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M40A6

Z

Zigjib

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Minuteman
Jul 19, 2014
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Recently put together my M40A6 build. Thing is sick. Went the old school route with the Scope and as I couldn't get the right mount just went with the LT845 mount.

I'm cloning M118LR for it and I got some questions for dudes who have put M118LR through the A6.

I saw the initial data that said the gun would do 2650fps. I loaded up for that and got bad pressure signs and stiff bolt lift.

Spoke to a mate in the US who said that the initial plan was for that MV but due to pressure, it was dropped to 777m/s or 2550fps but he's not USMC - not to say I don't believe him, just looking for some more clarity.

I got the spec sheet that states 41.745gr of 4064. We can't get that in my country so I used the closest proxy which is Varget. Dropped 41.8gr of that in a FC 308 case with a 210m Match Primer behind the 175smk and got the below on the Garmin.

Am I done or does the USMC continue to push for higher MVs from the A6?

Cheers

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pmclaine said:
It's still 1989 where you are?

I'm getting a plane ticket than because the 2020's absolutely suck.
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Nah it's pretty much the same back here. Roadhouse is in the theatres in both time lines and the second Ghost Busters is coming. Michael keaton is trending as batman..... Only difference i can see is for us, Weekend at Bernie's is about to start screening.... where in your timeline, weekend at bernie's is an electoral campaign and when Harry met Sally is a documentary about gender affirming surgery
 
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2,650 is optimistic. 2,580 should be right about on the money. 41.75 was the old FGMM load, and I'm not an expert, but the Mk 316 Mod 0 load as well. The old M118 load used Reloader 15 IIRC (maybe that was just the "special ball" and not the "LR"), but they gave up on it due to the temperature sensitivity. It was a highly copied item 15+ years ago. Guys gave up on it because they were having to drop a grain of powder in the hot summers, and I certainly haven't paid it much attention since then.

Hopefully somebody with a better memory comes along and helps.

Your load looks close enough in velocity that if your accuracy is that good and repeatable...there is no need to tinker with it further.

I have 500 Lake City LR cases that I bought for my M24R to be "authentic". After testing H2O capacity, I am a firm believer that LC LR brass kind of sucks for consistency.
 
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FC brass is what you use. So that's correct. If you reference the book you'll see that it takes a bit more varget to achieve the same velocities as 4064 or rl15. You loose case capacity faster so the pressure will spike faster.
When I developed my load, 4064 was harder to get than rl15 so I used rl15 and was able to get 2640fps with zero issues. I would rather have used 4064 because its more temp stable but oh well. Rl15 responds ro temperature by approximately 1 fps per degree consistently which can be calculated consistently.
Varget it quite temp stable as well. All trade offs.
I think you'll find that 41.3 to 41.6 grains of rl15 will put you where you want to be.
 
Not sure if it’s any help to you, but I just looked in my old (20 years) data book for my TBA built M40A3. It had a Sneider 25” barrel. I had a few cases of the M118LR for it.

Temp was 82* F. 20 rounds fired over the old pro chrono chronograph. High- 2721 fps, low- 2682, average-2701, ES-39, SD-11
 
5Pweld said:
Not sure if it’s any help to you, but I just looked in my old (20 years) data book for my TBA built M40A3. It had a Sneider 25” barrel. I had a few cases of the M118LR for it.

Temp was 82* F. 20 rounds fired over the old pro chrono chronograph. High- 2721 fps, low- 2682, average-2701, ES-39, SD-11
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That's good info, thanks mate.

I cloned M118LR out of my M40A5 and my results are almost identical to yours so that makes me happy.

Cheers Mate
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Can you buy Federal Gold Medal Match 175gr where you're at? It's pretty much the same as the Mk316 Mod 0, and it has little better quality control than the M118LR. If you can buy that, use it (unless you just really enjoy reloading and/or reloading saves you money). It's too bad you're not in the country, otherwise I'd send you an unopened box of Mk316 Mod 0 to try out and dissect. That stuff and the FGMM has worked very well in my M40xx's. I don't reload for this round, so unfortunately I can't provide any advice that you were specifically looking for.

