308 PA-10 Heat vs Accuracy problem

[PA-10]

Hello I’m new here and hope somebody may have some knowledge/experience with an issue I have. I have 2 PA-10s both are 308 and have 18inch barrels one is free floated and one isn’t. I’m in the south so it can be hot and humid here and I seem to have accuracy issues after I’ve gotten the barrel hot. I’m using a 1x6 Acss Primary Arms Scope and have hit out to 600 yards with no problems.Our range is covered so I’m in shade while shooting. Is the heat an issue? 

Edited July 2, 2019 by PA-10

[Sisco]

Can very well happen. Are both barrels the same profile? One is free floated and one is not. Any differences in accuracy degradation between the two? And what is your rate of fire and what projectiles are you using. Weight and design.

[PA-10]

3 minutes ago, Sisco said:

Can very well happen. Are both barrels the same profile? One is free floated and one is not. Any differences in accuracy degradation between the two? And what is your rate of fire and what projectiles are you using. Weight and design.

One barrel is a nitrated and the other is a stainless steel barrel both 1:10 twist both have same optics. I have had the free floated about a year I just got the other a few weeks ago it has a rifle stock. But I’ve noticed both seem to have this issue when they get heated up. I do know if I let them cool for a good while accuracy improves but heats up quickly since the ambient air temp has increased. Is Ammo an issue also?

[shooterrex]

As metal heats up it expands.  Not always the same way throughout the barrel. Most rifles loose accuracy when the barrel gets hot compared when they are cold. A lot of times the point of impact will change as the barrel heats up. That's part of the reason target rifles have heavy barrels. They take longer to heat up.

[98Z5V]

2 hours ago, PA-10 said:

 Is Ammo an issue also?

Very well could be, and that was going to be my question - What ammo are you shooting?

I'm in AZ, so I can tell you heat does have an affect.  It shouldn't make your gun go crazy, though.

[PA-10]

7 hours ago, 98Z5V said:

Very well could be, and that was going to be my question - What ammo are you shooting?

I'm in AZ, so I can tell you heat does have an affect.  It shouldn't make your gun go crazy, though.

I have some steel case wolf 145 grain that I’m just using up, but I also have been shooting ppu same grain fmj which seems better. I have already replaced my extractor to a jp Enhanced because of steel case ammo. I not had any malfunctions from either weapon, and I did some research here and took your advice on the buffer system works perfectly fine.

[Magwa]

What is your average rate of fire? how fast are you shooting and how many rounds do you shoot before letting the gun cool?

[Belt Fed]

Mine will loosen up on hot days too, I bought a Caldwell barrel cooler, it seems to work. it's made to lock up in an AR15 but it will work on the 308. It just won't lock in place. I put it in when checking targets or anytime I stop for a bit. Here's a pic of it being used on a Ruger 7.62  I give around 30 bucks for it.

https://www.caldwellshooting.com/range-gear/ar-accessories/accumax-barrel-cooler/390247.html#start=1

 

Edited July 2, 2019 by Belt Fed

[RedRiverII]

 I generally use these.  A little extra Bourbon for a really hot day.  I know,  it doesn't really help the barrel at all.  After a couple,  I don't really mind waiting at all.  Belt fed's idea is good also.

Edited July 2, 2019 by RedRiverII

[PA-10]

I’m probably shooting too many and not allowing for proper cool down time but I’ve never really noticed any huge changes in accuracy until i began shooting longer distance.

[Sisco]

19 minutes ago, PA-10 said:

I’m probably shooting too many and not allowing for proper cool down time but I’ve never really noticed any huge changes in accuracy until i began shooting longer distance.

 

1 hour ago, RedRiverII said:

 I generally use these.  A little extra Bourbon for a really hot day.  I know,  it doesn't really help the barrel at all.  After a couple,  I don't really mind waiting at all.  Belt fed's idea is good also.

Shooting with Wolf steel case you can’t expect accuracy. The Russians manufacture it cheap for a reason. PPU from the Serbs will be better. Try some 175 gr Federal Gold Metal Match with a relaxed rate of aimed fire at longer distances. Then after you shoot, and put away the rifles, Red’s idea is outstanding.

