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7mm Practical

History

 

Updated August 2018.

The 7mm Practical is a cartridge of my own design. It was initially developed between the years 2010 and 2011, then underwent further R&D towards optimum throat geometry with batch reamer production beginning in February 2017. More than simply 'magnum power', the 7mm Practical has been engineered to produce a high degree of inherent accuracy, versatility, long term wear and user friendliness into consideration. Power, accuracy and usability are its key factors.

Having witnessed very short barrel life with the 7mm RUM, yet also having enjoyed the excellent power levels of the RUM, I set about exploring whether it would be possible to obtain the same or similar velocities from a smaller case capacity. One of the major downsides of the 7mm RUM is that it is very much overbore and requires excessive free bore (bullet jump) to reach full velocities. I had already experimented with a half throated 7mm RUM and found this combination to be potentially dangerous due to pressure spikes with mild loads (powder bridging / detonation). Only so much energy can be squeezed through a 7mm orifice and I determined to work towards developing a maximum power wildcat cartridge design, one that would not suffer diminishing returns or have to utilize excessive free bore. The cartridge had to be a simple design, easy to work with and without requiring an extremely long magazine. It had to be practical.

During this period of research I was already aware of and had tested the 7mm STW, an excellent cartridge which Remington adopted but soon discarded in favor of the 7mm RUM. The STW had only one fault, the need for a longer than factory length magazine box if seating long match style bullets close to the lands. For a time I contemplated the possibility that the STW (8mm Remington Magnum parent case) may well be the limit, but I also suspected that the case might still be a touch overbore. Either way, the issue of magazine length prompted me to look towards a shorter case.

Over the years, several hunters have necked the .300 Winchester Magnum case down to 7mm, I was certainly not the first to do so. Some claim that the 7mm-300 Win Mag is nothing more than the 7mm Mashburn however this is not quite true. The 7mm Mashburn Super Magnum wildcat was based on the .300 H&H case shortened, blown out and necked down - not the .300 Winchester Magnum. The Mashburn was designed by Art Mashburn during the mid to late 1950’s. Warren Page, editor of Field and Stream magazine put the cartridge into the public spotlight when he adopted Mashburn’s chambering and discovered its ability to comfortably launch a 160 grain bullet at 3200fps using the powders of the day. Page very much wanted Remington to adopt the Mashburn but instead Remington opted to standardize Les Bowman’s .338 Win mag necked down to 7mm, the now famous and very useful 7mm Remington Magnum.

Although the Mashburn never met fame the concept stayed alive - but only barely. During the mid 1990’s through to more recently, powder manufacturers have developed ultra-slow burning powders well suited to this case capacity. After studying the case capacity of the Mashburn, its similarities to the .300 Winchester Magnum as a parent case and reported velocities along with the occasional but hard to find anecdotal notes regarding the 7mm-.300 Win Mag, I settled on the .300 Winchester magnum necked down to 7mm as a basis for my wildcat case design.

The design premise for my version of the 7mm-.300 Win Mag was to obtain maximum power from the 7mm bore without excessive wear, suitable for the volume of shooting (practice and hunting) I prefer from a long range rig (approximately 12 shots per week on average). The cartridge was to be used for hunting light to medium weight game from point blank, out to true long range distances. The case capacity has since proven to be optimal for a balance of efficiency versus effective power at extended ranges.

I also took the opportunity to incorporate a long neck into the cartridge design. This was achieved by simply extending the neck area of the chamber forwards and allowing cases to grow rather than continually trimming. The shoulder angle was also changed from 25 to 30 degrees. Had I selected a 40 degree shoulder, I would have arrested case neck growth.

There would be no need for special dies or special operations when reloading for this wildcat. The cartridge was designed to utilize a basic and generic 7mm Magnum neck and seating die, (though custom dies can enhance accuracy further).

The wildcat was also designed in such a way that it would utilize an easily sourced parent case. The belted .300 Win Mag case design is easy for gunsmiths to work with, without need of custom head spacing gauges. The Smith can use standard 7mm Remington Magnum gauges to check fit.
 

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Finally, I had to come up with a name for the wildcat. I chose the 7mm Practical based on the premise for the design.

