M40A6 USMC trial rifles

[molonlave]

I'm looking for some information about the trial for the M40a6 upgrade. The specific area I'm trying to obtain clarification is the stocks provided by Accuracy International and the configuration of the barreled actions used during testing. It appears that AX AICS stocks were utilized. The prototype stock is engraved "M40a5".

So the question is, did they use M40a5 barreled actions or the new M40a6 configuration to trial the Accuracy International chassis?

Anyone who may have been involved in that phase of the trial, please educate us on this small side note of USMC sniper rifle history.

 

[molonlave]

Bump this up! Hoping to catch the attention of anyone who's in the know.

 

[Skunk]

I don't know anything, but question how and why they ended up with the chassis they did when they could've had an AICS.

 

[molonlave]

I'm in complete agreement!

 

[nn8734]

I don't know anything, but question how and why they ended up with the chassis they did when they could've had an AICS.

Probably the same reasons (cost vs perceived value and perhaps politics to an extent) Remington ended up with the PSR contract instead of AI even though the AI PSR was in all likelihood, the superior platform.

You can’t help but wonder if the ASR program would have even been initiated if the AI PSR was selected.

 

[molonlave]

You bring up an excellent point. I doubt the ASR program would have been initiated had they selected the AI PSR. But, I'm a self admitted AI fan boy, and thus my opinion is heavily biased

 

[macethetemplar]

One of your best options would be to contact badgerord in the below thread. They submitted a prototype mount (Badger Unimount with USMC engraved on one side and PN 306-64M on the other) for the M40A6 contract and had been involved with other contracts previously.

This thread was from the early A6 days.

M40A6 Build Guide - M40rifle.com

So the M40A6 build begins…. Barrel: Schnider .30 cal, Finishes 20" OAL This is the same barrel contour as the A3/A5, just cut to 20" P form rifling was

www.m40rifle.com

 

[Random Guy]

"

The specific area I'm trying to obtain clarification is the stocks provided by Accuracy International and the configuration of the barreled actions used during testing. It appears that AX AICS stocks were utilized. The prototype stock is engraved "M40a5".

So the question is, did they use M40a5 barreled actions or the new M40a6 configuration to trial the Accuracy International chassis?

...based on the below thread, the chassis submitted for evaluation were supposed to work with an M40A5 with M40A5 lug....but that was a problem for a variety of reasons and resulted in the accuracy issues that were encountered back in 2016 with that transition. Here's a good thread on that history:

M40A6 Chassis - M40rifle.com

Chassis available.... http://www.eurooptic.com/Remington-Defense-RACS-Chassis-86485.aspx?utm_source=eoic2017&utm_medium=JAB

www.m40rifle.com

...from a former Scout-Sniper on that forum:

"The 12's are literally pulling their hair out trying to get these things right.....This was from a 12 friend of mine the is there.

"We have to measure from the receiver face to the backside of the recoil lug closest to the receiver to figure out how much of the receiver has been removed from truing, then turn the shoulder back on the lug to move it back towards the receiver. If you don't it causes binding and terrible accuracy issues".
"Plus the top rail springs on the action when tightening down which also causes binding and accuracy issues"...."When we get them to shoot, they shoot. It just takes allot more time"...."Surefire brakes and cans are a whole another story in itself".
"Twice the custom machine work of the previous A series bolt guns".

...From Marty, owner of Badger Ordnance:

"There is additional fun, the A6 stock is called the M40A5 RACS chassis, why you may ask, well when the Corps put out the RFQ for the stock, all they said was make it fit the M40A5, it was the only gun they had at the time.

So when Remington, AI, Cadex, APO and others scrambled to make a chassis they used a spec M40A5 barreled action.
Then after the contract was awarded, a new lug was spec'ed and manufactured.

However, someone did not do their homework and made the lug too wide for the chassis. So not only are the lugs being fit for thickness are also being fit for width.

Badger offers a "Spec lug" that will require fitting as done in the PWS shop."

...and this nugget:

"In addition to adjusting the lug front to rear (Thickness), the width (Side to side) of the A6 lugs are TOO WIDE for the chassis and must be hand fit.

...The manufacturer was told to make it fit an M40A5, they were not told to make it adjustable or functional in any way beyond making it fit a stock Remington action with an A5 lug and a #7 contour barrel.

My opinion is that pay grades above the PWS made some decisions without input from Snipers or the 2112 gun builders.

Lastly, fitting the lug for receiver length variation is unfortunate but an artifact of the extended service life of the (M40A5) actions, the PWS has done a very admiral job of making great firearms out of nothing for many years.

In an Army contract gun, if the lugs were worn or set back, the receiver would be destroyed immediately. In the Corps, the question is "How many times can we make it work again?"

....

My thoughts? I suspect that prototype AICS chassis is designed for the old M40A5 lug per Marty's posts, but that's just a guess. As to why the AIC chassis was not selected? Probably have to find and contact the AICS federal sales Director for that particular answer. Typically the vendors can (and do) request a de-brief on why their product was not selected, and usually the USMC will not publicize the internal selection process. (Factors include cost/value, technical performance/technical approach, key personnel, or past performance/core capabilities of the vendor, etc.).

