6GT

@kiwi303 was kind enough to donate me 10x 105gr Aeromatch and I got the weather to shoot them today. 3x fired brass (annealed) with 34.5gr 2208, 0.050" jump. Pretty good. Conventional load development methods continue to be a joke

Avg 2735 SD 11.9
Attachment 284074

Also gave 108 bergers a crack with 2208 to see if it would be better than 2209 for velocity consistency. My SD with 2209 floats around 11-12 which isn't amazing

Avg 2693 SD 7.7. A bit slow but I've struggled to get velocity with 2208. I didn't have to hammer the bolt open so maybe I'll try another couple of tenths.
Attachment 284076

interesting . . . I was talking with a shooter today who runs two identical 6mm CMs. He was conducting an experiment running the 6CM at 6mm Dasher velocities. He was using a reduced load of 2208 (he mentioned "book starting load, but I can't recall the number of grains) and getting 2850 with single digit SDs and extremely good accuracy. I think he mostly shoots 108s

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Originally Posted by Tentman

interesting . . . I was talking with a shooter today who runs two identical 6mm CMs. He was conducting an experiment running the 6CM at 6mm Dasher velocities. He was using a reduced load of 2208 (he mentioned "book starting load, but I can't recall the number of grains) and getting 2850 with single digit SDs and extremely good accuracy. I think he mostly shoots 108s

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Hmm there's no 6mmCM book data with 2208, maybe Hodgdon have some for varget

Oops, typo, 2209.

Interesting to think about. The CM case is so inefficient in 22/6mm



Running some numbers in preciseload calc -


6GT with book max 2209 (38.1gr) @ 24" & 108ELD = 2903fps & 61400psi
6CM to match that speed = 40.2gr of 2209, but only 56,000psi
6CM at book max 2209 (41.6gr) = 2990fps & 60400 psi


So you can run a CM at lower pressure to match the GT speed, but it still burns 5% more powder to do it. Wonder if the lower pressure but more powder still means faster barrel wear

Quote:

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Originally Posted by gimp

Interesting to think about. The CM case is so inefficient in 22/6mm



Running some numbers in preciseload calc -


6GT with book max 2209 (38.1gr) @ 24" & 108ELD = 2903fps & 61400psi
6CM to match that speed = 40.2gr of 2209, but only 56,000psi
6CM at book max 2209 (41.6gr) = 2990fps & 60400 psi


So you can run a CM at lower pressure to match the GT speed, but it still burns 5% more powder to do it. Wonder if the lower pressure but more powder still means faster barrel wear

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Good question.

You would hardly worry about an extra 2-3 grains of powder? At $150/kg it’s a cent a grain. Your powder price might be more but even at double, you wouldn’t worry about it.


Sent from my iPhone using Tapatalk

Quote:

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Originally Posted by Dicko

You would hardly worry about an extra 2-3 grains of powder? At $150/kg it’s a cent a grain. Your powder price might be more but even at double, you wouldn’t worry about it.


Sent from my iPhone using Tapatalk

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Extra powder burnt is extra recoil is another consideration.

Quote:

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Originally Posted by Dicko

You would hardly worry about an extra 2-3 grains of powder? At $150/kg it’s a cent a grain. Your powder price might be more but even at double, you wouldn’t worry about it.


Sent from my iPhone using Tapatalk

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I think it's the least of the reasons why I wouldn't do it

Quote:

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Originally Posted by gimp

Interesting to think about. The CM case is so inefficient in 22/6mm



Running some numbers in preciseload calc -


6GT with book max 2209 (38.1gr) @ 24" & 108ELD = 2903fps & 61400psi
6CM to match that speed = 40.2gr of 2209, but only 56,000psi
6CM at book max 2209 (41.6gr) = 2990fps & 60400 psi


So you can run a CM at lower pressure to match the GT speed, but it still burns 5% more powder to do it. Wonder if the lower pressure but more powder still means faster barrel wear

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How does the 243win fit in there?

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Originally Posted by Shearer

How does the 243win fit in there?

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effectively identical to the 6mmCM


40.3gr 2209 for 2904fps and 56300 psi to "match the GT" or about 42gr for just over 3000fps for max pressure @61k psi

Just a casual observation my 243 win putting the 108gr eldm out at 2800 was noticeably more snappy and more felt recoil than my 6cm does, most probably related to the rifles themselves? (243= Kimber Montana, 6cm = Howa Superlite) but actually very impressed with how soft shooting and easy the 6cm has been to shoot. Also interesting to note have only shot the factory Hornady 108gr eldm Match ammunition and the Precision Hunter 103gr eldx and the Match is doing 2800 (18.5") with the heavier projectile while the Precision Hunter only did 2730. Early days on a brand new barrel and things might jump around a bit once its had a hundred or so down the barrel but I assumed hornady would have stoked the hunting load up a bit over their Match load.