After building the first test rifle, load development soon proved that the 7mm Practical was a potent cartridge, meeting my every expectation. The wildcat did however fall slightly short of the RUM by around 50fps even though we used a 28” barrel. Much of this would be addressed via the Revision B reamer (discussed ahead). Following my initial tests, we commenced building rifles for clients, utilizing the expertise of True-Flite NZ to supply and fit their excellent barrels. All of the rifles produced gave sub .3 MOA accuracy which was outstanding. But as more time went by, the Practical began to show stiff chambering and sticky extraction with continually neck sized cases. I had just worn out a .308 Winchester barrel using 60 Hornady cases, neck sized from start to the end of barrel life and saw no reason why the Practical could not do the same - back to the drawing board.

After exploring where the tight spot in the chamber lay, it was found to be occurring at the case body in the area of the shoulder junction - but not the shoulder itself as this sprang back nicely after each firing. I contacted PTG and we re-designed the Practical body dimensions in the same manner as the .284 Shehane, the slightly wider dimensions allowing more room for both expansion and hopefully - spring back. I was greatly concerned about potential accuracy loss but something had to be done to keep the wildcat a simple proposition for end users.

The first rifles were produced using the revision B reamer in December 2011. This final body design proved to be extremely effective with regards to both accuracy and power, allowing end users to adopt shorter 26” barrels and still remain within 50fps of the RUM. Of greater interest was the accuracy. Time after time, barrel after the barrel, these rifles have proven to be very accurate. Sweets spots are generally easy to find and the Practical has proven immensely effective in extreme range match events.

The third and final phase in development came with the help of David Manson, owner of Manson reamers. Over the course of a few years, we had developed a keen friendship which was initially based on our mutual interest in cartridge development and ballistics. When I first designed this cartridge, I opted for a no-throat reamer that would allow smiths and end users to select a throat length to suit individual rifles. However with the passage of time, I found that many end users were making choices that compromised the practical aspect of this cartridge. The most common mistake was making the throats extremely long to hopefully boost velocities with heavy pills including the 195 grain Berger. The problem with this approach, was that the shooter would be committed to this one bullet. If the rifle did not like this bullet (poor accuracy), the job was a bust. This style of throating also failed to account for throat wear and in many cases, the final COAL was too long to feed through M700 magazines. At the opposite extreme, there were a few cases of rifles that were chambered by gunsmiths who failed to make the second cut, resulting in no throat guns, producing dangerously high pressures. A final problem was the potential for eccentric throating.

Following these mishaps I decided to fix the throat length using a base OAL dimension that had worked well in past rifles. The set OAL achieved a balance of accuracy, velocity and versatility (various bullet weights and designs) without compromise. After a great deal of difficult math, David Manson redesigned both the leade length in relation to the optimum leade angle that was necessary to obtain the desired OAL's while  at the same time easing the projectiles into the bore without excessive stress. David also offered to batch produce these reamers. The advantage of this is that it allows the reamer maker to produce more uniform tolerances from reamer to reamer (CNC rather than grind to order) while lowering the costs for the end user. Production commenced in February 2017 and the rifles built with these reamers have been incredibly accurate.

The 7mm Practical reamer is now finally a stock item available from Manson Reamers.
 

7mm Practical C reamer group

The Manson 7mm Practical reamer  produces outstanding accuracy when combined with a good barrel. This group was shot  during proof testing of  a new barrel produced and fitted by Grant Lovelock (True-Flite barrels).  Utilizing a basic load in fire formed cases , the group was shot prior to any actual load development.

The Practical was designed to do what its name suggests, to provide a simple, practical cartridge for precision long range hunting. The Practical also excels at closer ranges with suitably well constructed bullet designs. Since my first online research article charting the development and performance of the 7mm Practical, the cartridge has steadily grown in popularity worldwide.



7mm rem mag and Practical for web-980

7mm Remington Magnum at left, Practical on right.


Performance


Over the years, I have developed some extremely potent loads for this cartridge but for long range precision work, accuracy is the key. A long throated gun can drive a 162 grain bullet at around 3275fps. The same goes for 28-32” barreled guns or suppressed rifles which also boost velocities. But publishing such data has a tendency to create over optimistic expectations with folk chasing velocity over accuracy. Taking into account the many rifles in circulation and from a 26” barrel, extreme accuracy sweet spots for the 7mm Practical and 160-162gr bullets are generally between 3200 and 3225fps. Bullets weighing 175 to 180 grains generally produce sweet spots at around 3000 to 3050fps. The 195 grain Berger can be driven at velocities of 2950fps to 3000fps.