[98Z5V]

3 hours ago, PA-10 said:

I have some steel case wolf 145 grain that I’m just using up, but I also have been shooting ppu same grain fmj which seems better. I have already replaced my extractor to a jp Enhanced because of steel case ammo. I not had any malfunctions from either weapon, and I did some research here and took your advice on the buffer system works perfectly fine.

145gr outof a 1:10" twist barrel is gonna be marginal at best, even if it was loaded to match-standards.  Too light of a projectile for that twist rate.

50 minutes ago, PA-10 said:

I’m probably shooting too many and not allowing for proper cool down time but I’ve never really noticed any huge changes in accuracy until i began shooting longer distance.

I'm sure it's getting worse if you shoot it fast.  A little bit of barrel-heat difference is gonna make a bigger difference, because that little bullet is being spun so fast... 

[RedRiverII]

22 minutes ago, Sisco said:

 

Shooting with Wolf steel case you can’t expect accuracy. The Russians manufacture it cheap for a reason. PPU from the Serbs will be better. Try some 175 gr Federal Gold Metal Match with a relaxed rate of aimed fire at longer distances. Then after you shoot, and put away the rifles, Red’s idea is outstanding.

Too true.  Alcohol and firearms is not an acceptable mix.  Now back to seriousness.  Heat and barrel rifles are never a good mix,  always going to be a challenge.  I ordered a barrel with a dissipater,  just a fancy coil wrapped around the barrel.  JP has them.  Accuracy will be affected,  if in competition everyone will have the same challenge.  Better ammo will always be superior.  What do you find acceptable?  Why are you shooting?  Guns will melt after a while.  50,000 lbs of pressure equates to beaucoup heat.  I think it's a terrific idea to have 2 rifles.  

[Belt Fed]

You ain't shooting fast enough til you set the handguard on fire.

[RedRiverII]

I saw that Colt experiment,  mag after mag,  auto.  It did just that^^^

[Cunuckgaucho]

3 hours ago, Belt Fed said:

You ain't shooting fast enough til you set the handguard on fire.

 Or the bacon is done...

 

Edited July 2, 2019 by Cunuckgaucho

[washguy]

PA   don't forget you are shooting a pa10.....a match barrel it aint.....once you find a weight and type of ammo the barrel likes you will be okay....but cloverleafs and one hole from 3 bullets will be just a dream....better barrel = better groups       Wash

[Rsquared]

6 hours ago, RedRiverII said:

Too true.  Alcohol and firearms is not an acceptable mix.  

Not so sure about that. You guys would be surprised at one of the fall shoots. There's ALOT of alcohol sitting around and being consumed. Now granted, we ain't no lightweights. It's not like guys are getting falling down blackout drunk. Though I have been known to nod off in a camping chair around 1 AM from time to time. There's pictures around here somewhere.

[SimonSays]

Sisco asked a few questions that haven’t been answered yet. I think they were important. He asked about the barrel profile. Incase you didn’t understand the term, I’ll take a stab at it. To keep it simple, here are 3 examples.

Heavy profile: the barrel doesn’t taper (the barrel doesn’t narrow) from the chamber to the muzzle. It’s very thick and weighs a lot. The barrel remains very accurate because it takes longer to heat.

Medium profile: there is a taper or narrowing from the chamber to the gas block. Forward of the gas block the remaining portion of the barrel is thin. This profile saves weight. It will be less accurate with the same number of rounds through it when compared to a Bull barrel, but it will remain accurate longer than the last example, a Pencil barrel. 

Thin (Pencil) barrel: it tapers from the chamber to the gas block and is very thin for the remainder of the barrel. It is a light weight barrel. Many hunters prefer it for that light weight. It’s accurate for the first handful of shots but it heats up rapidly and looses accuracy.

Measurements of your barrels would be great but, if that’s not possible, a guesstimate of the profile would really help. 

2nd: he asked about the accuracy between the rifles with the free floating and the non-free floating  hand guards. My guess is the free floating is more consistently tighter with group size than the non- free floated. ie, At 600 yards, when hot, the free floated opens up to, let’s say 8 inches whereas the non opens up to, say, 10 inches. Is this correct?

