stated that in a AR it really doesn’t matter , single load , mag feed, as soon as the bullet hits the barrel extension or anything in its way as it slams home you’ve turned your .001 runout round into a banana
He also stated that using uncrimped rounds can cause the bullet to push back and maybe cause popped out primers if your loads are on the borderline
I later confirmed all this myself at home with my case indicator
I started using the Lee factory crimp die for all my short line loads and I did see an improvement in accuracy
My slow fire rounds are all single loaded, and crimping made no difference
I’ll say that single loading did not push the bullet back but did still increase runout when chambered

When you single load, are you starting with the round already partially chambered?

 

[Jeff Porter]

As a point of reference … OAL between 52’s 69’s and even the 75/77’s does not correlate to jump. The stubby light weight bullet profiles are actually jumping less at mag length than the heavier longer bullets. If you have not measured the Base to Ogive when touching the lands you may be surprised to find out that you are already touching or slightly jammed with a 52 or 69 at 2.250” where the 75/77 will be jumping close to 0.020” or more.

 

[akajun]

When you single load, are you starting with the round already partially chambered?

Yep
Didn’t matter
Pushing it in a bit with my pinky or just on the bobsled