Gunsmithing What is the secret to making a 243 barrel last

[MakeSawdust]

For anyone truly still interested I have been running CBI 243AI savage prefits on my match rifle. I have run H1000 exclusively. I have used JB to scrub the carbon out of the throat every 200 rds. 1st barrel went 2700 rds under 1 moa. 2nd barrel went 2500 rds under 1 moa. 3rd barrel went 1700 rds and was still under 1 moa, but I took it off as it had opened up over 5/8 moa and I was sick and tired of missing the sub moa targets that match directors think they have to include in the course of fire now.

Also worth noting, the 3rd barrel had as much throat erosion in the 1700 rds as the 2nd barrel did at 2500. I think it may have been a soft chunk of steel.

 

[RTH1800]

It is, the guy’s grandkids are shooting it as I type.

 

[Vettepilot]

So, does going to 243AI improve durability, given that in this case you convert to AI for that purpose, and not to load to higher, AI levels??

How tough is it to setback and rechamber an AR10 barrel? (Actually DPMS LR308 .243 in this case.) Is it indeed the throat that takes a beating in .243, or does the rifling wear out quickly as well?

Sorry for the elementary questions. Just trying to learn here....

Thanks,
Vettepilot

 

[MakeSawdust]

I don't think the ackley shoulder has much to do with it. By using a cooler burning single based powder like h1000 and scrubbing the throat area with a mild abrasive when the fire cracking is still microscopic you can keep the throat in good condition for a lot of rounds. This last barrel had really deep fire cracking at 1700 rds. I dont know why. The other 2 barrels were shot out before I had a borescope, but I pulled them out and looked down them. There was very little to no fire cracking, but the lands and grooves were imperceptible for a long way down the bore.

There are guys that claim they were getting 3000+ rds on 4 groove Krieger cut rifled barrels, and they likely were. There was a bunch of hype around a cartridge called the 6 mm competition match several years ago. Some claim it is magic. Some claim it is bullshit. They are both likely right. The guy that was pushing it was claiming 3000+ rounds of useful barrel life using 107 smk or 115 dtacs at 3000fps in 28" barrels. He said you need to use h1000 or n165 and scrubbing the throat with jb bore paste every 200-400 rds. When other people caught on they started pushing it as something it wasn't. 3400fps with 105s and they were using r25 and r26 and retumbo to get it there. The barrel life dropped off and everyone cried foul.

Based on my experience, I would say they were both right. I was running 26" button rifled barrels at 3050fps with 115 dtacs and 3175 fps with hornady 105 amax and 105 bthp bullets. The numbers seem to fit in between the two camps.

 

[FCS]

So, does going to 243AI improve durability, given that in this case you convert to AI for that purpose, and not to load to higher, AI levels??

How tough is it to setback and rechamber an AR10 barrel? (Actually DPMS LR308 .243 in this case.) Is it indeed the throat that takes a beating in .243, or does the rifling wear out quickly as well?

Sorry for the elementary questions. Just trying to learn here....

Thanks,
Vettepilot

I have an AR-10 in 243AI, wouldn’t recommend it. Blown out body and 40 degree shoulder made getting reliable feeding a bit of a PITA.
243 gas gun, running slower powders creates other cycling issues as it increases port pressure and gas volume that is cycling bolt.

Setting back an AR-10 bbl is a significant challenge as you must time barrel extension perfectly to the existing gas port AND you need to trim gas tube or get a new gas tube that accounts for portion of bbl that was cut off for the set back. Juice isn’t worth the squeeze, just buy a new bbl.

Barrel is shot out when it no longer gives needed / desired accuracy the per the end users requirements; cleaning bbl and adjusting load doesn’t return accuracy.

 

[smoothy8500]

That's pricey for a "play gun" barrel from my personal financial perspective

Barrels are consumables, kind of like tires on a Vette....Right?

 

[RTH1800]

No frequently shot .243 Win barrel will approach the life of this zombie thread.

 

[Thud]

The only way to make a 243 Win barrel last is to not shoot it. Not trying to be a smart ass but that is the reality. Some use slow burning powders like H 1000 and it does help. I run a 6mm Competition Match and use H 1000 exclusively and the barrels do last quite a bit longer.

Thats the only thing that works is _ Don't shoot it"

 

[Vettepilot]

Thanks for the info guys. Will consider all, and grab a back up barrel too!!

And yep, those Vette tires have a habit of going fast, and they're not cheap either! Talk about your money "going up in smoke....!"

;~)

Vettepilot

 

[Disfunctional_Engineer]

hots per second, or one shot
every second) is done, accuracy life will be much less.

