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6mmBR v’s Quickload


Brian_K

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Hi Gentlemen,

 

I wonder if I might pick your brains – took my 6BR out today for its first shoot after having a new barrel fitted (Bartlein 1:8.5 progressive twist) and using new Lapua brass and Berger 105gr Hybrids.

 

I decided to use RL15 and start at 28.5gr and work up in .3gr increments to 30gr.

 

28.8 and 29.1gr seemed to shoot pretty well (5 to 7mph right to left wind which I ignored)

 

6mmBRloads_zpsddd9fd00.jpg

 

My question is, according to Quickload, I should be getting a speed of 2844fps with 29.1gr RL15, but after running some rounds over the chrono I’m only getting 2643

 

Is Quickload normally this far off, or have I made a mistake somewhere?

 

ScreenClip_zps5c7bbda8.jpg

 

Any advice appreciated.

 

Brian

 

 

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Perhaps the load depressurised itself a bit in blowing the new cases as well as driving the head out??I,m no scientist just thinking "outside the box"

I might be a "Hillbilly" I do not have "Quickload" but can understand the pleasures of playing with such a program but with so many other factors contained in one similar rifle build to another there are gonna be differences!! There must be infinite variations some almost imeasurable and then there is the inaccuarcy of "the chronagraph".

 

I get 2800,,,"just" out of a 27" tube with 29.5 of 140 with a 105 grainer according to my "chrony",,,,and all that goes down the same hole!! and tight on a 200 zero which follows ballistic charts to around 500/600 most of the time.

 

Again I have not had the benefit of "Quickload" but does it allow for head position ,distance from lands,,chamber dimension etc ,,,all this can make huge difference in pressure and velocity I would imagine???Apologies but my "Hillbilly" regard to a computer prediction of velocity results in exteme pressure firearms,,just toooo many variables mmmmm dunno?,,,,,,,

 

Oh! by the way ,,you can shoot well too,,brill,,,,,,,,

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Thanks for all the replies lads.

 

I think I'll wait until all the brass has been fire formed and as suggested put a hundred rounds or so down the barrel, then start again. Maybe with Varget this time.

 

I love this accuracy stuff me :D

 

Brian

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  • 1 month later...

Just an update after spending the weekend at Bisley.

 

I had a Barnard S action fitted to the Bartlein barrel after deciding to sell the RPA. The barrel was rechambered and I lost about ½” off the length, so it’s now a dead 28”

 

Barnard_zps442d0566.jpg

 

Loaded up the remaining 50 of my new Lapua brass with 29.1gr of RL15 and the 105gr Hybrids as above.

 

After about 15 rounds the newly chambered barrel started to shoot well, more vertical than before, but these were 5 shot groups.

 

6BRBarnard_zps9abcc5b9.jpg

 

Having recently acquired one of the MagnetoSpeed Chronongraphs (highly recommended, I put it on six different rifles over the weekend, never missed a shot).

 

I ran several rounds over this:

 

MAX – 2623fps

MIN – 2613fps

SD – 4

 

Pretty much the same speed as previously recorded, but still 200+ fps down on Quickload.

 

I’ll throw some more coals on the fire and work my way up to 30.5gr of RL15 and see what it looks like.

 

Brian

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Just an update after spending the weekend at Bisley.

 

I had a Barnard S action fitted to the Bartlein barrel after deciding to sell the RPA. The barrel was rechambered and I lost about ½” off the length, so it’s now a dead 28”

 

Barnard_zps442d0566.jpg

 

Loaded up the remaining 50 of my new Lapua brass with 29.1gr of RL15 and the 105gr Hybrids as above.

 

After about 15 rounds the newly chambered barrel started to shoot well, more vertical than before, but these were 5 shot groups.

 

6BRBarnard_zps9abcc5b9.jpg

 

Having recently acquired one of the MagnetoSpeed Chronongraphs (highly recommended, I put it on six different rifles over the weekend, never missed a shot).

 

I ran several rounds over this:

 

MAX – 2623fps

MIN – 2613fps

SD – 4

 

Pretty much the same speed as previously recorded, but still 200+ fps down on Quickload.

 

I’ll throw some more coals on the fire and work my way up to 30.5gr of RL15 and see what it looks like.

 

Brian

Brian,

I've just stuck a 6BR 28 inch tube on a Quadlock for a forum member - first loads with Elcho 17 powder (basically Reloader 17 but cheaper) were topping 3000fps with a 105gn bullet and showing good accuracy.

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Brian,

I've just stuck a 6BR 28 inch tube on a Quadlock for a forum member - first loads with Elcho 17 powder (basically Reloader 17 but cheaper) were topping 3000fps with a 105gn bullet and showing good accuracy.

 

Funny you should mention that Vince, guess what I came back from Bisley with :) I was given half a tub to test.

 

Can I ask the load you used ( and I should work up to).

 

Timmney trigger is excellent by the way :D

 

Brian

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Also bear in mind that your new barrel will speed up over the next 100-150 rounds, so expect to gain 75-100fps.

