MPA 6.5SL chamber specs

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
Picking up a Masterpiece Arms (MPA) switch-lug rifle later this week. In 6.5CM.

Has been told it has a “match chamber” apparently optimized for the factory Hornady 140 ELD-M ammo.

I presume the free-bore is set for a small jump for this particular bullet for a book length COAL of 2.80”. Any idea how much jump works well for this chamber setup? Does anybody know the details of the chamber reamer they use?

For reloading, should i start off by simply replicating the load? Same COAL, assume H4350 powder, aim for the same speed? Any idea what primer brand Hornady uses?

I know, asking a million questions...
 
Last edited:

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
If your going to load for it why don’t you seat the bullet by finding the lands and doing load development. Might shoot better than factory ammo.
Got the rifle in hand now. Had a high quality bore scope in the chamber and barrel last night. Wow! Superb workmanship!! Mirror shine, lands are near perfectly cut, and the crown is unmolested. Pristine condition.

Chamber is throated for 140 Hornady ELD-M bulletd/factory ammo. Could not buy the right factory ammo at Academy today, so will have to research COAL and typical speed. This particular 6.5 CM MPA rifle has a 26” Spencer barrel (MPA acquired Spencer).
 

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
If your going to load for it why don’t you seat the bullet by finding the lands and doing load development. Might shoot better than factory ammo.
Picture of new MOA BA in 6.5 CM. MPA chassis, Curtis Axiom action in a v-block in the chassis, burnt bronze color, barricade stop, super adjustable chassis system.

Right handed but left eye dominant, and once you get to middle age, you will wonder what happened to your eye sight, so 4 years ago switched from shooting right handed to left handed. Got lucky and found a left hand action at Xtreme Guns and Ammo in Houston. They seem to have a lot of them in stock.
 

Attachments

Last edited:

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
Checked the distance to the lands with a Stoney Point / Hornady tool, and the MPA BA rifle is definitely short throated compared to other factory guns. Optimized for the Hornady 140 ELD-M factory ammo, which i presume has a COAL somehere close to book length.



Good for 140 grain factory ammo, which is always sized on the small side, which in standard chambers (if there even is such a thing) will cause a lot of gap between brass and chamber. I guess a minimum size chamber will work better if factory ammo is used.

A fairly tight chamber with short throat is good for factory ammo, but perhaps not ideal for hand loading the 147 grain ELD-M or 156 gn Berger EOL Hunter bullet. Then again: Every chamber configuration is a compromise of some kind, will just have to load them deeper, lose some case capacity in the process and down load some amount. Twist rate is 1:8, which will in any case exclude the Sierra 150 SMK.

Will post some measurements when i get home.
 
Last edited:

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
BTW: The chamber is on the tight side. On the barrel is engraved “Match Chamber”. In my case, brass FL sized in my Redding Type S die will cause the bolt to stop 1/4” before it can close, so body diameter is too large to allow the brass to go all the way in. LE Wilson case gauge shows that the case is on spec, and fairly near minimum dimension. [Assuming that the Wilson case gauge is cut correctly.]

Then resized it using the LE Wilson standard FL die with the bushing and decapping rod and button removed, and then the bolt closed very easily.

So not a big deal for me, but still noteworthy that some comp dies cut such that they will resize the brass as little as possible might not work in this type of rifle. Just a different compromise compared to the usual oversize chambers you get from the likes of Remington and Savage.

Will shoot it soon. If it gets below the 3/8’th MOA guarantee with Hornady 140 ELD-M Match ammo, i will be a happy camper.
 
Last edited:
  • Like
Reactions: RJ13

tinbndr

Private
Minuteman
Oct 16, 2018
14
25
18
I have the Same rifle and actually emailed MPA and asked them what the rifle wants to shoot . Was told ELD-M 140 grain .015 off the lands,
H4350 powder cci 250 primers and 41 to 43 grains of powder . I found my best node at 41.3 grains . Hope this helps some .
 
  • Like
Reactions: NamibHunter

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
I have the Same rifle and actually emailed MPA and asked them what the rifle wants to shoot . Was told ELD-M 140 grain .015 off the lands,
H4350 powder cci 250 primers and 41 to 43 grains of powder . I found my best node at 41.3 grains . Hope this helps some .
Thanks TinBender for the info, very good to know. Will try 15 thou (0.015”) jump.

Did barrel break-in today, using Berger 140 factory ammo, and that went very well. No green copper residue at all on the little patches i ran through the barrel. Only carbon fouling. Black carbon residue on the neck shows a sine wave.

Hornady 140 Match ammo arrived late, will try that the weekend.

What size groups are you getting at 100 with the factory ammo?

Namibian
 

tinbndr

Private
Minuteman
Oct 16, 2018
14
25
18
Can’t say ,as I don’t shoot factory ammo. I will say with my hand loads ,it is by far the most accurate rifle I have ever shot . Happy to help with anything else I can . ...good shooting
 

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
Can’t say ,as I don’t shoot factory ammo. I will say with my hand loads ,it is by far the most accurate rifle I have ever shot . Happy to help with anything else I can . ...good shooting
Fair enough!

