Accuracy build help

[bamban]

Are the mag length 77's something longer than 2.260. What length were the 80 and 90 gr single shots?

77s for rapid fire matches at 200 and 300 are at 2.250 to mitigate any possible mag differences. The 80s and 90s are loaded with boat tail above shoulder. By CMP/NRA rulebook, slow fire prone matches, rounds must be single load only. You can shoot mag length ammo, but still single load only.

We shoot the 77s mag length in the Rattle Battle events. 6 shooters on 8 targets. Match starts at 600 prone. eSilhouette targets in the pit. The last command on the line is "Load and be ready" When the targets go up in the air, dump as many rounds as you can in 50 seconds. The 2 shooters on each end must engage 2 targets. Some guys put 28/30 in 50 seconds.

2nd stage, rifles in safe condition, shooters walk to 500 and race to the firing position on the last few yards. Get in prone, targets go up, dump as many rounds as you can in 50 seconds.

3rd stage is at 300 is sitting on half size silhouette.

If the team still have ammo left after 300, they have to shoot them at 200 standing on the half size silhouette.

The catch, the whole team is only allowed 384 rounds. The coaches determine fire plan.

Edit: In the 90s when I shot for the state adult team, before the 77s were available, we shot the 69 SMKs in the Rattle Battle.

Before Perry the kids go through a week of rehearsal, shooting bullseye and rattle battle. Most of the times in one week of rehearsal the kids go through 12K+ rounds of 77s and 80s combined.

 

[ARlife4me]

Are the mag length 77's something longer than 2.260. What length were the 80 and 90 gr single shots?

Most likely they WON'T fit into the mag @ 2.260". I will say that Berger 90's WILL fall into an empty case (I know this because the load data from Berger is wrong). 80's will fit deep, but still might fit into mag (depending on brand and type). Berger told me they did make a mistake on their 223/5.56 load data with the 90's.

 

[wilkup]

Most likely they WON'T fit into the mag @ 2.260". I will say that Berger 90's WILL fall into an empty case (I know this because the load data from Berger is wrong). 80's will fit deep, but still might fit into mag (depending on brand and type). Berger told me they did make a mistake on their 223/5.56 load data with the 90's.

They've got load data for 5.56 and those 90s!? I'd love to hear those numbers

Maybe use a mag primer cuz you'll need all the help you can get with how little powder fits in the case

 

[ARlife4me]

So I've heard several different ways to skin this cat.
- Heavy bolt with lighter buffer/spring combo
(This sounds like it'd smooth out the recoil impulse to me)
- Lightweight bolt with heavier buffer/spring combo
(This is claimed to work like a dead blow hammer and rather than smooth recoil, it sort of eliminates it)
Explaining how the gas effects everything was very helpful.
I'll be picking up a WOA Predator barrel which has the mid length system for a 16" barrel.
Also planning to run that Lantac Enhanced bolt in conjunction with the VLTOR A5 buffer/Geissele Super 42 rifle spring in my new Magpul UBR stock with plug removed.

You've done some backwards thinking on recoil. In my experience a heavier bolt will (depending on gas system) have more felt recoil. Going lighter buffer and spring could make/cause bolt bounce even with full auto and heavier bcg's. I have a lite weight bcg with a jp lite rifle buffer (spring is unknown) that shoots very soft without bounce. 20" (wylde chambered) w/rifle gas adjustable block shooting m855's/m193's. Going lite bcg with heavier buffer and standard weighted spring does a good job! Too bad you didn't go intermediate length on that 16"? It's a great combo! My interm length might be an 18", but still a good choice? As far as "enhanced bcg's you could get a buffer tube like this https://nemoarms.com/product/buffer-tube-ar15/ . I have a few on 15's and 10's.

 

[wilkup]

As far as "enhanced bcg's you could get a buffer tube like this https://nemoarms.com/product/buffer-tube-ar15/ . I have a few on 15's and 10's.

The Magpul UBR has an integrated buffer tube. What do you like about that tube?

 

[ARlife4me]

They've got load data for 5.56 and those 90s!? I'd love to hear those numbers

Maybe use a mag primer cuz you'll need all the help you can get with how little powder fits in the case

Well just for 223 as I thought they had data for 5.56. Here's the 90 data. Those bullets are long and I only bought some because of their data stating @ 2.260". I couldn't send the bullets back to midway, so Berger sent me a paid return label and replaced them with 135gr classic hunter 26cals. 5 boxes of 90's for 5 boxes of 135's. GREAT cs for sure!

 

[ARlife4me]

The Magpul UBR has an integrated buffer tube. What do you like about that tube?

I forgot you're using the ubr, so the 2a tube won't work. The 2a tube has that slope for an ease of bcg going into it if you don't have a tapered type (enhanced).