 

[8208]

Contact Marty. He would most likely have some specifics. Another option would be to reach out to AI on the US side directly. Random you could save the research paper and just say according to ......... they were required to use the A5 lug.

 

[Trigger Monkey]

"We have to measure from the receiver face to the backside of the recoil lug closest to the receiver to figure out how much of the receiver has been removed from truing, then turn the shoulder back on the lug to move it back towards the receiver. If you don't it causes binding and terrible accuracy issues".

I did an interview with Scott at Accuracy International some years ago and we talked a little bit about the USMC chassis solicitation. The AX AICS mitigated this issue by using action screw holes that were slightly oval shaped. This and other design elements were carried through to the post-2014 AX AICS, including fitting a M40A5 recoil lug.

 

[molonlave]

This is exactly the info I was looking for. Many Thanks!
I had the pleasure of speaking with Marty a while back while ordering a couple M40a6 lugs and he was a wealth of knowledge about the issues related to this topic. He focused primarily on the challenges with the RACS chassis. I wasn't sure of the specifics as it related to the AICS chassis.
My intention is to build a barreled action for the AX AICS trial chassis to accurately represent the set-up as tested. From the information gathered thus far, it is pointing to an M40a5. One piece to the puzzle that is eluding me is the barrel length. Meaning, should I build it using an M40a5 barrel at a5 length or cut down to 20" oal per a6 specs? At what point in the process did they decide to go with the 20" barrel? From the very beginning of the solicitation or after the trials were completed?

 

[Trigger Monkey]

Here's an interesting tidbit from Soldier Systems Daily

Sneak Peek - USMC M40A6 Prototype | Soldier Systems Daily

I recently got a look at a prototype of the proposed USMC upgrade to the M40A6 configuration for their venerable sniper rifle based on the Remington 700 act ...

soldiersystems.net

 

[Random Guy]

At what point in the process did they decide to go with the 20" barrel? From the very beginning of the solicitation or after the trials were completed?

I think you'll have to ask Marty that question as well. My guess is that the 20" barrel was likely in the solicitation, but that is just a guess.

 

[8208]

This is exactly the info I was looking for. Many Thanks!
I had the pleasure of speaking with Marty a while back while ordering a couple M40a6 lugs and he was a wealth of knowledge about the issues related to this topic. He focused primarily on the challenges with the RACS chassis. I wasn't sure of the specifics as it related to the AICS chassis.
My intention is to build a barreled action for the AX AICS trial chassis to accurately represent the set-up as tested. From the information gathered thus far, it is pointing to an M40a5. One piece to the puzzle that is eluding me is the barrel length. Meaning, should I build it using an M40a5 barrel at a5 length or cut down to 20" oal per a6 specs? At what point in the process did they decide to go with the 20" barrel? From the very beginning of the solicitation or after the trials were completed?

The M40A5 barrel is a 12 twist Schneider. The A6 is a 10 twist Schneider. Just giving you the information. I would not build a short barreled 308 rifle with a 12 twist as the faster rifling helps stabilize the projectile in that shorter length.

 

[molonlave]

Makes good sense, thanks!

 

[FUNCTIONAL]

Just as a side bit of info. I built my A6 thhis past weekend and with a fresh action the badger A6 lug slipper right in without binding. The lug is A TIGHT FIT, hardly any movement at all. As mentioned the issue is with old setback actions, anything other than a once trued action i could see being an issue.

The scope base rail was a binding issue and i was just about to accept it and bed there rail when i looked at the front stock tube. The front tube is actually 2 pieces, the tube and the mounting block. The tube protruded past the mounting block face surface causing a downward kick of the tube and causing the rail to have a good gap over the action causing bending/ binding when tightened. I suspect whoever assembles thre chassis from the factory need to be re-educated since they are mounting the tube to the mount block first and then to the chassis. It should be mount block to chassis and then tube to mount block to avoid that issue. 2112s are smart but id be interested to know if they picked up on that or what their fix was.

As far as i know the 20" was the intention of the A6. I wonder 1) if they pulled from the darpa xm-3 study and decided 20 wasn't much of a loss in performance and 2) why they decided to suddenly measure the barrel oal instead of from lug face as they traditionally have. In thre end it went 5" shorter with the A6 over the A5 due to measurement differences.

 

[Forgetful Coyote]

Isn’t the RACS chassis the same as Cadex’s?

 

[Trigger Monkey]

Not really, as I recall Cadex worked on the RACS for the XM2010 but only in the very beginning, after Remington got the award I believe they started making the RACS themselves.

 

[Forgetful Coyote]

Not really, as I recall Cadex worked on the RACS for the XM2010 but only in the very beginning, after Remington got the award I believe they started making the RACS themselves.

Interesting. I knew I remembered there being some type of relation.