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Info on the 6.5 Mystic

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Old 03-02-2006, 11:47 AM
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Info on the 6.5 Mystic

Since posting about my 6.5 Mystic in another post, there has been a number who have requested info and specs. Here it is:

The purpose of the design was to make a 1000yd BR cartridge that used a readily available, accurate, strong and cheap brass. Had to allow for near or 100% load density. Enough neck length for proper neck tension. Sufficient velocity to make it effective at 1000yd/m. Of course, be accurate, low in recoil, give relatively long barrel life, feed from mag in case of rapid fire requirements, use ballistically superior bullets, easy to get dies and components.

I studied the 6.5-284, an excellent cartridge in its own right, and found that max velocity was not often the most accurate, throat wear was considered high, recoil moderate but still a little on the high side, case rarely if ever full (this is a personal opinion. I like full cases of powder), components were a bit pricey. BUT it shoots very well. Most seem to launch 140/142gr match bullets around 3000fps.

What to do? For me, the answer was to make a slightly smaller case and basing that case on readily available brass. That lead to the use of the 308 Win case.

This is an improved wildcat where the shoulder is moved as far forward as possible and still leave a calibre long neck. Shoulder angle is 35 degs. Throat is extended to allow 140/142gr match bullets to seat well out to reduce case intrusion. If you look at the picture, you will see the comparision with the parent 308 case.

This case will not fit in a short action mag. A medium length action ie 7X57 mauser length is ideal. Of course, a standard length '06 action would also work just fine. Push feed actions are prefered as the sharp shoulder will not work in some controlled feed actions.

Of course, this is moot in most BR single shot actions.

Prep of this brass is very easy. First 308 win brass is sized at 30 cal and neck turned to 12 thou. The brass is then run through a 7mm neck sizing die to form the secondary shoulder. Location is such that when chambered, the bolt requires firm pressure to close. Cases are then fireformed using the cream of wheat method and out pops a case with a shoulder 90% formed. The first high pressure load finishes the job. I have yet to loose a case using this forming method.

I did my testing in a 25" aftermarket barrel, a bit short but was cheap. Velocites reached 2800fps but accurate vel for that barrel was around 2750fps. In a 28 to 30" match barrel, reaching 2850 to 2900fps should be no issue.

The slight difference in velocity isn't going to amount to that much more wind drift in the real world. Something I was willing to live with.

The rifle proved very easy to load for and accurate. A full, ever so slightly compressed load of H4831SC, gave the best results when lit with either Fed 210M or CCI BR2 primers. I used Fed Gold Medal brass which has a smaller capacity then Winchester. I was able to use 48gr of my lot of H4831SC and would expect up to 49gr using Win brass in this rifle.

The bullets are seated way out. In the picture, the bullet used is the then new 140gr SST which measures a very long 1.40". The boattail sits right at the shoulder/case juction leaving the whole case neck to hold on to the bullet. Perfect. The chamber throated so that the bullet was just off the lands. That could be adjusted to suit your style of land engagement.

At 200m, groups were 5rds in 1/2" or less. I am no BR shooter and this was no BR rifle, but was still very happy with the results. A match rifle/shooter would probably do much better. I did shoot several groups which were one hole. I believe the shooter was the weak link here. :lol:

So the design has met all my criteria for function and performance. Using approx 3/4 the powder of the 6.5-284 will help extend throat life and of course, reduce recoil. Case life is great and trimming not really needed when using the collet die.

Some testing the 6.5 WSSM improved case are using the same amount of powder to get the same velocity. For me, I trust that I can always get 308Win brass. Not so sure about the WSSM.

The best part is that custom dies do not need to be used for this wildcat. I use Lee Collet neck die in 260Rem with a shim (metal washer actually). Works perfectly. I seat bullets using the 260 bullet seater with no problems. One can easily adapt all available 260 bushing and sizing dies to work. This saves you a bunch of money. Can't be said for the WSSM wildcats.

I have really enjoyed this project from concept through to creation. The fact that it has met my expectations is a wonderful bonus. I am about to build a 16.5lbs BR type rifle in this cartridge to fully explore its potential.