 

[ARlife4me]

Well just for 223 as I thought they had data for 5.56. Here's the 90 data. Those bullets are long and I only bought some because of their data stating @ 2.260". I couldn't send the bullets back to midway, so Berger sent me a paid return label and replaced them with 135gr classic hunter 26cals. 5 boxes of 90's for 5 boxes of 135's. GREAT cs for sure!

Those WILL be a single feed round in an AR15 unless there's a mag that's ~1/4" longer. Almost all of the bearing surface is in the shoulder on those 90's. I'd love to shoot those from a 22-250/22-250ai!

 

[wilkup]

Well just for 223 as I thought they had data for 5.56. Here's the 90 data. Those bullets are long and I only bought some because of their data stating @ 2.260". I couldn't send the bullets back to midway, so Berger sent me a paid return label and replaced them with 135gr classic hunter 26cals. 5 boxes of 90's for 5 boxes of 135's. GREAT cs for sure!

Curious about your notes…
Berger claims a 24" test barrel.
You've got two different notes on velocity it looks like. One for unknown barrel (16"?) and another with what appears to be an 11.5" barrel? Unknown barrel was 2425' and 11.5 was showing 2125'.
With those slow velocities, it doesn't really seem like an advantage using those aerodynamic heavies.

 

[ARlife4me]

Curious about your notes…
Berger claims a 24" test barrel.
You've got two different notes on velocity it looks like. One for unknown barrel (16"?) and another with what appears to be an 11.5" barrel? Unknown barrel was 2425' and 11.5 was showing 2125'.
With those slow velocities, it doesn't really seem like an advantage using those aerodynamic heavies.

1 was for hopeful velocities in 5.56 compared to 223. The 11.5" was for sub rounds/cqb type.

 

[budlight]

Bamban being a very technical high end shooter uses a full auto bolt and even adds a brass weighted plug. Every comp gun I come across at meets has a heavy bolt.

So in one rifle to make everything the same. Let's just change out the bolts. The heavy full auto bolt and the one with the brass plug get hit with the same amount of pressure from the gas tube as say installing a light weight skeleton type bolt.

The more mass bolts would travel rearward slower and impact the buffer weight at a lower velocity.

So does this increase the felt recoil? Which is really nill in a 223 anyway.

The installed brass plug does two things IMO. Extra weight and it creates more surface area striking the buffer weight to make the buffer weight not get just beat up in a ring shape. The lower weight buffer also moves easier when pushed back.

 

[ARlife4me]

Bamban being a very technical high end shooter uses a full auto bolt and even adds a brass weighted plug. Every comp gun I come across at meets has a heavy bolt.

So in one rifle to make everything the same. Let's just change out the bolts. The heavy full auto bolt and the one with the brass plug get hit with the same amount of pressure from the gas tube as say installing a light weight skeleton type bolt.

The more mass bolts would travel rearward slower and impact the buffer weight at a lower velocity.

So does this increase the felt recoil? Which is really nill in a 223 anyway.

The installed brass plug does two things IMO. Extra weight and it creates more surface area striking the buffer weight to make the buffer weight not get just beat up in a ring shape. The lower weight buffer also moves easier when pushed back.

It'll take more gas to move a heavier bcg.

 

[budlight]

It'll take more gas to move a heavier bcg.

In my example it's the same rifle and only changing the bolts. NO, too takes more gas.

I will word it another way: Total weight. Weigh the skeleton BCG and a heavy H3 buffer weight. Lets weigh a full auto bolt with a added brass plug and it's Standard buffer weight with even a steel slug or two removed. They have equal total weight and both eject the same loaded shells to 3:00 - 4:30.

The heavy bolt is going to be moving slower as it takes up the air gap to the buffer weight, but it's striking a lighter object which moves easier.

The lighter bolt is going faster as it takes up the air gap and crashes into a heavier H3 buffer weight just beating up the front of it.

These two examples probably require a different spring to balance out an ejection pattern.

Just like my buddy with his cheap off the shelf AR. It requires a heavy buffer weight and spring to get the correct ejection pattern because it's also dealing with the added pressure of a short gas tube. These rifles figure that you are also going to be shooting cheap off the shelf lower pressure 223 rounds. Where as the well thought out brass slug gun can do thousands of trouble free rounds without ever replacing parts that just got beat to death. They also use hand loads with up near max pressure and were designed to balance out with small gas holes and long gas tubes.

AR-15 Ejection Patterns - Wideners Shooting, Hunting & Gun Blog

Learn about AR-15 ejection patterns in this helpful article, we'll show you how to figure out where your casings should be going.

www.wideners.com

 

[budlight]

You have to remember how the gas tube is fixed length and only sticks into the female carrier key a short distance. So the pressure wave only pushes the BCG for short distance and then it's free momentum as it travels towards the stock. Excess gasses just carbon up ejection chamber. That's why I'm all for small diameter gas holes and long tubes to limit the carbon mess. Then I went to piston guns for high volume shooting.