Thread: CBTO new projectile

Originally Posted by gimp

I bought some 105gr 6mm VLDs to test and see if I can identify any difference. I dunno why I keep doing this

Just admit it, you have an addiction

Originally Posted by johnd

Just admit it, you have an addiction

To building the understanding, not to actually testing loads

Ok @Kelton I loaded & shot some 105gr "hunting" VLDs from my 6mm GT. Granted the 6GT is a modern case specifically designed to be precise. However 1) I have to use the rifles I have and 2) I'm not sure why you'd select a cartridge that isn't known for precision if you want precision.

The hunting VLD was what I could get in stock.

I followed the Berger process https://bergerbullets.com/vld-making-shoot/

Found the lands at 1.980" CBTO

loaded 6rd each at 0.010", 0.050", 0.090", and 0.130" jump, with a random 34gr of 2208.

I also loaded 4 bonus rounds of the 0.050" jump load, as shooting these on the same target as the 2x 3rd groups would be more or less the same as my normal load selection approach.

Shot groups this morning, letting barrel cool (although it makes no difference). I shot 2x 3rd groups of each increment on different targets, with the exception of the 0.050" jump. For this load I shot both 3rd groups on the same target then added the bonus 4rd for a 10rd group.

Here is the results:

All targets


0.050 group 1 & 2



And the table of results


I don't see any obvious difference here. Taking my process of "load 10rd at 0.030-0.050 off, shoot, etc" gives me a predicted ø95 of 27.04mm(+ or - lets say 10%, so 24-30mm) centred about 0.2mrad right. Every single shot from the other seating depths falls comfortably within that circle. By my estimation it's a 0.8 - 1.0 MOA system. Exceptionally good for 8.5LB.


I have fired 28 of my 100x 105gr VLDs, I will take any suggestions and shoot any (reasonable) amount of any suggested load to verify. But what I'm seeing is that with this rifle, cartridge, bullet, powder, shooter combination - there doesn't look to be any meaningfully resolvable difference in precision at different seating depths, following the Berger method.

I bet if I overlaid all 28rd they'd make about a 0.9moa group centred about 0.2mrad right.

And for any combination of these components with my loading technique and gear I would predict an SD of 10, +-2, fps. If measured with enough shots to get a meaningful result.

Also also 34gr of 2208 is probably too hot for this particular bullet in my 6GT, published data is 36.6 max for a vapor trail 103 or 34.0 for a 107 SMK. The 0.236 barrel may not handle quite so much powder as a 0.237.

Originally Posted by gimp

Ok @Kelton I loaded & shot some 105gr "hunting" VLDs from my 6mm GT. Granted the 6GT is a modern case specifically designed to be precise. However 1) I have to use the rifles I have and 2) I'm not sure why you'd select a cartridge that isn't known for precision if you want precision.

The hunting VLD was what I could get in stock.

I followed the Berger process https://bergerbullets.com/vld-making-shoot/

Found the lands at 1.980" CBTO

loaded 6rd each at 0.010", 0.050", 0.090", and 0.130" jump, with a random 34gr of 2208.

I also loaded 4 bonus rounds of the 0.050" jump load, as shooting these on the same target as the 2x 3rd groups would be more or less the same as my normal load selection approach.

Shot groups this morning, letting barrel cool (although it makes no difference). I shot 2x 3rd groups of each increment on different targets, with the exception of the 0.050" jump. For this load I shot both 3rd groups on the same target then added the bonus 4rd for a 10rd group.

Here is the results:

All targets
Attachment 273453

0.050 group 1 & 2
Attachment 273454
Attachment 273455

And the table of results
Attachment 273456

I don't see any obvious difference here. Taking my process of "load 10rd at 0.030-0.050 off, shoot, etc" gives me a predicted ø95 of 27.04mm(+ or - lets say 10%, so 24-30mm) centred about 0.2mrad right. Every single shot from the other seating depths falls comfortably within that circle. By my estimation it's a 0.8 - 1.0 MOA system. Exceptionally good for 8.5LB.


I have fired 28 of my 100x 105gr VLDs, I will take any suggestions and shoot any (reasonable) amount of any suggested load to verify. But what I'm seeing is that with this rifle, cartridge, bullet, powder, shooter combination - there doesn't look to be any meaningfully resolvable difference in precision at different seating depths, following the Berger method.

