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Thread: 7mm - is this .275 or .284 in imperial?

  1. #1

    7mm - is this .275 or .284 in imperial?

    I'm in the process of filling out my FAC application and I want to get a 7mm08.

    The BASC guidelines to completing a FAC application form say to put down both the metric & imperial for the calibre of the rifle. They state that 7mm is .284.

    The Home Office document "Firearms Law - Guidance to the Police 2002" states that 7mm is .275.

    Can someone in the know tell me which is correct please

  2. #2


    Mathematically the answer is .275. Hope that helps

  3. #3
    I think the groove diameter of a 7mm is .284 but the diameter at the lands is .275. Hence the .275 rigby is the same as a 7x57 but shoots .284 bullets...make sense...??!!
    Personally I would put 7mm/.284 as this would allow any the 7x57, 7-08 7x64, 7mm RM, 7mm WM, 7mm WSM, 7mm RUM etc
    I dont know if you would get a .280 remington though even though this fires the same .284 projectile.
    Do you know what level of performance you want from the 7mm? ie general stalking 7x57 or 7mm08 vs longer range or larger beasties 7mm RM or 7mm WSM


  4. #4
    A 7mm08 is .284.

    you will love it.

  5. #5
    A 7mm08 is .284.

    you will love it.

  6. #6
    Ask your FAC Dept or just put 7mm-08, after all that's the cal you would like I take it.

    Mine is on my ticket as 7mm-08, I have seen other's that just show 7mm.

    I guess its down to your FAC Dept, they dont all seem to sing from the same hymn sheet.



  7. #7
    Thank you all for your responses. I am speaking with my local Firearms Enquiry Officer tomorrow so will get his take on it.

    I have read many reports on the 7mm08 on this forum and the consesus seems to be that it is a very versatile calibre. My intention is to use it for general stalking, mainly fallow & roe. However I hope to eventually have a go at red & sika deer as my experience grows and opportunities arise.

  8. #8
    srvet is correct - most English Calibres are measured by the land diameter - ie the top of the rifling, whereas Metric and American claibres measure the bore diameter.

    The .275 Rigby, H&H etc all shoot 7mm bullets, indeed the .275 Rigby is identical to the 7x57, but when it was launched in the 120's (I stand to be corrected) it was loaded with a 140 gn bullet at 2,800 fps, whereas the standard 7x57 was a 176 gn bullet at c2,450 fps.

    Thus 7mm bullets are .284 inch in diameter, so if you put down 7mm as I have done it gives you a choice of all the 7mm calibres.

    7mm-08 is great all rounder by the looks of it, but probably doesn't have quite enough case capacity to shoot big bullets (ie 176gn) at a reasonable velocity. If you are wanting to shoot big plains game / wild boar, possibly have a look at the 7x64 / 280 Remington or 7mm Rem Mag.

  9. #9
    Thus 7mm bullets are .284 inch in diameter, so if you put down 7mm as I have done it gives you a choice of all the 7mm calibres.
    This is spot on - FAC's state calibre they do not state cartridge, so 7mm would give you felxability to change if needed and is acceptable for all RFD's. If they try to designate a cartridge on your ticket argue the point - the NFLS only needs calibre.

    I had a similar issue with Avon and Somerset regarding this and finally managed to get my 243 entry changed to 6mm.



  10. #10
    I asked for a variation for a 22" centre fire. The FIO insisted I nominate which 22" I wanted, in discussion I asked him how land checks for a hornet varied from those foe a 22/250, showed him a copy of cartridges of the world (lots of different 22") and said as I was buying second hand, I could potentially get any of them.

    I got a 22" variation, but didn't use it and it was renewed with no problems.

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