Fourth, the accuracy levels are for ranges through 600 yards. Once the
barrel life calculated limit is reached, groups will probably start to
get bigger at the longer ranges before they are noticeably bigger at the
shorter ranges.

My formula, or rule-of-thumb process, is:

1. Calculate the bore area in square millimeters.

2. Use one grain of powder for each square millimeter. This is what
I call the reference, or base powder charge.

Example: .30 caliber bore = 45.6 square millimeters.
Base powder charge for .30 caliber is 45.6 grains.

A .30 cal. cartridge that burns 45.6 grains of powder should give a
barrel life of about 3000 rounds of good accuracy.

3. If a larger cartridge is used and it burns more powder, the
accuracy life in rounds for that bore size is reduced. The amount
of reduction is determined by

a. Divide the increased charge by the base charge, then square
the answer.

b. Divide that answer into 3000.

Example: .28 caliber bore has a base charge of 38.5 grains.
Cartridge burns 57.8 grains of powder.
(57.8/38.5) squared is 2.25.
3000 divided by 2.25 is 1,333 rounds.

I have to post this on SH every two years, the life of a thread.
1992 Bart Bobbitt's forumula for barrel life
https://groups.google.com/forum/?fromgroups=#!topic/rec.guns/iC-CoKQCeW8

Bart Bobbitt
11/4/92


I finally completed my research on a way to calculate how many rounds
a rifle barrel can be expected to deliver its accuracy level. By that,
I mean the barrel can be expected to have an average group size for
so many rounds before that average group size starts to get larger.
First, the rule-of-thumb formula I derived will produce a barrel accuracy
life of about 3000 rounds.

Second, if a lot of rapid fire (one shot every 5 to 10 seconds) is done,
the accuracy life will be less.

Third, if full-auto or very fast fire (a few shots per second, or one shot
every second) is done, accuracy life will be much less.

Fourth, the accuracy levels are for ranges through 600 yards. Once the
barrel life calculated limit is reached, groups will probably start to
get bigger at the longer ranges before they are noticeably bigger at the
shorter ranges.

My formula, or rule-of-thumb process, is:

1. Calculate the bore area in square millimeters.

2. Use one grain of powder for each square millimeter. This is what
I call the reference, or base powder charge.

Example: .30 caliber bore = 45.6 square millimeters.
Base powder charge for .30 caliber is 45.6 grains.

A .30 cal. cartridge that burns 45.6 grains of powder should give a
barrel life of about 3000 rounds of good accuracy.

3. If a larger cartridge is used and it burns more powder, the
accuracy life in rounds for that bore size is reduced. The amount
of reduction is determined by

a. Divide the increased charge by the base charge, then square
the answer.

b. Divide that answer into 3000.

Example: .28 caliber bore has a base charge of 38.5 grains.
Cartridge burns 57.8 grains of powder.
(57.8/38.5) squared is 2.25.
3000 divided by 2.25 is 1,333 rounds.

If anyone can shoot a hole through this theory, I welcome that shot. This
is more or less an emperical process based on accurate barrel life in
several calibers as reported to me by lots of folks. All I did was study
the data and determine what math would give a best-fit formula.

And if someone has a better method, I'd like to know what it is. My
formulas may not be the best.

Throwing 243 against this formula I got ~1238 rounds. That's a 44 grain charge and a 6mm bullet.

 

[MakeSawdust]

Throwing 243 against this formula I got ~1238 rounds. That's a 44 grain charge and a 6mm bullet.

The way I read this is that groups will open up at that round count, not that it will be a 2 moa gun at that point. If we are talking PRS, a half moa gun will win with a good shooter behind it. A one hole 243 will TYPICALLY take longer than 1200 rounds to go over half moa. If you need the gun to shoot half moa, and it starts out shooting half moa, it probably won't shoot half moa for as long. Comparing what a benchrest shooter says to prs or hunting is a pretty big stretch in this instance. Benchrest shooters need their guns to agg. in the .2's at close range to be competitive. A gun that will never shoot in the .2's can win a lot of prs matches in the hands of a talented shooter.

Having said that, I will contradict myself a bit. A gun that is hammering is easier to win with than one that is so-so. I used to try to convince myself otherwise because barrels are expensive. I have watched my placing drop as my barrel wore out for 3 seasons now, only to jump back up when I screwed on a new one. This is why the guys with barrel and smith sponsorships run barrels for 1200 rounds in 6 Dasher and 800 rounds in 6 creed and then pull them from competition use. Some guys are starting to run them longer and doing well, but the guys that hate losing the most are running barrels during the sweet spot for matches and then using them for practice after that.

