45 colt velocity deviations.....

[markp]

I loaded some rounds of 45 colt using unique for the first time. Very mild loads of 6.5 grains with a 250 grain
cast bullet. When I had the chance to shoot them over my crony it was a partly cloudy day. When the sun
poped out I would get a shot or two and then the sun would be coverd again and I would wait for it to return to shoot over the crony. Not sure the sun was always fully out but mostly when I shot.
My deviations were from 690 to 840 fps.  Really a pretty wide  spread with 5 shots.  I weighed each charge with a scale. My quesion is would the perhaps differing degree of brightness of the sun  affect my crony readings  and cause my deviations? Or do I need to look further for  the explanation ?

[Lloyd Smale]

your load is to light and its not ingniting properly. Either bump that charge weight up to 8 grains or if you insist on the velocity level your trying to get with that light load switch to something like bullseye or reddot Bullseye is about the best powder for loading real light loads.

[Sweetwater]

+1 on the light load and ignition problem. Each powder has a "pressure reange" that it operates accurately in, though it will go bang at lower and higher pressure. Light loads call for fast powder as posted.

I'm curious: if I waited for the sun to come out to use my Chrony, I'd never get to shoot here in North Idaho. Your skyscreens on your Chrony simply set up a "false cloud" for the light from your photocell to reflect against. I don't use skyscreens; just headless nails to hold drinking straws in place. Works like a champ and don't have to think about hitting a skyscreen - though I do have to worry about hitting the Chrony! LOL! (which I have done). We put up a beach umbrella over the Chrony to keep the snow and rain off it; other than that we let the natural cloud cover do its thing. In S. Cal. I got crazy readings sometimes - that's where I first started using the Chrony. Maybe the erratic bright light is doing something to your readings?

Regards,
Sweetwater

[markp]

Thanks Sweetwater and Lloyd smale . I am going to try a heaver charge.
 

[Lone Star]

Yep, too light a load for Unique.  Maybe with 300-grain bullets and 6.5 grains, but I never had great accuracy in my Blackhawk until I was over 8.5 grains with a 250 cast.

According to Oehler, you'll have better results with skyscreens on a cloudy day because there is more light entering the slots than on a bluebird day.   There is more light being reflected down to the screens.  Point a camera exposure meter up into a clear sky, then do the same on a cloudy day and you'll see the difference.  Don't worry about waiting for bright sun, that could actually reduce the chances of registering a bullet passing by.


.

[Steve P]

Your screens can vary based on amounts of light, but you should not get the deviations you mentioned.  As stated by some of the other posters, that is a light load.  I use the 8.0 grain load in my colt and it is very accurate with SD in the teens or twenties.

Depending on the primer, you could also have problems with position sensitivity.  If the gun is pointing to the ground and you bring it up to level to fire, all of the powder is down by the bullet.  If you are pointing the gun up, and bring it down to fire, all of the powder is near the primer.  You can see, depending on the load, several 100 fps difference pending on the method you shoot.

I do have some loads that I like mild and will use a small wad cut from the styrofoam trays found in the meat department to hold the powder in position at the primed end.  Use a fired brass to cut out wads and tap them into place over your powder in a sized case.  They will lower your SD and disintegrate on firing. 

AS usual, use book loads and work up to your charges.  If you are using a book load and the powder is taking up less than half of the case capacity, the foam wad may help your consistency and accuracy.

Steve

[LaOtto222]

+1 on position sensitivity. While the other posters are correct on powder pressure ranges, position can make a difference too. Take some of the loads you have and point the gun down before firing, then point the gun up on another batch before firing. I think you will find a surprising amount of difference. I would not do this unless you have a very light charge of powder. I read about experiments along those lines and it made quite a bit of difference. I can not remember what they were shooting, but it was a straight walled pistol case and they used a light powder charge. BTW - with Unique, it seems to do well when you reach the 900 - 1000 fps range, no matter what straight walled case you shoot it in. Good Luck and Good Shooting

[beerbelly]

                              I loaded some 250 grain bullets that I cast myself, with 5.6 grains of tight group and had an extreme spread of 42.
 I also loaded some with 7.3 grains of Unique and got an extreme spread of 48. This is out of a Ruger Old Army  with R&D cylinder.
                      Beerbelly

[Luckyducker]

I was building a full power load for my Vaquero 45Colt with 335 grain LBT GC bullets over H110 in Starline 454Casull brass and until I pushed them to my limit of recoil the velocity was all over the place.  At a charge weight of 23 grains the chrono was giving 1140 to over 1300 ft/sec, with one round showing 1408 but I don't know if it was an accurate measurement.  When I increased the charge to 23.5 the velocity leveled out to 1276 to 1301 ft/sec with most of them running into the 1290s.   I just recently bought this revolver and started with this bullet but will find some lighter bullets and milder loads to shoot for pleasure, as I can assure you the load above will not deliver any pleasure but will git-er-done on about anything that breathes.

[Sweetwater]

FWIW - In my 7.5" Ruger Bisley:

Herco 8.5gr 260grLeeCast 900fps ES=24 (less and more ranged from ES=55 to ES=94)

Blue Dot 16gr 260grLeeCast 1300fps ES=32

W296 21gr 335grWLNGC(castperformance) 1100fps ES=30

I also found that changing from my 260gr Lee cast bullet to my 250gr Lyman#452424 could change the ES by a significant number, but not hurt my grouping any - open sights - offhand - 50ft. (winter range)

Regards,
Sweetwater

[markp]

I increased the load to 9.2 grains of unique. Velocity was a 5 shot average of 930 fps.
Variation also closed a good bit. 



Happey Trails

[markp]

I also loaded some with 7.3 grains of Unique and got an extreme spread of 48. This is out of a Ruger Old Army  with R&D cylinder.
                      Beerbelly

Beerbelly  what  primor  and what velocity did you get?

[beerbelly]

I was using Rimington primers, they were all I could get. I had a high of 887 FPS, a low of 839 FPS with an average of 856 FPS.  This is with my cast bulletts out of a lee mold that is suppose to thow 255 grain bullets . They actualy wege 250 grains, made of wheel weights.
                                                 beerbelly