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Old 07-18-2012, 07:16 PM   #1
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Default Problem w/long throat in Rem 700

I need a little help. Despite my age (old + a few), I'm new to the sport (both shooting & reloading). I'm retired military, and a precision CNC machinist in my "second life" (although not a gunsmith by any stretch). I have a "situation" which prompts me to seek the wisdom/advise of more experienced enthusiats & gunsmiths.

I recently purchased a Rem 700 BDL in 22-250 cal. My initial factory ammo choice is Hornady Superformance Varmit, 50-gr V-Max, 4,000 fps (claimed) with a C.O.L. of 2.340" (0.010" less than SAAMI max). Although purchased initially for varmit hunting, I'm going to reload with the intent of getting the most accuracy out of the gun as possible, not necessarily the highest velocity. I've been reading (a lot!) about ballistics (internal, external & terminal) and reloading, and have outfitted a respectable reloading bench.

Today, I was disappointed. Here's why: I've read that the best accuracy usually occurs when a bullet is seated close to the rifling. Zero inches of clearance, up to .030" clearance is often quoted, although I've read comments that more clearance sometimes produces good results. I measured the clearance of my chosen factory ammo, and was shocked to find that, in my arm, it has 0.147" clearance from factory's bullet seating depth to the engagement of the rifling. Granted, the V-Max bullet has a sharp ogive (which increases the clearance), but this is MUCH more than I expected, and 10 times the clearance I was hoping to achieve.

The factory round is already close to the SAAMI max C.O.L., but my magazine & receiver is plenty long enough to extend my rounds beyond the SAAMI max .... BUT ..... placing the bullet near the rifling means only 0.125" of the bullet is gripped by the case. I'm guessing this is way too little.

So ... I want to shorten the throat, but the only two ways to acheive this is to move the rifling backwards (not possible!), or to move the chamber forward. Since it's not possible to replace rifling that has been reamed away by the factory, my only option is to remove the barrel, shorten the breach end by 0.100" and then re-ream the chamber to the correct depth (by extending it by the same 0.100" the barrel was shortened). The intended result would be simply shortening the throat (free-bore) by 0.100", thus allowing me to seat my chosen bullet (Hornady V-Max 50 gr.) MUCH closer to the rifling. I know this is an over-simplified explanation, and there are several other concerns & dimensions to maintain, but you get the idea. (I know that a new custom barrel is also an option, but I'm calling that Plan-B.)

Question: Is this a ludicrous thought .... or something that just may work if done correctly? (As a machininst, I own a precision lathe capable of the task, and plenty of inspection equipment, but that doesn't make it a wise venture......)

Intelligent comments born of wisdome and/or experience would be GREATLY appreciated. Redneck jabs fueled by an alcohol induced stupidity can be kept to one's self.

Thanks in advance (and sorry for the long post, but better too much info than not enough)
Mike

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Old 07-20-2012, 09:10 PM   #2
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Re-chamber the gun to .22 Cheetah or .22/243.

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Old 07-20-2012, 10:34 PM   #3
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How did you measure it?? When you reload don't do a full length resize, only a neck resize. You will be fine. Resize the neck. insert a bullet into the case, it should be snug. carefully, slowly chamber it and extract it. Measure the OAL. You will be good to go. I usually will back off .005

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Old 07-21-2012, 12:51 AM   #4
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If'n it were me, I'd take the barrel off and recut it.

A rule of thumb on the gripping area of the case is to insure that you have at least one diameter of bullet of bullet to case contact. This is not a hard fast rule as some rifles shoot very well with less, but in your case unless you fix the rifle it will be problematic.

It could be that the barrel has been shot quite a bit and you'd be better off "refreshing" it.

What you need to do is determine how much to cut off, say .100 and then move the shoulder back the same amount. You may have to rethread it, but usually you dont have too.

Then, using a finishing reamer, ream slowly until the bolt just closes on the go gage. That will refresh your chamber, get rid of the long throat and your chamber will be like new. The gun ought to shoot well as long as the rifling isnt worn totally out.

I did two Sakos this way that were prarie dog shooters. One had 15,000 rounds logged, the other 20,000 and the groups were opening up to around two inches at 100 yards. The owner wanted me to "refresh" the barrels. I told him that it might be a waste of time since the barrels had been shot so much, but he figured he had nothing to lose it if worked and if it didnt, he'd just get me to rebarrrel them.

So I did in the same way I just outlined. He called me back and he was estatic as both rifles were now shooting like new with less than 1/2 groups at 100.

So, the way I see it, you have nothing to lose and everything to gain, plus, it'll be a good experience for you.

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Old 07-21-2012, 11:40 AM   #5
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New or used 700?

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Old 07-21-2012, 03:33 PM   #6
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seems like a whole lot of work to me for something that may or may not work in the end. you might find that your barrel does not like the bullets you've chosen and you're doing the work for nothing. i would load what you have now and see how it performs before modifying the rifle. you may find that the accuracy far exceeds your expectations. you may also find that it's a lost cause and need to find a better bullet. I have a few remmy 700's and i've never had a problem being able to seat out far enough for the bullet to jam into the lands. now, i don't shoot it that way, but there is the ability to do so. if you jam the ogive into the lands, and then look at the bullet under a magnifying glass, you will see rectangular marks left from the lands on the jacket of the bullet. If it's not touching there will be no marks, obviously. I seat my bullets into the lands just enough that there will be little square marks left on the jacket when i look at it under the magnifying glass. I've had great results with this and it is my starting point for seating depth when working up a new load.

factory ammo is short. it is always short. it needs to be able to feed reliably in every gun out there. it doesn't have to be the best, it just needs to work. and it usually works well. but if you're loading for accuracy, your ammo tolerances need to match your gun, not work well in everyone else's.

Try working up a load with the bullets you've chosen. if you can't get them to shoot to your liking, try other bullets and repeat. I would modify the gun barrel/chamber ONLY as a last resort. that's my personal opinion. but you can still do a trigger job, pillar bed, free float, etc before trying loads. Since you're already a precision machinist (must be nice!) you can go ahead and blueprint the action and true the lugs while you're at it.

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Old 07-21-2012, 07:34 PM   #7
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A long throat is a long throat, whether its new or used. I have seen guns that never fired a shot have long throats and they are not conducive to accuracy.

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Old 07-22-2012, 12:56 PM   #8
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Thanks (again) to all.

I mentioned that I just purchased the gun, but failed to mention that I purchased it new. My decision was based on Remington's stellar reputation, but I have to say their "new stuff" just isn't made to the same standard of old. I don't (yet) know if Remington is using SAAMI's recommended 2-degree lead on the rifling, or whether it's something much steeper. I'm going to take some more measurements when I get the chance and calc it out. (I suppose a chamber cast might also work, but I don't know if a gunsmith can cast all the way up to include the rifling ..... probably not.)

As for all the opinions ...... they seem to range from the far right to the far left. Some "seem" to be backed by wisdom, knowledge & experience ..... others "seem" to be just from people who are bored and want to type on their PC. To those of you in the former group ..... thanks ..... I've gotten several good ideas, and a lot of things to think about .... much of which I hadn't thought of before. (Ah ..... the power of a forum.)

I posted my question on a few other forums, and got squat back. I LIKE THIS FORUM.

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