Barrel beeak-in is now done, so later this week i will get the scope zeroed and shoot some groups at 100. Cannot wait, pretty excited to try it out!

Curious what groups size you are getting with reloads too .... Post a pic, and don’t be shy, if you and the gun shoot good groups, you are allowed to show off a little! 😁
 

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
Nice!

0.42” is superb, especially for a five shot group. If you shoot three shot groups, you will get a few 0.2” and 0.3” groups too. Good for bragging rights, but only five shot groups count. [Too easy to get lucky with a three shot group...]
 

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
Shot the first set of 12 groups today, using the recommended Hornady 140 “Match” ammo: Best group was 0.38”, average was 0.55”. Most were around 0.45”.

Shooting from the bench, with a good rear sand bag, front was on a random heap of sand bags, so did not have a good front setup. Still need to buy a good bipod.

Very happy with this result, for factory ammo. I expect group size to come down some more once i complete the equipment setup and do proper load development.

Hornady ammo gave an SD of 15.3 fps, which is kinda ok but not great. Hand loads should improve a lot on this. [Not sure that qualifies as “match” ammo, probably just the usual marketing hype.]

We will now see what load development can do for this gun... i have high hopes now!

BTW: PMAG magazine feeds like a champ. Perfect fit, came with the gun, clear signs of being corrected with a file. No issues at all with feeding (ever), and extraction is now perfectly reliable. Plunger needed to be worked loose, probably some gunk in there before. Minor issue.

So far so good!
 
Last edited:

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
Was zeroing the scope at 50, so i just continued shooting at that distance for a while. Groups (center to center) were around 0.24”, with the exception of the first group being a little wild (no bipod yet, the heap of sand bags were slipping). So 0.49 MOA for all six groups, 0.42 MOA if you ignore the first group (average of 5 best groups).

Shooting very affordable Hornady 140 gn ELD-M factory match ammo. SD was 15.4 fps. Hand loads will do better than that.

Very happy with this result, given that it is factory ammo. MPA intentionally sizes the chamber and throat for this particular ammo and they have achieved their goal. Pretty confident that with a better rest and rear bag, i will get below their guarantee of 0.375” (3/8’ths of an inch).

Hope the hand loads will get me below 0.3”.... but we shall see!

TriggerTech trigger is superb, light with a clean break and no creep. That helps a lot.

Adjusted the butt pad to be angled and moved it up because my scope has to sit high (prescription glasses cause problems if i am too low on the stock). That certainly also helps.

Happy camper. This rifle is a bargain. Shoots and feels like a custom for 65% of the price of a full custom gun.
 

Attachments

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
Do you guys have any issues using standard FL dies with your MPA reloads? My Redding Type S full length sizer die does not size the case enough to chamber. I have another Wilson FL die (internals removed) and that one works fine. Must be a tight chamber reamer, to better fit the Hornady factory ammo? Rifle worked fine with Berger (Lapua) factory ammo and Hornady 140 ELD-M ammo.

Not a bad idea for the chamber to be cut fairly “tight”, but just curious if anybody knows the reamer spec, or have a pdf for the reamer print used on the MPA 6.5 CM chambers.

I may soon want to get a custom die made for this rifle. Presume MPA would be happy to do that.
 
Last edited:

Pilotscrappy

Winter is coming
Belligerents
Minuteman
Jul 21, 2018
416
164
49
Medford,OR
I use a forster full size with expander button removed. I open necks back up with mandrel. Works great for my mpa 6.5 creed
 

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
I use a forster full size with expander button removed. I open necks back up with mandrel. Works great for my mpa 6.5 creed
Good to know. Maybe my Redding FL die is a little on the large side. Oh well, at least the Wilson FL die works fine. Use the Sinclair mandrel die to open up the necks. Good combo.
 
Last edited:

natchomamma

Sergeant of the Hide
Belligerents
Minuteman
Jul 4, 2019
111
39
34
I have the Same rifle and actually emailed MPA and asked them what the rifle wants to shoot . Was told ELD-M 140 grain .015 off the lands,
H4350 powder cci 250 primers and 41 to 43 grains of powder . I found my best node at 41.3 grains . Hope this helps some .
Interesting my MPA likes 41.3 Gr of H4350 too. I have to run mine at .035 off the lands to get sub .30 @ 100 yard accuracy. Im using cci 200 primers
 

natchomamma

Sergeant of the Hide
Belligerents
Minuteman
Jul 4, 2019
111
39
34
Do you guys have any issues using standard FL dies with your MPA reloads? My Redding Type S full length sizer die does not size the case enough to chamber. I have another Wilson FL die (internals removed) and that one works fine. Must be a tight chamber reamer, to better fit the Hornady factory ammo? Rifle worked fine with Berger (Lapua) factory ammo and Hornady 140 ELD-M ammo.

Not a bad idea for the chamber to be cut fairly “tight”, but just curious if anybody knows the reamer spec, or have a pdf for the reamer print used on the MPA 6.5 CM chambers.

I may soon want to get a custom die made for this rifle. Presume MPA would be happy to do that.

Are you picking up range brass? I ran into this when I accidentally mixed my brass with range brass. My Redding type S dies work fine on my MPA.
 

