Odd velocity issues with inline.

[JimG]

I've been having some trouble with a CVA Optima concerning POA vs POI. The rifle is very accurate however it seemed to want to shoot low. I now think it has less to do with the rifle and more to do with loads and loading techniques. I know CVA's are sometimes not well thought of but could we keep this thread on topic concerning pressure and velocity and not on CVA quality or lack there of? Important specs on the rifle-

Bergara 26" barrel (although effective length is less due to false muzzle and breech plug) with a 1 in 28" twist.

Projectile- 223gr Aerotip Powerbelt

Pyrodex Select RS or Goex FFG BP

The manual has conflicting info regarding max loose powder loads, it's either 100 or 110 grs.
It can handle up to 3 pellets but I generally dislike pellets and prefer to shoot loose powder in all BP rifles. I have consulted two Lyman BP loading manuals and cannot figure out why this happens.

Shooting 100gr. Pyrodex gives 1529 avg fps
100 gr. Goex gives 1546 avg fps
110 gr. Pyrodex gives 1728 avg fps

According to Lyman and everything I've ever been taught about BP this is impossible. The gun does recoil harder so I know that it's not just an error on the chrony. Also I doubt the error would be repeatable over many shot strings. 10 grs. of powder by volume should not generate nearly 200 extra fps given same projectile. I also have found that a dirty bore produces less velocity than a clean bore. I personally think that it should be the opposite due to the dirty bore generating more pressure, but I could be wrong. I've also found that ramrod pressure is crucial. Avg velocity can vary by up to 83 fps by simply varing ramrod pressure from firm to light. I don't find that so odd but it does show the need for consistent loading techniques. But what gives with the strange velocity increase. As an added note Lyman does not show loading data for my specific barrel length/twist/projectile combo. The closest I can find is a 22" barrel/1 in 24 twist/240gr. sabot. Until I load 110 grs. of Pyro my velocities are on the low side compared to the books. Any thoughts on how 10 grs of Pyro  can generate that kind of velocity increase and why real BP generates slightly more velocity than Pyro when it should be the other way around?

[JimG]

An added thought, the only reason I can think of is that the added 10grs are just enough to 'flare' the sabot skirt on the Powerbelt and 100 gr loads or less simply are not generating enough pressure in my gun to do so and pressure/gases are escaping past the 'non flared' sabot skirt generating lower velocites. I wonder if a heavier projectile would help to keep pressures up? Say a 245 or 275 gr. or a full bore conical in the 300 gr range? Basically my thought is the light 223 gr Powerbelt is too light to generate the proper pressure. According to Powerbelts website 100grs and a 245gr Powerbelt should generate about 1900 fps from a 26" barrel. I'm way off the mark if Powerbelt's site is to be believed.

[Semisane]

the only reason I can think of is that the added 10grs are just enough to 'flare' the sabot skirt on the Powerbelt and 100 gr loads or less simply are not generating enough pressure in my gun to do so and pressure/gases are escaping past the 'non flared' sabot skirt generating lower velocites.

Hey JimG, I agree with your thinking regarding gas seal with just a little more powder.  In my Lyman Mustang 50 caliber with 250 grain Speer Gold Dots in Harvester Crush Rib sabots and Triple 7 FFG powder, I get 1738 fps with 90 grains of powder,  1761 fps with 100 grains of powder (only 23 fps more), and 1894 with 110 grains (a jump of 139 fps).  All of these velocities are for 5-shot averages.

[JimG]

Thanks Semisane, anyone else have any ideas?

[Landngroove]

Jim, Just for the heck of it, why not try a "Wonder Wad", or "Bore Button" over your powder, before loading the projectile. I use these in my traditional ML's, when I shoot conicals, and get more consistant grouping. They protect the base of the projectile from hot gas, heat, and deformation.

[dmurphy317]

Another idea, instead of a wad is to use about 10 grains of cream of wheat or corn meal as a buffer.

I have seen similar jumps in velocity when moving from one powder level to another. I've always attributed it to finding the sweet spot for that load combination. Sort of like finding the point where the most efficient burn of powder for a given barrel length happens. After that point the increases of velocity will be less with an equal increase in powder.

