Accuracy of HOT rifle.

[FireInTheHole]

Just got back from some quality range time with my FAL.

First mag= 2.5 inch group @ 100 yards. (SA surplus)

By my 5th mag I was getting groups about twice that of the original group with the rounds going all over the target.

After 100 rds I let the gun cool (was uncomfortable to hold) then repeated the process... with the same results.

Question: How much accuracy degradation can be expected as a weapon heats up and is there a way to keep the weapon cool during the warmer parts of the year?(wet towels around the barrel etc)

 

[C.R.Sam]

Unless you have a supply of taxpayor barrels...
Keep the rapid fire to a minimum.

Try concentrating on each shot as if it was the only one you are going to get. Rapid fire only occaisionaly, and briefly, so you know that you can do it effectively.

Sam

 

[4v50 Gary]

What Sam sez. Fastest way to ruin a barrel is full auto. The military can afford to swap them out - we can't.

 

[FireInTheHole]

How would you define 'rapid fire', 100 rds in less than 5-10 min?

Note To Self: There appear to be problems with moving from primarily handgun shooting to shooting rifles.... :banghead:

LOL.

 

[Double Naught Spy]

Something is not right. The accuracy should not degrade that much with just 100 rounds. Even if you rapid fired or full auto fired, 5" is pretty huge. Are there some other mitigating circumstances such as the barrel already being shot out, crown damage, bore damage, or anything like that? How about cleaning?

 

[FireInTheHole]

Rifling in the barrel is sharp, and I always clean it.

Might just be human error(fatigue). My fal always kicks my @$$.

Perhaps now would be the time to invest in a muzzle-brake.

These were fired prone BTW.

 

[CWL]

My bet is fatigue.

Firing prone, probably not fully slinged with leather. "was uncomfortable to hold"...

Try it benched with sandbags if you really want to test this further but still think fatigue.

 

[Steve Smith]

Depends on the rifle, too. At Perry this year, my 500 yard NTIT group was a little smaller than a pie plate. That's 30 rounds in 50 seconds. That there's a good rifle.

 

[goon]

I have found that rapid fire or not, I generally can't hit crap with my AK.
I have hatched a plan to solve this problem. It involves procuring two twenty round mags, then going out every day and shooting 20 rounds for practice.
I know that I can shoot.
I am pretty good with my M-39 and my Savage Scout, but the AK eludes me.
I guess practice is the only answer.

FWIW I have found that I can point shoot with it pretty well out to fifty yards or so.
I cant the gun about 30 degrees to the left when I do this. I don't know why, but it seems to work.
Just wish I was better with aimed fire.:banghead:

Also, it isn't uncommon for groups to open up as a gun heats up.
The bullet traveling down the barrel causes the barrel to vibrate all over the place.
When the gun is cool, the barrel vibrates the same way each time, and the bullet goes more than less to the same place every time.
When the barrel is warm, the steel flexes with less consistency and the groups open up.
That is one advantage of a heavy barrel. They are thicker, so the absorb the heat better. They are also stouter, so they have less difference in how they flex when they are warm.

 

[Dr.Rob]

Well first off slow down. Second off, as your barrel heats up you will invariably find your shots stringing verticly. As you rush to adjust your sights and get back on target you are still heating up and compounding your problem.

 

[FireInTheHole]

Why would the rds move vertically as the temp increases? Higher barrel temps=higher pressure=increased velocity=flatter trajectory?

 

[Dr.Rob]

The exact science of why escapes me.

Has to do with altering barrel harmonics. Even in a bolt action rifle, after 3-4 shots while dialing in a scope you need to back off and let it cool down.

The more surface area a barrel has the faster it cools. ie bull barrels cool faster than standards, fluted ones even faster.

Even in military grade rifles like the FAL fluted bull barrels are available.

You really cannot expect to hold 1 inch accuracy at 100 yards with sustained rapid fire from a rifle that has not been prepped to do so, there are just too many moving parts.