The 7mm Remington Magnum with a 26” barrel (e.g Remington Sendero) tends to produce average high end sweet spots of 3070fps with a 160-162 grain bullet though some rifles boast velocities of 3125fps. Sweet spots for 175-180 grain bullets can be as high as 2925fps however the 180 grain ELD-M tends to work best at around 2860fps in the Remington. The Practical therefore produces velocities which are on average 125 to 150fps faster than the Rem Mag. The 7mm RUM generally produces sweet spots with 160-162 grain bullets at 3275fps. The Practical (without mucking around with long barrels or long throats) is therefore 50-75fps behind the RUM but with much greater barrel life and with much greater (or easier) accuracy. The Practical can last to and beyond 1200 rounds while the 7mm RUM can fall over anywhere between 400 to 600 rounds. A bore scope is all that is needed to provide hard evidence of this. The Practical truly is a common sense limit for the 7mm bore.

The 7mm Practical is best suited to light through to mid weight game species but is also able to tackle larger game species with new select bullets, more so now thanks to new heavy weight bullet designs. The high velocities of the Practical can be used as a means to maximize wound trauma at extended ranges with minimum wind drift. The Practical cannot however fire the very heavy 200-285 grain bullets that prove so effective in the .300 and .338 magnums when used on large heavy bodied game. Elk are the upper limit for the 7mm Practical.

This is a very flat shooting, wind beating cartridge and at times, it feels as though one is almost cheating, such is its good performance. The Practical makes the .338’s seem like old Cadillac’s in comparison. Due to the nature of my work, I spend a great deal of time testing the .338 bores and it is always a relief to go back to the laser like performance of the Practical. At “extended ranges” of 400-600 yards, shots can be taken with a great deal of ease. At 700 to 800 yards, the Practical really begins to come into its own. At truly long ranges, one becomes infinitely grateful for its abilities.

Below is a video study of the 180 grain ELD-M bullet. Please note that this video contains graphic footage with no editing relative to the speed of kills. It is therefore set to 'unlisted view' on youtube to prevent general public access.



Those who wish to lean more about 7mm bullet performance can find this information within the 7mm Remington Magnum , 7mm STW and 7mm RUM texts within this website knowledge base. For more detailed information on long range killing performance, please see my book, the Practical Guide to Long Range Hunting Cartridges. This book covers bullet performance from the ground up in a manner that is not described on this website. My book also uncovers the faults in several bullet designs that can lead to slow killing at long ranges. If a person wants to shoot and kill at long ranges, I believe that they must develop a deeper understanding of the rifle, the cartridge, shooting techniques and hunting strategies. And besides, I have given enough away freely via this website. The book series provides both the new and experienced long range shooter with this deep understanding while helping to fund this free knowledge base that you are currently reading.



vital wounding at 1125 yards WL-210

Liver wounding at 1125 yards (see video at bottom of article).

Happy practical shooter WL-47

A happy Practical owner with a Pitt Island ram

Throat wear for the Practical is approximately .1mm / .004" per 400 rounds with general hunting and light practice- provided the throat is kept polished to close pores within the bore steel. Barrel life is approximately 1200 rounds. Having said this, the most aggressive wear we have seen so far is one rifle which grew .040" at 400 rounds as a result of heavy gong shooting sessions. Another grew .040" at 700 rounds with high round count field shooting and no throat care. In the opposite extreme, a comp rifle finally came in to True-Flite for a new barrel after firing 2000 rounds at which point the owner said that the rifle was still shooting well to 800 meters but no further.

Most shooters tend to think that abrasive polishing will literally wear the bore down but the opposite is true when it comes to throats. It is very important to keep the pores in the steel closed as is the same in other engineering practices such as stainless food grade vessels and stainless marine. Please see my book, the Practical Guide To Bolt action rifle Accurizing and Maintenance for more details on this subject.

 
 
Manson web
 

Gunsmith notes

7mm Practical- Manson reamer. Fixed throat, removable pilot.

When reaming a 7mm Practical chamber, the one piece of advice that you must adhere to for non-finicky performance, is to give the Practical (and other belted magnums) some breathing space. This is important whether the end user intends to use this cartridge for hunting or competition. To be absolutely clear, all True-Flite barreled tack driving Practicals are reamed 6-7 thou forwards.