I tend to lean more toward a heavier bullet for all my CVA rifles. I find the lighter weight bullets are too inefficient at ranges much over 120 yards and the trajectory is not that much better than even a 300 grain bullet. Especially if your are planning to shoot out to around 200 yards as the energy is not there for a 223 grain bullet, at 1550fps its down to 800fpe at 100 yards, 700 at 150 and below 600 at 200 yards. At 1728 it's better with 1000 at 100, 825 at 150 and about 690 at 200. Many consider 700 the minimum for deer and 1000 for larger game. The 300 by contrast will have around 825 at 200 when launched at 1600fps. Drop on the 223 vs the 300 at 200 yards when sighted in for a 5" point blank range using 1728 and 1600 fps respectively is 11.87 and 12.5, not much difference at all.

That's my 2 cents.

[JimG]

Landngroove- Yes I've wondered about using a Wonderwad. Never have tried them in any ML I've ever had but I do think I'll order a bag and try them and see what happens.

dmurphy317- What bullets have you found to be good in your CVA? Powerbelts/conicals or sabots? I tend to lean towards the full bore projectile side of things more than the sabots. I've thought of trying some of the T/C MaxiBalls or MaxiHunters. The Powerbelts do load easy though. I'm pretty sure Powerbelt offers a 338 or 345 gr bullet or something to that effect. Have you had any experience with them?

[sabotloader]

JimG

Just a couple of thoughts...

Shooting 100gr. Pyrodex gives 1529 avg fps
100 gr. Goex gives 1546 avg fps
110 gr. Pyrodex gives 1728 avg fps
 

One of the principles of the PB is that the force of the pressure of the burning powder is suppose to cause the bullet to obturate, force itself up against the lands and grooves.  Moving from 100 to 110 might cause a tighter obturation creating a better gas seal also.

To me, and just to me, your velocities seem slow for that weight bullet.  I normally do not shoot anything that light, but i have been doing a lot of experimenting with 10mm 200 grain XTP's.  I shoot them at 2000 ft/sec with 100 grains of T7.

I am not sure that a wonder wad would aid that much under a powerbelt other than protect the skirt from getting to hot.  I shoot a .125 x .510 shot card under 460 grain Bullshop conicals - there is no difference with or without the card in velocity.

I really need to tell you 'I am not a PB fan" so take everything from here on as biased.... I really believe there are far better bullets out there than any of the projectiles you mentioned.  In one sentence you mention how easy they are to load - well in todays world there is no reason that a sabot and bullet needs to load hard - snug yes - hard know....  The new polymere sabots of various sizes are so much better than they use to be and seal a lot better.

You do not say what caliber your gun is and I do not know enough about PB's to tell from the weight but i guess I am leaning to it being a 45 cal. rather than a 50 - but it really doesn't matter if you want to try something.  If you want to stay with a light bullet that really works, far better than I ever thought, get a box of 10mm 200 grain XTP's and some MMP sabots - either the tan ones for a 45 or the blue ones for a 50.  With the blue sabots I can insert them down the barrel with thumb pressure.  You will not believe how they shoot and how hard they hit.

I do not have an Optima - but my Omega is close, I normally shoot 260 grain Noslers or 250 grain Gold Dots with MMP HPH-24 sabots.  Omega's do have a tight barrel, but even then if the Optima barrel is tighter MMP make a HPH-3p-EZ load sabot that will load very easily - shoots great also.  I am shooting these 250/260's with 100 grains of T& also @ 1860 ft./sec.

Just running off the top here - hope some of it is usefull....

[SHOOTALL]

does the rifling at the chamber end extend all the way or stop ?
The extra 10 grains may keep the bullet in contact with the lands , where the 100 gr. charge does not ! thus the bullet in contact ( although indexed ) may take a longer time to start forward movement ! thus giving more time to increase pressure and bullet speed !
Which load shoots lower/higher  ? If both shoot to same spot it may indicate a longer time in bbl. for faster load which might indicate higher pressure before bullet movement .
this is just speculation but an idea just the same
good luck !

[SHOOTALL]

my last post was not a cut toward the rifle
by the way .
another thought , you used a 10% increase in powder to get a 12 % increase in bullet speed , maybe you could decrease powder by 10% and see what the bullet speed does , or take it up  1 grain at  a time to see where the biggest increase in bullet speed happens  .