Quote:

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Originally Posted by gimp

Interesting to think about. The CM case is so inefficient in 22/6mm



Running some numbers in preciseload calc -


6GT with book max 2209 (38.1gr) @ 24" & 108ELD = 2903fps & 61400psi
6CM to match that speed = 40.2gr of 2209, but only 56,000psi
6CM at book max 2209 (41.6gr) = 2990fps & 60400 psi


So you can run a CM at lower pressure to match the GT speed, but it still burns 5% more powder to do it. Wonder if the lower pressure but more powder still means faster barrel wear

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Inefficent meaning ? Ineffective at killing or a perfect absolute burn rate? Everyone seems to be going heavy but the 270 and 308 with bugger all recoil running death at speed using 110gr pills is hard to beat. Best not mention 53gr TSX . 2C.

I shot the PRS Finale with this rifle on the weekend, and I think I have reached/exceeded the limits of the usefulness of shooting this style of match with this rifle


I got off 158 out of 188 possible shots. However my hit rate was not great - only 27% hits from shots fired (vs 63% of the winner).

Conditions were hectically tough. AB only calculates windage up to a wind value of 22.4 M/S. At one firing position I was getting 25+ M/S on the kestrel.

Taking the principle that I need to trust my gear and data, I did not zero on the Friday - but did fire 2 rounds at the 450m and 802m steel plates with hits. I was shooting the 108gr Berger EH this time around @2746fps - the Bergers shoot consistently very well for precision. I did not have any data issues to my knowledge. I did have elevation difficulties as there were a lot of high angle shots for which I was accounting for the angle in AB, not knowing that the ranges in the match book were EHD/TBR. This probably cost me a few points. There was probably also some unaccounted-for aerodynamic jump component due to the massive difficulty of making an accurate wind call.


The weight of the rifle was very limiting at this match with the wind and the positions. It was impossible to achieve stability in most cases with buffeting from the wind - trying to time shots in a 2MIL wobble zone is a waste of time and ammunition. It is also extremely difficult to spot shots downrange with the light weight. Spotting misses and making corrections was critical for points at this match. Wind holds were up to 5 MIL and some of my wind brackets were like 2.5 mil for a 0.5mil target - where it was close to a 12 o'clock wind and it could have been a 1.25mil bracket either side. I simply could not see most of my shots downrange to make corrections.

It is very different to try get a stable and solid position prone on a flat range with no time limit to spot misses, vs from improvised field positions on tight time limits (10-12 shots in 120 seconds with multiple target ranges and positions - you have to hustle) particularly with targets where the backdrop is very difficult to spot impacts from small 6mm bullets.

The ultralight support bag with Spexlite fill (approx 300gm) is absolutely a massive handicap on time pressured shots compared to a 5kg sand-filled bag. It just takes time and effort to settle the gun. Fortunately, I got a heavy bag from the prize table at the end

I did manage to get the top score on one stage where it was suited to my setup - prone with good stability. I got a favourable wind condition but the system worked.


All in all, after having shot a few PRS style matches with this rifle now here are my reflections.

- A quality hunting weight rifle can provide excellent precision, practically speaking on par with a full-on competition rig. If you're shooting limited numbers of shots (e.g. hunting) and have a spotter or can take the time to build a really solid position, you should be equally as effective at making hits at long range.
- For matches like the Sparrowhawk ultimate hunter, or the upcoming NRL hunter style series, a hunting weight rifle can absolutely perform competitively
- For PRS style matches, with the high proportion of positional shooting - a hunting rifle is a handicap but you can make it work well if you have good data and are a good shooter, in good conditions. In conditions like this weekend - forget it.
- After 1200+ rounds through this rifle in the past 12 months, most of them shot in rapid 10+ round strings - the throat looks pretty mint still. Worrying about barrel heat in a good quality lightweight barrel really isn't a thing
- If all you have is a hunting rifle, you can and should still go shoot a match with it to see how you like it, and to test your prep and your system. I'm really comfortable that my prep, system and process are actually really good. This rifle cannot take me any further in PRS matches, but my knowledge and process base isn't limiting my success in practical or match scenarios.
- If I was to do it again with a light rifle I'd consider something like a 6.5CM shooting a 147gr + bullet as slow as possible, to maximise downrange signature and hopefully have a better chance of seeing it, even with the increased recoil.

Attachment 284659


So, I think I'll be retiring this rifle from PRS match duties for next year, it'll still come out for the Ultimate Hunter & the NRL Hunter - but something else will happen for the PRS series, and I'll have a proper crack at getting in the top 10. or top 30.

Quote:

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Originally Posted by TeRei

Inefficent meaning ? Ineffective at killing or a perfect absolute burn rate? Everyone seems to be going heavy but the 270 and 308 with bugger all recoil running death at speed using 110gr pills is hard to beat. Best not mention 53gr TSX . 2C.

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Powder burnt/recoil generated vs terminal/ wind performance i would guess