3rd: you stated your rate of fire was faster than it should be. Please give us another guesstimate. 1 round per second, 1 round every 15 seconds, 1 round a minute? Just go from memory. This isn’t a morality question. There is no right or wrong, good or bad answer. The answer along with the barrel profile will give us some idea how fast the barrel is heating. 

Final few points. As many others have stated,  the higher the quality of the ammo, the more consistent it will be. At 600 yards, you’re at the upper end of the mid range and entering into long rang shooting. The difference between 0.900 inches and 1.200 inches at 100 yards doesn’t look like much to the naked eye. At 600 yards, yea, it’s huge. All those little things at 100 yards that don’t seem to make a difference are suddenly very big things at 600 and beyond. 

The last final point...

1 hour ago, washguy said:

don't forget you are shooting a pa10.....a match barrel it aint

He’s absolutely right, a PA-10 barrel is ....  adequate at best. Sorry this was so long, but I had to get it out there. I wish you the best of luck

[PA-10]

42 minutes ago, SimonSays said:

Sisco asked a few questions that haven’t been answered yet. I think they were important. He asked about the barrel profile. Incase you didn’t understand the term, I’ll take a stab at it. To keep it simple, here are 3 examples.

Heavy profile: the barrel doesn’t taper (the barrel doesn’t narrow) from the chamber to the muzzle. It’s very thick and weighs a lot. The barrel remains very accurate because it takes longer to heat.

Medium profile: there is a taper or narrowing from the chamber to the gas block. Forward of the gas block the remaining portion of the barrel is thin. This profile saves weight. It will be less accurate with the same number of rounds through it when compared to a Bull barrel, but it will remain accurate longer than the last example, a Pencil barrel. 

Thin (Pencil) barrel: it tapers from the chamber to the gas block and is very thin for the remainder of the barrel. It is a light weight barrel. Many hunters prefer it for that light weight. It’s accurate for the first handful of shots but it heats up rapidly and looses accuracy.

Measurements of your barrels would be great but, if that’s not possible, a guesstimate of the profile would really help. 

2nd: he asked about the accuracy between the rifles with the free floating and the non-free floating  hand guards. My guess is the free floating is more consistently tighter with group size than the non- free floated. ie, At 600 yards, when hot, the free floated opens up to, let’s say 8 inches whereas the non opens up to, say, 10 inches. Is this correct?

3rd: you stated your rate of fire was faster than it should be. Please give us another guesstimate. 1 round per second, 1 round every 15 seconds, 1 round a minute? Just go from memory. This isn’t a morality question. There is no right or wrong, good or bad answer. The answer along with the barrel profile will give us some idea how fast the barrel is heating. 

Final few points. As many others have stated,  the higher the quality of the ammo, the more consistent it will be. At 600 yards, you’re at the upper end of the mid range and entering into long rang shooting. The difference between 0.900 inches and 1.200 inches at 100 yards doesn’t look like much to the naked eye. At 600 yards, yea, it’s huge. All those little things at 100 yards that don’t seem to make a difference are suddenly very big things at 600 and beyond. 

The last final point...

He’s absolutely right, a PA-10 barrel is ....  adequate at best. Sorry this was so long, but I had to get it out there. I wish you the best of luck

Sorry I didn’t  answer correctly earlier, both of my barrels will be a medium profile. And you’d be correct in saying my free floated barrel is a bit more accurate, and I’d say I’m shooting about every 10-20 seconds typically but slower once I know it should cool down. I realize the PA-10 is not a match grade barrel and I don’t shoot for groups, I’m shooting at a 18x30 steel target and want to hit as central as I can. I’m shooting 200-600 yards. I didn’t buy my PA-10s to be competition shooters and with or without my optics I can hit out to 600,just better with it. I realized since I’ve started shooting at longer ranges heat has become a issue, at 100 yards doesn’t seem to make a difference. Sorry I didn’t understand the question earlier and thanks for helping.

[98Z5V]

YOu guys are completely missing the boat on this one, and it's about projectile weight vs. barrel twist rate.  145s through a 1:10 is gonna suck, and it's gonna keep getting worse the hotter the barrel gets.  This isn't about rate of fire - it's about the right ammo for a 1:10 twist barrel. 