Do you have any other pics of your A6? That's the real reason I clicked on this thread! Post up some more pics of your rifle! And, what's up with the vertical foregrip? Are you taking a lot of standing shots or something? Does it actually help on a bolt action sniper rifle? Definitely haven't seen that before, and I'm interested to know why you're using it on the A6.
 
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USMCSGT0331 said:
Can you buy Federal Gold Medal Match 175gr where you're at? It's pretty much the same as the Mk316 Mod 0, and it has little better quality control than the M118LR. If you can buy that, use it (unless you just really enjoy reloading and/or reloading saves you money). It's too bad you're not in the country, otherwise I'd send you an unopened box of Mk316 Mod 0 to try out and dissect. That stuff and the FGMM has worked very well in my M40xx's. I don't reload for this round, so unfortunately I can't provide any advice that you were specifically looking for.

Do you have any other pics of your A6? That's the real reason I clicked on this thread! Post up some more pics of your rifle! And, what's up with the vertical foregrip? Are you taking a lot of standing shots or something? Does it actually help on a bolt action sniper rifle? Definitely haven't seen that before, and I'm interested to know why you're using it on the A6.
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I stock piled before the world went to hell so i still have 10,000 FGMM LRPs and powder and projies etc.

I'd love to get some real mk316, we come across it from time to time but it's been burnt up in other guns. We can absolutely get FGMM with the 175s so i'll give that a go and see what the difference is.

The fore-grip is for Precision Service Rifle Series. We shoot hawkins and it's a very dated firing position that favours older stock designs. The fore-grip closes the gap for me between the bottom of the fore-end and the ground. Not sexy but it's totally necessary.

This is the only other pic i got sorry mate

moopy.jpg
 
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For my m118lr clone I'm getting the following. Seems the 3 of us are in line.

M40a5: 2702
Xm3: 2540
AIAT 20": 2556 (would be same in A6)
 
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FUNCTIONAL said:
For my m118lr clone I'm getting the following. Seems the 3 of us are in line.

M40a5: 2702
Xm3: 2540
AIAT 20": 2556 (would be same in A6)
Click to expand...
It's cool to see people's data like this.

Only one i can't contribute to is the XM-3..... i chambered mine in 300 blackout

Thanks mate
shapoopy.jpg
 
I’m getting 2540 out of my a6 and 2660 out of my A3 and a5 with factory 118lr. There is a higher node if your reloading but I reloaded to match factory velocity plus it shoots lights out.

Also 845 mounts are correct for the A6 so are the badger SASR rings as well
 

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Topgun117 said:
I’m getting 2540 out of my a6 and 2660 out of my A3 and a5 with factory 118lr. There is a higher node if your reloading but I reloaded to match factory velocity plus it shoots lights out.

Also 845 mounts are correct for the A6 so are the badger SASR rings as well
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Awesome photo! thanks for that mate.
 
I've been loading m118lr to this. If I'm correct this is the most recent recipe for it. I use different primers and load to I think 2.820 coal.

20180523_222221.jpg
 
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FUNCTIONAL said:
I've been loading m118lr to this. If I'm correct this is the most recent recipe for it. I use different primers and load to I think 2.820 coal.

View attachment 8380871
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Yeah mate, we've been referencing that document. We can't get IMR4064 here unfortunately so we are stuck with Varget but it's certainly pretty close if results are to be believed
 
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Zigjib said:
Yeah mate, we've been referencing that document. We can't get IMR4064 here unfortunately so we are stuck with Varget but it's certainly pretty close if results are to be believed
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Can you get Accurate 4064? It is a little slower then IMR 4064, so you will need to add around 0.6 or a tad more to get the same speed as IMR gets.
 
Lost_Phil said:
Can you get Accurate 4064? It is a little slower then IMR 4064, so you will need to add around 0.6 or a tad more to get the same speed as IMR gets.
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I'm not too sure, i'll have a look. Typically we are limited to ADI powders (Hogden) and Vita Vouri (but Vita Vouri is rare and expensive as hell).

I'll have a look around but Varget is doing well .
 
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