I guess if you figure what it costs to go across the country to a 2 day match it could be argued that it makes financial sense. Even if I'm traveling 7 hrs to a one day regional match and staying in a motel, I can still shoot 2 matches before I can pay for a barrel. I run them till they open up. If they die during a match, so be it.

If it is a hunting gun, it will do very well as a 1 moa gun. It takes a lot of rounds to take a good barrel outside of a 1 moa accuracy standard.

Barrel life is relative to expectations.

 

[Disfunctional_Engineer]

A few good points there:
1-A person who's not skilled will not live up to the potential of good tools at the time of use and therefore they are wasted on them in some regards. They can certainly grow into them.
2-A good shooter will be able to get everything out of a gun that's possible but if the gun's then ultimately there's nothing they can do. It would be like the most skilled WRC driver doing a rally in a stock Civic. It's still a Civic even if he's super skilled, he'd do better given the circumstances than virtually anyone else would but he'd still do worse than a good driver with a great car.
3-Cost, I don't know that I would consider a barrel a concern. Lets say that you have $800 into a barrel, maybe even $400 into smithing to install. That's $1200. So say $1/shot. Lets factor this out a bit.
-Factory basic ammo is about .50 a shot. This isn't "good" ammo but just blasting junk. Lapua breaches $2/shot.
-If you reload (if you're shooting a gun of this caliber, that's probably a yes) What's a Berger Bullet, primer and 40 grains of powder cost? I'd guess .60-.70 a shot.
-What's the amortization rate of a reloading setup to make ammo for a high end shooter? Dies that cost hundreds of dollars, presses that probably cost similar, cleaning, trimming hell lets not even get into powder dispensing. Even for someone that shoots tons of ammo.
-This says nothing of the stuff you mentioned+the cost of the gun, storage and immense amounts of other gear that one buys like a chronograph. How much per shot on average does that cost?

If you think about it even at a buck a shot a barrel's not horridly expensive. I also think that one needs to be conscious of what accuracy constitutes for a person. I was reading a thread and the guy was referring to "minute of white tail." If you think about it that way junk to one of these competition shooters could probably last his grandchildren if they're checking zero and firing a few rounds a year at a deer. Hell mil-spec on an infantry M4 is what 4 MOA or something like that and they shoot to 2?

 

[iceng]

I went 2992 rounds on a 24" 8 twist, 243ai. Nosler 105rdf @ 2820fps. Yes it's a low node, but it shot awesome. I was able to run it at 3150fps but the normal brass didn't like it. Eventually went 308 Palma small primer, necked to 243 and inside / outside neck turned. Worked great.

I've since rebarreled to a 26" 7 twist, same brass. Only just done, and so far 108eld-m work well. Once I hit 150/200 rounds I'll be able to report how well the velo / node works

 

[Bluesman]

Nobody ever replied to this thread about a chrome moly barrel vs stainless. Or maybe a coated barrel? Has anybody shot a 243 barrel beyond 2000 rounds with good accuracy and velocity? If so give me your barrel specs.

My first build for PRS was a 243. I ran a Broughton 5C, 26”, 1:8 in a Sendero contour. I had been reloading and running my factory varmint rifles until then - all 224 variants for groundhogs, coyotes. I was so impressed with the tiny groups coming from my first custom barrel, I didn’t bother chasing speed. I ran the 105 Berger HVLD’s because their BC was slightly higher than the hybrids in 2016, and I thought it would be simple to just take the match rifle & load to the deer stands come fall. I ran 38 grains of H4350 and had the slowest 243 on planet earth @ 2844 FPS (except for iceng’s 243ai above ). I got 2400 rounds out of that first barrel before it fell apart at 2-day Peacemaker Fall Scramble. The next barrel was a Kreiger. I switched to RL26 pushing the same projectiles at 3150 FPS. It was gone at 1700 maybe less. I have the Kreiger twin on it now with 500 rounds down it. It’s in hammer mode. But I bought a new rig in 6BR from my ‘smiths personal rack so the 243 is waiting patiently right now.

I’m loving the 6BR for the reduced recoil and <30 grains of powder load.
At this point I think I’m qualified to say the 243 is really “2014” and not a choice for PRS-type competition because of short barrel life, felt recoil, and powder volume. But guess what - you get to load and shoot whatever you like to. Do that and have fun.

 

[acudaowner]

you got to sing to your barrel make it last all night man spread the love

lol