Author Topic: Inconsistent A -bolt  (Read 1354 times)

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Offline Minnow

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Inconsistent A -bolt
« on: September 18, 2010, 10:05:24 PM »
I have a Browning A bolt 1 stainless synthetic stalker .270win that groups about a 1.6" @ 100yds on average. Today my first group of three shots on a cold/clean barrel was not consistent. My second group of three measured .070" which I consider super for a stock hunting rifle/sporter barrel with factory ammo. At 200yds my groups average 3.44" with some as small as 1.80" and as large as 4.45". I was shooting mostly Winchester PowerMax, along with some Hornady BTSP 140gr. and Winchester Ballistic silvertips.
I'am resting the forend and butt stock on sandbags and getting a nice steady hold with a slow trigger pull, but my groups seem to dance around. I'll be the first to suspect human era plays some roll in this to a small degree, but this rifle as never been a tack driver even with trying various ammo. It seems like this rifle groups much better when it gets warmed up.
My scope is a Leupold VX3 10X with Leupold two piece mount and rings.

I would like get this rifle consistent and shrink the groups down a little bit. MOA or better? Please advise...

Offline mjbgalt

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Re: Inconsistent A -bolt
« Reply #1 on: September 19, 2010, 02:55:16 PM »
my abolt liked the bullet kissing the lands of the rifling slightly. try seating them out a bit.
I have it on good authority that the telepromter is writing a stern letter.

Offline tjrod

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Re: Inconsistent A -bolt
« Reply #2 on: October 07, 2010, 11:57:13 AM »
Sell it and get a marlin XL7.  That is what I did and glad of it.

Offline Bigeasy

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Re: Inconsistent A -bolt
« Reply #3 on: October 07, 2010, 01:47:04 PM »
1.6 inch groups with a factory rifle and ammo is not all that bad.  Lots of guns shoot 1/2 inch, on the internet that is....

I would check the basics - Make sure the scope mounts are tight, with a little lock-tight applied for good measure.  Take the action out of the stock and make sure it fits properly, and make sure the action screws are tight.  Some times applying a little upwards pressure to the barrel (Slide a credit card under the barrel at the forearm) helps stabilize barrel vibrations and improve accuracy and consistency.

If you reload, experiment with different bullets and seating depths, as these two variables in particular can make a big difference.  Human error may play a part - It takes real concentration and good technique to shoot sub MOA groups.  It sounds like your rifle wants to shoot better, and with a little tuning and load development, it might.  The .70 groups at 100 yards, and 1.80 at 200 sure seem to point that way.

Larry
Personal opinion is a good thing, and everyone is entitled to one.  The hard part is separating informed opinion from someone who is just blowing hot air....

Offline D Humbarger

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Re: Inconsistent A -bolt
« Reply #4 on: October 07, 2010, 05:32:48 PM »
Free float the barrel.
Try to look unimportant.   Your enemy might be low on ammo.

Only Handi so far is a 375 JDJ.

Offline 1sourdough

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Re: Inconsistent A -bolt
« Reply #5 on: October 08, 2010, 01:40:26 AM »
 I'm more in the camp of Bigeasy. I was at the public range yesterday. There seems to be a big difference between the average guy at the range & internet posters. With my A-Bolts most have a Timney trigger spring, 'medium' on big game rifles & 'light' on varmint types. Easy change out if you want to go below 4lbs on the pull, not that that's an issue with you. I'd try a few types of ammo if you don't reload. If your at 1.6" your in a very workable area, no need to send the gun 'downrange'. Last I heard the vitals on a deer offered a larger target than that.
NRA, Veteran

Offline Minnow

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Re: Inconsistent A -bolt
« Reply #6 on: October 08, 2010, 06:16:18 PM »
Have not checked my post in awhile. Since I posted last, I removed the stock from the gun for the first time. I've had the gun since I was 14 and I'm about to turn 30 now. What I found when I removed the action was the factory bedding job had been compromised. Browning had used some type of epoxy and it had become soft and the hump where the chamber area of the barrel rests had a series of sharp points and provided an inconsistent bedding surface. I removed this material and used the "Bedrock Home glass bedding kit" to rebed the recoil lug and first inch or so of chamber area with success. The barrel is free floated from the factory and remains so. Next I ordered the Timney trigger spring set and installed the lighter spring that resulted in a 2.5lb trigger pull on average according to a Lyman digital trigger gauge and is very consistent with no creep. Love it!
Next I used the wheeler "Fat Wrench" to torque the action screws to 30in lbs. I reinstalled the scope bases, rings with Leupold recommended torque settings again with the Fat Wrench. I also used a "CTK Precision" level on the scope base along with a short level on top of the scopes elevation turret to insure that the scope is mounted without cant.
I decided to sight in with Hornady 130gr. Interlok factory ammunition as this round has a good rep for its performance on game and is consistent with regards to accuracy. It is also priced at 25.99 at my local Academy Sporting Goods so it won't break the bank either.
The result is a rifle that is now much more consistent and as the barrel is "seasoned" with a little fouling, the accuracy increases. I'm still working with the rifle, but things are looking good and some groups are sub MOA, but better yet, the groups strike in the same area consistently. The rifle is shooting better than it ever has. I'd say the groups are probably averaging about 1.25" at 100yds, with groups as small as .80".  ;D

Offline hillbill

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Re: Inconsistent A -bolt
« Reply #7 on: October 08, 2010, 07:00:22 PM »
sounds like yu figured it out and fixed it. those groups will kill any deer ive ever seen!

Offline Minnow

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Re: Inconsistent A -bolt
« Reply #8 on: October 12, 2010, 07:33:19 PM »
sounds like yu figured it out and fixed it. those groups will kill any deer ive ever seen!

Yes Sir! I'm excited about the rifle for the first time in a long time and plan on getting back out to the range tomorrow for some more fine tuning. At 100yds it's shooting pretty close to 1.5" high, but is still about .5" or .75" left. I expect to move the scopes horizontal adjustment two or three clicks to the right and shoot some more groups and hopefully that will be that.

Offline Minnow

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Re: Inconsistent A -bolt
« Reply #9 on: October 13, 2010, 05:15:36 PM »
Well got out to the range late and wanted to work with my Encore with my .308 barrel since I had just mounted a scope on it. I only shot one group with the .270 and it is still shooting great but slightly more center today, shot .70". I'll continue to test cold bore. Here's a pic:




Offline rugerfan.64

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Re: Inconsistent A -bolt
« Reply #10 on: October 13, 2010, 05:34:15 PM »
Typical Browning A bolt. When I first got my 280 I took the action out of the stock and pulled the bedding compound out with it. It shot like crap. I replaced the bedding compound with an NRA membership card cut to fit. Took her to the range and shot a .58 inch group followed by a .44 inch group. She is still carrying that NRA card today. She's about 15 or 16 years old. She still shoots that good when I do my part.