[dmurphy317]

Jim,

I use several different bullets in my CVA rifles. In my Magbolt I have used everything from patched round ball to 460 conicals to saboted bullets. Most bullets I can find a load that shoots 2" or less at 100 yards (round ball at 50 to 75 yards). My favorites in that gun are the 460 No Excuse and Bull Shop conicals with 90gr of 777 2F, the 300 Shockwave with 90 to 100gr of 777 2F, the 348 Powerbelt (most accurate bullet I've tried yet) with 100gr of 777 2F, and the 285 Buffalo SSB with 100gr 777 2F. In my older sons Apex it does well with the 250 Shockwave and 130gr of Pyro pellets. I've got some 460 Bull Shop conicals I'm going to try in it when I get a chance. In my other sons Optima it likes the 250 and 300gr Shockwaves with anywhere from 80 to 100gr of Pyrodex P. I also want to try the 460's in it but he is unable to handle the recoil yet. I've had my Magbolt for much longer than the other 2 so I haven't worked up as many loads for them yet. I guess I need to spend some more time at the range making smoke but for some reason my boss just won't let me, not to mention the wife.

[Buckskins & Black Powder]

120 grains pyrodex rs loose is the sweet spot when i shoot either 245 or 295 powerbelts in my winchester. Anything under and they start to open up.

[gt2003]

dmurphy,
Try the precision rifle QT or dead center bullets and see what kind of accuracy you get.  Go to www.prbullet.com and check out the bullet selection chart.  It will give you a good idea of what bullet will perform best with the twist of your rifle.  My shots aren't too long, less than 50 yds, but right now I'm sticking with 80 grains of 777.  From what I'm seeing, this charge should be quite accurate out to 125 yards.  If I remember correctly, I'd be dead on at 50 yds, about an inch or so high at 75 and 100 yds and just below my original mark at 125 yards.  Thanks, Greg

[JimG]

Shootall- yes the rifling does extend all the way to the face of the breech plug.

dmurphy317- the 348gr Powerbelts you say are the most accurate, are they the "Pure Lead Series" hollow points or the "Copper Series" hollowpoints or the "Copper Series" Areotip?

Also what exactly are the avantages of the Platinum series Powerbelts over the lead or copper plated ones?

[Buckskins & Black Powder]

Platinum's are supposed to have a harder "jacket" that holds the bullet together better. Ive never had problems with the copper jacket powerbelts but would like to try the new bullets out.

[SHOOTALL]

Most likely sales !

[dmurphy317]

gt2003,
Thanks for the suggestions. I have looked at the PR bullets but have several others that shoot well and quite a few rounds of each that I need to use up before investing in more. I have several hundred bullets of different types right now. More reasons to go to the range.

JimG,
I was shooting the copper HP version of the 348. It averages less than 1" at 100 yards it good conditions and me being on my game. In my Lyman GPH I have shot the 460 No Excuse conical into a .280" 3 shot group at 75 yards using a peep sight, thats as good or better than my scoped Magbolt does with the 348PB. I was really on my game that day. I've never shot the platnums, too expensive.

[AndyHass]

One useful tactic in load development for centerfires is to pick a range of powder charges in .1-.2 grain increments below the max book charge and test them at 300yd where drop begins to be very significant.  Now if velocity was directly proportional to powder charge, what you would see is a vertical line of holes in the target as more power would equal more velocity and hence less drop.

This is NOT what happens.  What you get (assuming you fire enough shots in the string, last time I did 15 different loads) is a vertical line of GROUPS.  We term them "nodes".  Very unscientifically described, what happens as I understand it is that each node represents an area where the barrel reaches an efficiency level balancing burn rate, efficiency, etc etc and it is not until you significantly increase the powder that you "jump" to the next node and hence velocity level.  Within each node, you have a range of different powder charges delivering roughly equal velocity.  This is called a "ladder test" as the nodes can be analgies of rungs on a ladder climbing up the paper.  The theory is that you pick the node around the velocity you want, and test fire groups with each load falling into the node to see which is most accurate in your barrel.

This worked spectacularly for my 300WM, but I have never thought to test and see if it worked with a ML.  But it could be an explanation for what you are observing.

[flintlock]

Jim...I'm am not sure I am understanding your problem but I can tell you something odd that happens with my friends Optima...He bought it about 3 years ago and shoots 2 Pyrodex pellets and a 295 PowerBelr...

He had a heck of a time sighting in, first shot hit 2 inches below the rest at 100 yards...He was cleaning the barrel between shots...After 2-3 range sessions we decided to pull the breech plug between shots and clean it as well as the barrel...This fixed the problem...The face of the breech plug on that rifle was very shallow (the depression the touchhole goes through)...So the plug was full of crud from the last shot...Evidently this was restricting the flame from the primer and slowing velocity, thus letting recoil help kick the 2nd shot higher....

Don't know if this might help, just wanted to let you know.