Note that your go gauge is -5 thou while your no-go guage is +5 thou. Please ream forwards until the bolt is either able to almost close or is able to close on the no-go gauge but with a measure of resistance. This will set the chamber 6-7 thou forwards of its mid headspace point. The customer can then fire form and headspace his brass at the shoulder. The shoulder will stretch well before the case head is able to move forwards. This will make reloading easy and saves a great deal of headaches. A common problem for example, is rifles being returned to the smith after the customer has stretched cases during initial case forming operations (such as extruding the case by accident over an expander button). This and other belted case reloading dramas can all be avoided by letting the case breathe. And as suggested, this approach is optimal for belted magnum accuracy.

The optimum twist rate for this cartridge is 1:9. The velocity generated ensures that all bullet weights will be stable. If a 1:8 twist is used, the rifle may prove immensely finicky with 162-180 grain bullets. Groups sizes at 100 yards may be up to or over 4 MOA and projectiles may also tumble mid flight regardless of whether the bore has 3, 4, 5 or 6 grooves. About the only time you may wish to choose a 1:8 twist is if the rifle is to be used for competition only (not hunting) using the 195 grain Berger bullet. But note that this comes with risks. If the rifle does not like this bullet, the barrel may have to be pulled as it is unlikely that the rifle will behave with other bullets. If a client insists on an 8 twist barrel, you must inform the client that should the rifle prove inaccurate, the onus for replacement is on him- not at your cost. The only advantage to using the 8 twist rate with this bullet is for those who wish to shoot through the transonic barrier. Again, this is purely relative to extreme range shooting contests and has nothing to do with hunting. It is unethical to attempt to hunt with this cartridge at these ranges as bullet performance is wanting, regardless of whether the bullet has labeling attached to it such as the words Extreme or Hunter.

As a side note the Remington Sendero 7mm Rem Mag 9.25 twist is generally fine with all bullet weights up to and often above 180 grains. These can therefore be rechambered to 7mm Practical without twist rate concerns.

The Manson reamer will cut the chamber to produce a max COAL of approximately 91mm (3.583) using the 162 grain ELD-M or 92mm (3.622") using the 180 grain ELD-M. This COAL suits a very wide range of bullets without compromising magazine space. Suitable actions include the Win M70, the M700 and its clones. The Howa / Vanguard and traditional Sako (e.g Finnbear) magazine is 91mm or 3.543” in internal length. This is the shortest magazine one can utilize resulting in bullet jumps between .5 and 1.5mm or 20 to 60 thou or longer depending on the bullet used. I would nowadays rather (if push comes to shove) lengthen the Howa magazine than ream short, simply because we are now seeing more and more long bullets (regardless of whether the customer opts for the Practical or parent Win Mag).

 


7mm Practical Rev C Manson Web large

 

Hand loading

Brass for the 7mm Practical can be obtained from readily available .300 Winchester Magnum brass. My favorite brass is Winchester due to its tough nature followed by Hornady. Norma / Nolser brass has unfortunately a tendency to be weak at the case head (primer pockets) and I have also come across batches with thick necks that must be neck turned before they can be put to use in the Practical.

My favorite dies for extreme accuracy are custom Lee die sets, currently stocked (limited supply) both here in NZ (via this website) and in the U.S via Manson Reamers. These die sets consist of full length dies, neck collet dies, seating dies plus a spare undersize mandrel for neck tension / ES experimentation.

Other suitable neck dies include the Redding .300 Win Mag neck bushing die fitted with 7mm neck bushings, Forster 7mm Remington Magnum neck dies and the Hornady 7mm “Magnum” neck die. The Forster die has a 25 degree shoulder angle therefore it cannot fully size the neck shoulder junction of the Practical however the same can be said of Redding which never fully sizes the neck regardless of the case design.

Hand loading practices are straight forwards without any special processes. The .300 Win Mag case is necked down, primed, charged, a 7mm bullet is seated. The first shot forms the case, after which the hand loader simply continues neck sizing. As previously mentioned, the Practical has what we might call inherent accuracy built into its design. Those who focus solely on power comparisons between this and other cartridges will fail to understand this and other factors. The point being; provided the rifle has a good bore, a sound bedding job and is held the way a man should hold a rifle, the hand loader can achieve good results by focusing on basic principles such as determining OAL's, safe incremental load development and concentricity.

