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> 7mm Rem mag new barrel
7mm Rem mag new barrel
@ 05:28 pm (GMT) |
MalmacHello All,Long time reader, first time poster. My 7 rm requires a new barrel. I have decided on a #5 contour Maddco, .7 at the muzzle at 26 inches, 1:9 twist. This will be going into a Hs 029 bdl stock (rem 700) with a Timney elite trigger. My shooting to date has been at traditional ranges and as such my go to was the 160 partition. I have also tried the eld x and Berger in the similar weights. They all shot Around .5 if I was doing my job properly. My question today relates to setting up the new barrell. We have been asked which projectile we will be using, and a dummy round so they can set it up. With this new barrel, my intention is to learn how to shoot some longer distances. We wish to initially use one projectile. Upon reflection on usage short and longer shots, hunting and steel, we are considering using the Sierra 160gn TMK, however never having used it we are not sure and can not find any data on a overall length., and or any other requirements we should ask or request in the setting up of this new barrel. Any suggestions would be appreciated. |
Replies
@ 06:31 am (GMT) |
Thomas KitchenRe: 7mm Rem mag new barrelhi Malmacit sounds like your gun smith is using a separate throat reamer to set the coal. just double check its of match style so the lead angles will less finicky with match projectiles. i don't have any 7mm here to experiment with but i don't think the 160tmk is overly long. i would set the tmk so the start of the boat tail is inline with the bottom of the neck. this hopefully still gives you plenty of magazine room. if your smith can set it to exactly that touching the lands then you can experiment with jump seating them deeper, the 162gr amax should be longer from memory and the 180gr eld-m longer again. you may loose out a little on using traditions soft point projectiles but they normally can handle bit of a jump, plus if you want a harder projectiles there is the 175 eld-x and accubond long range that could be used. hopefully others will comment and make sure im on the right path |
@ 10:12 am (GMT) |
Nathan FosterRe: 7mm Rem mag new barrelHi Malmac, yes, sounds like they have a no throat reamer and will be using a PTG uni-throater to cut the throat. If they are using the uni-throater, it will produce the ideal leade angles Thomas spoke of.For the TMK, please pass on the following: TMK, projectile length 36.5mm, max OAL 88.mm. Error range -0 / +.3mm. This will not only set the rifle up well for all long range pills but it will also be SAAMI spec. This will put the 162gr ELD-M at 87mm and the 180gr ELD-M at around 88.3mm. The 162gr ELD-X will be around 86.8mm while the 175gr will be around 88.3mm. Do not cut the Rem Mag longer than SAAMI as there is no need, it simply makes the throat too long after throat wear. If you want more power, do not do this via the throat. Instead, go with something like the 7mm Practical which would suite your action nicely. |
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@ 12:16 pm (GMT) |
MalmacRe: 7mm Rem mag new barrelHello Nathan and Thomas,Thank you both for this information. I will pass it on and hopefully end up with a well balanced shooter. The future projectile selection will be the 180gn Eldm. Also an overdue but special thank you to Nathan. Your published information, both online and in book form has been an inspiration and a continual source on which to reflect. |
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@ 02:49 pm (GMT) |
MalcolmRe: 7mm Rem mag new barrelHello Nathan and Thomas,Thank you both for this information. I will pass it on and hopefully end up with a well balanced shooter. The future projectile selection will be the 180gn Eldm. Also an overdue but special thank you to Nathan. Your published information, both online and in book form has been an inspiration and a continual source on which to reflect. |
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@ 06:53 pm (GMT) |
MalcolmRe: 7mm Rem mag new barrelHello again,I am just trying to understand this. The 162 ELD x we had used had an oal of 86.3. The Berger 168 oal 86.6.In my old factory barrel that indicated a jump of 20 thou. Should we prepare a dummy round of 162 TMK set at 88mm as you described and present that as well as your information. Would this mean we would have to utilise this length or would it just be an indication of maximum length and we would be free to adjust oal as required? Nathan, in your notes you mention that the maximum oal is 88mm with an error range of -0/+.3%. Does this take into account the differing lengths of each individual projectile? At 88mm long or longer for the heavier projectiles will these still fit in the magazine of my rifle or will they need to be individually fed? |
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@ 09:23 am (GMT) |
Nathan FosterRe: 7mm Rem mag new barrelHi Malcolm, thanks for your kind words, much appreciated.OK here we go. The 88mm/ TMK measurement will set the rifle up correctly for the other pills. You need only supply this one piece of info to the smith. Or- you may wish to supply the 180gr ELD-M set to 88.3mm. Supply one bullet type only so that he cannot be confused on a busy day. If the chamber is cut to 88mm, you will seat your ammo to (for example) 87.8mm). Ideally, along with your max OAL dummy round, you should also give the smith a case with only the mouth sized (say .5mm of the neck), not the whole neck. This should be supplied with a projectile. That way he can chamber this dummy round, pushing the bullet into the case neck, checking the max OAL as he goes. This can be a bit tricky though because you really need to use a once fired case to obtain a case with an expanded neck. But if your existing chamber is larger than the new chamber, the fired case will not fit. You could size the case with a body bump die which does not size the neck. Or you could take a new case and try to flare the neck. There are a few ways to skin this cat with a bit of creative thinking. I hope this makes sense. The error range is to take the heat off your smith. He may stop and start several times. With each start, its hard to feel the actual start of the cut- that first bite. if you give him an error range, it will take the pressure off and it also ensures he does not cut too short. So lets say that you ask for 88mm with the TMK and the rifle comes back at 88.2mm max OAL. This means that there is a .2mm / 10 thou error forwards. This simply means that you will seat your ammo to 88mm and will still have plenty of room for throat wear. Head space is much the same. On the belted mags, you can use my 7mm Practical head spacing info (see 7mm practical page). This will make reloading a whole bunch easier than a tight fit belted mag which can do your head in. Regarding mag length. You said that your rifle is an M700. It should have enough room for an OAL of 93mm plus 1mm or 40 thou clearance for smooth feeding (total internal mag length 94mm). You can check this for yourself. Do not cut longer than what I have mentioned, otherwise your jump will be too long with some pills and or after throat wear. As suggested, if you want more poke, go with the Practical. |
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@ 12:09 am (GMT) |
MalcolmRe: 7mm Rem mag new barrelHello All again,Just thought to provide an update on my new barrel. The finished product from Maddco is excellent and to complete it we have mounted a Sightron s111 6-24 with Moa 2 reticle. Max OAL is just a touch under 88mm. My impression on the complete rifle is that while it does have an amount of weight, it is now a mild recoiling, well balanced and easily carried rifle. The clarity of the Sightron is impressive as judged against my Swarovski's. The longer barrel will take some time to get used to as to not knock the muzzle on things and the the higher scope rings now necessitate a pad on the stock to maintain a better cheek weld. It does appear to be a shooter though. Working up a load for the 160gn TMK (OAL 2.66 with 15 thou jump ) as follows; 68 gns 2217 fed210 primer 3shot average 2840ft/sec group size .265 68.6gns , 3shot ave 2878 f/s group size .423 69 gns, 3 shot ave 2900f/s group size .510 69.6gns, 3 shot ave 2936 f/ s group size .496 We will continue to work up this load until we hit the next accuracy node. |
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