What BC for 22LR

[RedDawn]

When you start chasing impacts at varying distances MV and BC are useful tools in part of an equation. Do you run with manufacturers BC or do you adjust accordingly to your MV reads and confirmed impact ? You would think the BC is a given and MV would change somewhat based on the length of barrel. What BC do you use for Center X , SKRM , Eley Match or Edge? What method works best for you ? Is the given BC by manufacturer a win or your own custom number ?

Thanks for the input and help in this spiral

 

[Matt_3479]

Im using a g7 bc of .064 with dope to 350 yards. I’ve connected out too 430 but shooting hell Mary’s on crazy winds. Will be retesting at 400+ again next available weekend that isn’t high winds.

 

[DFOOSKING]

b.c. is a function of velocity....so it can change slightly with different speeds. How much I honestly can't say. You can bench race it if your curious.

At somewhat close ranges its probably not as critical to be nuts on with b.c.

But to make 300yd and beyond data line up day to day it will be way more critical.

I start with manufacturers stated b.c. and velocity (I don't own a chrono...otherwise I speed check it initially). If I can't find a published b.c. I just use .125 G1 to start. I've seen some ammos above and some below that spec.

Shoot the ammo at common yardages (50, 100, and 200) and write down the hard data. You don't really need an app for that if you have any relative experience shooting .22LR.

Then I make my app match my hard data.

Hard verified data trumps any b.s. your app is trying to spit.

Having a chrono obviously gives you a solid point to somewhat base your software editing to.

I'm a cheap broke fuck....take my methods with a grain of salt.

 

[littlepod]

As others mentioned, BC is based on velocity... at 50 yards, the BC of say SK/Lapua is published at .172. By 300 yards, the BC is down to .11 due to the velocity being a lot slower.

Generally if you're not doing a custom curve (varying BC per velocity) then .135 usually gets you to around 200 pretty well.

 

[RedDawn]

Yes I do start with given data shoot my 50yd 0 group move to 100 and then 200 but I can’t use the given BC using G1 that works well with most any other make when I add and use the Magnetospeed MV of the projectile.

Confirmed
Eley Club: .130 G1
SKRM : .140 G1

I’m shooting in a CZ 457 Pro Varmint 16.5
Also using the Kestrel 2700’

 

[BLJ]

Are you all getting these BC numbers from shooting and then correcting on your ballistic calculator or has someone done the work and published it somewhere? I was discussing this with a friend yesterday. I'm really curious about solid BC numbers out to 350. If that's even realistic with the ammo I'm shooting.
I'm shooting SK Standard Plus from a 16.5 standard chamber 457. I have access to a Magneeto Speed and Kestral.
I'm also curious about weather effects on BC. Rimfire BC seesms to toe the line of marginal from the get go. Any idea how temp., humidity, or barometric pressure effect BC? At say 250-300 yards? Or is the BC so marginal to begin with that it doesn't matter? Thanks.

 

[RedDawn]

I talked to other competitors in matches about the BC they use and compared to what I’m using and they are similar but all seem to be slightly different. I tried using the manufactures BC but it’s not close to my confirmed impacts when I put my MV in the kestrel. So I was wondering if everyone adjusts the BC to fit or not.

 

[021411]

Shot a PRS Rimfire match yesterday using Eley Semi-Auto out of my RimX. Before the match I was shooting steel around the field to check my dope. Using the avg velocity of 1123 (Magnetospeed) and G1 0.140 I was making impacts at 250 on a 12” plate. I didn’t have to tweak any numbers. I shot well throughout the entire match and only dropped 9 out of 80 so the data was good.

 

[DFOOSKING]

Are you all getting these BC numbers from shooting and then correcting on your ballistic calculator or has someone done the work and published it somewhere?

I was discussing this with a friend yesterday. I'm really curious about solid BC numbers out to 350. If that's even realistic with the ammo I'm shooting.

Some run one b.c. profile on their app.

But I've heard others make multiple profiles for a single gun.

A profile for say shooting +200 yards.

And a profile for shots under 200 yards.

It allows them to better edit the software to the results as the solver's software isn't designed for the dogshit performance of .22LR necessarily.

I personally run only one. But I don't really care to shoot much beyond 300. If a match requires it....so be it. But I'm not shooting King of the .28 Mile where they are intentionally stretching their shots out.

I'm shooting SK Standard Plus from a 16.5 standard chamber 457. I have access to a Magneeto Speed and Kestral.

SK states that bullet is rated at .130

I believe its written on here somewhere...

I would start there and your solid MV. You can edit the b.c. then if needed.

I'm also curious about weather effects on BC. Rimfire BC seesms to toe the line of marginal from the get go. Any idea how temp., humidity, or barometric pressure effect BC? At say 250-300 yards? Or is the BC so marginal to begin with that it doesn't matter? Thanks.

Think of it as environmentals effect air density. The density of the air effects the bullet's speed as it fights through it. Speed then effects b.c.

Tad easier way to wrap the mind around it I think than worrying about each one's effect individually.

I do not tend to chase b.c. much as I probably should. I spend more time getting solid zeros after changing ammo lots and getting drop data to 200 and 300...then get MV from it.

