Thread: 6GT

For many years - since reading about the Steel Safari back in about 2008 - I have been keen to shoot field-style or PRS matches and haven't prioritised doing so. After shooting the Sparrowhawk hunter course in Jan, I realised that these matches are a lot more common and accessible than in the past. Earlier in the year, I had a spare Remington 700 short action with .378 bolt face sitting around. I decided to use this action to put together a rifle that would be, optimistically, reasonably suitable for both shooting matches and hunting.

The intent was to build a rifle precise enough to compete, light enough to carry hunting, and chambered in a SAAMI standard cartridge with available components, dies etc - with sufficiently good ballistics to hit targets downrange, with sufficiently low recoil yet sufficient splash down-range to self-spot, and efficient enough, with long enough barrel life, that I can actually shoot it affordably. Terminal ballistics on animals weren't a significant concern, because we know that .223 is sufficient so anything larger is clearly also sufficient. AICS mags required.

Cartridge selection based on these criteria narrowed the field - On the low end, .223 does not have sufficient splash downrange to spot shots reliably, other .22 cal rounds lack barrel life.

6mm, 6.5mm or 7mm gives sufficient splash to spot downrange. All have good ballistics, and barrel life probably increases with bore size. I did not consider .25 cal rounds as there were none SAAMI standard. 7mm has excessive recoil for spotting shots from positions. This leaves 6mm and the smaller 6.5mm rounds.

Considering the 6.5CM, .260, 6.5x47, 6mmARC, 6mmBR (and variants), 6GT, 6CM, .243. Ultimately, I felt that the extra recoil of the 6.5 cartridges would be too much for good spotting, and outweigh the benefits of the higher BC, extra splash and potentially longer barrel life.

For 6mm cartridges, the 6mmCM is very short on barrel life, as is .243. The 6ARC uses a non-standard bolt-face, and mags are limited. 6BR and variants are notorious for feeding issues.

This narrowed it down to the 6mm GT.

The 6mm GT is a moderately sized case with a .473 and SRP case-head, developed specifically for PRS use to fix the feeding issues found in BR variant cases. It was initially developed from a shortened 6.5x47 case by George Gardner of GA Precision and Tom Jacobs of Vaportrail bullets

It is optimised to shoot 105-110gr 6mm bullets with common powders like 2208/2209/N150 etc. Case capacity is between 6BR/variants, and the x47 case. Brass is available from Hornady and Alpha, and factory ammunition is available from Hornady.

Greg at Terminator put the rifle together for me with a variety of bits I sent him & he supplied -

700 SA with bolt fluting & oversize knob. Greg supplied a 2nd bolt with the appropriate bolt face, so I still have the .373" bolt spare - may end up a .223 in future....
Brux #3 (Bartlein 2B) .236 1:8" twist barrel, fluted, at 18 inches
Timney HIT
Hawkins M5 DBM
GRC elite stock
DPT

I have put a 3-18x44 Mk6 on top in Talley rings. The comb of the GRC stock was too low, even in the lowest possible 34mm mounting option, so I have added a Victor Company cheek riser. Next to my M7 .223




The rifle shoots very well using alpha brass - I tested - noting that the barrel has sped up around 60fps over the first 200 rounds -
an old, slow batch of 2209 - at book max of 38.1gr gives 2710fps (once barrel sped up)
a new batch of 2209 - book max gives 2790fps (same)
2208 - book max of 33.1gr gives 2670fps or there abouts.
This target was the extent of load testing.


I have chosen to go with 2209, as I was looking for 2700-2850fps speed range. Once I get through my old stock of the slow 2209, I'll switch to new powder and drop 1gr or more under max to stay at around 2700fps.

I did also try the 109gr ELDM, which gives 2780fps with a book max load of 2209, but does not stabilise in the 1:8 barrel - I would have preferred a 1:7 or 1:7.5 but unfortunately only a 1:8 was available in the contour I wanted. Barrels are consumable anyway so it will be shot until it dies and replaced.

I have had good feeding with the 5 (6) round Magpul AICS mags, however the Magpul 10rd is no good. An AI 10 rounder works well once the feed lips were tweaked.

I have shot 6 red deer with the rifle since I got it, out to 500 metres. It worked well as expected.


