Author Topic: 7mm-08 inconsistencies (Read 1296 times)

bandina · « **on:** April 12, 2003, 12:46:34 PM »

I have a 22” 7mm-08 barrel from the TC Custom Shop and have shot 180 rounds through it. I am currently shooting 42 gr. of Varget with 140 gr. Sierra boatial spitzer. Groups vary from 2-6 inches at 100 yds with an occasional shot into the bull. I had TC manufacture this barrel with a muzzle tamer (muzzle break) to this barrel making the actual length 21".

My questions are:
Should I be shooting a flat base bullet rather than a boatail?

Is my bullet weight (140gr) the best selection for my barrel rate of twist (1:9)?

Should I be using a faster burning powder with this short barrel (22”)?

My 22” factory .223 rem bull barrel shoots like a house on fire. No complaints with this set-up.

:?

Hi-Wall · « **Reply #1 on:** April 12, 2003, 03:34:24 PM »

is it a tapered barrel. The runout is greater on them. also the muzzletamer is soldered on after the barrel is bored and chambered causing even more stress. teh choice of bullets and powder usually will not turn a 6"er into a tackdriver. I would send it back for replacement. :cry:

stratocaster · « **Reply #2 on:** April 13, 2003, 03:36:27 AM »

For what its worth, I had a similar experience with a .243 24" factory barrel. Now bear with me on the details because its been quite a few years but this thing would group between 8 - 12 inches @100 with either a 105 or 115 grain bullet (can't quite remember exactly and I'm not sure what the rate of twist was) . I called T/C and their first suggestion was to run an over-size bronze bore brush down the barrel in an attempt to "clean up any rough spots on the rifling". Sounded pretty lame to me but I gave it a shot, went back to the range, and still had the same lousy groups. After many trial and error efforts with scopes, mounts, powder, seating depth, etc I tried a 90 grain (may have been 85g) nosler b-tip and I was getting an honest 1" group! So I guess what I am trying to say is before you go through the expense and hassle of sending it back to the shop, first try a lighter bullet. Good luck and let us know how it turns out.

Duffy · « **Reply #3 on:** April 13, 2003, 10:54:17 PM »

How far are you seating off the lands? I have a regular 15" encore bbl that won't shoot worth beans when it's seated closer than .045 off the lands. My 22 Hornet needs to be .035 off for best performance too. The Hornet goes from 4" down to an inch and I'm still messing with the 708 but I did polish the barrel and that seemed to help also. Hope this helps some.

Possum · « **Reply #4 on:** April 14, 2003, 11:05:55 AM »

Duffy, funny you should say that. I have a 250 Sav that I have been messing around with and the closer you get to the lands the worse it shoots. I have been loading now about what the MOL (Minimum Overall Length) says in the reloading books and getting better results. It is a TC Custom Shop Barrel. I thought it was quite odd.

Duffy · « **Reply #5 on:** April 14, 2003, 07:29:25 PM »

It sort of goes against everything that we've been told! I did the same thing on the 708, seated what the manual said and group's shrunk quite a bit. Just happened to be .075 off the lands. Another thing was that the extreme spread shrunk and everything seemed to really settle down. Was getting ES in the 60-90 range now they drop down to 10-20. Go figure.

bandina · « **Reply #6 on:** April 15, 2003, 03:58:32 PM »

Thanks Guys. Looks like I have some measuring to do.

KYODE · « **Reply #7 on:** April 16, 2003, 01:58:39 AM »

:idea: i know, check the forearm. make sure the forearm doesn't touch the barrel. try to free float it some way.

bandina · « **Reply #8 on:** April 18, 2003, 10:50:21 AM »

Thanks KYODE. I am using the same forearm (made for tapered barrel) for both the .223 bbl & the tapered 7-08. I will look into floating it.

bandina

bob whittaker · « **Reply #9 on:** May 16, 2003, 12:08:23 AM »

:eek : had a 70/8 that did the same thing it was a 24inch. i tryed from 120s-to 175s to 139s round noses,spits,an flate baces. i also tryed four or five diffrent powers,still could not get any thing under 3to4 inch.tryed different seating depths,finly tryed different scopes,three different ones. finly sent barle back to tc an found out thay could not get it to shoot any better.they tolled me thay had a run of 70/8 barles that the crouneing pilot had chattered the rifling .an thay would replace the barlle ,now iv got a 25/06 . i had enouf of the 70/8s :roll: :roll: :roll:

Bullseye · « **Reply #10 on:** May 16, 2003, 01:03:06 PM »

Hey Bob,

How does that 25/06 shoot. I have one in a 26" heavy barrel and am not getting very good groups. I think the problem is the scope but am still working on it. Also, mine seems to kick like a mule which really surprises me when comparing it to other 25-06's I have shot (Rem 700, Ruger #1).

Thanks for any info you can provide on the 25/06.

bob whittaker · « **Reply #11 on:** May 16, 2003, 04:31:03 PM »

hey: you got me on that one,since i got it ive loaded ,five difrent powers in five round lots an havent had a chance to try it out yet loaded all with 100gr spear,looking forward to trying it soon. but now ya gots me worred ,iv shot rem 2506s an though the recoal was mild.i also have the 26inch bull barrle . dident care much for the 708s recoal though it was a bit much??? will let ya know how it shoots soon as i try her out. :oops:

Bullseye · « **Reply #12 on:** May 16, 2003, 06:15:48 PM »

Thanks Bob, let me know how it works out. I am ashamed to say that the thing kills my shoulder, but my wife says that it does not kick that bad and she loves to shoot it. Good luck and I will be waiting to hear the results of the tests.