Berger 55g FB bullets

[TommyD11730]

Hey Guys hope your doing well.

I have a pretty good load for my 12FV worked up. Shooting 69smks @ 200y mostly.

Thinking of trying some 55g flat base bullets. Just wondering if anyone has used then with good suscess.

Thanks!

[NF1E]

I use 55 gn Bergers over 25 gn of IMR-8208 with fine results.

[CFJunkie]

I have a 12 FV .223 and loaded #22810 Berger 55 gr Flat Base bullets with N133 averaged 0.343 shooting 5-round groups at 100 yards.

For a comparison, 5-round groups with the same rifle at 100 yards has averaged:
0.289 with 69 grain Sierra SMK # 1380 with N140 powder for 32 groups
0.287 with 69 grain Sierra TMK # 7169 with IMR4166 powder for 96 groups
0.283 with 77 grain Sierra SMK #9377 with N140 powder for 40 groups
0.279 with 77 grain Sierra TMKs # 7177 with IMR4166 for 205 groups.

My 12 FV likes heavy bullets and even though it has a 1:9 twist and isn't supposed to stabilize 77 grain bullets, it shoots 77 grain Sierra bullets better than any other bullets.
I wouldn't be afraid to try some heavier bullets with powders that are a bit slower - like those that I shoot im my 0.308s.

[TommyD11730]

I'm still shooting 69s on the exit time you suggested (with Varget). Maybe I'll plug 77s into quick load and see what it would take to get the same time.

Thanks 4 your hard work and documentation CF.

[TommyD11730]

Thank you for your reply sir. (NF1E)

[CFJunkie]

TommyD,

Hope you have as much success with the Sierra 77s as I have had.

Even if you don't, the 69s seem to do really well also as you probably have already determined.
I tested some 69 gr RMR HPBT bullets on Monday that a buddy just bought 2,000 of and wanted my opinion of them.
The loads set up for the exit time for our 12 FVs averaged 0.283 for 12 groups which is about the same as for 69 SMKs at that exit time.
The average listed above for 69 SMKs includes some loads off the exit time (I always have to check to see if it makes a difference.)
The Sierra 69 SMKs on exit time averaged only 0.001 smaller than the RMRs which says they are essentially the same.
It probably means that the shooter (me) can't do any better no matter how good the bullets are.

500 count of 69 grain RMR bullets cost $80 (16 cents a bullet) so they seem to be worth the money since I spent more than that on a recent purchase of 300 69 grain SMKs (31 cents a bullet).
The lower cost for 2,000 count 69 grain RMR bullets gets the cost down to 14.2 cents a bullet.

[Mr.Snerdly]

^^^What are RMR bullets? That sounds like an excellent price and if they shoot well, what's not to like. I just bought 500 69 grain SMKs for $125, plus tax and shipping. I don't feel there is enough difference between the 69 and 77 to pay the price difference but I understand if you are going for the last little bit of accuracy why some will.

[Robinhood]

^^^What are RMR bullets? That sounds like an excellent price and if they shoot well, what's not to like. I just bought 500 69 grain SMKs for $125, plus tax and shipping. I don't feel there is enough difference between the 69 and 77 to pay the price difference but I understand if you are going for the last little bit of accuracy why some will.


That is back to the regular price. Nice purchase.

[CFJunkie]

https://www.rmrbullets.com/shop/bullets/rifle/224-5-56mm/224-69-gr-rmr-jacketed-hollow-point-boat-tail-3-gun-hunter-bullets-new/

Link to RMR web site

[Texas10]

TommyD,

Hope you have as much success with the Sierra 77s as I have had.

Even if you don't, the 69s seem to do really well also as you probably have already determined.
I tested some 69 gr RMR HPBT bullets on Monday that a buddy just bought 2,000 of and wanted my opinion of them.
The loads set up for the exit time for our 12 FVs averaged 0.283 for 12 groups which is about the same as for 69 SMKs at that exit time.
The average listed above for 69 SMKs includes some loads off the exit time (I always have to check to see if it makes a difference.)
The Sierra 69 SMKs on exit time averaged only 0.001 smaller than the RMRs which says they are essentially the same.
It probably means that the shooter (me) can't do any better no matter how good the bullets are.

500 count of 69 grain RMR bullets cost $80 (16 cents a bullet) so they seem to be worth the money since I spent more than that on a recent purchase of 300 69 grain SMKs (31 cents a bullet).
The lower cost for 2,000 count 69 grain RMR bullets gets the cost down to 14.2 cents a bullet.

