Differences between GGG ammunition?

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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.
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Plecotus
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Differences between GGG ammunition?

#1 Post by Plecotus »

I took my newly acquired Magnetospeed V3 to our 100yd range last night. I'm just about to start re-loading and wanted to baseline the ammunition I'm shooting in my .308 now so I have something to compare my own loads with.

I use two types of ammo....both GGG. I've shot quite a few hundred rounds of both types. The 147grn NATO Ball and the 155grn Imperial Match. At 100yds, I consistently achieve 1.5+ MOA groups with the 147 and sub-MOA groups with the 155.

Given the difference in performance, I was expecting the ES and SD for the 155 to be significantly better....it wasn't. After putting two fouling shots through, I shot two consecutive strings, as below:-

GGG 147 Nato
Series 3 Shots: 10
Min 2914 Max 2951
Avg 2931 S-D 12.6
ES 37

GGG 155 Match
Series 4 Shots: 10
Min 2921 Max 2983
Avg 2957 S-D 20.9
ES 62

Given that the measured COAL for both rounds seems to be identical, I'm now wondering what could be causing the difference in group size? I know the bullets are different and I'm also wondering if the 147 NATO might have greater neck tension to make the round more resilient in the field (and with automatic weapons)? Other than that, perhaps the 155 bullet stabilises better in my 32", 1:11 barrel?

I'd really welcome any thoughts and commentary on this. I'm probably just missing something which will obviously account for the performance variation for those with more knowledge tha
rox
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Re: Differences between GGG ammunition?

#2 Post by rox »

Plecotus wrote:Given the difference in performance, I was expecting the ES and SD for the 155 to be significantly better....it wasn't.
Which year is your GGG Imperial? The performance of 2018 GGG Imperial has been subject to significant doubts, and scores achieved have been consistently lower than the GGG supplied in previous years. Questions were first asked at the Inter Counties meeting in June. My own testing suggested significantly larger velocity spreads than last year's supply (ES=68 vs ES=22). Furthermore, numerous world class shots have experienced extremely wide flyers (think 3s and 2s at all distances including 300 yards).

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Maggot
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Re: Differences between GGG ammunition?

#3 Post by Maggot »

Lots of reasons for a big ES

Inconsistant load, neck tension, inconsistant bullet weight, different powder, crimped/not crimped, or anything that causes a different harmonic that does not suit your barrel.

I know nothing about the Imperial loads, except that I would expect them to be better than the STANAG offering IF THE RIFLE LIKES THEM.

I have seen similar issues with 5.56x45 where the owner has tried decent match ammo only to find that the rifle prefers RG for whatever reason. This I am afraid is why some of us handload, so we CAN control the variables better.
Plecotus
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Re: Differences between GGG ammunition?

#4 Post by Plecotus »

Very interesting. The batch number is 020-GGG-18 so I presume that's 2018 manufacturing year? I purchased it from the NRA shop at Bisley a few months ago.

I've had the odd flyer at 600m+ but because I'm relatively new to long-range precision, I always put that down to me...either pulling the shot or not reading a gusty wind correctly!!

I did the F Class course that Mik organises at Bisley back in Feb and the Imperial was recommended by a few of the coaches as a good factory ammo. Not sure what to try now....other than cracking on with loading my own!!
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breacher
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Re: Differences between GGG ammunition?

#5 Post by breacher »

I have noticed a difference in the 155 Imperial too. Not quite as good as it used to be.

Back to 168g GGG for me once I use up the last few hundred 155 I have.
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Plecotus
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Re: Differences between GGG ammunition?

#6 Post by Plecotus »

I've got a couple of hundred Imperial left...I'm hoping to have started loading my own by the time I get through those. Sounds like you've found the 168grn to be a good round. I've never tried anything heavier than 155 in mine.
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Re: Differences between GGG ammunition?

#7 Post by Triffid »

I think that at short range - maybe 100 or 200 m, the velocity ES is simply not a very important factor in determining group size. Other things such as optimum charge weight, run-out, bullet selection etc determine the group size.

So plugging your figures for the 155gn GGG (SMK) into a ballistic calculator gave just 5mm difference in elevation between those bullets with muzzle velocity of 2921 fps compared to those going at 2983 fps.

At longer range the ES becomes much more important, which is why the F-Class people chase very low ES by measuring powder charges carefully. At the other end of the scale, I've heard that some 300m Benchrest competitors just use powder measures to throw charges.

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Re: Differences between GGG ammunition?

#8 Post by rox »

Triffid wrote:I think that at short range - maybe 100 or 200 m, the velocity ES is simply not a very important factor in determining group size. Other things such as optimum charge weight, run-out, bullet selection etc determine the group size.
Of course, but GGG Imperial has that covered too - they made some of the bullets oval, so that even Queen's prize winners and Commonwealth games medallists can get maggies and outers as close as 300 yards.


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Plecotus
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Re: Differences between GGG ammunition?

#9 Post by Plecotus »

I thought the GGG 155 Imperial used a bought-in Sierra bullet.....have I got that wrong?
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Re: Differences between GGG ammunition?

#10 Post by rox »

Plecotus wrote:I thought the GGG 155 Imperial used a bought-in Sierra bullet.....have I got that wrong?
It's supposed to, yes.

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