Head Space Question- re-barreled 204

[Brent]

I recently installed a 26" barrel on one of my 204s and have some questions. This barrel does not allow me to shoot as high of pressure ie powder charge as my stock 22" rifle. As a result the velocity is also not as high.

For example I can load 24.7 grains of h4198 in my 22 and get 3780. With the 26 I max out at 23.5 and 3700.

I am using PTG hs guages and tried to set hs as close to same spec as the stock rifle as possible. Using the go Guage I run it to where I just get a little resistance, similar to the stock rifle. If run a piece of tape on the base of the go guage the bolt won't close.

Ok so is this a problem with not enough hs? Should I set the barrel a little looser? I just don't get it. I expected 100 fps faster at same powder levels but can't get there. Another weird deal is factory Hornady ammo will in fact shoot about 100 faster. Accuracy is fine with my hand loads. Shooting around .25 or less moa.

[foxx]

I don't think headspace is the issue. You seem to have done that correctly, and it should not be installed any differently.

Are you saying the bullets must be seated into the case deeper than before so as to not touch the rifling? If so, the chamber was not cut as deep as before. (The rifling starts sooner?). The only fix for that would be to have it reamed deeper. Not sure it is worth doing if you are getting good accuracy. I could be wrong, of course. :)

I imagine you are getting more speed from the factory loads b/c of the longer barrel. That would make sense to me.

[AZ_GUN_NUT]

There is a point when all the powder is consumed and you reach maximum velocity, so even with the longer barrel it's not going to give you a lot more velocity as you're expecting, especially when you stated you dropped your powder charge from 24.7 to 23.5 and expected a higher velocity return. I'm trying to find an article that explains it better, I'm sure someone else will chime in and do a better job than I have.

"Cartridges with high expansion ratios lose less velocity per inch than do those of low expansion ratios, regardless of caliber. To put it another way, cartridges with high ERs are more efficient. Take the 7mm-08, for example. It’s the smallest cartridge of the current commercial 7mm lineup. To impart a muzzle velocity of 2,800 fps from a 24-inch test barrel, the 7-08 requires (based on published reloading data) a propellant charge of around 47.5 grains, give or take 2.0 grains, depending on the powder being used. Cut the barrel 4 inches, and you’ll lose about 75-80 fps, or about 20 fps per inch."

[foxx]

AZ, I think Brent's quandary has more to do with WHY he can't load as much powder with his new barrel. But certainly, you are right, less powder will mean less speed, in spite of the longer barrel.

[Brent]

Foxx- I am not sure I mentioned the bullet seating depth. This barrel has a deep throat actually, deeper than my other 204. I seated the bullets at .100 off the lands, which when measured for the 40 grain Vmax is 2.020. If you measure COAL it is 2.375. On the other shorter barreled 204 I also seat a .100 off the lands. That particular rifle shoots Sierras and Hornady's at .100 for .25MOA at 200 yards.

AZ- Gun - nut. No, I was not expecting to see higher speeds with less powder. I expected higher speeds with the same powder level but I can not shoot the same amount of powder due to increased chamber pressure. I have to back off the charge which defeats the purpose of the longer barrel. The factory ammo from Hornady shoots about 100 FPS faster in the longer barrel then the shorter barrel. Which made me question HS and if it is correct.

If in fact HS is correct, regardless of the chamber, then something else must wrong in my process. It could be I need to rethink the approach to resizing the brass. I use a forster neck sizer with shoulder bump. Perhaps I need to full length size or go a tad tighter on the neck bushing. Right now I am sizing down .002 from a loaded round outside neck diameter.

[AZ_GUN_NUT]

That could be your issue right there. if you're using fire formed brass from one barrel in another it could be causing the higher pressure?

[Patch700]

There's also the probability that as mentioned earlier your x amount of powder in the shorter barrel is indeed being fully consumed...
If you went with a slightly slower burning powder with the longer pipe you may get the results your expecting.

[Brent]

It is possible. I have some 1x fired brass in the new barrel I will work with next outing.

