Sierra "Gamechanger" Gameking Tipped

This section is for reloading and ammunition only, all loads found in here are used strictly at your own risk, if in doubt ask again.
All handloading data posted on Full-Bore UK from 23/2/2021 must reference the published pressure tested data it was sourced from, posts without such verification will be removed.
Any existing data without such a reference should treated as suspect and not used.

Moderator: dromia

Forum rules
All handloading data posted on Full-Bore UK from 23/2/2021 must reference the published pressure tested data it was sourced from, posts without such verification will be removed.
Any existing data without such a reference should be treated as suspect and not used.

Use reloading information posted here at your own risk. This forum (http://www.full-bore.co.uk) is not responsible for any property damage or personal injury as a consequence of using reloading data posted here, the information is individual members findings and observations only. Always verify the load data and be absolutely sure your firearm can handle the load, especially older ones. If in doubt start low and work your way up.
Post Reply
Message
Author
Philiphn
Posts: 9
Joined: Sun Nov 07, 2021 8:47 am
Home club or Range: NRA; Bassingbourn Rifle and Pistol Club
Location: Cambridge

Sierra "Gamechanger" Gameking Tipped

#1 Post by Philiphn »

Hello all

I'm a new member (just introduced myself in the Newbie section) with decades of reloading experience but also with a puzzle.... I wonder if anyone can offer a thought?

One of the calibers I shoot is .243. When I'm not target shooting I'm a deer stalker (maybe it's the other way around) and so my .243 is a reasonably (operator error aside) consistent sub .5MOA group shooter and my go-to Muntjac rifle. I never use factory ammunition: my default head is a 90g Nosler Ballistic Tip and I use N160 to push that comfortably beyond the required muzzle energy minimum. I use a V2 Autotrickler with an A&D Fx 120i, Redding competition dies and routinely trim cases, measure headspace and keep on top of the details. So in theory I know what I'm doing. Haha.

At the moment the 90g Nosler is unavailable. So I decided to buy a few hundred 90g Sierra Gameking Tipped, the so-called Gamechanger. Ordinarily I would work up a load using QuickLOAD and my Labradar chronograph but I got lazy and decided to try 20 rounds using the same load as I use with the Noslers. I felt there was a fair chance the results would be worth looking at, even though I knew that finding exactly the right load might take longer.

At Bisley last weekend on Short Siberia I shot three other rifles before getting out the .243. I was having a 'meh' morning: I was a bit tired. But with the Noslers I held a few reasonable groups and then loaded 5 rounds of the Sierras. First shot was so wide of the mark I didn't notice it. Each subsequent shot landed in a different place relative to the target (a patch) and the average distance from the patch to each bullet hole was around 5 inches. Holes were round, no suggestion of tumbling. My moderator was untouched. I fired five more Noslers, got a half inch group. Then fired a second batch of Sierras and got a nine inch group.

Now, maybe I've lived a charmed life and groups like that happen to everyone now and again. But I've never seen one. I know what I'm going to try - the bullets were (are) incredibly long (2.4mm longer than the Noslers) and seated the same distance from the lands, the Sierras cause the overall cartridge length to exceed the SAAMI maximum. So I am going to take the back to the standard and start from there. I may also try a few different loads, but I don't like messing with more than one variable at a time so that will come later.

Question is, am I missing something? The heads themselves seem fine (albeit with a surprising weight range from 90.02g to 90.16g) so I'm ruling out a duff batch. I think it has to be how they're seated but can anyone offer another view please?
Peter Leigh
Posts: 49
Joined: Sat May 16, 2020 8:45 am
Home club or Range: chepstow Rifle Club
Location: South Wales
Contact:

Re: Sierra "Gamechanger" Gameking Tipped

#2 Post by Peter Leigh »

This might be your problem.....

I believe this is a known problem with 10:1 twist 243 rifles using the new sierra gamechanger 243 rounds 90gr. the bullet needs a 9 twist to stabilize properly see https://www.sierrabullets.com/product/6 ... 90-gr-tgk/. Some people have been lucky with a 10 twist but is a 50% lottery if it works or not. My target 10 twist 243 was ok with it. There are unofficial fixes for it as well.
Philiphn
Posts: 9
Joined: Sun Nov 07, 2021 8:47 am
Home club or Range: NRA; Bassingbourn Rifle and Pistol Club
Location: Cambridge

Re: Sierra "Gamechanger" Gameking Tipped

#3 Post by Philiphn »

Ha! Bingo. Well, sounds pretty much like bingo anyway. Not a detail referenced in the spec when I bought them (but to be fair I didn't go onto the Sierra website to explore further). Thanks, I much appreciate you replying.
User avatar
Graham M
Posts: 943
Joined: Sun Nov 07, 2010 1:14 pm
Location: Brum
Contact:

