20BR Load Development Results

[Big Al]

I managed a couple of hours this afternoon to try what I hoped would be my final load for 39r SBK's in my 20BR. I have spent what seems like ages on the 55r Bergers and as things stand Ive got things down to 1/2" or less but on Thursday I decided to have a look at the 39 SBK's as I was getting frustrated with the 55 Bergers.

 

I started with seven charges of N550 and having found that the 55r Bergers liked to be jumped some 0.130" I set the SBK's up the same just to see how they liked it. I think this seems like a crazy distance to be jumping bullets but it seems to work, initial results were as follows;

 

31.0 - 1.00"

31.4 - 1.00"

31.8 - 0.75"

32.2 - 0.75"

32.6 - 0.50"

33.0 - 0.35"

33.4 - 0.30"

 

As you can see the faster I pushed the bullets the better the groups were getting and no pressure signs at 33.4 so I went back home and loaded another three rounds at 33.4 and an extra three at 33.6 - after shooting both again I got 0.30" again but from both charge weights which was really encouraging. Today I decided to load up twenty rounds at 33.5gr in the hope that this would give me 0.1gr of leeway either side of my target weight and still give me the accuracy I wanted.

 

These were my first shots today and then I put the gun away.

 

 

The top three were was my first group at 100yds which at 0.25" was a great result, the others were at 200yds this one was 0.5" including the obvious flyer. My final charge of 33.5gr of N550 was chromo'd today at 3920fps with an ES of 16fps, this is from a 26" LW barrel. I appreciate what some say about three shot groups and repeatability but this isn't a competition gun so Im very pleased with these results as they are and it will give me great confidence going forward.

 

Next its time to verify my drops out to 400yds and set up my Shooter app to correspond with my real world data and then the local crow population will be in for a hard time. I think a little bit more tuning with the big 55's will have me in the same ballpark and with half the drift of the SBK's I will have the long range rifle I wanted just in time for the spring

[22cf]

I used the 39 SBK's in my 20Prac, they generated the tightest groups I have ever generated, every groups was sub 0.25" at 100yds. If I were you I would try a few loads with only a 5-10thou jump.

[247sniper]

Good going Al and good write up buddy.

 

What twist rate is you rifle?

 

It looks like you have found your optimum charge weight, you could fine tune the vertical stringing by seating depth if you want to chase crazy accuracy ;-)

 

Keep us upto speed on how you get on bud.

 

I was vaping rabbits at 620 yards with mine last week end ;-)

[Big Al]

I used the 39 SBK's in my 20Prac, they generated the tightest groups I have ever generated, every groups was sub 0.25" at 100yds. If I were you I would try a few loads with only a 5-10thou jump.

 

Yes I will try a much smaller jump at some stage but then again with results like this its questionable if its really worth the time and effort? I only went with this long jump as it was similar to that of the 55r Bergers.

 

If I was to bring the bullets some 0.120" forward I guess my pressures would drop and my load data would become invalid?

[Big Al]

My barrel is a 9 twist Steve, these Bergers at 3500 compare very favourably with 75gr Amax at 3300.

[garyw]

n550 in a 20br-order another barrel.!the 20 br is overbore as is- with the powder your using it will eat that barrel up fast.

[Big Al]

n550 in a 20br-order another barrel.!the 20 br is overbore as is- with the powder your using it will eat that barrel up fast.

 

Someone else said that to me very recently as well Gary.

 

Im using N550 because the previous owner who also built the rifle had used it for his load development and then limited shooting, his shot count was only 200 when I bought it, I am now at 400 after a lengthy load development. The bore was scoped last week by the guy who built the rifle and he said it looked in good nick. Ive heard you say before that the 20BR is overbore but Ive also read some stuff on American sites that suggest in the real world the cartridge doesn't actually behave that way and barrel like is decent so long as your not pushing well over 4000fps.

 

Barrel life is a concern for me since my round count is now 400 or so, Im not looking for 3000+ shots from a rifle like this but I would hope to get 1500 which would last me a good while considering the rifles application.

 

Whats the problem with N550, I assume its something to do with it being double based?

[gbal]

Al,Laurie has often explained this series of powders from Vihtavuori (the 500 series) in some detail.

In a sentence,they are single base powders (like N150) with an addition of nitroglycerine;

modern powders are more complex,and may have 'burn cooler' coatings etc-the V 100/500 ranges do allow comparisons-500 burn slower,may need more powder for fps gains,but less wear is very unlikely.

g

[Sherlock]

Post below

[Sherlock]

 

Someone else said that to me very recently as well Gary.

 

Im using N550 because the previous owner who also built the rifle had used it for his load development and then limited shooting, his shot count was only 200 when I bought it, I am now at 400 after a lengthy load development. The bore was scoped last week by the guy who built the rifle and he said it looked in good nick. Ive heard you say before that the 20BR is overbore but Ive also read some stuff on American sites that suggest in the real world the cartridge doesn't actually behave that way and barrel like is decent so long as your not pushing well over 4000fps.

 

Barrel life is a concern for me since my round count is now 400 or so, Im not looking for 3000+ shots from a rifle like this but I would hope to get 1500 which would last me a good while considering the rifles application.

 

Whats the problem with N550, I assume its something to do with it being double based?

