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Posted: 2/28/2006 6:41:56 PM EDT
Can anyone tell me how much variance can I expect to see in point of impact after heating my barrel up from shooting?

Right now after 15 rounds or so my SPR's point of impact will drop roughly 2'' @100 yds. Is this normal?? Its very consistant and groups well. It just tends to drop after the barrel warms up.
Link Posted: 2/28/2006 6:50:14 PM EDT
Link Posted: 2/28/2006 7:11:44 PM EDT
Its a Douglas SS barrel with a .750 profile. 1/7'' twist shooting 75gr BH bluebox ammo.
Groups are good. I shoot the first 15 rounds relatively quick. Sometimes I even shoot a little more.

This will cause my point of impact to change this much?

Just want to make sure that this is normal.
Link Posted: 2/28/2006 7:26:57 PM EDT
Man, I'm no sniper, but that sounds... wrong. No rifle I've ever owned or helped sight in walked that much in 15 rounds unless something was LOOSE!

...hey, wait a minute, you're not following your bullet holes and walking yourself off the paper, are you???
Link Posted: 2/28/2006 7:30:18 PM EDT
What shooting position? Barrel free floated or not? More input needed.

Cheers,

Phil
Link Posted: 2/28/2006 7:33:01 PM EDT
Yes free float barrel. Shooting off of the bipod.
I guess Ill have to get me a vise to rule human error out, but it still groups consistantly.
Nothing is loose. I have checked everything including the barrel nut and scope mounts.
Thanks for the input guys.
Link Posted: 2/28/2006 8:14:34 PM EDT
Your bullets are dropping with respect to your POA,... so your barrel is going limp on 'ya in it's FF tube? It's bowing down after a few shots? Weird!

Try shooting next time not so much from a vise, but put a cork or something in between your FF tube and the bottom of your barrel that won't hurt it, yet keep it relatively in place. At 100yds, you shouldn't notice any real big change, maybe an inch, tops. See if after 15 shots you're relatively in the same hole still.

If you don't feel like doing that, or can't find a cork, actually rest the barrel on the sandbag, not the FF tube.

Regardless of results, maybe Douglas would be willing to maybe take a look at your upper or gauge/lay-out your barrel? Something sounds amiss, obviously. See if you can make heads or tails of it, though, shooting with the actual barrel supported.
Link Posted: 3/1/2006 2:51:46 AM EDT
[Last Edit: 3/1/2006 2:52:28 AM EDT by SWO_daddy]
Guys, here's a newsflash.

Every now and then, a button-rifled barrel can't be stress releived enough to rid it of all the internal stresses imparted to it by the rifling process. As the rifle heats up, the heat allows the molecular structure to change in response to those mechanical stresses built into the steel and the barrel changes shape. That's normally why you see a POI shift after the barrel gets warm.

You might be in that situation. I recommend making sure nothing is in contact with the barrel along its length, then discussing the situation with whomever sold it to you. If you get no satisfaction there, talk to Douglas.

ETA: The barrel material is irrelevant.
Link Posted: 3/1/2006 3:38:46 AM EDT
SWO_daddy,

Thats why I prefer cut rifled barrels. On the other hand I haven't seen a GOOD button rifled barrel shift that much in a long time. I'm still wondering if he isn't shifting his hold somewhat during the string. Especially shooting rapidly (he hasn't said yet HOW rapidly) from a bipod.

Ever shoot the Snowbird match at Atterbury? Maybe they don't do that one anymore. Lots of fun trying to shoot well when it was so damned cold that your teeth wouldn't stop chattering.

Cheers,

Phil
Link Posted: 3/1/2006 4:01:38 AM EDT
[Last Edit: 3/1/2006 4:03:16 AM EDT by SWO_daddy]
Phil, agree with the cut rifled barrel. That said, it is rare to get a bad button rifled barrel from a good maker. I've been pretty happy with both Wilsons that I've had, and I'll probably make HM with the one on the gun now.

I've shot at Atterbury a few times, usually the big regional and state shoots. I'm going to try to make a few of the 1000 yd matches there as well. I'm shooting for DR this year, so I will be at one of their EiCs, at the least. I like shooting there. It's pretty cool to hear all the small arms and artillery fire going on all around you, sometimes on the next range over, while shooting a match.

ETA: I haven't shot the Snowbird match, but we shoot informal matches at Miami RPC from Dec to March. Some of the February ones started with the mercury on single digits and warmed up to 20 by the time we were done.
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