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> Bedding a T3. Should I relieve this section?
Bedding a T3. Should I relieve this section?
@ 04:42 am (GMT) |
Bush ChookHi Nathan and Everyone else. I've been a long time TBR fan and lurker on these forums. However, I have a question that I would appreciate some expert input on so I have finally put in an appearance.I and a friend recently bedded his wooden stocked T3 and as far as I could see the job was a real success. No disasters occurred during the process and the result looked really spot on. However on shooting it the results were rather disappointing. With factory ammo it consistently grouped (for both of us shooting with a bag rest and butt rest - no bipod) approximately 3-5 moa with a distinct tendency to double group on a rough horizontal plane. It didn't double group that tightly, each pair of holes was about 1" apart but it did show a consistent pattern of doing this. Neither of us usually shoot that badly. On reading the section in Nathan's book about double grouping he mentions that action pinching is a possible cause of this problem. However, when we bedded the rifle we took extra care to relieve all the required ares including the top and rear of the lug and the parallel side walls. When put in the stock, the action slips in and out nicely with only the slightest hint of catching. This is between the front of the recoil lug and the curving section of bedding formed where the action in front of the recoil lug recess curves up to meet the barrel. This seems like it might be creating a pinch point of the section of action between the recoil lug and the curving bedding. Should I lightly sand this conchoidal section of bedding to relieve this potential pinch point? If I did this the only section of bedding stopping the action slopping back and forth would be the barrel knox bedding. Is this sufficient? Another issue that might be causing this problem is that the barrel is lightly-moderately copper fouled. Of note here is the fact that one side of the barrel is only lightly fouled on the lands and the other side is moderately fouled on both the lands and the grooves. We are going to de-foul it as soon as we can get some Boretech (living in the boonies of Vic makes that a mission) and I am trying to convince him to give hand lapping a nudge. What do you think would be causing the uneven fouling? It's a new barrel thats fired 100 rounds max. Any other ideas as to what might be causing this accuracy issue? Thanks a lot!!! |
Replies
@ 07:47 am (GMT) |
Bob MavinRe: Bedding a T3. Should I relieve this section?G'day mateWork on one mod at a time to find the problem. I would clean the barrel before doing anything, forget about lapping at this stage also check that the magazine follower isn't pinched. The barrel bedding forward of the recoil lug shouldn't be a problem The recoil lug should only be touching on the surface at the back (closest to the recoil pad) with clearance on the bottom front & left & right. I assume the barrel is not touching the fore end anywhere forward of the bedding. Cheers Bob |
@ 08:25 pm (GMT) |
Nathan FosterRe: Bedding a T3. Should I relieve this section?Hey Chook, lets see if we can help.First off- Bob, its the other way around. You've gotten mixed up with a normal lug set up. Happens to all of us. The front of the T3 lug has to touch the action, not the rear. 1. Perform the 1-Oclock test from book 1 and book 3. Screw the front action screw in and out to see if the stock is stressed / was stressed during bedding. 2. You can try relieving the areas you wish to relieve but it sounds as though the fit is already very good. I am not 100% certain that more needs to be done here. If the action is lubed and passes nicely in and out of the stock (even with a small 'bump' when fitting the action over the lug), then there is little more to do. Very minor tight spots will not open groups up to 3". 3. Final test is to put release agent on the action and lug, then run a small smear of Araldite (double syringe epoxy) along the front of the recoil lug recess in the action. Assemble the rifle, leave to set, then test shoot with the action essentially cemented in place. The bond will not be strong, testing will need to be done inside 10 shots if using different brands of ammo. There is a possibility that this rifle has a heat treatment flaw in the bore (How did it shoot before?). I have come across this before in T3 rifles. It is rare but unfortunately a small percentage do have dud bores. A heat treatment facility could perhaps de-stress at around 525c but the normal course of action is to replace the barrel. |
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@ 02:57 am (GMT) |
Bush ChookRe: Bedding a T3. Should I relieve this section?Thanks Bob and Nathan for your replies.Bob, the T3 has a box magazine which is not being impeded or pinched in any way. Also the barrel is definitely floating forward of the bedding. Nathan, With the 1 o'clock check the barrel showed no perceptible flex or movement on the forward action screw being loosened and tightened. On further scrutiny of the job we did find that the bedding was a little restrictive behind the tang which we removed in case it impeded proper movement. We also did a recoil lug relief test by placing a small amount of plastercene between the barrel and the lug and the result was what we were after - a tiny gap above and behind - so no problems there. Following this we did another test fire and the results were the same - approximately 3 moa. However it did not seem to be double grouping this time. Given your reluctance to suggest I relieve the section in question, I think I will leave it for now. The rifle definitely fits in and out smoothly and any further loosening might be counterproductive. The plan from here is to give the barrel a good clean and try again. If no luck then we will do #3 from your list to temporarily remove the bedding as a potential inaccuracy factor from the equation. I will keep you posted. The rifle shot approximately 3" before the bedding job so there has been no perceptible change. At least the bedding didn't make it worse!! Thanks again for your response. |