CFJunkie,

I am helping set up a shooting buddy to compete in light varmint for score at the local club, he's shooting a stock Savage 223 model 10 and doing well. We've been using 69 SMK's so far with Varget, but I'd like to check the load against your exit time load. Can you provide a link to your article on exit time? I just bought RMR 69 grain bullets to try out and don't want to waste precious components if it can be helped.

You've really got your Savage dialed in and the 12FV's have proven to be remarkably accurate right out of the box. MY son has shot several groups in the zeros at 100 yds with his, but the initial accuracy has fallen off a bit. I'm looking to recapture the magic!

[CFJunkie]

Texas10,

First, I don't even start to worry about exit time unless the rifle will shoot around 0.4 inches on average.
It sounds like your son is already shooting well below that kind of average.

The article that got me started is all theory and doesn't give particulars for a specific rifle.
I did write an article that describes my work in testing the theory and the results, but it is not on the internet.
Send me a PM with your e-mail address and I'll e-mail it to you.

I did develop a spreadsheet that lets you enter your barrel length and the reflection velocity of the type of steel so you can figure out the exit time you should plan for.
It also has a added feature to calculate the effect of a muzzle brake as well.
I can e-mail that to you as well.

However, to calculate anything, you need to know the type of barrel steel that you have because each type of steel has a different reflection time depending upon the amount of carbon.
Then you need to measure your barrel (the length listed in the rifle specs is sometimes not the actual length from bolt face to muzzle. One of my Savages was long by 0.125 inches.)

Reflection velocity for types of steel.
Generic barrel steel = 18,916 fps (old steel used around 1900 to the mid 30's to WWII) My Remington 700 as well.
.3% Carbon steel = 19,107 fps (Savage barrel steel - non-Stainless)
4150 or 4140 stainless or CV steel = 19,969 fps
Generic Stainless steel (Materials Manual) = 20,000 fps
416R Stainless steel = 20014 fps

From that information, you can calculate how long it takes a reflection to get from the chamber to the muzzle.
Then you double that time to get the reflection back to the chamber.
Since you want the reflection at the chamber, you only care about the even reflections.

The theory says the best performance occurs when the reflection is at the chamber because it reduces the harmonic vibration at the muzzle and keeps the crown the tightest. The reflection is the barrel swell caused by the initial blast of firing which migrates down the barrel and reflects back to the chamber. and does it again and again.
Since you want the reflection at the chamber, you only care about the even reflections.

Most of my barrels calculate out to 10, 12 or 14 reflections (depends upon barrel length, and the pressure curve for the powder you are using).
Most powders fall around the 12th reflection for a Savage 22 to 26 inch barrel with normal powders, but some powders are particularly energetic.
The reason it takes so many reflections is that the bullet takes between 1 to 1.5 msec to get down the barrel depending upon the barrel length and how fast the powder burns and builds pressure.
Different powders have different burn rates and pressure curves and the bullet doesn't begin to move out of the neck until the pressure gets great enough to force it out of the neck. The bullet then accelerates down the barrel based upon how the pressure is sustained as the powder burns.

Some shorter barrels or regular length barrels get to Pmax at 10 reflections depending on the powder.
Slower powders may get there in 12 reflections in a short barrel.
I use QuickLOAD and it calculates the bullet exit time.

Once you know the powder and the charge that gets pretty close (and stays under Pmax), you can adjust your seating depth and trim length to get the exit time right on.
I find that if you stay around the exit time +/- 0.005 msec., you get about the same group sizes - 'shooter induced variation' masks seeing any more detail than that.
If you load for the reflection to fall at the muzzle, your group sizes grow by 0.060 to 0.1 inches on average.

This might help you get an idea of what the exit times are for a Savage rifle based upon steel and barrel length:

A Savage 24 inch Standard barrel (19,107 fps) has an exit time of 1.256 msec. at the 12 reflection, 1.465 at the 14th reflection and 1.047 at the 10th reflection.
A Savage 24 inch 4150 Stainless barrel (19,969 fps) has an exit time of 1.201 msec. at the 12th reflection and 1.402 for the 14th reflection.
A Savage 22 inch standard barrel has an exit time of 1.154 msec. at the 12th reflection and 1.343 msec. at the 14th reflection.
A Savage 26 inch Standard barrel has an exit time of 1.361 msec. at the 12th reflection and 1.587 msec. at the 14th reflection.