Laurie I need you

[Tozguy]

Laurie, been reading your posts on certain topics that relate to my dilema and maybe you have some ideas for me.
My CZ527 American in 222 barrel heats up so quickly that two shots is all I can rely on before bullets start to wander. This using H322 max loads with 50 and 45 grain bullets. Is there a powder that would more efficiently than the H322 (and hopefully cooler) in this situation? Thanks

 

[bheadboy]

im not Laure but have a suggestion,

it is not the powder, bullet, it is the bedding, barrel contact or recoil lug, tang, etc. as you shoot the gun is moving in the stock,

i have had light barrels that shoot well if action/lug are solid and barrell very clear of contact, you may want to bed the first 1-1.5" of barrel under the chamber.

Bob

 

[Tozguy]

Thanks Bob,
It didn't occur to me to check the clearance between the barrel and forend when the barrel got hot. Clearance is ample when cold. Checked and rechecked the stuff you mentionned but found nothing wrong. Hammer forged barrels are supposed to be more sensitive to heat than other types. Point of impact returns when the barrel cools back to normal. On cooler windier days I can get three shots in a bug hole before shots wander. On warmer days only two shots stay together. All this is very predictable and repeticious. Anyway, I traded the CZ 527 American in on the new Browning A-bolt target rifle in 223. It has a 29'' button rifled heavy barrel so it should be fun discovering how many shots it takes to over heat it.
Happy new year folks. Mike

 

[15Tango]

I couldn't help but scratch my head on this one as wondering with a heated hammer forged barrel is the opposite of what I've always understood and seen with hammer forged barrels as it's said that stresses are allegedly even throughout so it has no tendency to go one way or another when heat's applied. I can get 25 shots through my hammer forged rifles during F-class in a short time without getting any wander and they get very hot.

Like Bob, I think something was goofy about that particular rifle for some reason other than it being hammer forged.

Let us know how the Browning shoots, it's interesting that Browning is trying to get into the target market and it should be interesting to read some feedback.

Wayne

 

[markr]

After you check for clearance in the barrel channel...and be sure to check that clearance when your rifle is in the "normal" firing position, on the bags I assume, if you are checking for ultimate accuracy. Many times the weight of the rifle...and or you positioning the rifle on the bags in a different place on the forearm each time, or putting pressure on the rifle through your shooting position, could cause contact at that time. Just some things to be aware of!
Secondly, some rifles with sporter weight barrels will actually shoot more consistantly with a single pressure point between the forearm and barrel. You could try shims of various thicknesses to provide this pressure point and see how it shoots.
Last but not least...and the least desireable, is that many (most) barrel makers straighten barrels after they are rifled and contoured. As the barrel heats it will try to assume it's natural position (pre straightened shape) and this will cause your shots to wander as the barrel heats.
If your intended useage of this rifle is for varmints, then it would be to your advantage to sight it in with a "cold barrel zero", meaning to consistantly place your rifle on the bag in the same way each time, hold the rifle the same way with the same pressure each time, and to fire one shot...allow the rifle to cool completely (not just 5 or 10 minutes either) and strive for consistancy of bullet placement with that cold barrel shot. In a hunting situation, that first shot and its placement is far more important than any followup shots that you may need.
Hope this helps
Mark
Oh, sorry, I'm not Laurie either, but I did stay at a Holiday Inn Express several nights...

 

[bheadboy]

15 tango is right, to my knowledge, all barrel makers stress releave barresl after rifling, and in some cheaper barrels straightening, thus heat does not cause the movement,

the points re shooting position, pressure on the bags, cheek, shoulder, hand on stock, all can move a point of empact, but again, bedding will fool you it may seem clear under the barrel and the recoil lug may be in poor contact, the action pressured on one side or the other and the tang bent down, much to consider.

Bob

 

[Tozguy]

Hey folks,
Thanks for your thoughts. The CZ is a sweet little rifle. The first two shots from a cold barrel were always completely satisfactory. I am convinced that barrel heat is a factor that remains to be better understood. Maybe I should have shot groups with a HOT barrel instead of a cold one. My original question on whether choice of powder affects rate of heating a barrel remains unanswered.
The CZ American is a fun gun but not the best for my needs.The Browning A bolt target is a significant departure from the CZ although its still not a bench gun. Too bad the local range only opens again next April. Happy New Year everyone

 

[Laurie]

Hello Tozguy.

I don't know if it's me you're after, but I'd certainly agree with the other posts that there's probably something not right with the rifle mechanically to give you this problem. My first thought was also bedding. Try slackening the stock bolts then thumping the rifle down sharply on its buttplate on a hard surface a couple of times to ensure the barrelled action is fully back in its bed before retightening them. It might just help if this is the problem.