My new plan going forward is simply make a new bullet profile every time I buy new lot/brick and simply label it that lot #. I find it easier to track than going back 9 months when I spent two weeks running some oddball round for whatever reason then having 9 profiles stacking up. And you never know when you might fall into a prior lot.

 

[BLJ]

It’s interesting that you’ve talked to people with an under 200 yard profile and an over 200 profile. That’s where consistency kinda starts getting finicky for me. It doesn’t drop completely off, but out of 10, sometimes 4 shots will make me wonder. And that’s only sometimes. That’s where the thought of the weather started to come into play.
I’m probably wrong, but I think the dogshit performance like to you said starts to make things really difficult beyond 200/250. Just the nature of the ammo we’re dealing with. Then throw some worse than average environmentals in there and it goes sideways quick.
Shooting more and taking better notes may be where I need to go with it. Thanks.

 

[chevy_man]

First, start by using the RA4 bc curve. G1 is a little off, g7 is way off.

Go shoot with a Chrono and true the bc according to your actual drop.

 

[BLJ]

I plan on shooting over a chrono soon.

What’s the RA4??

 

[Manning5R]

RA4 is the rimfire specific drag curve. Similar to, but not the same as G1.

I generally run .12-.13 RA4 BC for SK, Lapua and RWS round nose bullets.

 

[6.5SH]

I plan on shooting over a chrono soon.

What’s the RA4??

You can convert among the the different drag functions at JBM

JBM - Calculations - Drag Function Conversion

www.jbmballistics.com

 

[DeathBeforeDismount]

I use .173 for SK+ and get reliable hits out to 300 at PRS22 matches. Not many other shooters are getting the same hit% at longer distance as I am.

 

[littlepod]

I use .173 for SK+ and get reliable hits out to 300 at PRS22 matches. Not many other shooters are getting the same hit% at longer distance as I am.

I don't want to be naysayer/disbeliever but I am pretty certain a flat .173 bc for SK+ without any other truing / DSF is going to be inaccurate for hits out to 300.

 

[b6graham]

.132 at sea level for me out to 600y

 

[DeathBeforeDismount]

I don't want to be naysayer/disbeliever but I am pretty certain a flat .173 bc for SK+ without any other truing / DSF is going to be inaccurate for hits out to 300.

I did adjust the DSF but it was very minimal and only at 200 after zeroing at 50. Used a kestral for everything.

My first match i placed well out of like 50 shooters and beat a bunch of pro-prs guys.

Went back and looked and I got 7/8 on the 300 stage. Only 5 guys cleaned it.

I haven't shot past 300 with it yet.

 

[6.5SH]

I did adjust the DSF but it was very minimal and only at 200 after zeroing at 50. Used a kestral for everything.

My first match i placed well out of like 50 shooters and beat a bunch of pro-prs guys.

Went back and looked and I got 7/8 on the 300 stage. Only 5 guys cleaned it.

I haven't shot past 300 with it yet.

What size targets at 300?

 

[littlepod]

I did adjust the DSF but it was very minimal and only at 200 after zeroing at 50. Used a kestral for everything.

My first match i placed well out of like 50 shooters and beat a bunch of pro-prs guys.

Went back and looked and I got 7/8 on the 300 stage. Only 5 guys cleaned it.

I haven't shot past 300 with it yet.

If you're using DSF then basically the whole BC is pointless (well not pointless, but you're basically designating the curve + custom BC using the DSF points).

If you don't have a Kestrel and you're using a single BC value, then .135 / .13 is basically what has worked well for LRN. I also use a Kestrel, and I just use the AB Custom Curve for Center-X and it has worked out to 350 w/o any adjustment (no DSF).

 

[DeathBeforeDismount]

What size targets at 300?

Not sure but maybe 10-12inches. So about 2.5-3moa, which seems reasonable for .22 based on everyones hit%. It was a prone stage too so it wall all wind and elevation calls.

 

[DeathBeforeDismount]

If you're using DSF then basically the whole BC is pointless (well not pointless, but you're basically designating the curve + custom BC using the DSF points).

If you don't have a Kestrel and you're using a single BC value, then .135 / .13 is basically what has worked well for LRN. I also use a Kestrel, and I just use the AB Custom Curve for Center-X and it has worked out to 350 w/o any adjustment (no DSF).

Ok that makes sense. I use a Kestral Elite for everything so whatever it tells me, I roll with. Even better if there is a Custom Drag Curve from AB, I find them to all be spot on out to 14-1500.

Are you shooting any of the 22 matches at Lead Farm?

 

[Hardpan]

If you're using DSF then basically the whole BC is pointless (well not pointless, but you're basically designating the curve + custom BC using the DSF points).

If you don't have a Kestrel and you're using a single BC value, then .135 / .13 is basically what has worked well for LRN. I also use a Kestrel, and I just use the AB Custom Curve for Center-X and it has worked out to 350 w/o any adjustment (no DSF).

+1
I had a similar experience with SK Long Range Match and the custom curve, it was lined up perfect out to 310 yards. Center x for me out of my 12 T barrel was faster at 310 then the kestrel custom curve so I had to use dsf at 310 and adjust the elevation down. I will check dope at 375 to see if I need to adjust or if it still lines up that far.