Short barrel 7 Rem Mag loads?

Discussion in 'Ammunition & Reloading' started by McX358, Jun 15, 2014.

  1. McX358

    McX358 New Member

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    I have a customer, and a friend who recently purchased a S&W 1500 in 7 Rem Mag; what is interesting is the barrel length, of 20"! I told him there was a formula {we are rebuilding/revamping so its awol } which used bore dia. to case size ratio. I used this in building a couple .358 WCF's with 19" Bbls, and lost very few FPS from a 22 or 24". I told him, the std 7-Mag is based on a 24", and some go with a 26" to get max use of all the powder. If he was going to get best benefit, he should try a faster powder, so combustion is complete. I would appreciate any help with this matter, so I can help him out.
     
  2. hardluk1

    hardluk1 Active Member

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    I believe it will be a trial and error and a dangerous process to find a reduced load of faster powder that works and does not over pressure the rifle. I can't understand why a person would want 7rem mag in a 20" barrel. Bet it was damaged and cut down from 24". Try some minumim loads and see how it chrony's. See it it gets 280 velocity or 7-08. Far better to rebarrel or re chamber to a shorter cartridge but with a .512 base diameter it does not leave many short options. A 7rem saum maybe , a 22" barrel is standard?? There still some brass out there.

    7mm rem mag reloads ! Maybe a 120gr nosler ballistic tip and 4831 minimum loads. You may want to look at how some of these powder deal with below minimum load levels and look at some burn charts and find the faster powder for 7RMM. . Compare 280 to 7mm mag . The max load for a 280 would be a just below minimum for a 7mm rem mag with 4831. but that still wants a 22 to 24" barrel.

    Good luck.
     

  3. McX358

    McX358 New Member

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    hardluk1,

    That was my original take right off the git-go; why a 20" Bbl? I haven't examined the rifle, he is suppose to bring it over Monday. The short barrel large magnum syndrome came much later after these 1500's were built; I think your correct, someone cut the Bbl. I honestly don't get the short barrel large magnum syndrome; the Savage 111- Hog Hunter in .338 Win Mag is an example of ..why??? My little Rem 788 in .358 WCF rolls them over on the spot, measured 180 Barnes @ 2700 FPS; what more do you need? Except for Barnes to make the 180 again..Which bring's me to your point....you need a CHRONY to build loads; especially for morpho guns like this one. I have one; but I do not lend it out, I'll shoot across the screens; so if I put a slug through the ye, it's my fault...I believe a trip to the range is in order to help my friend out. Good suggestion on caliber, with the longer action, bullets could be seated out....already building in a 6.5X55...I'll put a bug in his ear..Thanks for your help.
     
  4. Axxe55

    Axxe55 The Apocalypse Is Coming.....

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    here are my thoughts on this.

    quite possible a person cut off the barrel to make a more easily carried rifle. possibly someone maybe trying to duplicate a light and easily carried rifle in the design of of the short mag rifles that were the rage once.

    most 7mm Magnums usually have 24-26" barrels and some even as much as 28" in length. my 7mm Ma. has a Magnum contour and is 26" in length. most of them need that barel length to completely burn the powder to gain the velocity the magnums are known for.

    the short mag and super short mag rifles were pretty much designed to get the results of the older magnum cartridges from a shorter and fatter case, using less powder, using a short action and a shorter barrel, and getting the same or near the same results in performance, velocity and accuracy as the older and larger magnum cartridges were capable of.

    is it possible to make this short 20" barreled magnum perform well? possible. but it's going to take a lot of load working to find out. with that 20" barrel, i think if it were me, i would also look at the faster powders and start at he minimum loads and chronograph them and just work up to see what works well. this may mean trying different powder and bullet combinations to see what works in that particular rifle. as a general rule, the shorter the barrel, there is a loss in velocity compared to the same cartridge in a longer barrel and it can vary from load to load as to how much variance there is.
     
  5. John_Deer

    John_Deer New Member

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    A friend has a 7mm mag with a 20" barrel. The way the rifle is set up with buckhorn sights like many lever actions it is a gun to fend off bear or moose. The 20" barrel has no effect on the accuracy of the rifle. Every deer he kills is shot in the head or the neck. I saw him shoot a deer way across a field it went down first shot right below the ear. Honestly I thought he was wasting ammo. It is hard to estimate the range he shot the deer. I was about 500 yards away from him.
     
  6. mseric

    mseric New Member

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  7. McX358

    McX358 New Member

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    When he bring the rifle over, I will give a very hard look over to see of the barrel has been shortened. As far as I'm concern the rifle as it is; is just a platform for a proper length barrel for a magnum size cartridge. He had been talking about going to a 300; but I told him, unless he just likes to collect, jump too the .338 or .375; he already has a moa 30/06. But hey what do I know...I have everything from a .17 too .45 in rifles..my dream was to take game with every one of them; an't going to happen running out of time, and the collection is still growing. Thanks for the input.
     
  8. hardluk1

    hardluk1 Active Member

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    McX358 The 375ruger would be an interesting cartridge too. There are concern with changing or modifying the mag box's

    mseric Powder may not need 20" to burn but it expands for beyond 20"

    I have a 788 to but in 308 21" barrel version. Love that ole rifle and a custom 27" barreled 7RM and I can tell you at still making velocity over a 24" barrel
     
  9. mseric

    mseric New Member

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    Velocity is a result of the gases produced by the "Burned" powder pushing the bullet down the bore. The longer the barrel the more barrel time, the more barrel time the greater the acceleration. it has nothing to do with powder burning it's way down the bore.