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Forum Index > Rifles general discussion > 6.5x55 loss in pressure

6.5x55 loss in pressure

30 Apr 2015
@ 09:57 pm (GMT)

Tyler Campbell

Hi guys,

It seems I am losing pressure after about 2 reloads with Lapua brass. The necks are becoming soft, I'm getting low pressure signs and losing velocity as a result. The bullets are seated as far out as I can fit in the mag.

Is this normal? Should I seat the bullets deeper to make up for the lost pressure?

Thanks

Replies

01 May 2015
@ 01:13 am (GMT)

Warwick Marflitt

Re: 6.5x55 loss in pressure
Tell us what type power, charge weight , bullet weight and seating depth. Then the guys who know can help you.
cit[b]OTHERWISE

It's like being on the phone and asking the bloke on the other end to tell me how long the piece of string is that I have just cut?
01 May 2015
@ 04:52 am (GMT)

Thomas Kitchen

Re: 6.5x55 loss in pressure
warwick is a wiseman the more details the better.

when you worked up loads was it in new brass never fired? then when you reloaded 2nd time pressure seemed to drop?
03 May 2015
@ 08:37 pm (GMT)

Tyler Campbell

Re: 6.5x55 loss in pressure
Sorry guys, using:
Lapua brass
46.0 grains Vihtavouri N560
140 grain remington corelokt
COAL about 81mm I think

Brass was brand new and yes second time around pressure seems to have dropped.

Thanks
03 May 2015
@ 08:45 pm (GMT)

Tyler Campbell

Re: 6.5x55 loss in pressure
And I am neck sizing only
03 May 2015
@ 10:10 pm (GMT)

Warwick Marflitt

Re: 6.5x55 loss in pressure
Hey Tyler. In Nathans reloading book he explains all . have you got it? His whole series of books are worth every penny you will have them for life and so full of good sound knowledge . Look at this it's from Nathan.

http://www.ballisticstudies.com/Resources/Discussion+Forums/x_forum/17/thread/6405.html
03 May 2015
@ 10:25 pm (GMT)

Martin Taylor

Re: 6.5x55 loss in pressure
Yep Warwick is spot on Tyler, you will find the answer to this question many you haven't come to yet contained in it for less than a tub of powder!!!

One thing l will say to your question, treat the first firing as a fire forming/ruffing in load, then do your development. You won't be far away, then tune to suit.
03 May 2015
@ 10:28 pm (GMT)

Nathan Foster

Re: 6.5x55 loss in pressure
Thanks Warwick and thanks Marty. In this instance I think there is specific info in the book that may help and there is also some info of use on the site (see determining cartridge COAL).

I am a bit concerned that you have the Core-Lokt seated out too far. COAL should be around 79mm. You will need to check using either the above quoted article or via the book for methods. My only concern here is accuracy. The Core-Lokt is not the most accurate bullet to begin with so you need to make sure you have all of your ducks in a row to make the most of it. It will be a good game hunting bullet once you are fully up and running.

The necks will be getting harder, not softer. But your brass is pre-annealed so it will take some time for this to occur.

Sounds like a very basic loss in pressure from increased case capacity after fire forming. It should not take much to get the load back up to speed. But there are other factors such as weather effecting chrony readings. Changes in temperature from summer to Winter can also effect results.
03 May 2015
@ 11:08 pm (GMT)

Tyler Campbell

Re: 6.5x55 loss in pressure
Great thanks guys. Yes it's a great hunting bullet and I have had surprisingly good accuracy with it. I'm still getting half inch groups at 100m but it is dropping nearly 6 inches at 200m (used to be about 4.5). I will try seating deeper and let you know how I get on. Sounds like I need to get your book.

03 May 2015
@ 11:34 pm (GMT)

Warwick Marflitt

Re: 6.5x55 loss in pressure
+ get them all as a complete package. I have paper backs and the ebooks so good to have ebook for travel reading. I leave the books at home.
04 May 2015
@ 04:39 am (GMT)

Thomas Kitchen

Re: 6.5x55 loss in pressure
hi tyler.
you just cant go wrong when you have nathans books on hand. one thing a didn't realize til after i had the first 3 books was if you get the ebooks you get all the photo's in colour which would be very handy specially for the accrurizing book (bedding etc)
 

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