Note that the "average" group size is not the group size of all 6 rd for each, it's just the mean of the 2x 3rd groups. I'll get a proper overlaid 6rd group for each another day

Cheers @gimp il have a read shortly iv also shot this morning was an educational trip re my 708 also shot saum 10 rounds of a random depth and 10 of what I had considered to be my best tested so far il get back once iv finished my jobs and post findings

Next is seated a lot deeper and this photo is at 5 rounds before the suppressor cooling and removal of the bush

This next one is the last string of 5 with the bush gone into the same target but marked with ballistic x its left me wanting to shoot some more with the bush gone though its level of accuracy hasn’t cost me an animal yet

Not much to see with the 7mm08 but being suppressed I was removing the can after 5 shots more or less to try and cool it quicker to reduce the mirage threw the scope shooting the notoriously fussy Nosler LRAB and when removing the second time I noticed how polished my barrel is from the suppressor bush so I shot the last 5 with the bush out and things took a turn for the better. I never faffed around to much with this rifle got it good enough for hunting which is is and just go hunting it’s left me wanting to do it again with the bush gone and see if it has really helped or if it was luck .


First 10 shots with can removed at 5 for 5 mins


Attachment 273482

Next is seated a lot deeper and this photo is at 5 rounds before the suppressor cooling and removal of the bush Attachment 273485

This next one is the last string of 5 with the bush gone into the same target but marked with ballistic x its left me wanting to shoot some more with the bush gone though its level of accuracy hasn’t cost me an animal yet Attachment 273488

Order jumped around their but I’m sure you’ll make sense of it neither of those were depths I’d shot before one closer to saami and one closer to mag max of 2,955

Then with the saum again I choose a length that was shorter than my max and my other is near my max that iv shot before and has produced good 3 and 6 shot groups

I shot the shorter length first these were shot in 3 3 and 4 with a walk to the target between so say again 5mins max?



This is it after 10 looks a lot better than it did with the first 3



Next was my longer length that iv shot before for some reason and im open to suggestions 3 of my 10 were tight to close the bolt on at first i though brass but then projectiles showed marks when i extracted them but not the whole way around like it was jamming in the rifling could they be seated on the piss? I don’t have means to measure runout quality Forster dies 2x fired ADG brass bergers and a Redding press I wouldn’t have thought so I’m yet to clean the rifle after this morning so il be sure to keep an eye on anything foreign. Anyhow I put those three aside and shot them in the last 4

First three


Started finding the right to chamber rounds here





This one clearly looks like rifling but it’s just the 2 marks nothing on the other side



I did measure most of them as I loaded and think it’d be very unlucky if I happened to miss the 3 long ones when I would have measured near all of them at random

Shots 4-6



Shot 7-10



Their was a scope adjustment of 1moa up and 5 clicks right between the 2 saum photos to.


I still favour the longer seating depth for accuracy while not much it has the edge to me 1.310moa and 0.886 I don’t have the means to measure mean radius as ballistic x wants more money out of me for the feature .

Over all I think a 10 shot group can reveal the 3 shot group that looked bad probably isn’t as bad as id thought every time iv shot the 10 which would only be maybe 5 times iv being pleasantly surprised 40 today and did 10 with eldx in my 708 a few weeks ago.



That’s never being a crash hot load even at 3 shots but 10 shots showed me it’s well and truely enough for my hunting needs .

I thought I’d experience more “shooter fatigue” than I did 20 shots from a 3.3kg 708 shooting a stiff 150 load and 20 from a 3.4kg short magnum shooting 180gns with the best of the 4 groups shot last I was surprised. Was a good shooting day for me they all felt good.

Il check sd soon but their was nothing in it maybe 14.1 and 14.2 I’ll also add the other 17 rounds of that load iv shot to todays 10 and see where that leaves me over 27 shots .

That’s enough testing for me with the saum anyway I’m satisfied tell you what bergers and LRAB are not the best pills to conduct higher volume tests with $$$

Based on the group I favour @gimp what if any scope adjustments could you recommend. I’d missed my gong 4 times over the weekend while validating and looking at the dirt behind the target I thought they went high the next day I put a bit of ply behind the target and realised they were 3 inch’s right . So I’d adjusted 1 moa to the left and hit it center center for the last 2 shots . Then the short seating depth this morning was hitting left of POI so I moved it back right thinking maybe there was more wind than I thought when shooting the gong . But then my tried load was connecting right of POI for the first 3 shots then slowly to the left and back right again for the last couple . I thought it was a pretty calm day when I shot the gongs evening then following morning so pretty much rolled out wind distance was 350 and the gongs 6 inch’s so the 1 moa right was just enough to get a miss.

Cheers

And mean radius for dummy’s is that from poa to the outside of the furthest shot from point of aim?

Originally Posted by Kelton

And mean radius for dummy’s is that from poa to the outside of the furthest shot from point of aim?

Scratch that had a quick google and think I understand it, from the center of the group to the center of the furthest shot that’ll I close the group in its radius?


Edit nope still don’t get it I get where to measure from but not understanding where to measure to

Hey thanks for posting, very interesting. Good shooting too.