6mm BR Load Conundrum

[Brillo]

I've posted this query on this forum because there isn't one specifically for bench rest.

I've just taken delivery of my factory class 6mm BR rifle. I made up 50 rounds of various loads to run in the barrel.

Now, I know you can't expect good groups when going through the run-in process but I did notice something odd.

 

I loaded 50 rounds for the process using 105 grain Berger VLD's (the barrel is a 1:8 twist so the bullet weight is correct) and used Varget, RL15 and Vhit N540 from 30 - 30.4 grains. I understand from stuff I've read that the velocity sweet-spot for the 6mm BR cartridge is about 2850 fps but I noticed I got best groups at about 2750 fps..

 

 

Any ideas what is going on. Any advice is welcome as I'm shooting at my first BR comp at Diggle next month.

[mole-e30]

Hi

 

I run a 6BR and found a nice accuracy node at 2910fps using the Berger 105 VLD, for powder I use Vit N150.

 

If you are going to do the 1000BR, try to get a bit more velocity out of the 6BR, it will pay dividends.

 

I would say that you have maybe got a low velocity sweet spot at 2750fps.

 

At 1000 yards at 2750fps you will need 32.5 MOA elevation (from 100 yard zero) and a 5mph cross wind will move the bullet 3.75 MOA, compare that with the same bullet but at 2910fps will give you 28 MOA elevation and 3.5 MOA windage.

 

I hope this gives you some food for thought.

 

Hope to see you at the 100 yard BR a week on Saturday.

 

Cheers

 

Bruce

[happyhunter]

Good topic Bruce,

having a 6mmbr built myself.

What brass prep did you do with the new cases?

 

Regards,

 

Simon

 

 

[mole-e30]

Simon

 

I will continue on here as although slightly off topic it may help the original poster........ Hope this is OK with you Brillo

 

New cases I check overall length then run them over a Sinclair Neck expander mandrel, load and then shoot.

 

After initial firing, I clean, neck size to give 1 thou grip, body size to bump the shoulder back 1-2 thou, then cut the primer pocket with a primer pocket uniformer (this cleans and uniforms the pocket)........ job done (I check case length and trim if necessary, but they dont grow very much).

 

Hope this helps to all.

 

Cheers

 

Bruce

[Brillo]

Simon

 

I will continue on here as although slightly off topic it may help the original poster........ Hope this is OK with you Brillo

 

New cases I check overall length then run them over a Sinclair Neck expander mandrel, load and then shoot.

 

After initial firing, I clean, neck size to give 1 thou grip, body size to bump the shoulder back 1-2 thou, then cut the primer pocket with a primer pocket uniformer (this cleans and uniforms the pocket)........ job done (I check case length and trim if necessary, but they dont grow very much).

 

Hope this helps to all.

 

Cheers

 

Bruce

Jees, there's more this game than I thought, but it adds to the interest. My wife always tells me I'm not happy with easy stuff and i think she's correct. Can't beat a good challege.

If it was easy everyone would be doing it.

Looking forward to meeting you guys at Diggle.

[skany]

Hi

 

have found that with every custom tube ive tried if it liked the bullet it shot them from the first time i tried to shoot a group!(within reason)

 

I havent been able to get near 2900 & to be honest of the 4x br users i know 2700-2850 seems to be the norm!

 

30.2g of vit 150 gives me 2850 ish & around 100fps ish over varget!

 

this is with a 27 " tube

 

the berger is a "fat bullet" in 6mm if i remeber with 2 normal 6mm bore sizes .236 & .237 some barrel manifactures do both options!

 

if its the berger they are more likely to shoot better in the .237 where as the lapuas & amax are slightly thiner & more suited to a .236 bore!

 

I went for a tighter bore for the Amax bullet!

 

works very well!

 

cheers Andy

[mole-e30]

Hi

 

I should point out that I am running a 29" barrel

 

Brillo your Savage barrel I believe will be 30" so you should have plenty of chance to get good velocity.

 

Like Skany I too found that Vit N150 got me significantly better velocity than Varget.

 

Powder charge is going to vary with the reamer design as the freebore will change the available powder space a fair bit, but mine has a short freebore.

 

Cheers

 

Bruce

[Brillo]

Hi Bruce,

 

My Savage is advertised as a 29" barrel, so it looks like N150 might be a good option for me too.

 

The measured COAL with the Berger 105 VLD is 2.344" and the rounds I made to run the barrel in were jammed 0.015" into the lands.

I started at this point because of an interesting conversation I had with someone at Diggle on the day I bought the rife, whereby it was stated that the 6BR can group best anywhere between jammed the bullet 0.015" into the lands up 0.070" bullet jump. So, apart from finding the right powder charge I also have to find the sweet spot for the COAL as well.