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Please note that while the case necks are at their shortest prior to growing, it is possible to collect carbon in the neck area of the chamber (more so if using a suppressor). If this carbon builds up, chamber neck dimensions are reduced, lifting pressures and ruining accuracy. It is therefore extremely important to occasionally clean the neck area of the chamber with a bronze brush and solvents (use a spiral cleaning motion, not back and forwards). A simple test is to pass a projectile fired through a fired case neck. If the projectile passes easily into the neck, all is well. If the case pinches the projectile, there is a problem with either carbon build caking or heavy walled brass.

The very best powder for the Practical is H1000 (ADI 2217). Retumbo (ADI 2225) also works extremely well, along with other similar burn rate powders.

Basic case specifications are as follows:

Max case length: 2.657 (67.5mm)
Case trim length: 2.645 (67.2mm)
Neck length for the Practical when trimmed is .289 (7.3mm). Several shots are required before cases will grow to the ideal 2.645 length.

Load data for 26” barrel, Manson reamer. Winchester brass, Federal 210 standard primer, bullet jump .2mm / 10 thou. H1000 (ADI 2217) Retumbo (ADI 2225) Yes- data is for both due to powder behavior in this case.

Approach accurate column loads with extreme caution!!!
 

Bullet weight

Start load

Accurate 

Velocity

Comment

162gr ELD-M

76

78.5

3200-3225

Always reliable.

160gr TMK

162gr ELD-X

73.5

76.5

3200-3225

Caution with TMK as bearing surface raises pressures. Caution with ELD-X and other heavy jacket bullets (pressures).

175 ELD-X

70

73

3050

Caution with this heavy jacket bullet (pressures).

180gr VLD
 

72

75

3050

 

180gr ELD-M 71 74 3000 Extremely accurate. Watch
for pressure spikes, approach 74gr with extreme caution.

195gr Berger EIEIO

70

73.5

2950

 

 

Please use a magnum primer if you intend to shoot in freezing winter conditions. Reduce loads by 1 grain in comparison to above non magnum primer loads.

Please do not try to “guess the COAL” based on the max COAL’s that were quoted in this article. You must have a good understand of reloading practices and how to determine your COAL before beginning to reload for the 7mm Practical. This and other subjects are covered in my book, The Practical Guide To Reloading. Furthermore, do not think that by simply mating a barrel to an action that this will give you 1000 yard reach. Both the rifle and the shooter must be in optimal form. These subjects are again covered in the book series, laid out clearly for all to follow. The 7mm Practical is the tool while the books are the means to understand how to use this tool. There is nothing worse to me than seeing this very straight forwards cartridge ending up as some tactical nightmare with a thousand add ons that spends more time “doing the rounds” at every available chop shop because it just won’t shoot right, costing the shooter many thousands of dollars with the cartridge never living up to its name. So please make sure you do this right, from the ground up. The rifle and the shooter must progress together.

The 7mm Practical can be hand loaded to perform well at both close and exceptionally long ranges. It can also be put to great use with lower BC hunting bullets, enchancing effective ranges in a meaningful manner. As an example, the Practical loaded with either the 160 or 175 grain Nosler Partition bullets, maintains very wide wounding out to ranges of around 550 yards, wounding steadily tapering off thereafter with a maximum effective range of around 850 yards. The Practical has an effective hunting range of over 1400 yards with the ELD-M bullet designs.


My Practical-182

My 7mm Practical. Remington M700 action, True-Flite barrel, HS Precision stock, Warne base, Leupold rings and Sightron SIII 6-24 x 50 Mil Dot scope. So many wonderful adventures.
 

Closing comments

The 7mm Practical is a simple, effective wildcat. The Practical is a joy to work with, a potent wind cheating hard hitting cartridge which delivers on all fronts. I do not believe this is a cartridge for those new to extended or dedicated long range shooting; the 7mm Remington Magnum is more than enough gun for most folk. On the other hand, the inherent accuracy within its geometry can sometimes make it easier to work with than factory chamberings.  In any case, for those who really wish to shoot long, the Practical is an honest cartridge that achieves its goals of reaching maximum velocities from the 7mm bore without need of excessive free bore and without excessive barrel wear.

Although this cartridge has been around for several years, it really is only just coming into its own now thanks to new bullet designs.

Reamers (and dies) can be purchased directly  from Manson Reamers (world wide shipping).

Dies can also be purchased (world wide shipping) from this website (please shopping pages for stock).

New Zealanders can contact True-Flite NZ directly for rebarreling and reaming operations. True-Flite produce an exceptionally accurate 4 groove canted land 9 twist barrel. These are simply wonderful barrels.

 






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