Thread: Accuracy expectations

@Tentman stats as follows:

Barrel length = 18” bolt face to muzzle (plus 4” of suppressor)
C.O.A.L = 2.277” at -0.010” jump.
Bullet = Sierra 85gr HPBT
Case capacity = 31.1gr of H2O. Average of three
Velocities (group average) BM8208 (IMR8208XBR)
25.7gr - 2689fps
25.9gr - 2679fps
26.1gr - 2702fps
26.3gr - 2730fps
26.5gr - 2733fps Powder compressed

Gidday - I took a quick look and I can't get GRT to closely correlate with your supplied data, it'll be something I'm doing wrong - its not the right time of day for me to be doing this sort of analysis ! I would say that it shows that your top load is at 71100 PSI, which in an action like the Hunter (which doesn't handle gas well) is not at all safe.

I'll try again when I'm in a better space.

All good mate, appreciate the offer! No hurry at all, the problem isn’t going anywhere in a hurry!

Just had a quick look at this & was wondering if you have a barrel that just doesn't like boattail bullets much?
Have seen some barrels that just dont like them but will shoot flatbase fine.
Just a thought for what it is worth??

Originally Posted by TARGEX

Just had a quick look at this & was wondering if you have a barrel that just doesn't like boattail bullets much?
Have seen some barrels that just dont like them but will shoot flatbase fine.
Just a thought for what it is worth??

Yes I have been wondering the same. I’m off hunting this weekend, but following that I’m going to try a bit of a different path and load up some 70gr flat base. Give them a go and see what happens.
I’m also wondering if it’s a barrel timing thing, and getting a bit more velocity through lighter projectiles might find a sweet spot.

Let me know if you need something to try, nothing more frustrating than fighting with a rifle that should shoot but won't.
Think I have a few 95gr FB/HP moly coated that I was playing with & can send you some 70gr FB/HP.
If that's any help just let me know.
Cheers

Thanks very much @TARGEX I’ll be in touch after the weekend. Champion

My play with GRT didn't want to match up either. I ran the OBT calibration which changes burn rate or something to make predicted match actual and that made things fit a lot better, but also reckoned they are compressed loads at close to (or above) max pressure.
Have you tried lower charges? The Optimal Barrel time function reckoned there may be a node at 25.3gr of 8208 at a mv of about 2609fps.

Originally Posted by Cigar

My play with GRT didn't want to match up either. I ran the OBT calibration which changes burn rate or something to make predicted match actual and that made things fit a lot better, but also reckoned they are compressed loads at close to (or above) max pressure.
Have you tried lower charges? The Optimal Barrel time function reckoned there may be a node at 25.3gr of 8208 at a mv of about 2609fps.

Thanks very much for that @Cigar I was just thinking too, that the chrono distance was 10 yards. Maybe that was a missing element that made calcs difficult?

Funny you say that about the lower node, the first group of the test was 3 fouler shots 24.2, 24.7 and 25.2gr which made a beat wee group. Average velocity across the three of 2550fps. The 25.2gr load was 2616fps, so pretty close to the GRT prediction.

Originally Posted by Hunter_Nick

Thanks very much for that @Cigar I was just thinking too, that the chrono distance was 10 yards. Maybe that was a missing element that made calcs difficult?

Funny you say that about the lower node, the first group of the test was 3 fouler shots 24.2, 24.7 and 25.2gr which made a beat wee group. Average velocity across the three of 2550fps. The 25.2gr load was 2616fps, so pretty close to the GRT prediction.

Attachment 172806

Looks to me like you have your load right there. Load up another 10 or so and go shoot a 5 shot group at 200, and another at 300 and see if it holds 1moa for them. If it does you will have the confirmation you need, and some handy verified drops.

Originally Posted by Arthur McBride

You know what I will say...

That being??…

I still dont think tweaking the load will make this a varmint rifle - it’ll just log nick more and more range time.

I bet if you get a new truflite cut to 6x45 the first components you try will shoot 3/4 and you can just get on with it, neck shooting fallow at 200m, small goats bullet well placed in the chest, turkeys, body shots on south island wallabies, any rabbit or hare will be history.

Nice hear your bench test setup. Sounds great.

Originally Posted by Bagheera

I still dont think tweaking the load will make this a varmint rifle - it’ll just log nick more and more range time.

I bet if you get a new truflite cut to 6x45 the first components you try will shoot 3/4 and you can just get on with it, neck shooting fallow at 200m, small goats bullet well placed in the chest, turkeys, body shots on south island wallabies, any rabbit or hare will be history.

Nice hear your bench test setup. Sounds great.

Defo. Whilst the bush thing probably doesn't have any negative impacts if done properly, clearly something is negatively impacting the groups so that's got to be near the top of the list of likely culprits.

I've never had great results with Winchester brass either and try to avoid like the plague.

Bit of an update on this. After a bit of a break, I sourced and loaded up some 70gr ballistic tips with BM8208 in Win cases. I had a good feeling about the combo, because these bullets had shot well in a previous 6x45, and the throat/seating depth/mag length/case capacity was just perfect. Like it was designed to go together….

Results were also very pleasing.


Very happy with the accuracy, and the velocity is bang on for an 18” barrel. Pressure is up there but not too hot, so cases will last.

Reviving an old thread….

Turns out that the groups above were a bit of a ‘flash in the pan’ and I’ve still struggled to get consistent results.

So during lockdown, I set about proving a theory I had. That theory was that there is nothing wrong with the hardware, it was the software that was causing problems. In other words, I can’t shoot for sh*t! So I set about building a purpose built benchrest stock for the wee BSA, in order to remove my influence as much as possible. I had a hunch that the narrow light standard stock was feeling the influence of any change in hand pressure, torque through the pistol grip, and the steep rise from toe to grip cap was partial to creating vertical groups under recoil. I wanted a stock that would recoil straight back, have a wide flat forend to ride the sandbags better and a more vertical pistol grip with palm swell.

So a couple of months later, this is what I produced. Built the old school way with chisels, gouges, scrapers and some inletting black.







Was my theory correct? Well, I think it was. I found the rifle a lot ‘nicer’ to shoot, recoiling straight back creating a much more satisfactory follow through from the shot. I tested 4 different projectiles with the following results:

80gr Speer SP 26.5gr 2206h average 18mm
70gr Ballistic Tip 26.3gr BM8208 average 25mm
100gr Core Lokt 24gr 2206H average 22mm
85gr HPBT 26.1gr BM8208 average 22mm

Best of all, there was no large variance across groups like I had been finding in the sporter stock. Do you sum it all up, I’ve proven that shooting a svelte, light walkabout hunting rifle isn’t that easy. Technique is everything, and now I know that the rifle is ok, I’ve got a lot of work yo do sorting out my shooting technique.