 

The method I adopted to find the best load and bullet jump combo for my other rifles was:

 

1. Shoot 3 rounds with powder charges increasing in 0.3 grain increments up to the recommended maximum with the bullet just kissing the rifling.

2. From the best groups, load and shoot more 3 round groups with powder charges 0.2 grains either side of the best.

3. From the best group's corresponding powder weight make more 3 round batches with the bullet seated away from the lands in 0.010" increments up to the manufacturers recommended seating depth.

 

In total this means at least 3 to 4 separate shooting sessions. It could be more than that because I have found you can get more than one set of 'best' groups in the initial test for different velocity nodes.

 

Any comments?

[garyw]

Hi Bruce,

 

My Savage is advertised as a 29" barrel, so it looks like N150 might be a good option for me too.

 

The measured COAL with the Berger 105 VLD is 2.344" and the rounds I made to run the barrel in were jammed 0.015" into the lands.

I started at this point because of an interesting conversation I had with someone at Diggle on the day I bought the rife, whereby it was stated that the 6BR can group best anywhere between jammed the bullet 0.015" into the lands up 0.070" bullet jump. So, apart from finding the right powder charge I also have to find the sweet spot for the COAL as well.

 

The method I adopted to find the best load and bullet jump combo for my other rifles was:

 

1. Shoot 3 rounds with powder charges increasing in 0.3 grain increments up to the recommended maximum with the bullet just kissing the rifling.

2. From the best groups, load and shoot more 3 round groups with powder charges 0.2 grains either side of the best.

3. From the best group's corresponding powder weight make more 3 round batches with the bullet seated away from the lands in 0.010" increments up to the manufacturers recommended seating depth.

 

In total this means at least 3 to 4 separate shooting sessions. It could be more than that because I have found you can get more than one set of 'best' groups in the initial test for different velocity nodes.

 

Any comments?

just forget about manufacturers seating depth -if your rifle is a mag feed load to the longest a.o.l you can enabling the rounds to feed -unless you find the sweet spot before that.and seating into the lands will work start nearer work out.

[The Gun Pimp]

Hi Bruce,

 

My Savage is advertised as a 29" barrel, so it looks like N150 might be a good option for me too.

 

The measured COAL with the Berger 105 VLD is 2.344" and the rounds I made to run the barrel in were jammed 0.015" into the lands.

I started at this point because of an interesting conversation I had with someone at Diggle on the day I bought the rife, whereby it was stated that the 6BR can group best anywhere between jammed the bullet 0.015" into the lands up 0.070" bullet jump. So, apart from finding the right powder charge I also have to find the sweet spot for the COAL as well.

 

The method I adopted to find the best load and bullet jump combo for my other rifles was:

 

1. Shoot 3 rounds with powder charges increasing in 0.3 grain increments up to the recommended maximum with the bullet just kissing the rifling.

2. From the best groups, load and shoot more 3 round groups with powder charges 0.2 grains either side of the best.

3. From the best group's corresponding powder weight make more 3 round batches with the bullet seated away from the lands in 0.010" increments up to the manufacturers recommended seating depth.

 

In total this means at least 3 to 4 separate shooting sessions. It could be more than that because I have found you can get more than one set of 'best' groups in the initial test for different velocity nodes.

 

Any comments?

 

OK Brillo, we all want to maximise on ballistics so, the first job is to find out what your rifle will 'take'. All rifles/barrels are different.

 

You do this by starting with your chosen powder and bullet - loaded off the rifling - and, using the 'starter' load from whatever loading manual you are using - increase your load by about 0.3gn at a time.

 

Fire each one (preferably over a chrono) and 'feel' the bolt lift, check the primer for flattening/cratering, watch the case-head for marking.

 

When you reach maximum, step back half a grain or so and find your accurate load by shooting three shot groups - adjusting the powder charge by say 0.2gn at a time.

 

Then, experiment with seating depth - until you get your very best grouping. Try a five-shot group just to be sure.

 

That's all there is to it. One session - providing you take your loading gear to the range. i usually prep. about 20 cases and take scales, powder, bullets, dies and press to the range. You can do this under cover at Diggle - we even have power for your electric scales.

[foxing2night]

OK Brillo, we all want to maximise on ballistics so, the first job is to find out what your rifle will 'take'. All rifles/barrels are different.

 

You do this by starting with your chosen powder and bullet - loaded off the rifling - and, using the 'starter' load from whatever loading manual you are using - increase your load by about 0.3gn at a time.