Last weekend I shot the individual match at Sparrowhawk, the first match with the rifle. Round count of 64, across 9 stages, with targets from 400-900m, 2-minute time limits per stage. This is clearly not a dedicated match rifle. The total weight is 3.6kg (8lb) with scope and suppressor, the bare rifle is 2.5kg. Most people shooting these matches are largely using mild 6mm cartridges in 20+ LB chassis-based rifles with 26+ inch straight taper barrels, muzzle brakes, etc. The light weight is a handicap for shooting from positions and for spotting my impacts downrange, which is key for success in PRS type matches. I however didn't feel that the rifle held me back, and there is plenty of room for skill development which will get me more points than buying gear. I placed tied at 13 out of 19 - improvements will include time management, some better work on stage planning, etc. My goal is to shoot all the South Island based PR matches for 2025 where I don't have scheduling conflicts.

Great set-up!

Nice practical set up - very cool.

PRS can be challenging at the best of times - definitely fun but challenging. As you say, if you go into it with a good attitude there are big skill gains to be had.
Have you thought about two bipods - a lighter one for hunting and a heavier one for PRS to help balance up the rifle to sit and settle into a barricade bag better. Another thought would be something like the DST Precision "Da'Rail" to provide a better balance point, some weight, and a flatter surface to sit on a bag.

Nice setup, I like your thinking. You said what projectile you weren't using but I can't see what you actually shot, it is certainly plenty accurate for all tasks at hand.

I've always wondered about "ballasting up" a hunting weight rifle for PRS style shooting, if your barrel will handle the strings of fire why not? Getting the balance right would be the key.

Whoops. 108 ELDM.

Originally Posted by Gillie

Nice practical set up - very cool.

PRS can be challenging at the best of times - definitely fun but challenging. As you say, if you go into it with a good attitude there are big skill gains to be had.
Have you thought about two bipods - a lighter one for hunting and a heavier one for PRS to help balance up the rifle to sit and settle into a barricade bag better. Another thought would be something like the DST Precision "Da'Rail" to provide a better balance point, some weight, and a flatter surface to sit on a bag.

A Ckye pod would be nice...

I'm initially keen to test/build my proficiency with what I view as a "practical" rifle rather than getting too into the game - for now.

Great post Gimp, very interesting. Looks like youve done some good research in cartridge and component selection.

Are you using 10 shot groups for testing now ? Needs a steady temperament to get 10 good releases on demand …

Is this a 2.8” .308 length action ?

Thats a great build, GT is a tidy little cartridge and I have wanted to build something along those lines. your max 2208 book load sounds quite low, we have generally found 2208 to perform better than 09 in competition GT's.

Gillie is right about a heavier bipod, another option to balance is out for positional shooting is a heavier braked suppressor like an A-tec PRS 2 mod. it would help with recoil and tidy the balance up a bit for matches.
Will hopefully see it in action at a south island match next year.

Originally Posted by Bagheera

Great post Gimp, very interesting. Looks like youve done some good research in cartridge and component selection.

Are you using 10 shot groups for testing now ? Needs a steady temperament to get 10 good releases on demand …

Yes - 10 gives a more reasonable idea of precision and consistency in a practical round count

Originally Posted by Bagheera

Is this a 2.8” .308 length action ?

Yes - the COL of the round is around 2.5"

Originally Posted by gimp

Whoops. 108 ELDM.

There is a 109 ELDM, only seen it for sale through GA Precision though.

Originally Posted by Beetroot

There is a 109 ELDM, only seen it for sale through GA Precision though.

Yes. I've tried them. They're available on the general market now. They're a higher BC than the 108s and I would be using them if available and if I had a 1:7.5

Tried 109s, am using 108s. It's very confusing

Originally Posted by gimp

A Ckye pod would be nice...

I'm initially keen to test/build my proficiency with what I view as a "practical" rifle rather than getting too into the game - for now.

If you decide to spend the money on a nice bipod for competition make sure it's ARCA compatible, you'll thank yourself in the future.

You can do pretty well in in PRS type shoots with a practical rifle, but the top guys are heavily into the gear race now.
The P is for Precision not for Practical, hence why PRS is not overly practical anymore.

If you did want to add some weight buy not go full retard with the Da rail, I've been working with a gun to get some steel ARCA rails made up. Don't have any yet but might pull finger next year and get it done.

Very nice set up and effective on both animals and targets.

Great post.