The .222 produces so little heat relatively that it shouldn't affect the barrel that much after so few shots and changing powders to produce less heat is most unlikely to change anything - it would just be marginal. Hammer forged barrels can change their point of impact as they get hot due to stresses in the steel coming out. (The hammer forging process imports enormous stresses into the barrel and although manufacturers destress them, you can still get this tendency to a greater or lesser extent. It's why hammer-forged barrels tend to be less consistent in their performance and are now rarely used in match quality rifles, only Lothar Walther in Germany seemingly able to produce top quality examples.) However, it usually takes more than a couple of shots to heat the barrel up enough to cause this.

I would experiment with loads a bit - it may just help. Your velocity might change after a couple of shots simply due to barrel fouling and the barrel doesn't like the new speed / pressure. I'm not really confident about this - but anything is worth trying. Back the charges down a bit to below maximum - the Cz527 mini-Mauser action is a neat little thing but it's very small and so won't be anything like as rigid as a Remy 700 or similar. try some of the classic 222 recipies - IMR or H4198 was always a favourite in this cartridge and I also got very good results from Alliant Reloder 7 when I had a .222 some years back.

Apart from those thoughts, there's not much else I can suggest I'm afraid.

Good luck, and a Happy New Year,

Laurie,
York, England

 

[Klong]

15Tango, I see what you are saying regarding hammer forged barrels, but if there is stock contact in any part of the barrel, it will move the barrel as it heat up due to the expansion of the metal. This could be the cause of the shot movement. Right?

Are your F-Class barrels free floated?

 

[bheadboy]

I agree with Laura, the 2 -3 shots from a 222 case will not heat the barrell enough to cause this major change, yes clear the barrel from the forend, but most important, the recoil lug (the bump Laura is talking about) to the tang is moving around - and you may be changing bag position,

shoot 5 shots, then shoot a group, the barrel may like it dirty

Bob

 

[15Tango]

Klong,

Maybe I'm not posing my question or point well, the hammer forging process exerts the stresses on the barrel uniformly as the steel is ran through the hammers with the mandrel inside the overbored barrel crushing the steel around the mandrel. Everything I've read regarding stress relieving with hammer forged barrels is that there's no noticeable increase in accuracy or behavior when heated or cooled. Maybe there are others out there that have done more testing that have found the opposite to be true? Here's a pretty interesting article about the hammer forging process: http://technology.calumet.purdue.edu/met/higley/Precision%20Shooting%20Magazine%20-%20November-%202005%20(Vol_%2053%20-%20No_%207).htm

Placing a button rifled barrel in juxtaposition for the sake of the stresses involved I've read that button rifled barrels usually benefit quite a bit from stress relieving because the manufacturing process for button rifling involved putting the barrel longitudinally in a press forcing a button through the undercut line bored barrel. Here's a picture of what those presses look like: http://www.firearmsid.com/Feature%20Articles/RifledBarrelManuf/image016.jpg

I'm not trying to say one method's better than the other and there are other methods such as cut and single cut etc that many feel are superior. I think when all is said and done if the tolerances are there, the stresses are relieved if need be and they're lapped well that they'll shoot.

As for the expansion of the metal when heating up I'm not sure that it would be measurable or not, it depends on how much heat is there, I doubt it would be enough from a .222 after a few shots to really be making a difference which is why it was making me wonder if there wasn't some other issue at play. CZs are pretty well-known for their barrel quality, they're the only OEM mass manufacturer that laps their barrels, and they actually do it twice (before and after the hammer forging). It just makes me wonder what was goofy on your rifle.

My F-class rifles are free floated, yes.

Please be sure to let us know about that Browning though, it should be interesting.

Wayne

 

[Tozguy]

Thanks for the thoughts Laurie, I was looking forward to reading your comments. The powder choice was a 'long shot' but worth asking considering what I have read about QUIK LOAD. Re barrel heating of the CZ American, yes I was using max loads to keep the RPMs up with the 14'' twist. I can assure you that after three shots the barrel was almost too HOT to touch. Bear in mind that the CZ barrel is skinny, not in the varmint category. I wish I knew how to post some pics of my targets, it would be worth a 1000 words.
Wayne, thanks for the references on barrel forging, etc. Catch you later folks, Mike

 

[cheek9075]

i had 22-250 that did the same thing, but after about 5 shots. nothing helped. threw money down the drane trying to get it to to better. the only thing that helped is slowing down the bullet, which helped with heat. got a friend that has the same problem in 220 swift. it;s a shooter up to about 5 or 6 shots but then goes verticle. after it cools, it good agian.
both are, or was great ground hog guns, not that may shoots in a roll one or two here and then a brake, barrel stayed cool. in a shoot, well might as while stayed home.

 

[Tozguy]

Cheek,
That pretty well ressembles my observations. When barrel temperature is the main variable from shot to shot there doesn't seem to be much one can do short of a great deal of patience or a barrel cooling provision. I opted instead for a different gun with a very heavy profile.