Pilotscrappy

Winter is coming
Belligerents
Minuteman
Jul 21, 2018
416
164
49
Medford,OR
Interesting my MPA likes 41.3 Gr of H4350 too. I have to run mine at .035 off the lands to get sub .30 @ 100 yard accuracy. Im using cci 200 primers
I just finished load development for h4350 and the 140eld on my mpa
I ended up with 40.4gr (h4350) cci#200 primer
Hornady brass
. 010 off lands and its shooting in the. 2 to. 3
2780fps avg s/d 6.78

I was running a good load with reloader 16 but that damn powder is so dirty I think I'm gunna stick with the hodgdon powder
 

pbatesaz

Online Training Member
Online Training Access
Belligerents
Minuteman
Jul 12, 2018
187
135
49
Phoenix, AZ and Cimarron, CO
Picking up a Masterpiece Arms (MPA) switch-lug rifle later this week. In 6.5CM.

Has been told it has a “match chamber” apparently optimized for the factory Hornady 140 ELD-M ammo.

I presume the free-bore is set for a small jump for this particular bullet for a book length COAL of 2.80”. Any idea how much jump works well for this chamber setup? Does anybody know the details of the chamber reamer they use?

For reloading, should i start off by simply replicating the load? Same COAL, assume H4350 powder, aim for the same speed? Any idea what primer brand Hornady uses?

I know, asking a million questions...

I have that rifle. Al will send you a print of you ask. It is a Pacific Tool reamer. I have both 6.5 CM and 6mm CM barrels... very easy to switch and both shoot very well. In the 6.5 I am using Berger 130 hybrids loaded to 2.82 in COAL with CCI 450 primers, Lapua brass and RL 16 41.8 gr to get 2953 fps... can’t recall SD, but it is mid single digit. Accuracy has been very good. I clean every 100 to 200 rounds to keep the carbon ring at bay. Trying to decide if I want to order a 224 Valkyrie barrel, bolt and mag for it or just get another 6mm CM barrel in anticipation of burning up the one I have... what a terrible first world dilemma🤑. Good luck with your rifle. I think you will enjoy it.
 

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
Thanks for the info! Will request the reamer print.

Guys: Want to have a custom FL die ground for the MPA chamber. Have not gone this way before, so need good advice: Is it better to send Forster three fired unsized cases? Or send the reamer print? Both??

Who do you recommend (best bang for the buck) to make such a die? Shooting steel at 600, at some point in the future 1000 yard F-Open.

Namib
 

Pilotscrappy

Winter is coming
Belligerents
Minuteman
Jul 21, 2018
416
164
49
Medford,OR
I think sending forster some fired brass from your chamber is good enough... That's what I plan on doing.
 

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
Got some groups to show now: Hornady 140 ELD-M hand loads in Alpha brass.

Slowly getting used to shooting a left handed chassis gun (right handed but left eye dominant), and I’m getting the groups fairly routinely below 0.5” now.

Shooting four shot groups. Best so far is a nice 0.35” group with three bullets through one enlarged hole. The typical group size is around 0.45”.

i had some trouble with horizontal movement, did not take a sand bag along, just an empty dirty sock. No free recoil here. Shot from a nice steel bench though. [The horizontal movement should go away with a better setup.]

Quite happy with the accuracy of the rifle. VERY comfortable rifle to shoot.

Speed was limited to about 2770 fps for H4350 and 140 gn bullets by a combo of the tight chamber and rather thick alpha brass, so less case capacity, and pressure signs arrived early. You have to download about a full grain plus a bit more compared to a sloppy Savage or Rem700 chamber. SD was 7.6 fps, which is a little better than most of my reloads.

But: Hornady 140 gn factory ammo shoots remarkably well. Berger factory ammo (Lapua brass, Berger 140 Hybrid) achieved 2820-2840 fps which is quite fast for a 26” barrel. Also shot well (0.45” average 5 shot group size). I would guess that speed is better because Lapua brass is not suite so thick, and they are probably using a proprietary powder. [Lapua in Finland acquired Berger some time ago.]

The tight chamber and lower max speed is the price you pay for the improved accuracy you get with a factory load. Not a bad compromise, bu
 

Attachments

Last edited:

NamibHunter

Sergeant of the Hide
Belligerents
Minuteman
Dec 26, 2018
328
141
49
BTW: What looks like a two shot group is indeed 4. Two through each hole. Pity about the horizontal offset, that was mostly “user error”... All are four shot groups, believe it or not!
 

Pilotscrappy

Winter is coming
Belligerents
Minuteman
Jul 21, 2018
416
164
49
Medford,OR
BTW: What looks like a two shot group is indeed 4. Two through each hole. Pity about the horizontal offset, that was mostly “user error”... All are four shot groups, believe it or not!
Lookin good man, I've been very pleased with my mpa rifle as well.
I've settled on 40.4 grains of h4350 under a 140eld ,hornady brass,cci primer and it shoots lights out. Mostly one hole 5 shot groups.
Avg velocity is 2770 fps out of 24" barrel.

I'm already at 767 rounds on mine and I think I got it in August of this year lol