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@ 03:27 am (GMT) |
Bob MavinRe: Bedding a T3. Should I relieve this section?G'day ChookI was a bit hasty with my previous reply, forgetting about the recoil lug design. Check the crown of the barrel Also if hand loading, I had a bad batch of core-locks that had slight deformities at the heel of the pill (last bit that leaves the barrel) gives the same result as a damaged crown. Cheers Bob |
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@ 10:20 pm (GMT) |
Nathan FosterRe: Bedding a T3. Should I relieve this section?No double grouping is a good thing. There is hope yet.It could be a malformed land, burred throat or land, dimensions or the muzzle. Work through the steps in the accurizing book as best as you can. You may yet have to fire lap (last ditch). You are on the right track by starting with a good clean. Avoid any self pressure. Just take it real easy as a "subject of interest", one step at a time. If you get frustrated, back off for a bit. Keep your expectations open. Please trust me when I say that the bore is most likely at fault- no questioning yourself as to "did I do this or that during bedding". Attitude is major factor from here forwards. Try to stay light of heart and allow whatever is going to happen to happen. Shooting technique is the other biggie with this rifle design. The gun is light, it needs to be held properly. Use Federal blue box during testing as a base line. Bore, shooting technique, attitude towards problem solving, willingly accept potential failure. |
@ 12:34 am (GMT) |
john feyereisnRe: Bedding a T3. Should I relieve this section?I think the advice given here has all been good, however one thing that has not been mentioned is to go over the basics if you have not done so. If you are hand loading buy a box of factory loads to see if they shoot acceptable. A check of the scope and mounts or trying a known good scope are simple things to check.Good luck, and remember to follow up with what you find |
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@ 11:46 am (GMT) |
Bush ChookRe: Bedding a T3. Should I relieve this section?There's bad news and good news to report.Nathan, You were on the money with your comment about internal damage. The barrel was substantially more copper fouled than I initially thought and it took us approx 8 hours of work to get clean. Unfortunately, we couldn't find any Boretech so had to make do with Hoppes No 9 Copper remover which is quite inferior. As we scrubbed away at it and the copper slowly came off the problem became clear. The barrel looked substantially damaged inside with severe pitting running up 3 of the grooves with at least 2 lands pitted along their centers and edges. My mate has had the rifle since new (less than a year) and has always oiled the barrel after use. However, he didn't know that further cleaning was required so has never cleaned or defouled it. From here for the sake of approaching things methodically we did another 2 four shot groups which showed no change. These 8 shots completely fouled the barrel again so we undertook another 4 hour mission with the bore brush and white polypads to get it mostly clean again. Next we lapped the barrel as per the breaking-in procedure in Book 3. We then repeated this procedure as it was clear that the barrel needed a lot more work. After this we tried another test fire and the results were pleasantly surprising. We used mostly Remington factory loads with a group of Winchester loads for comparison. (Nathan, we have no Federal, and the nearest shop is 3 hours away - a challenge during work days! I will tell my mate to get some asap but ammo availability over here is like it is back home - it comes and goes.) The first group was approx 3 moa, the second was 1 moa, third was 3 moa again (Win Ammo) 4th was 1.5 moa. After those 16 shots it was badly fouled but promisingly the grooves were evenly fouled, not just a couple like before. So, its a very good start in the right direction. From here I'm trying to convince my mate to give it several more good lappings but he is a little reluctant to put more abrasives down his barrel. I'm sure I will get him round though. Do you have any recommendations as to where to from here? I am trying to avoid self pressure but I'm finding that working on someone else's rifle is more traumatic than working on my own! Fortunately it looks like progress is being made. John, The scope is a near new Leupold 3-9 x 40 so there's no Chinese rubbish there. The rings are a bit more suspect as they are Chinese but look fairly solid. Thanks!! |
@ 06:30 pm (GMT) |
Thomas KitchenRe: Bedding a T3. Should I relieve this section?its great to hear progress bush chooksounds like you and your mate learning a lot on the way to. if you cant find any boretech try kg 2. best of luck |
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@ 08:22 pm (GMT) |
Nathan FosterRe: Bedding a T3. Should I relieve this section?Hi Chook, definitely order in some KG12 from reloaders or similar.Your friends concerns are somewhat vaild. There is only so much lapping we can do before we ruin tolerances. But this bore is a dud anyway, so you are on the right track. Keep an eye on the muzzle. Can pay to dock at a clean spot. The muzzle always has the final say. Long term plan will be to rebarrel and free float the knox. That should fix her up. Yes it can be very stressful. Make sure your mate fully understands that the bore is a dud and that you can do no worse. He has to let go of it now, allowing you to experiement and see how it plays out. Even if you get it shooting straight, the rifle will most likely need a new barrel within a year. All you can do is try to buy him a little time to save. |
@ 11:06 pm (GMT) |
Martin TaylorRe: Bedding a T3. Should I relieve this section?You will get Sweets 7.62 easier than any of the other copper remover, it may be a little slower? but it will do what you need.My guess this is a mountain Sambar gun, heaps of mist sitting in the barrel hey. |
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