6mm velocity figures.

[rogn]

Ive got a 6mmX44BR or a short 6X47L. Take your pick. Barrel is well regarded 6mm with 1:8 twist 25". Anyhow, I have reports of people using 6BR's with 100-110 gr bullets and getting velocities of 3000 and a tad over. Using the dreaded "Chrony" most of the velocities Ive recorded with Sierra 107gr MKs have fallen into the 2850-2930 FPS. Some with the ES being not extreme at all. My basic loads with H4350 and IMR 4451 are around 35.2 gr. Going higher up to 36.0 gr doesnt seem to provide much increase in V, but the primers seem threatening. The 7 1/2s I have dont seem to be the 7 1/2s I used years ago. BR4s are much happier looking. The action involved here is a Stolle Panda probably the 52nd ever made with the std firing pin diameter. Case expansion doesnt seem excessive primer pockets are tight. Extraction is relatively effortless.
Not having complete faith in the Chrony I started reverse engineering the data using JBM Ballistics as the tool. Working backwards with the 107yd "o" and the 300yd zero velocities work out to a calculated 2850 @37*, 30.05 mm hg, 10" above sea level etc.
Can someone explain how, even looking at longer barrel lengths how some shooters are realizing 150-200 FPS increases. My understanding is that the smaller the case(low expansion ratio?)realizes less increase per inch of barrel. What types of pressures are these folks operating at?
After lotsa machinations and finally shoving a throater into the works the accuracy/precision seems to be approaching its potential.

 

[JEFFPPC]

I have no knowledget of your case, but with the smaller 6BRX case and a 26 in. barrel, I shoot 106 EPS @ 2970 to 2990. I use Varget and 205m. PANDA action with a bushed firing pin. You might want to get your pin bushel, helps with the pressure. Velocity taken with Lab Radar. I have had barrels I shot in the 3010 range.

 

[4xforfun]

What he said^^^^^. But, to be honest......I never had any luck at that 3050 - 3070 node in the Dasher with the 105-108 class bullets. All of my tubes seemed to like that 2960 - 2990 area.

Why you are below that...hard to tell, but get the bolt bushed (if it isn't already)...that should help.

On the flip side...I asked the guys at BAT about weather or not to "bush" my BAT's and I got a HARD NO!! So....????

Good luck, and remember, your tube likes what it likes. Have you ever tried to MAKE a kid like Pea soup??

Tod

 

[rogn]

Jeff, the 6mmX44BR was the hottest thing going in the 1980s for hunter class BR. Its 45gr H2O capacity and was a Rem 308 URBR srp basic case formed to 1.75". Or look at it as a 6mmBR stretched to 1.75". I shot a lot of hunterclass in the late 80s and had all the hardware for the case so I got some Lapua brass went forward.
Im just puzzled by the higher velocities achieved by the smaller capacity 6BR rounds. Wondering what kind of pressures they are running at. Even std 6BR reporting velocity as high as 3050 with 100+gr bullets.
Like to have the higher velocities available, but as someone once said, he "didnt care what the velocity was as long as the bullet got there before they pulled the targets."

 

[243winxb]

less increase per inch of barrel.

Different Powder= Differeny Velocity?

 

[rogn]

The crux of my question is really why do these significantly smaller cartridges seemingly consistently produce higher velocities with less powder, powder capacity, faster powders etc. Smaller cases using faster powders, larger= slower powders.

 

[Milo 2.0]

The crux of my question is really why do these significantly smaller cartridges seemingly consistently produce higher velocities with less powder, powder capacity, faster powders etc. Smaller cases using faster powders, larger= slower powders.

IMO, it is case design, these BR cases and variants are way more efficient than older designs. More powder is burned in the case. You run different cases in QL and the bottom right number displayed is ballistic efficiency, these small cases are off the charts compared to a 243 or the like.

 

[rogn]

IMO, it is case design, these BR cases and variants are way more efficient than older designs. More powder is burned in the case. You run different cases in QL and the bottom right number displayed is ballistic efficiency, these small cases are off the charts compared to a 243 or the like.

6X44BR is such a variant.

 

[Milo 2.0]

6X44BR is such a variant.

I did not read your first post, sorry, and no clue what a 6x44BR is. I know dasher and 6br, that is it. From what you asked that I replied to, I was more right than wrong.

 

[hammerjack]

It sounds you should try some Varget or H-4895. Do you have a photo of this case setting beside 6MMBR?

 

[dmoran]

@rogn
My input; plain and simply because the cartridges based off the 6mmBR mother case are more efficient.
And likely your not running your 6x44 to the same pressure levels.

 

[22BRGUY]

Don't overlook that colder air and or lower elevations air are more dense also. How much that affects your particular situation I don't know but possibly something I would think.
It's so cold here today that bullets are exhausted about 5 ft. from leaving the barrel.……….@#?

 

[rogn]

@rogn
My input; plain and simply because the cartridges based off the 6mmBR mother case are more efficient.
And likely your not running your 6x44 to the same pressure levels.

Pressure I can believe.

 

[savagedasher]

I run my dasher at 3160
With no pressure signs
Node or no node I tune with tuner

FORUM BOSS: This recommendation is completely unsafe with the 105gr bullet which savagedasher later says he is running. DO NOT attempt to run a 100+ grain bullet at this velocity. IT IS UNSAFE.

Savagedasher will be permanently banned from this Forum for posting this.

3160 FPS with a 105gr bullet and a Dasher is INSANE over-pressure and is very dangerous.

I just discussed this with a past 600-yard IBS shooter of the year and his comment was "I run in the mid-2900s and even 3050 fps is very extreme"

Honestly I do not know if the person who posted that was serious but his numbers are way out of the extreme pressure range and I cannot allow this to recommended to our readers.

Accordingly, the post was annotated for Safety and poster savagedasher has been banned from this board forever.

 

[243winxb]

, I have reports of people using 6BR's with 100-110 gr bullets and getting velocities of 3000 and a tad over.

Reloading data from Hodgdon and Vihtavuori doesn't come close at normal pressures.

They must be shooting "proof" loads.

I see a 6 Creedmoor 100gr at 3200. Hodgdon

I see a 6 Dasher 100 gr at 3088. Hodgdon

I see 6 BR Remington 100 gr at 2661 fps . Hodgdon.

I sse 6mm BR Norma 100 gr at 2812 fps . Vihtavuori.

I see the 6XC 105 gr at 2936 fps Vihtavuori. https://www.vihtavuori.com/reloading-data/rifle-reloading/

Sorry, snowed in with 40 mph winds. Bored.

 

[rogn]

243;
See above ???????

 

[rogn]

I run my dasher at 3160
With no pressure signs
Node or no node I tune with tuner

With 105, 107, 115 gr? Barrel length?

 

[JEFFPPC]

I run my dasher at 3160
With no pressure signs
Node or no node I tune with tuner

Savgedasher, with what weight bullet, surely not 105 range.

 

[243winxb]

The crux of my question is really why do these significantly smaller cartridges seemingly consistently produce higher velocities with less powder, powder capacity, faster powders etc. Smaller cases using faster powders, larger= slower powd

Dont know, if they do or not?

Bore diameter, when comparing 45/70 & fast powder to 243 win & slow powder. Bottle necks need slower powders?

 

[savagedasher]

Savgedasher, with what weight bullet, surely not 105 range.

Yes t 105 hb