I've never experienced this - nor can I think of an explanation for it. I would expect a barrel to smooth out/slick up a bit after 100-150 rounds, thus lowering pressure and therefore giving LESS velocity if anything.

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Have you measured the water capacity of your fireformed cases?

 

Yes did that, very small difference with that listed by Quickload. Just can't get my head around why it's predicting 200fps more than I'm actually getting.

 

I'm sure it's something I'm not doing right, but after checking everything numerous times I can't see what it is.

 

Anyway, I'll load up with RL15 and Elcho 17 until I see pressure signs and see where we are then.

 

Brian

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Almost certainly you will have to adjust the powder burn rate variable "Burning Rate Factor Ba" in the charge window in QL in order to fine tune the powder data supplied.

This variable also changes when you alter the temperature variable, so what I do is input the actual temperature I tested at first and then tweak the Ba variable manually until the MV agrees with your measured data.

 

If you need to tweak the Ba variable by more than 10% there could be something else wrong, so double check the values for case capacity, cartridge length, barrel length and make sure you're not jamming the bullet as QL can't automatically adjust its outputs for that.

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Thanks for all the replies lads.

 

I think I'll wait until all the brass has been fire formed and as suggested put a hundred rounds or so down the barrel, then start again. Maybe with Varget this time.

 

I love this accuracy stuff me :D

 

Brian

Your first two targets show potentially top accuracy-classic wind report L-R but you were ignoring it's effects-maybe as the horizontal shows!

I'd agree-run it all in and test a few more in calm conditions.Varget too ,if you must,but I'd not be too concerned with 200 fps -if that is confirmed-if the precision improves.Nice maybe to have a bit more velocity,but not as a trade off against group-almost whatever you are shooting...?

Gbal

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I took a reading of the temperature, humidity etc with my Kestrel and I’m jumping the Hybrids .015” so no problem there.

 

Cartridge length, capacity etc are all correct so it looks like the burn rate variable could be the answer. I’ll spend some time with it tonight and see what it looks like.

 

Gbal

 

Agreed, groups are the most important. But I feel a little more speed is required (another 250fps would be nice), while trying to get rid of some of that vertical. The 6BR is mainly to be used for 300 to 600yds but very occasionally it will get used at 100 and 1000. On Sunday it was four clicks short of full elevation on the scope to reach out to 1000 with the last six rounds I had left. It shot them badly in the switchy 8 to 14 mph winds we had all day.

 

But all good fun :)

 

Thanks

 

Brian

 

 

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I took a reading of the temperature, humidity etc with my Kestrel and I’m jumping the Hybrids .015” so no problem there.

 

Cartridge length, capacity etc are all correct so it looks like the burn rate variable could be the answer. I’ll spend some time with it tonight and see what it looks like.

 

Gbal

 

Agreed, groups are the most important. But I feel a little more speed is required (another 250fps would be nice), while trying to get rid of some of that vertical. The 6BR is mainly to be used for 300 to 600yds but very occasionally it will get used at 100 and 1000. On Sunday it was four clicks short of full elevation on the scope to reach out to 1000 with the last six rounds I had left. It shot them badly in the switchy 8 to 14 mph winds we had all day.

 

But all good fun :)

 

Thanks

 

Brian

 

 

OK,so long as it's fun.

Actually a choice between .1moa better precision but 4 more clicks,isn't the heaviest decision to have to make,especially if shooting for group. In a twitchy wind,all bets are off,anyhow!!

Gbal

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Try putting a value of 0.4500 into the Ba variable for Reloder-15 in the charge window and you'll get velocities closer to the ones measured.

 

You're close to a predicted accuracy node with 28.8gns using this tweaked value, so it does seem to tie in with your results.

 

If anything, going a little lower with the charge might give you even better results (28.7 or 28.6gn).

 

According to the theory, 29.9gn of R-15 at a predicted MV of 2700 should also be accurate, but maybe you didn't find that? The theory doesn't always match reality, of course and I suspect you may need a few more rounds through the barrel for everything to settle down.

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Funny you should mention that Vince, guess what I came back from Bisley with :) I was given half a tub to test.

 

Can I ask the load you used ( and I should work up to).

 

Brian

The loads Vince mentioned were as follows, usual precautions apply

 

Elcho 17 powder

 

33g was 2805

33.5 was 2866

34 was 2929

34.5 was 2997

35 was 3058

No signs of pressure problems

 

Bob

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The loads Vince mentioned were as follows, usual precautions apply

 

Elcho 17 powder

 

33g was 2805

33.5 was 2866

34 was 2929

34.5 was 2997

35 was 3058

No signs of pressure problems

 

Bob

another new toy BOB?

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Dark Star,

 

Thanks, have now found and downloaded this .pdf: http://www.the-long-family.com/Tuning%20QL%20to%20achieve%20best%20results.pdf

Out of interest where do you get the theory’s you mentioned about predicted accuracy nodes?

 

Bob,

 

Thanks for the load data on the Elcho 17, I will certainly be working up to those….. carefully, they do look a little hot at the higher end.

 

Brian

 

 

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