Home Forums Hunting & Shooting BPCR Running BPCR across a chrony??

Still in my infancy here, so are there any techniques to getting consistent readings. I've chronied a ton of smokeless units, but not BPCR or muzzleloader rounds.

With all the particulates, wads, patches, and such, how far from the muzzle should one set up his unit.

Also, I've not noticed ballistic coefficients listed anywhere for the popular BPCR bullets. Do folks use that type of info in BPCR, or do we assume the slugs have the same coefficient as a cinder block. I've found the various ballistic calculator programs quite accurate when working up trajectory charts with modern arms and slugs, and have hopes of making some of the long range dialing in a bit easier with my 45-90. Thanks, 1Minute

I set mine up at about 10 ft. I also have some cardboard taped over the screen sensors to protect them from the wads.

We use BCs a lot but the really aren't that much use. You can figure that most bullets have a BC of around 0.45 if you are talking about a .45-70-535-550 gr bullet. That might be off by a few tenths but it will get you on target easily enough out to 1000 yds. If you want to get really anal about it then you can measure your own BCs which makes a bit of sense since they are velocity dependent. But again, it's only an approximation. The BC changes in flight quite a bit as velocity changes anyway.

If you post the bullet you are using, chances are we can get a good approximation of its BC pretty easily. If you add your muzzle velocity and your 100 or 200 yd zero, and sight radius, chances are we can work out sight settings without too much problem at all.

Brent

Brent: Thanks for the feed back. Being a newbie with about 20 rds of experience, I've not chronied anything yet, hence the prior question. Presently I'm pouring RCBS 405 Gov's that, from memory, are weighing in at about 419 or 20. Got a wonderful 100 yard group that would disappear beneath a quarter on my first effort, but don't really have it zeroed at 100 yards yet.

I have about 15 rds loaded, and on the next outing wanted to run about 5 across the chrony, and then try to dial it in. With a little ballistic data in hand, I thought I might start reaching out after that, and a BC would refine the initial guess work.

Subsequent plans are to go to a Postell at about 530+ grains, stock up on some powder, and start over with an objective of really reaching out.

This "work thing" seems to get in the way though. About this time next year, I might just cure that. Thanks, 1Minute

Well, a 405 is a darn small bullet. I'll if I can dig up a bc for it. Probably in the 0.40 range I would think. Venturino and Garbe's book may have it listed. I'll check tomorrow.

But for long range - if that means 800-1000 you definitely need that heavier bullet and a postell is not a bad choice at all.

Brent

I like to set my chrony out at 15 ft for smokeless and black loads.
The ballistics calculator at handloads .com gives pretty good numbers, altho it won't go past 1000 yds.
Johnboy posted a link either on bpcr.net, or the shiloh board to another online ballistic calculator that he thinks is pretty good.
My neighbor Doc and his old trap door do a pretty fair job of smackin most buffalo steels at 750-800 with the lyman 425 gr government bullet and a case full of 2f.

1minute,.....pm me,.....would like to send you some 550s to give a WHIRL,.....

Here, in my home district,we've just confused and agitated ourselves,....with formalizing BCs and SDs,....yada,.....

so embarrassing to see a "Thrown Together load" blow the shorts offa' the "Magic Load".......

that said ,.....the CONFIDENCE that one takes to the line , running wrung out and doped out loads,.....is certainly not without merit.

I got no more faith in "Ballistic Programs" in our BPCR velocity realm than I do in Chucky Schumer reducing the price of powder,.......

bleak outlook,.....that.

GTC

Guys: A follow question or two. Has anyone seen a pattern of increasing/decresing velocity as one starts through a string beginning with a clean barrel? Is there an approximate number of rds needed before things settle down. What's the general spread in velocity from round to round once things settle down?

Didn't chrony my unit this weekend but did shoot about 9 rds with apertures front and back. I'd been using a post up front previously. An interesting sight picture that looks like it should be quite accurate on properly scaled targets. I was still working on zeroing at 100 yards and did not generate any groups worth talking about. About 1 more minute right and 0.5 up and I should be tickling the bulleye. Man, this is fun!!! Wish some one would hire me to do this full time. 1Minute

In short, No.

If someone paid you, it would be work and then it would cease to be fun. Be glad for the hobbies you have and avoid making them into vocations.

Brent

That is likely true. I've had requests to tie flies,reload, and pursue wildlife photography commercially. I have a passion for all three, but sitting down and knowing I'd have to run off 5 gross of Royal Coachman flies might take the fun out of it.

Just dropping by, don't know much about BPCR, but I have a question.

1minute -

I have an RCBS 405 grain mould. So ... am I to understand you're shooting a gas checked bullet with blackpowder?

Curious .. how does that work out? Seems not necessary, but could it also be detrimental in some way? Any of the more experienced BPCR shooters want to comment? I need edjmacated on this.

Tom

PS: Howdy, Brent!!

T O M: I too posed the same question a couple months ago as the RCBS 405 Gov bullet does appear to be configured for a gas check. The general thought train here and over on the Shiloh forum was that with black powder there was no need.

If going smokeless in a modern arm, however, several thought the gas check was a good idea. Some day I may give that slug a try in my Marlin 1895 45-70, and I will likely start with the check there.

1minute and T O M -

In my 45-70 Marlin Cowboy rifle I shoot the Lyman 405 gr bullet cast from wheel weights and powered by smokeless. I do not use a "gas check", at least not in the normal sense. I do use a card wad (0.035" thick) under the base of the bullet and lube it as if I were shooting BP. The Lyman bullet (#457193) does not have provisions for a gas check, therefore I substitute the card. The primary reason, IIUC, of a gas check, whether it be copper or card stock, is to keep the cast bullet base from becoming distorted and/or cut from the force of the powder being "lit up". BTW - I have not chronyed a load from my Marlin, but would take an educated guess (by load chart interpolation) my loads would be in the 1600 fps range. My 45-70 single shots loaded with real BP and the 500 gr Gov't bullet (cast 30:1) are in the 1200 fps range and those have been run over a chrony.

Hey Tom, I hope all is well out there.

I don't think a gas check is a plus or a minus when shooting black. I've never shot gas check and they are illegal in the competitions that I shoot so I have never tried them. If I had such a mould and I wanted to shoot with it, I would put the checks on. Shooting a gas check bullet w/o the check might give you some accuracy and maybe leading issues.

Brent

Brent -

Things are good here. Ploddin' along. Focus right now is mostly on my daughter, she's graduating from college. Double major, already got top honors from one department, and gets inducted into phi beta kappa next weekend. You can imagine how proud I am of her. Her graduation brings interesting changes for all of us.

I haven't tried a GC design without the check but my expectation is you're right. At best it'd be a lumpy boat tail. Lot of times with a flat base, the bottom "band" is thicker to support the pressure. Might blow-by the thinner bands if they had to support the pressure and give bad leading. Then again, BP might act different than smokeless. Dangerous of me to assume too much. Well, maybe not dangerous, just foolish.

Take care.

Tom

Brent how fast can the 45-70 push a 550 grain bullet?

Don't know about a 550, but 73 grs of goex 3f express will do 1275, from one of my 45-70's

What wieght bullet?

530 gr

I can't say as I have not shot my .45-70 much and never over the chrony.

I have loads for my .45-100 that move a 550 Sharps Long range bullet at 1333 fps and a load for my .45-90 thave moves the same bullet at 1418 fps.

Brent