 

 

Hi Al. I think 1500 shots of top accuracy it is unlikely that you shoot a 55 grn Berger bullet at 3500 fps using a double base powder.

Accurate Barrel Life Inidcator Program suggests around 900 rounds of best accuracy.

That would also confirm a friend of mines experience of the 20 BR - when his barrel was totally shot out in 1100 rounds. ( mind you - he ran his loads HOT)

 

ATB

S

[Big Al]

Mmm, Im not liking the sound of this guys. Will changing to N150 or similar give me much more life, if so how much?

 

Im running the 55's at 3500 and the 39's at 3920 which is less than they could be run.

[247sniper]

That's what put me off the.20 BR. .. I want more than 1000 shots from a barrel.

[Finman]

And, looking at the speeds for the 39gn SBK, you can get these out of a .204 Ruger with considerably less powder and, subsequently, barrel wear...Perhaps why the .20BR is defined as 'overbore'?

[gunnery]

I told you Al 20 tac will be the gun to go then .260 or 6.5 x 47 for long range stuff good barrel life on both those calibres

[Ballistic Hamster]

Had a .20br using 39 g blitzkings shot well did around 3975fps using n140 good out to 600yds not tried 55g ,

moved on to 22br 75 Amax 5 barrels later using n140

[gbal]

Had a .20br using 39 g blitzkings shot well did around 3975fps using n140 good out to 600yds not tried 55g ,

moved on to 22br 75 Amax 5 barrels later using n140

BH: "5 barrels later'' sounds like it's relevant to 'barrel life' in the 22BR-or was in in 20BR-do you have any numbers?

[Ballistic Hamster]

No maxed out on range and potential 3000 rounds on .20br , moved on to .22br and changing barrels about every 3500 rounds because the 75g Amax can be push well out on distance and ballistically the .22 br is in my opinion one of the best .22cf there is , as BD can vouch for :-)

Also had a 20x47 satan a necked down 6x47 Swiss match case to .20 satan one after Bruce potts built by Steve bowers using a 50g burger doing 4000fps that was a barrel burner only 800 rounds :-(

By the way gbal have you shot or done any load development in either .20br or .22br ?

[Borisserge]

Al, you have a load, so options I see are you continue you as you are with your load and shoot your quarry, or spend another 100 odd rounds developing a loads that may eek you another 150-200.

Just another idea...keep the rifle and load as and enjoy, and invest in a larger cal for longer ranges........

[gbal]

BH thanks for that-the smaller BRs may give acceptable barrel life,perhaps,if velocities are kept less than absolute barrel burn levels,but if not......as ever....no free lunch.

[garyw]

AL =best powder in the br case for up to 70gn bullets imo is/are n135-h322 or even varget. i have a .22br that has 1400 down the tube and has a small amount of fire cracking but still holds velocity and accuracy im using n135 with 50vmax or 40gn blitzkings depending on what is getting dealt with.h322 also used but nearly out of it.

i also tried bergers but couldnt get what i wanted in a hurry -so gave up no point chasing something that isnt there.

[Big Al]

And, looking at the speeds for the 39gn SBK, you can get these out of a .204 Ruger with considerably less powder and, subsequently, barrel wear...Perhaps why the .20BR is defined as 'overbore'?

 

Yes a 204R can run those speeds but it will be pretty much flat out so no guarantee of there being a good accuracy node at those speeds whereas the 20BR has plenty left if needed and no signs of pressure. That said the main reason for the caliber choice was to run the 55r Bergers and a 204R cannot do that at speeds of 3550 which is comfortable for the 20BR.

 

The 20BR was an itch I needed to scratch, its been a learning curve which Im happy to have taken, I guess the proof of this particular pudding will be if once the barrel is shot out I choose to put a new one on or go a different caliber - time will tell

[Big Al]

I told you Al 20 tac will be the gun to go then .260 or 6.5 x 47 for long range stuff good barrel life on both those calibres

 

Ive just bought myself a nice 20Tac, apparently the guy who sold it to me was spotted in a motorway services on the M6 last Saturday afternoon weeping into his coffee!

 

I will shoot this 20BR out first them maybe come down to Diggle and see what these bigger guys are all about

[Big Al]

Al, you have a load, so options I see are you continue you as you are with your load and shoot your quarry, or spend another 100 odd rounds developing a loads that may eek you another 150-200.

Just another idea...keep the rifle and load as and enjoy, and invest in a larger cal for longer ranges........

 

I had this discussion tonight with a friend, realistically this rifle will be lucky to shoot 200 rounds a year so it doesn't really make sense to waste time on more load development on the off chance of getting another couple of hundred rounds. Its all if's and but's whereas I now currently have a very accurate load I can enjoy.

[gunnery]

 

Ive just bought myself a nice 20Tac, apparently the guy who sold it to me was spotted in a motorway services on the M6 last Saturday afternoon weeping into his coffee!

 

I will shoot this 20BR out first them maybe come down to Diggle and see what these bigger guys are all about

Watch you don't get lost Al coming this far south

[Big Al]

n550 in a 20br-order another barrel.!the 20 br is overbore as is- with the powder your using it will eat that barrel up fast.

 

My rifle is now up to 700 rounds, I had it bore scoped yesterday and was told it is in very good condition with only minimal wear on the throat.

 

The gunsmith felt that the current wear in relation to the number of shots fired was very good and that the 20BR was far from a barrel burner.