Steves' M1a may or may not be bedded (though I suspect it is) and that's one advantage a conventional stocked rifle fas over a more modern pistol gripped design. Ditto with AR's, though it took them a while to figure out how to do it.

Next, if the sling actually attaches to your barrel, you will not get good accuracy, as it heats up, combinded with the pressure you apply to the sling you can change your point of impact.

Think of it this way... every little shot is a laser beam. Each beam is trying to hit the same place every time. But add one little bump, change barrel temp, change op rod pressure, change the amout of fouling in the gas ports, change powder in the cartridge by .5 grains, none of these will affect the accuracy of your beam at short range. But a tiny change at the barrel becomes a larger change at 100 yards. You can lessen the variables with a positive hold, proper breathing and slowing down.

 

[Steve Smith]

Dr. Rob, that was done with an AR.

 

[BigG]

Dr. Rob: With all due respect, a properly made rifle should shoot into the same group whether hot or cold. The fact that most do not does not negate the assertion that some do.

I realize the shooting mentioned here was excessively fast and the dispersion may have been by human error but I have and have had rifles that kept their zero from first shot until red hot. Aside, a five inch group with iron sights at 100 yards is not that bad.

I think some of the walking vertical or otherwise can be due to a barrel that was bent and straightened. Once it heats up, the metal "remembers" the kink and slings the bullets as you noted.

 

[Dr.Rob]

Steve I said that, it took them a while to free float an AR. First free floated AR I ever recall seeing from the factory was in the 90's.

5 inches IS NOT bad from an FAL with iron sights zipping through magazines.

Do the same with a mini 14 and you'll get the same results faster. NO ONE claims the mini 14 has a factory bent barrel.

I am NOT doubting that trained riflemen do this daily.

I am suggesting that expecting an unaccurized, unsupported, non bull barrel rifle will not hold 2.5 moa when you treat it like a bullet hose.

 

[JShirley]

Dunno why, either, but vertical stringing from hot barrels is common.

"some do"- uh, you could say this of anything, brother. All kinds of anomalies exist. Not sure I understand your assertion that "most don't, but they 'should'". By whose criterion?

Weapons design, barrel weight, caliber...lots of factors, here. Hard to be dogmatic and honest at the same time.

 

[C.R.Sam]

I think some of the walking vertical or otherwise can be due to a barrel that was bent and straightened.

Which is a lot more common than not. Especially with barrels that are made in large lots and a lot of material is quickly removed. Barrel straightening is a normal and expected part of the barrel manufacturing.

Rapid fire is relative. 20 rounds in 5 minutes considered rapid fire at 1,300 meters. Group strung vertically, 7"wide X 15" high. 338 Lapua, Lilja barrel. Group and gun considered good to go.

My Fals are for fun and I have to buy the barrels. I do not shoot em till they are hot....and then keep on shooting. I have smoked a couple of barrels but the taxpayors were footin the bill then.

Sam

 

[goon]

I had an AK so hot once that it was smoking from the handguards. It was so hot that I couldn't hold the forearm and I had to hold it by the sling.
I can shoot a semi-auto at nearly a full auto rate, and I was out to prove it that day.
What did I learn from that day?
I am stupid.
What is the sense in burning up a perfectly good barrel?
Whether or not the problem is coming from your rapid shooting, what will it hurt to slow down and make your shots count.

One thing that the old military surplus rifles have taught is that one well aimed shot is priceless next to rapid spray and pray.
I thank the Finns for that lesson.
Those people can build a rifle.

 

[FireInTheHole]

Well thanks for the advice... I guess I'll just give the gun 5 minutes to cool between mags. That should keep the heat down. Winter will be here soon enough anyhow.

"Bullet hose"

 

[Steve Smith]

I am suggesting that expecting an unaccurized, unsupported, non bull barrel rifle will not hold 2.5 moa when you treat it like a bullet hose. -Dr. Rob

I agree.