Re: Sierra "Gamechanger" Gameking Tipped

#4 Post by Graham M »

Strange isn't it. I have a Tikka T3 Hunter that can shoot 100grn SPs but my friend who has the same rifle can't shoot anything above 90 grn.
Never argue with an idiot, he will drag you down to his level and beat you with experience.
Philiphn
Posts: 9
Joined: Sun Nov 07, 2021 8:47 am
Home club or Range: NRA; Bassingbourn Rifle and Pistol Club
Location: Cambridge

Re: Sierra "Gamechanger" Gameking Tipped

#5 Post by Philiphn »

Graham M wrote: Thu Nov 11, 2021 5:15 pm Strange isn't it. I have a Tikka T3 Hunter that can shoot 100grn SPs but my friend who has the same rifle can't shoot anything above 90 grn.
Yes, that sounds familiar. When I acquired my Sako 85 in .243 I defaulted to 100gr heads but using N160 always fell short of 1700 ft lbs for stalking because of the need to avoid excessive pressure. Dropping back 10gr made the difference. I'm about to try old school Speer 85gr spbt heads so that should be interesting.
Peter Leigh
Posts: 49
Joined: Sat May 16, 2020 8:45 am
Home club or Range: chepstow Rifle Club
Location: South Wales
Contact:

Re: Sierra "Gamechanger" Gameking Tipped

#6 Post by Peter Leigh »

Strange isn't it. I have a Tikka T3 Hunter that can shoot 100grn SPs but my friend who has the same rifle can't shoot anything above 90 grn.

It would be interesting to know if you both clean your barrels the same way?



(but to be fair I didn't go onto the Sierra website to explore further).



The addon of 9 twist on the sierra website was only added later after complaints when they looked into it !!. In an effort to produce a more efficient bullet you need cp/cg ratios to be closer together but if you go too far it becomes unstable.
User avatar
Graham M
Posts: 943
Joined: Sun Nov 07, 2010 1:14 pm
Location: Brum
Contact:

Re: Sierra "Gamechanger" Gameking Tipped

#7 Post by Graham M »

Peter Leigh wrote: Fri Nov 12, 2021 7:33 am It would be interesting to know if you both clean your barrels the same way?


I tend to clean every 25 shots or so. Think he does something similar.
Just one of those anomalies I think.
bangbang
Never argue with an idiot, he will drag you down to his level and beat you with experience.
User avatar
Dellboy
Site Supporter 2021
Posts: 2614
Joined: Wed Aug 31, 2011 11:49 am
Home club or Range: Star Shooting Club
Location: Essex
Contact:

Re: Sierra "Gamechanger" Gameking Tipped

#8 Post by Dellboy »

Before you knock yourself out was it electronic targets ? we were at Bisley on the 600 and my 6.5 was shooting shotgun size groups(after 3 others had shot ok , until we tried the target next door ..
2020 GOOD DEALS WITH

Cutch Vortex Scope
Mauserbill Enfield Books


Enjoy today as tomorrow might not come .

Noli pati a scelestis opprimi.

002515
Philiphn
Posts: 9
Joined: Sun Nov 07, 2021 8:47 am
Home club or Range: NRA; Bassingbourn Rifle and Pistol Club
Location: Cambridge

Re: Sierra "Gamechanger" Gameking Tipped

#9 Post by Philiphn »

Dellboy wrote: Fri Nov 12, 2021 11:16 am Before you knock yourself out was it electronic targets ? we were at Bisley on the 600 and my 6.5 was shooting shotgun size groups(after 3 others had shot ok , until we tried the target next door ..
Good thinking, but no, I was on Short Siberia shooting at 20mm patches on an otherwise clean target face, so able to monitor each shot. Sounds like you had an interesting time! I'm going to be shooting at 600 in the next few weeks: maybe I'll have a human marker...


Peter Leigh wrote: Fri Nov 12, 2021 7:33 am

The addon of 9 twist on the sierra website was only added later after complaints when they looked into it !!. In an effort to produce a more efficient bullet you need cp/cg ratios to be closer together but if you go too far it becomes unstable.


Hmmm. That sounds like rocket stuff? Clearly applicable though but a bit much for my brain. What I do know is that a very long bullet will take more work to stabilise it, so it's surprising/depressing that (if your point about an addendum to the Sierra website is accurate) it took users' complaints to prompt Sierra to add the information. It was quite surreal watching the bullets striking in such a random pattern, given the consistency of sight picture and trigger release.
Post Reply

Who is online

Users browsing this forum: Majestic-12 [Bot] and 7 guests