145s would do much better through a 1:12 twist barrel, but they're not gonna be the greatest, or anywhere near, through a 1:10.

OP, you need to move to heavier projectiles and ditch the 145s except for plinking ammo.  Your rate of fire is not that high, based on what you're describing.

Edited July 3, 2019 by 98Z5V

[PA-10]

1 hour ago, 98Z5V said:

YOu guys are completely missing the boat on this one, and it's about projectile weight vs. barrel twist rate.  145s through a 1:10 is gonna suck, and it's gonna keep getting worse the hotter the barrel gets.  This isn't about rate of fire - it's about the right ammo for a 1:10 twist barrel. 

145s would do much better through a 1:12 twist barrel, but they're not gonna be the greatest, or anywhere near, through a 1:10.

OP, you need to move to heavier projectiles and ditch the 145s except for plinking ammo.  Your rate of fire is not that high, based on what you're describing.

Thanks for this information what Ammo would be suitable for this 1:10 barrel? Thanks.

[Sisco]

16 minutes ago, PA-10 said:

Thanks for this information what Ammo would be suitable for this 1:10 barrel? Thanks.

 

13 hours ago, Sisco said:

 

Shooting with Wolf steel case you can’t expect accuracy. The Russians manufacture it cheap for a reason. PPU from the Serbs will be better. Try some 175 gr Federal Gold Metal Match with a relaxed rate of aimed fire at longer distances. Then after you shoot, and put away the rifles, Red’s idea is outstanding.

Answered what you should try already for 1 in10 barrels. Also M118LR Lake City is similar.

[98Z5V]

What are you trying to do with the gun, first off?  Be accurate with it, and test it's accuracy?  Start with 165s and 168s, and move to 175s.  You'll see an accuracy improvement, unless that barrel is completely FUBARd when it was manufactured.

1:10" twist rate is "Over-Stabilizing" 145 grain projectiles.

http://bulletin.accurateshooter.com/2013/07/over-stabilization-of-bullets-why-is-too-much-spin-a-problem/

https://sierrabulletsblog.com/2015/05/07/understanding-twist-bullet-stabilization/

I can shoot 55gr 5.56 projectiles 600 yards.  They suck, but it can be done, with an "average" of "accuracy" through a couple different badass guns - and they're built for distance, with badass barrels and everything else.   It's not gonna be MOA, though, but it'll hit a full sized IPSC plate most of the time.  Doesn't matter what the twist is for that projectile at that distance, as far as accuracy goes - but twist matters.  They're gonna suck from a 1:7 5.56 barrel.  They'll be a little better from a 1:8" barrel.  They do pretty damn decent from a 1:9" barrel.  They excel from a 1:12" barrel.  They just don't ever "excel" at 600 yards.  I can drive a 75 or 77gr 5.56 projectile to 800~900 yards, semi-accurately.  It's gonna hit more than it's gonna miss - but I wouldn't hunt that round at that distance.  I'd risk a shot on an IPSC plate at that distance, and hit it more than miss it. I wouldn't hesitate to hunt a (5.56) 70gr Barnes TSX at 500 yards on bigger animals, or 600 yards on a coyote, though.

You're doing the same thing with 145s in a .308 Win gun.  You just about blow through the ultimate range of the 145gr projo in a .308 Win load around 400 or 450 yards - IF you were shooting it through a 1:12" twist barrel... - after that, it's gonna be shiit.  It's not a long-distance projectile - it's too short, and too fat (sectional density comes into play here, as well as BC). 

Edited July 3, 2019 by 98Z5V

[Cliff R]

How tight are the groups with these weapons at 100 yards? 

Of course things start to move around some as things heat up, but if you aren't just about one holing the rounds at 100 yards right out of the box then things aren't going to be all that great at 600 yards before you add heat to the scenario.

I'm not or ever have been a fan of Wolfe steel case ammo.  Tried some WAY back when I built my first AR-15 and it didn't show me much in the accuracy department.  Can't image it being much better in 308........Cliff