[foxx]

Oh, I assumed too much.

I am quite certain you should full-length re-size your brass when going to a new barrel... absolutely. That brass was fire-formed to your old barrel. That would make sense to me.

[Brent]

Patch700- Agreed. So far I have tried Superformance, H4198, H4895, BLC2, varget, 4064, Benchmark. 4198 and 4895 both give highest velocity before topping out on pressure. Even though the shoulders are bumped back to spec and the cases load smoothly I think I will start over with fire formed and body sized brass for the new barrel. I have not spent much time with this new build so with the feedback from here I most likely can rule out the HS as being the issue and concentrate on other things. This is my first build so naturally I questioned the HS issue over other things first.

[Patch700]

Patch700- Agreed. So far I have tried Superformance, H4198, H4895, BLC2, varget, 4064, Benchmark. 4198 and 4895 both give highest velocity before topping out on pressure. Even though the shoulders are bumped back to spec and the cases load smoothly I think I will start over with fire formed and body sized brass for the new barrel. I have not spent much time with this new build so with the feedback from here I most likely can rule out the HS as being the issue and concentrate on other things. This is my first build so naturally I questioned the HS issue over other things first.

Regarding pressure.. Try taking a fired piece of brass , do not size it and if it will still hold a bullet then she's over due for annealing.
Looking at your velocities I'd say their about rite in that you've lost aprox 100fps by having to drop down a grain in powder.. If the brass is good then a possible shorter throat in the longer pipe? Easy enough to verify by doing bto measurements between the two , providing you have a bto measurement from the old pipe.

[Blitzfike]

I like the Accurate 2015 in my 204 Ruger. I have had more consistent results with that than any other powder I've used. As to the higher pressures, is the chamber tighter than the older one? A chamber cast would be the easiest way to determine that, or weigh water grain capacity from brass fired from each, of the same manufacturer and compare the results that way. Interesting issue.

[Nor Cal Mikie]

"Accuracy is fine with my hand loads. Shooting around .25 or less moa?"
Why mess with a good thing? So you want to go faster? You don't have to be fast to be accurate. Lower charge = longer brass life.
If you're getting good accuracy, time to stop messing around and get to shooting.

[Brent]

Nor Cal Mikie, that is funny right there. The point is there is something not right and it needs to be addressed and fixed. Sure I can live with .25 or better accuracy. However, when I am shooting 500-700 yards I am going to reach for the rifle that shoots 100 fps faster and has a 4" shorter barrel. That really doesn't make any sense to me. Might as well cut 4" off and re-crown which also doesn't make sense.

On another note, I do believe I need to anneal this brass. I think this is the problem plus I found another problem. Good tip. Some hold a bullet and some do not which made me start digging into WHY. What I did discover is that my kid mixed the brass when he cleaned it for me. He was working on pistol loads and figured he would run the brass through the cleaner. Neither of us realized this until I went to measure the brass from rifle A and compare it brass from rifle B. Old lots vs new etc. I think I now know why some of the brass extracted easily and the speed was really low, then the next round speed was higher and brass was tighter. DOH. No big deal, I will anneal all of it, body size, shoulder bump, trim, sort, and test. I have some Nozler Custom brass I can play with too but I want to save until I have solid load developed.

[Brent]

I annealed about 80 pieces of brass, body sized, and necked sized .223. Re-tested H4985 and H4198. Found max on both powders and those were in line with my short barrel 204. Both powders shot 100 plus faster in the 26" and I am back in business. I will be in the 3870-3900 range with either of these powders but want to re-test varget, benchmark, and super again. I know the 4895/4198 both give me .25MOA or less accuracy. The little bit of testing I did Saturday between the 2 powders put all the rounds .3 MOA. Some were same hole.

[foxx]

cool.

better than cool.

[Brent]

Thanks.

Max load of 4895 was 3961. Brass life would be short though. 28 grs. After I get all this done I have another 26" barrel for my 10 predator I will install. I am selling the Stainless rifle after I get it done. Such a sweet rifle though. Ugh, kind of want to keep it.