 

Fire each one (preferably over a chrono) and 'feel' the bolt lift, check the primer for flattening/cratering, watch the case-head for marking.

 

When you reach maximum, step back half a grain or so and find your accurate load by shooting three shot groups - adjusting the powder charge by say 0.2gn at a time.

 

Then, experiment with seating depth - until you get your very best grouping. Try a five-shot group just to be sure.

 

That's all there is to it. One session - providing you take your loading gear to the range. i usually prep. about 20 cases and take scales, powder, bullets, dies and press to the range. You can do this under cover at Diggle - we even have power for your electric scales.

Best advice on the net,,,,

[1066]

OK Brillo, we all want to maximise on ballistics so, the first job is to find out what your rifle will 'take'. All rifles/barrels are different.

 

You do this by starting with your chosen powder and bullet - loaded off the rifling - and, using the 'starter' load from whatever loading manual you are using - increase your load by about 0.3gn at a time.

 

Fire each one (preferably over a chrono) and 'feel' the bolt lift, check the primer for flattening/cratering, watch the case-head for marking.

 

When you reach maximum, step back half a grain or so and find your accurate load by shooting three shot groups - adjusting the powder charge by say 0.2gn at a time.

 

Then, experiment with seating depth - until you get your very best grouping. Try a five-shot group just to be sure.

 

That's all there is to it. One session - providing you take your loading gear to the range. i usually prep. about 20 cases and take scales, powder, bullets, dies and press to the range. You can do this under cover at Diggle - we even have power for your electric scales.

When I get to that stage for fine tuning I have my rounds loaded and bullets seated out to their maximum and then use my Lee hand press with Redding micro seating die. I shoot 5 shot groups and seat each group in a further 10 thou. If all goes well you should see the groops tighten then open up as you go through the sweet spot.

[Brillo]

OK Brillo, we all want to maximise on ballistics so, the first job is to find out what your rifle will 'take'. All rifles/barrels are different.

 

You do this by starting with your chosen powder and bullet - loaded off the rifling - and, using the 'starter' load from whatever loading manual you are using - increase your load by about 0.3gn at a time.

 

Fire each one (preferably over a chrono) and 'feel' the bolt lift, check the primer for flattening/cratering, watch the case-head for marking.

 

When you reach maximum, step back half a grain or so and find your accurate load by shooting three shot groups - adjusting the powder charge by say 0.2gn at a time.

 

Then, experiment with seating depth - until you get your very best grouping. Try a five-shot group just to be sure.

 

That's all there is to it. One session - providing you take your loading gear to the range. i usually prep. about 20 cases and take scales, powder, bullets, dies and press to the range. You can do this under cover at Diggle - we even have power for your electric scales.

 

Thanks for all the feedback. Great stuff. Regarding the "when you reach maximum", is this the powder manufacturers recommended maximum or the maximum noted by case head marking, primer cratering etc?

[The Gun Pimp]

Thanks for all the feedback. Great stuff. Regarding the "when you reach maximum", is this the powder manufacturers recommended maximum or the maximum noted by case head marking, primer cratering etc?

 

Sorry - need to clarify. By 'maximum' I mean the maximum YOUR rifle will SAFELY take - every rifle/barrel is different - manufacturers' recommendations are usually so conservative as to be meaningless.

 

So, how do we recognise when we are close to maximum SAFE pressure. Remember - we are increasing the load 0.3gn at a time.

 

The fired case tells us nearly everything. The primer will go through several stages - it will get flatter and flatter and may eventually exhibit cratering around the firing-pin strike (Not all actions will show cratering - if the pin is a close fit in the hole, as on a good custom action, there is nowhere for the 'crater' to form).

 

Eventually, the brass will start to flow into the ejector-pin hole and, when you open the bolt it will feel a little stiffer. You will start to see 'scuff' marks on the case head and, eventually, a bright circle - as a small circle of brass that has flowed into the ejector-pin hole is sheared off!

 

You've now gone far enough - step back half a grain or so and find your most accurate load by varying (by about 0.2gn) powder charges. If you shoot with marks on the case-head - too high a pressure - it may be very accurate but you will simply wreck your brass! Primer pockets will go slack and the case won't fit your shell-holder in the press. It's scrap!

 

When you find the best three-shot group - start seating the bullet out into the rifling but don't go into the rifling more than say 7 - 8 thou. You may find it shoots better just off the rifling - only testing will tell you.

 

A good idea when you come to your first benchrest match (Saturday) - bring six slightly different loads (five rounds of each) - varying powder and bullet seating. Shot off a bench with wind-flags - the target will tell you the best one.