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Fast barrel?

25 Nov 2014
@ 11:24 pm (GMT)

Jared Thibodaux

I always thought this was overplayed until I started using a chronograph, playing with my two 7mms the other day I found my Browning 7mm-08 was nipping at the heels of my Ruger 7mm Rem Mag (140gr @ 2950fps vs 150gr @2980fps respectively, Max loads for both) Using the manual as a reference the 7mm-08 is about 100fps faster then expected and the 7mm Rem Mag is about 150fps slower then quoted speeds, no hint of excess pressure was visible in either, both had nice rounded edges on primers and extracted easily, factory ammo for the 7 mag was equally slow about 120fps below norm.
Few quick questions.
1. Are certain manufactures known for "fast" barrels or is that a crap shoot?
2. Is there any cure for a slow barrel other then re-barreling a rifle?
3. Is there a connection between fast barrels and accuracy? Both my Savage 30-06 and Browning 7mm-08 are considerably faster then expected and both are easily capable of sub 1/2 MOA accuracy while the Ruger is a 1.5-2MOA shooter.
I would normally just replace the Ruger except I LOVE the feel of that gun, the wood is nice and it has an excellent feel to it despite the heavy creepy trigger.

Replies

25 Nov 2014
@ 11:34 pm (GMT)

thomas kitchen

Re: Fast barrel?
hi jared just quick question when you say max load are you talking bout reloading manual max or just before pressure signs max?[b]
26 Nov 2014
@ 12:03 am (GMT)

chris murphy

Re: Fast barrel?
Hi Jared what length barrels? what are your recipes (powder, primer, pill, bullet jump)?
26 Nov 2014
@ 12:33 am (GMT)

Jared Thibodaux

Re: Fast barrel?
Manual max loads, I normally don't exceed them unless I know the rifle VERY well. Loads are 47.5gr of Big Game, Rem Brass and CCI 200 primers for the 7mm-08 and the 7mm Rem Mag is Federal brass and CCI magnum primers, tried several powders and IMR 4350 gave me the best speed at 63gr. I think they are both .010 to .015" off the lands 2.775" in the 08 and 3.240" in the 7mm RM both using Sierra bullets.
Factory ammo for the 7mm Mag I tested was Federal "blue box" 150gr.
26 Nov 2014
@ 03:16 pm (GMT)

chris murphy

Re: Fast barrel?
and barrel length? your load for rem mag is normal for 24" barrel you can try a slower powder (2217 /h1000) to bump up speed or use a standard primer with 4350 at slow the burn. I'm not familiar with big game so looked at there web site it said max of 46.5grn giving 2809fps with 24" barrel. yours does seam fast with only 1 grn more but that seams like good luck, will have to wait for Nathans input.
i couldn't get my brothes tikka 7-08 22' barrel going faster than 2800 he struggles with distance and hold over and doesn't get out much so i loaded 120s for him to shoot a bit flatter give a bit more margin for error.
26 Nov 2014
@ 04:26 pm (GMT)

Jared Thibodaux

Re: Fast barrel?
Big Game is the BEST powder I have yet found for the 7mm-08 second place goes to H380 and third is H4350. Big Game gave the best speed without pressure signs (and darn accurate as well), the 47.5gr load is from Nosler #6 manual since I do not have the one from Sierra, they listed it at 2953fps and mine came darn close, not too temperature sensitive either, in freezing temps it still clocks 2920 average.
Tried H1000 with 160gr SGK in the 7 mag, but it hardly managed 308 speeds clocking around 2860fps at max load, 2MOA accuracy not really awe inspiring, I am going to try some flat base 7mm bullets next, no boat tail has given me any better then 1.5MOA. If that does not work I am going to try fire laping as a last ditch resort before re-barreling the thing.
26 Nov 2014
@ 05:08 pm (GMT)

chris murphy

Re: Fast barrel?
yes your 08 sounds like a goody rem mag does seam slow my sako gave 2970 with book max 70grn 2217(h1000) 160 accubound. just rebarreled it and 70 grn gave me 168 vld 2940fps pressure didn't come on till 73.5grn 3040fps
26 Nov 2014
@ 05:57 pm (GMT)

Randal Graham

Re: Fast barrel?
Throat length and how well the barrel was polished, how close to nominal diameter the barrel is, all kinds of things can account for variations in velocity.

I must say I have expirienced quite a few rugers that had barrels that underwhelmed me.
29 Nov 2014
@ 11:28 pm (GMT)

Randal Graham

Re: Fast barrel?
Saw your post on another thread about fire lapping this barrel... Have you bore scoped this barrel yet Jared?
I always hated chasing problems by throwing stuff at a gun waiting to see what might work, can go around in circles for a long time before issues get sorted out.
I'd consider having a proper look at the bore first off to see where the barrel is at for sure. If it's tool chatter, crappy lap job, pits, burrs, crappy chamber cut or throat, you'll see it right away.

Firelapping takes a lot of work to prepare the loads, then you are still essentially lapping one stroke at a time. Can add up to multiple dollars per stroke that may or may not address the issue with the gun.

If it's something like burrs or rough finish, you may very well be able to hand lap it and have it turn out good.

But in any case, I'd scope it first, then you will know.

Imho, of course...
30 Nov 2014
@ 09:09 am (GMT)

Randal Graham

Re: Fast barrel?
Jared, posted on the .35 thread, I'll put the lapping link here too...
http://youtu.be/ml-9oLLKYsM

Is the rifle shooting consistant groups?
Even at 2"... Are they consistant groups or all over the place and vary from small groups to large randomly?

Very very generally speaking, large but consistant groups are barrel finish related, very random all-over-the-place groups usually end up being throat/chamber issues or a bad crown.
Also, if you shoot a long string, like 5 groups of 5 rounds, and the groups tighten up a bit as you go, it can indicate barrel finish.

In any case, I still would reccomend finding somebody with a bore scope and having a good look as a first step. Everything else is guessing and it can eat a bunch of time up.

Good luck man!

Randal
30 Nov 2014
@ 07:50 pm (GMT)

Jared Thibodaux

Re: Fast barrel?
No never owned a bore scope but it is certainly one of the many things on my wish list. The rifle is shooting very consistent 1.5-2" groups triangular patter nearly every time so not vertical stringing. Many different powders and bullets and they all yield almost identical marginal accuracy, two different factory loads did the exact same thing Never seen a rifle behave like this before. The nice thing about it is it is the lightest kicking of the four 7mm Rem Mags I have owned over the years even with it's hard rubber pad.
30 Nov 2014
@ 08:21 pm (GMT)

Randal Graham

Re: Fast barrel?
Jared, habe you tried Nathan's bore polishing method with the 3m abrasive pads and polishing cream?
If not, maybe give that a shot. I've not tried it yet but in looking at the process it seems very sound to me, and if it makes some kind of positive difference, then that'll give you an indication of what is going on at least.

Personally my vibe is you have a rough bore.
 

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