If this is something you want to try, let me know and I will send you details on how to cut the chamber and a case to use as a headspace guage. Many gunsmiths already have the proper reamers on hand. Again a huge savings not needing another custom reamer.



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Old 03-02-2006, 12:59 PM
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Join Date: Mar 2004
Location: North Dakota
Posts: 649
Re: Info on the 6.5 Mystic

Jerry would it be safe to say this is pretty much the same as a 260 AI?
Fast, Flat, and Accurate
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Old 03-02-2006, 01:22 PM
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Re: Info on the 6.5 Mystic

No, the Mystic is bigger and needs the shoulder moved forward. You can't fireform directly from the 308 case.

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Old 03-02-2006, 01:57 PM
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Join Date: Jan 2005
Location: OK
Posts: 2,145
Re: Info on the 6.5 Mystic

Jerry whats the difference ? shoulder angle? [img]/ubbthreads/images/graemlins/confused.gif[/img]

49.5 grains of H4831 is giving me 2940fps out of a 26" 1-8 3 groove, chambered in 260AI. All from a short action with 140 A-max.

Not trying to beat up your round. Just seems like alot of work for little or nothing.

The 260rem already has a case neck length of .264, So forming from 308 to 260AI would also require moving the shoulder forward on the 308 case.

Congradulations Jerry, you developed the 260AI again. [img]/ubbthreads/images/graemlins/grin.gif[/img]
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Old 03-02-2006, 02:52 PM
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Re: Info on the 6.5 Mystic

Actually, the opposite is true. Attached is a link for SAAMI cartridge specs for the 260Rem.

The neck length on a 260Rem is 0.765" which is almost the same as the 308 (0.785") from which it is based.

A true 260AI will retain that neck length. The only changes would be shoulder angle and body taper.

Fireforming does not need any changes to the parent case and factory ammo can safely be fired in this chamber.

If your 260AI only has a 264" long neck, then the shoulder must be moved forward from its orig location (approx 0.501"). Factory 260Rem ammo cannot be safely fired in this chamber. A secondary shoulder must first be formed.

So in reality, you have made the 6.5 Mystic instead of the 260AI. You load data is definitely in the right ballpark. Maybe a bit hot but then each rifle is a story onto itself.

Are your loads compressed at all?

See, on the cutting edge and you didn't even know it.

So the question I have about your rifle is how did you form your '260AI' brass (264" neck length) simply by fireforming the 260Rem case in that chamber without first forming a secondary shoulder????????

The 6.5 Mystic maxes out the 308 case in every dimension, and with the extended throat, the highest capacity that can still hold a long 140gr class 6.5 VLD bullet securely in place.

Kind of neat being the first to wildcat something completely different. I have never seen any published wildcat that has the same increase or changes to the 308 parent case.


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Old 03-02-2006, 03:52 PM
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Join Date: Jan 2005
Location: OK
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Re: Info on the 6.5 Mystic

Jerry, I need you to look at your link. Your neck measurement is wrong, I think you read the wrong numbers next to the blue lines.

The cartrige OAL is 2.800, To the neck mouth is 2.035 this is wear you mistakenly got the .765" neck?

2.035 is brass length-1.7756 is where neck meets shoulder. This equals .260" neck length.

I load factory 260 brass and fireform. No headspace issue slight crush fit on 260 rem shoulder. The reamer is a 308-6.5 Ackley Imp.

Yes compressed load, I plan on switching to 4831SC. I had this load up to 3020fps before I showed any pressure signs(extractor marks, flattened primers) The current load has very good looking case heads, no marks what so ever.

Measuring one of my fired cases I get;

2.015" oal
1.760" base to neck shoulder junction.
1.660" body to shoulder junction.

Does this help?
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Old 03-02-2006, 08:20 PM
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Join Date: Jul 2001
Posts: 1,459
Re: Info on the 6.5 Mystic

Yep, read the diagram wrong. In any case, the Mystic does have more case capacity then a 260AI, the shoulder is moved forward (I will have to remeasure but think it is 0.25 or 0.24"), and the design maxes out the 308 case.

The performance you are getting is great. Never seen those numbers from any other published 260AI. A nice fast barrel.

Whether it works for you or not, hey, that's a chevy ford thing.

It works for me...

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